



Network Working Group                                        N.B. Sopher
Internet-Draft                                              O. Finkelman
Obsoletes: 8007 (if approved)                                      Qwilt
Intended status: Standards Track                               S. Mishra
Expires: 23 April 2026                                           Verizon
                                                          J.K. Robertson
                                                                   Qwilt
                                                           A. Arolovitch
                                                                  Viasat
                                                         20 October 2025


  Content Delivery Network Interconnection (CDNI) Control Interface /
                          Triggers 2nd Edition
               draft-ietf-cdni-ci-triggers-rfc8007bis-18

Abstract

   This document obsoletes RFC8007.  The document describes the part of
   Content Delivery Network Interconnection (CDNI) Control interface
   that allows a CDN to trigger activity in an interconnected CDN that
   is configured to deliver content on its behalf.  The upstream CDN MAY
   use this mechanism to request that the downstream CDN preposition,
   invalidate, and/or purge metadata and/or content.  The upstream CDN
   MAY monitor the status of activity that it has triggered in the
   downstream CDN.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 23 April 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Model for CDNI Triggers . . . . . . . . . . . . . . . . . . .   6
     2.1.  REST Architecture . . . . . . . . . . . . . . . . . . . .   6
     2.2.  HTTP Methods  . . . . . . . . . . . . . . . . . . . . . .   7
     2.3.  Trigger . . . . . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Trigger Access Control and Multi-Tenancy  . . . . . . . .   8
     2.5.  Trigger Index and Trigger Collections . . . . . . . . . .   9
     2.6.  Session Overview  . . . . . . . . . . . . . . . . . . . .   9
     2.7.  Trigger Processing  . . . . . . . . . . . . . . . . . . .  11
       2.7.1.  Timing and Order  . . . . . . . . . . . . . . . . . .  11
       2.7.2.  Scope . . . . . . . . . . . . . . . . . . . . . . . .  12
       2.7.3.  Results . . . . . . . . . . . . . . . . . . . . . . .  12
     2.8.  Trigger Extensibility . . . . . . . . . . . . . . . . . .  12
     2.9.  Multiple Interconnected CDNs  . . . . . . . . . . . . . .  13
     2.10. Loop Detection and Prevention . . . . . . . . . . . . . .  14
   3.  CDNI Trigger Interface  . . . . . . . . . . . . . . . . . . .  15
     3.1.  Creating Triggers . . . . . . . . . . . . . . . . . . . .  16
     3.2.  Modifying Triggers  . . . . . . . . . . . . . . . . . . .  17
     3.3.  Cancelling Triggers . . . . . . . . . . . . . . . . . . .  18
     3.4.  Checking Status . . . . . . . . . . . . . . . . . . . . .  19
       3.4.1.  Polling Trigger Collections . . . . . . . . . . . . .  19
         3.4.1.1.  Extended view representation  . . . . . . . . . .  19
       3.4.2.  Polling Triggers  . . . . . . . . . . . . . . . . . .  20
     3.5.  Deleting Triggers . . . . . . . . . . . . . . . . . . . .  20
     3.6.  Expiry of Triggers  . . . . . . . . . . . . . . . . . . .  21
     3.7.  Error Handling  . . . . . . . . . . . . . . . . . . . . .  21
       3.7.1.  Error Propagation . . . . . . . . . . . . . . . . . .  22
   4.  CI/T Object Properties and Encoding . . . . . . . . . . . . .  25
     4.1.  Trigger Resource  . . . . . . . . . . . . . . . . . . . .  25
       4.1.1.  Trigger Action  . . . . . . . . . . . . . . . . . . .  29
       4.1.2.  Trigger Specs . . . . . . . . . . . . . . . . . . . .  30
         4.1.2.1.  Generic Spec Object . . . . . . . . . . . . . . .  32
         4.1.2.2.  Trigger Subject . . . . . . . . . . . . . . . . .  33
         4.1.2.3.  Spec Constraints  . . . . . . . . . . . . . . . .  34
         4.1.2.4.  URLs Spec . . . . . . . . . . . . . . . . . . . .  34
         4.1.2.5.  CCIDs Spec  . . . . . . . . . . . . . . . . . . .  35



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         4.1.2.6.  URI Pattern Match Spec  . . . . . . . . . . . . .  35
         4.1.2.7.  URI Regex Match Spec  . . . . . . . . . . . . . .  37
         4.1.2.8.  Object List Spec  . . . . . . . . . . . . . . . .  39
       4.1.3.  Trigger Extensions  . . . . . . . . . . . . . . . . .  39
         4.1.3.1.  Enforcement Options . . . . . . . . . . . . . . .  39
         4.1.3.2.  GenericExtensionObject  . . . . . . . . . . . . .  42
         4.1.3.3.  Trigger Extension Objects . . . . . . . . . . . .  44
       4.1.4.  Trigger Labels  . . . . . . . . . . . . . . . . . . .  53
       4.1.5.  Trigger State . . . . . . . . . . . . . . . . . . . .  54
       4.1.6.  Trigger Errors  . . . . . . . . . . . . . . . . . . .  55
         4.1.6.1.  Error.v2 Description  . . . . . . . . . . . . . .  55
         4.1.6.2.  Error Code  . . . . . . . . . . . . . . . . . . .  58
     4.2.  Trigger Index Resource  . . . . . . . . . . . . . . . . .  59
     4.3.  Trigger Collection Resource . . . . . . . . . . . . . . .  61
       4.3.1.  Trigger Collection View . . . . . . . . . . . . . . .  62
     4.4.  Other CI/T Objects and Properties . . . . . . . . . . . .  63
       4.4.1.  URL Type  . . . . . . . . . . . . . . . . . . . . . .  63
       4.4.2.  ObjectList  . . . . . . . . . . . . . . . . . . . . .  64
         4.4.2.1.  ObjectList Type . . . . . . . . . . . . . . . . .  68
         4.4.2.2.  JSON Serialized Object List . . . . . . . . . . .  69
         4.4.2.3.  Text Object List  . . . . . . . . . . . . . . . .  69
         4.4.2.4.  ObjectEntry . . . . . . . . . . . . . . . . . . .  69
       4.4.3.  CDN Provider ID . . . . . . . . . . . . . . . . . . .  71
   5.  Footprint and Capabilities  . . . . . . . . . . . . . . . . .  71
     5.1.  CI/T Endpoint Capability Object . . . . . . . . . . . . .  71
       5.1.1.  CI/T Endpoints Capability Object Serialization  . . .  72
     5.2.  CI/T Trigger Scope Capability Object  . . . . . . . . . .  74
       5.2.1.  CI/T Trigger Scope Capability Object Serialization  .  75
     5.3.  CI/T Object List Type Capability Object . . . . . . . . .  76
       5.3.1.  CI/T Object List Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  77
     5.4.  CI/T Private URL Capability Object  . . . . . . . . . . .  77
       5.4.1.  CI/T Private URL Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  77
     5.5.  CI/T Extended Status Capability Object  . . . . . . . . .  78
       5.5.1.  CI/T Private URL Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  78
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  79
     6.1.  Creating Triggers . . . . . . . . . . . . . . . . . . . .  79
       6.1.1.  Preposition . . . . . . . . . . . . . . . . . . . . .  79
       6.1.2.  Invalidate  . . . . . . . . . . . . . . . . . . . . .  81
       6.1.3.  Invalidation with Regex . . . . . . . . . . . . . . .  83
       6.1.4.  Preposition with ObjectLists  . . . . . . . . . . . .  85
     6.2.  Changing, Cancelling and Deleting Triggers  . . . . . . .  86
       6.2.1.  Modifying Triggers  . . . . . . . . . . . . . . . . .  86
       6.2.2.  Cancelling Triggers . . . . . . . . . . . . . . . . .  88
       6.2.3.  Deleting Triggers . . . . . . . . . . . . . . . . . .  90
     6.3.  Examining Trigger Status  . . . . . . . . . . . . . . . .  90



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       6.3.1.  Trigger Index . . . . . . . . . . . . . . . . . . . .  90
       6.3.2.  Trigger Collection  . . . . . . . . . . . . . . . . .  92
       6.3.3.  Individual Trigger Resources  . . . . . . . . . . . .  94
       6.3.4.  Polling for Changes in Status . . . . . . . . . . . .  95
     6.4.  Extensions  . . . . . . . . . . . . . . . . . . . . . . .  98
       6.4.1.  Execution Policy Extension  . . . . . . . . . . . . .  98
       6.4.2.  Extensions with Error Propagation . . . . . . . . . . 102
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 106
     7.1.  CDNI Payload Type Parameter Registrations . . . . . . . . 106
       7.1.1.  CDNI ci-trigger.v2 Payload Type . . . . . . . . . . . 107
       7.1.2.  CDNI ci-trigger-index.v2 Payload Type . . . . . . . . 107
       7.1.3.  CDNI ci-trigger-collection.v2 Payload Type  . . . . . 107
       7.1.4.  CDNI FCI CI/T Payload Types . . . . . . . . . . . . . 107
         7.1.4.1.  CDNI FCI CI/T Endpoints Payload Type  . . . . . . 107
         7.1.4.2.  CDNI FCI CI/T Trigger Scope Payload Type  . . . . 107
         7.1.4.3.  CDNI FCI CI/T Object List Type Payload Type . . . 108
         7.1.4.4.  CDNI FCI CI/T Private URL Type Payload Type . . . 108
         7.1.4.5.  CDNI FCI CI/T Extended Status Payload Type  . . . 108
     7.2.  "CDNI CI/T Trigger Types" Registry For Trigger Actions  . 108
     7.3.  "CDNI CI/T Trigger Specs" Registry  . . . . . . . . . . . 109
     7.4.  "CDNI CI/T Trigger Subjects" Registry . . . . . . . . . . 109
     7.5.  "CDNI CI/T Object List Types" Registry  . . . . . . . . . 109
     7.6.  "CDNI CI/T Trigger Extensions" Registry . . . . . . . . . 110
     7.7.  "CDNI CI/T Error Codes" Registry  . . . . . . . . . . . . 110
     7.8.  "CDNI CI/T URL Types" Registry  . . . . . . . . . . . . . 110
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . 111
     8.1.  Authentication, Authorization, Confidentiality, Integrity
           Protection  . . . . . . . . . . . . . . . . . . . . . . . 111
     8.2.  Denial of Service . . . . . . . . . . . . . . . . . . . . 113
     8.3.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 113
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 113
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . 113
     9.2.  Informative References  . . . . . . . . . . . . . . . . . 115
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 116
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 116

1.  Introduction

   [RFC6707] introduces the problem scope for Content Delivery Network
   Interconnection (CDNI) and lists the four categories of interfaces
   that may be used to compose a CDNI solution (Control, Metadata,
   Request Routing, and Logging).

   [RFC7336] expands on the information provided in [RFC6707] and
   describes each of the interfaces and the relationships between them
   in more detail.





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   The CDNI Control Interface / Triggers 1st edition [RFC8007],
   deprecated by this document, describes the "CI/T" interface -- "CDNI
   Control Interface / Triggers".  It does not consider those parts of
   the Control interface that relate to the configuration,
   bootstrapping, or authentication of CDN Interconnect interfaces.
   Section 4 of [RFC7337] identifies the requirements specific to the
   CI/T interface; requirements applicable to the CI/T interface are
   CI-1 to CI-6.

   This document is a second edition of the CDNI Control Interface /
   Triggers, which defines a new version, "v2", of the interface
   objects.  The new version aims to support REST [REST] architectural
   style in a way that improves the interface's flexibility,
   extensibility, and interoperability, and allows encoding of the
   interface using OpenAPI.  The new objects replace the main CI/T
   objects as follows:

   *  The "ci-trigger-command" object and its matching "ci-trigger-
      status" object are replaced with the "ci-trigger.v2" object
      representing a trigger resource

   *  The "ci-trigger-collection" object is replaced with the "ci-
      trigger-collection.v2" that is expanded to support filtering by
      trigger state and trigger labels

   The second edition of the CI/T interface further allows the use of
   separate Control interface endpoints for content and metadata.

   The document also provides a trigger extension mechanism that MAY be
   used to provide further instruction on the trigger execution.

   This second edition also includes cascaded CDN error propagation and
   extended trigger status reporting for improved trigger execution
   monitoring, as well as the use of external object lists for improved
   scale and integration of trigger-based APIs with existing content
   workflows.

   *  Section 2 outlines the model for the CI/T interface at a high
      level.

   *  Section 3 defines the CI/T interface offered by the downstream
      CDN.

   *  Section 4 defines the encoding of the standard CI/T objects and
      introduces trigger spec and trigger extension types.

   *  Section 5 describes the FCI capabilities objects used to inform on
      the supported CI/T-related capabilities.



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   *  Section 6 contains example messages.

1.1.  Terminology

   This document reuses the terminology defined in [RFC6707] and uses
   "uCDN" and "dCDN" as shorthand for "upstream CDN" and "downstream
   CDN", respectively.

   Additionally, the following terms are used throughout this document
   and are defined as follows:

   *  HLS - HTTP Live Streaming

   *  DASH - Dynamic Adaptive Streaming Over HTTP

   *  MSS - Microsoft Smooth Streaming

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Model for CDNI Triggers

2.1.  REST Architecture

   The CI/T interface utilizes the HTTP/1.1 protocol [RFC9112] and
   follows the principles of the Representational State Transfer (REST)
   architectural style.  The uCDN, in its capacity as a CI/T interface
   client, requests the dCDN to carry out an action ("trigger") related
   to metadata or content stored by the dCDN on behalf of the uCDN.

   The dCDN, as a CI/T interface server, governs the triggers as a set
   of resources, which can be dynamically created and deleted, and whose
   state can be retrieved and/or modified by the uCDN.  Each such
   trigger is identified by a unique Uniform Resource Identifier (URI)
   as defined in Section 4.2 of [RFC9110].

   Once a trigger is created, the uCDN can retrieve its representation
   from the dCDN or request the trigger to be modified by transferring
   an updated representation of it to the dCDN.  The CI/T interface
   supports the representation of trigger resources using JSON
   [RFC8259].







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   This RESTful data model, built around a common "trigger" resource,
   replaces the command-oriented model of [RFC8007], wherein the uCDN
   passed commands to the dCDN using "ci-trigger-command" objects, and
   the dCDN generated "ci-trigger-status" objects in response.

2.2.  HTTP Methods

   Section 9.3 of [RFC9110] defines the set of methods in HTTP.  The CI/
   T interface uses some of these methods for resource creation,
   retrieval of resource state, modification of resources, and deletion
   of resources.  The HTTP methods not listed here are not supported by
   the CI/T interface.

   *  GET - used to retrieve the current state of a resource.  The GET
      method doesn't cause any state change on the server side.

   *  POST - used to request that the target resource process the
      representation enclosed in the request.  If a resource has been
      created on the server as a result of successfully processing a
      POST request, the server sends a 201 ("Created") response
      containing a Location header field that contains an identifier for
      the newly created resource.

   *  DELETE - used to request the server remove the target resource.

   *  HEAD - used to request metadata associated with the target
      resource, in the form of HTTP response headers that would have
      been sent if the GET method were used instead.  The HEAD method
      can be used to verify that the target resource exists on the
      server.

2.3.  Trigger

   The uCDN requests creation of a trigger resource to instruct the dCDN
   to perform an action.  If the dCDN accepts the request, it creates a
   new trigger resource and returns its unique URI to the uCDN.  The
   uCDN MUST use this URI for all requests associated with the created
   trigger resource.

   Note that the version of the trigger resources that the uCDN requests
   to create MUST match the version of CI/T trigger objects reported as
   supported by the dCDN.

   The CI/T interface supports the following types of trigger action:

   *  preposition - used to instruct the dCDN to fetch metadata from the
      uCDN or content from any origin, including the uCDN.




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   *  invalidate - used to instruct the dCDN to revalidate specific
      metadata or content before reusing it.

   *  purge - used to instruct the dCDN to delete specific metadata or
      content.

   Note that additional action types can be defined and registered in
   the future.

   The trigger resource has a "state" attribute.  The dCDN creates new
   triggers in the "pending" state.  Once the dCDN starts processing a
   pending trigger, the trigger state is set to "active".  The uCDN MAY
   explicitly request the trigger to be created in the "active" state.
   If accepted by the dCDN, it may create the new trigger in the
   "active" state and start its processing immediately upon creation.
   Once the trigger processing is complete, the state is set to either
   "complete" or "failed", depending on the processing outcome.

   The uCDN MAY request the cancellation of a trigger from the dCDN.  If
   such a request is accepted, the trigger state is changed to
   "cancelling", and when the cancellation is complete, the trigger
   state changes to "cancelled".

   For a full description of the trigger resource, please refer to
   Section 4.1.

2.4.  Trigger Access Control and Multi-Tenancy

   The dCDN MUST only allow the uCDN access to the trigger resources it
   created.

   The dCDN MUST ensure that triggers created in response to a uCDN
   request apply only to content and metadata objects associated with
   that uCDN.

   In case of content prepositioning, the dCDN MUST be able to associate
   content objects referenced in a trigger created by the uCDN with
   delivery CDNI metadata objects in its possession that are associated
   with the same uCDN.  These CDNI metadata objects include HostIndex,
   HostMatch, HostMetadata, PathMatch, PatternMatch, and PathMetadata,
   as described in Section 3.1 of [RFC8006].  For example, if the dCDN
   has no MI metadata objects that enable the dCDN to respond to
   requests for video.example.com, it MUST NOT allow prepositioning of
   content objects with this hostname in the object URL.







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   In case of metadata prepositioning, the prepositioned metadata
   objects MUST be consistent with pre-existing metadata, e.g.,
   prepositioning of the MI HostMatch object in the absence of MI
   HostIndex would be rejected.

   If such association between a trigger and pre-existing delivery
   metadata cannot be established, the dCDN MUST reject it.

   Furthermore, the dCDN SHOULD reject a trigger from the uCDN A that
   seeks to preposition delivery metadata objects that are in conflict
   with the pre-existing metadata objects belonging to another uCDN B,
   e.g., if it could cause the dCDN to match a content request with
   metadata objects from multiple uCDNs.

2.5.  Trigger Index and Trigger Collections

   The Trigger Index is the top-level resource that references all
   trigger resources belonging to a particular uCDN.  The dCDN maintains
   one Trigger Index resource for each uCDN, and each uCDN has access
   only to its own Trigger Index.  The Trigger Index contains references
   to Trigger Collection resources.  Each collection contains triggers
   that are optionally filtered by parameters - for example, all
   triggers in the "pending" state or all triggers labeled "video".  The
   same trigger resource can be present in more than one collection.
   The supported trigger collection representations are listed in
   Section 4.3 and include filtering of triggers by state and label.
   Note that additional trigger collection representations can be
   defined in the future.

2.6.  Session Overview

   Figure 1 is an example showing the basic message flow in a CI/T
   interface session used by the uCDN to trigger activity in the dCDN
   and for the uCDN to discover the status of that activity.  Only
   successful triggering is shown.  Please note that the example below
   uses simplified trigger identifiers for brevity.  It is recommended
   that the actual implementation uses unique UUID identifiers as
   specified in [RFC9562].  Examples of the messages are shown in
   Section 6.












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      uCDN                                                   dCDN
       |  (1) POST https://dcdn.example/cit/uCDN               |
      [ ] --------------------------------------------------> [ ]--+
       |                                                      [ ]  | (2)
       |  (3) HTTP 201 Response                               [ ]<-+
      [ ] <-------------------------------------------------- [ ]
       |     Loc: https://dcdn.example/cit/uCDN/123            |
       |                                                       |
       .                           .                           .
       .                           .                           .
       .                           .                           .
       |                                                       |
       | (4) GET https://dcdn.example/cit/uCDN/123             |
      [ ] --------------------------------------------------> [ ]
       |                                                      [ ]
       | (5) HTTP 200 Trigger resource representation         [ ]
      [ ] <-------------------------------------------------- [ ]
       |                                                       |
       |                                                       |
       | (6) DELETE https://dcdn.example/cit/uCDN/123          |
      [ ] --------------------------------------------------> [ ]--+
       |                                                      [ ]  | (7)
       | (8) HTTP 200 OK                                      [ ]<--
      [ ] <-------------------------------------------------- [ ]
       |                                                       |

               Figure 1: Basic CDNI Message Flow for Triggers

   The steps in Figure 1 are as follows:

   1.  The uCDN requests creation of a new trigger resource by POSTing
       its representation to the trigger index resource with a well-
       known URI "https://dcdn.example/cit/uCDN".

   2.  The dCDN authenticates the request, validates the trigger
       resource in it, and if the request is accepted, creates a new
       trigger resource.

   3.  The dCDN responds to the uCDN with an HTTP 201 ("Created")
       response status and the location of the trigger resource.

   4.  The uCDN MAY query, possibly repeatedly, the trigger resource in
       the dCDN.

   5.  The dCDN responds to each query with the current trigger resource
       representation, including the trigger state, that reflects the
       progress of the uCDN request.




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   6.  Once the trigger reaches a terminal state ("complete",
       "processed", "failed" or "cancelled"), the uCDN MAY request
       deletion of the trigger resource.

   7.  The dCDN validates the request and the trigger resource state.
       If successful, the trigger resource is removed by the server, and
       subsequent requests for this resource MUST result in 404 ("Not
       Found").

   8.  The dCDN responds to the deletion request with a 200 ("OK")
       status code.

   This section provides an overview of a regular session.  For detailed
   discussions of trigger modification, cancellation, and deletion, see
   Section 3.2, Section 3.3, and Section 3.5.

2.7.  Trigger Processing

2.7.1.  Timing and Order

   The uCDN MAY place limits on the timing and order of execution of a
   trigger through optional TimePolicy (Section 4.1.3.3.2) and/or
   ExecutionPolicy (Section 4.1.3.3.3) extensions.  If neither of these
   extensions are present in the trigger resource, the timing and order
   of the trigger execution is under the dCDN's control, including the
   start time, pacing of the activity in the network, and order in which
   the dCDN chooses to process pending triggers.

   The CI/T "invalidate" and "purge" trigger actions MUST be applied to
   all data acquired before the dCDN begins the trigger processing
   (i.e., enters "active" state).  The dCDN implementation SHOULD apply
   "invalidate" and "purge" triggers to content acquisition that is in
   progress when the trigger becomes active, to avoid placing purged or
   invalidated content into the cache upon completion of the content
   acquisition.  The dCDN SHOULD NOT apply CI/T "invalidate" and "purge"
   actions to data acquired after the trigger processing started, but
   this may not always be achievable, so the uCDN cannot count on that.

   If the uCDN wishes to invalidate or purge content and then
   immediately preposition replacement content at the same URLs, it
   SHOULD ensure that the dCDN has completed the invalidate/purge before
   initiating the prepositioning.  Otherwise, there is a risk that the
   dCDN prepositions the new content, then immediately invalidates or
   purges it (as a result of the two uCDN requests running in parallel).
   The uCDN MAY use the Execution Policy (Section 4.1.3.3.3) extension
   to condition the start of preposition trigger processing on
   completion of the earlier invalidate/purge trigger(s).




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2.7.2.  Scope

   Each trigger can operate on multiple metadata and content elements.
   These elements are targeted by specifying both their subject (i.e.,
   "metadata" or "content") as well as specification method (e.g., URL
   Regexes) and value.

   Multiple representations of an HTTP resource may share the same URL.
   Triggers that invalidate or purge metadata or content apply to all
   resource representations with matching URLs.

2.7.3.  Results

   Possible trigger states are defined in Section 4.1.5.

   Trigger state MUST NOT be reported as "complete" until all operations
   listed in the trigger have been completed successfully.  In case of
   CDN cascading, the completion of operations includes processing of
   the trigger in downstream CDNs.  For detailed discussion of the
   cascading use case, see Section 2.9.  The reasons for failure, and
   URLs or patterns affected, SHOULD be made available in the trigger
   state representation.  For more details about error handling, see
   Section 3.7.

2.8.  Trigger Extensibility

   The CDNI Control Interface / Triggers 1st edition [RFC8007] defines a
   set of properties and objects used by the trigger commands.  This 2nd
   edition defines an extension mechanism to the triggers interface that
   enables applications to add instructions for finer control over the
   trigger execution, for example indicating a time window in which to
   execute the trigger.  This document specifies a generic trigger
   extension object wrapper for managing individual CDNI trigger
   extensions in an opaque manner.

   All trigger extensions are OPTIONAL, and it is thus the
   responsibility of the extension specification to define a consistent
   default behavior for the case the extension is not present.

   All trigger extensions MUST be registered in the IANA "CDNI CI/T
   Trigger Extensions" registry (see Section 7.6).

   This document also defines an initial set of trigger extension
   objects and registers them in the IANA "CDNI CI/T Trigger Extensions"
   registry:






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      +==================+=========================================+
      | JSON string      | Description                             |
      +==================+=========================================+
      | location-policy  | Allowing the control over the locations |
      |                  | in which the trigger is executed.       |
      +------------------+-----------------------------------------+
      | time-policy      | Allowing the scheduling of a trigger to |
      |                  | run in a specific time window.          |
      +------------------+-----------------------------------------+
      | execution-policy | Allowing the control over the order and |
      |                  | timing in which triggers are executed.  |
      +------------------+-----------------------------------------+

                                 Table 1

2.9.  Multiple Interconnected CDNs

   In a network of interconnected CDNs, a single uCDN will originate a
   given item of metadata and associated content.  It MAY distribute
   that metadata and content to one or more dCDNs, which in turn
   distributes that metadata and content to additional dCDNs located
   further downstream.

   A transit CDN is a dCDN that passes on CDNI Metadata and content to
   the dCDNs located further downstream.

   The dCDN that creates trigger resources at the request of such
   transit CDN MUST associate the triggers with the transit CDN from
   which it receives the request, regardless of where the trigger
   request may have originated.

   A "diamond" configuration is one where the dCDN can potentially
   acquire metadata and content originated in one uCDN from that uCDN
   itself and a transit CDN, or via more than one transit CDN.

   The "diamond" configuration may cause configuration consistency
   problems, where the dCDN may end up in possession of multiple,
   potentially conflicting metadata objects belonging to the multiple
   uCDNs that match the same content request.  The conflict may arise
   due to the differences in trigger processing by the transit CDNs and/
   or variances in trigger propagation time across different paths in
   the "diamond" topology.

   Because of this, the "diamond" configuration is considered a
   configuration error.  A dCDN that receives identical trigger creation
   requests from different uCDNs SHOULD reject duplicate trigger
   requests, as described in Section 2.4.




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   Security considerations are discussed further in Section 8.

   If the dCDN is also acting as the uCDN in a cascade, it MUST forward
   trigger requests to any dCDNs that may be affected.  The trigger
   state MUST NOT be reported as "complete" by a transit CDN until it is
   "complete" in all of its dCDNs and in the transit CDN itself.  If a
   trigger is reported as "processed" in the transit CDN or any one of
   its dCDNs, transit CDNs MUST report the trigger as "processed" as
   well.  If a trigger is reported as "failed" by the transit CDN or any
   one of its dCDNs, the transit CDN must report the trigger as "failed"
   only after its processing is finished in it and all of its dCDNs.  A
   cancelled trigger MUST be reported as "cancelling" until it has been
   reported as "cancelled", "complete", or "failed" by all cascaded
   dCDNs.


2.10.  Loop Detection and Prevention

   Given three CDNs, A, B, and C, if CDNs B and C delegate delivery of
   CDN A's content to each other, CDN A's trigger creation requests
   could be passed between CDNs B and C in a loop.  More complex
   networks of CDNs could contain similar loops involving more hops.

   When such CDN topologies become possible, it is RECOMMENDED that CDNs
   participating in it utilize a CDN Provider ID (PID) (Section 4.4.3)
   to detect and prevent loops as follows:

   *  The uCDNs that originate a new trigger request SHOULD specify
      their CDN provider ID using the trigger "cdn-path" attribute (see
      Section 4.1 for details).

   *  A dCDN that receives a trigger creation request that contains a
      "cdn-path" attribute SHOULD check it for its own CDN PID.  If the
      dCDN's PID is already present, and the dCDN is not the CDN
      initiating the trigger, this condition likely indicates a loop.
      In such case, the dCDN MUST reject the trigger, which would result
      in a trigger rejection being returned to the originating uCDN.  If
      the dCDN receives a trigger that it itself originated, the dCDN
      MAY process the trigger as required.

   *  A dCDN that cascades trigger requests to additional dCDNs (so-
      called "transit CDN") SHOULD NOT reject triggers that have CDN PID
      of its downstream CDNs in their CDN path, allowing each CDN to do
      their own loop detection.

   *  Transit CDNs MUST append their CDN PID to the CDN path of a
      trigger before sending it to its downstream CDNs.




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   *  The dCDNs SHOULD advertise their CDN provider ID to the uCDNs
      using the "cdn-id" attribute of the trigger index (Section 4.2)
      resource.

3.  CDNI Trigger Interface

   This section describes an interface to enable the uCDN to trigger
   activity in the dCDN.

   The CI/T interface builds on top of HTTP, so the dCDNs may make use
   of any HTTP feature when implementing the CI/T Interface.  For
   example, the dCDN SHOULD make use of HTTP's caching mechanisms to
   reduce the uCDN's trigger status polling overhead by indicating the
   modification status of a requested resource representation.

   The dCDNs MAY implement separate CI/T interfaces per Section 4.1.2.2,
   i.e., one CI/T interface for trigger operations on metadata and
   another for operations on content.  In this case, the dCDN MUST
   advertise separate interface endpoints via Section 5.1.

   All dCDNs implementing CI/T MUST support the HTTP GET, HEAD, POST,
   and DELETE methods as defined in [RFC9110].

   The only resource representation specified in this document is JSON
   [RFC8259].  It MUST be supported by both the uCDN and the dCDN.

   The CI/T interface uses a root URI for the retrieval of the trigger
   index resource and creation of new triggers.  The mechanism for
   discovery of that URL is part of the CI/T interface bootstrapping and
   is outside the scope of this document.

   The uCDN requests to create a new trigger resource by POSTing its
   representation to the trigger index resource URI, discovered at the
   time of interface bootstrapping, e.g.,
   "https://dcdn.example/cit/ucdn/triggers".  If the request is accepted
   by the dCDN, it creates a new trigger resource and returns its URI to
   the uCDN in an HTTP 201 ("Created") response.

   Once created, the new trigger URI also becomes available via the
   trigger collection resources described in Section 4.3.  Additionally,
   the uCDN may discover the URIs of multiple trigger collection
   representations by retrieving the trigger index resource, which is
   accessible at the interface root URI.  This means that the URIs for
   all trigger resources and trigger collection representations can be
   discovered by the uCDN through the top-level trigger index resource,
   allowing dCDNs to use any URI structure they choose for CI/T
   resources.  Therefore, the uCDNs MUST NOT make any assumptions
   regarding the structure of CI/T URIs or the mapping between CI/T



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   objects and their associated URIs.  The URIs used in the examples in
   this document are purely illustrative and are not intended to impose
   a definitive structure on CI/T interface implementations.

3.1.  Creating Triggers

   To create a new trigger, the uCDN makes an HTTP POST request with the
   trigger representation to the trigger index resource URI.  The
   trigger representation MUST include the mandatory attributes of the
   trigger resource (Section 4.1).

   The uCDN MAY also optionally specify optional trigger v2
   specification attributes, namely trigger labels and trigger
   extensions, as well as the optional "cdn-path" attribute of the
   trigger resource.

   The dCDN validates the trigger resource representation sent by the
   uCDN.  If the representation is malformed or the uCDN does not have
   sufficient access rights, the dCDN MUST either respond with an
   appropriate 4xx HTTP error code and not create a trigger resource or
   create a trigger resource with a "failed" state and an appropriate
   Error.v2 Description (Section 4.1.6.1).

   The new trigger resource is created in a "pending" state.  If
   successful, The HTTP response to the uCDN trigger creation request
   MUST have status code 201 ("Created") and MUST convey the URI of the
   newly created trigger resources in the Location response header field
   [RFC9110].  The HTTP response SHOULD include the updated
   representation of the trigger resource.  This is particularly
   important in cases where the dCDN processed the trigger immediately.

   Once a trigger resource has been created, the dCDN MUST NOT reuse its
   URI, even after the trigger resource has been fully removed.  It is
   therefore recommended that the dCDN utilize unique UUID identifiers
   as specified in [RFC9562].

   The dCDN SHOULD provide continuous updates of the trigger processing
   progress by responding with updated trigger resource representations
   to the subsequent uCDN requests sent to the created trigger URI.  If
   the dCDN is unable to do that, it MUST indicate that it has accepted
   the request but will not be providing further status updates.  To do
   this, it MUST set the trigger state to "processed" at creation time.
   In this case, CI/T processing should continue as if it were a request
   in the "complete" state.  In this case, the dCDN SHOULD also provide
   an estimated completion time for the request by using the trigger
   "etime" property.





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   The uCDN MAY request the new trigger to be created in the "active"
   state so that its processing begins immediately.  If agreed to by the
   dCDN, the dCDN MUST start the new trigger processing immediately.

   Otherwise, the dCDN MUST set the state of the new trigger to
   "pending".  Once trigger processing has started, the status MUST be
   changed to "active".  Finally, once the trigger processing is
   complete, the trigger state MUST be set to "complete" or "failed".

   Once created, trigger resources can be cancelled, modified, or
   deleted by the uCDN, subject to the constraints described below.

3.2.  Modifying Triggers

   Modification of existing triggers is useful for the uCDN to correct
   an error in trigger specification or trigger extension(s) that may
   govern when the trigger is to be processed.

   The uCDN can request modification of an existing trigger resource by
   sending an updated trigger representation to the trigger URI using
   HTTP POST command.

   The dCDN MAY accept modifications of the trigger specifications,
   trigger extensions and trigger labels, when the trigger is in a
   "pending" state, i.e., the dCDN didn't start its processing yet.

   The dCDN MAY also accept a request to change the trigger state
   subject to the following constraints:

   *  the requested state is "cancelled", and the trigger was in either
      "pending" or "active" state when the dCDN receives the request

   *  the requested state is "active", and the trigger was in a
      "pending" state when dCDN received the request

   Section 3.3 describes the processing of the trigger cancellation
   requests in detail.  The uCDN MAY request to set the trigger state to
   "active" to prompt the dCDN to re-examine the trigger resource and
   start its processing immediately.












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   The dCDN MUST respond to the trigger modification request
   appropriately.  Thus, the HTTP status code 200 ("OK") should be
   returned if the modification has been processed, 202 ("Accepted") if
   the command has been accepted but the modification is not fully
   complete yet, 404 ("Not Found") when the trigger resource does not
   exist, 409 ("Conflict") when the trigger resource is in a state that
   doesn't allow the requested modification, 501 ("Not Implemented") if
   the modification is not supported by the dCDN or an appropriate 4xx
   HTTP error code in case of a malformed request.

   In case of successful 2xx response, the dCDN MUST provide the updated
   trigger resource representation in the response body.

3.3.  Cancelling Triggers

   The uCDN MAY request cancellation of a trigger by requesting its
   state to be set to "cancelled", as described in Section 3.2.  The
   dCDN MUST respond to such request, however, the actual cancellation
   of a trigger resource is optional to implement.

   The dCDN MUST respond to the trigger cancellation request with an
   appropriate HTTP response status code as documented in Section 3.2

   If cancellation of a "pending" trigger is accepted by the dCDN, the
   dCDN SHOULD NOT start the processing of that activity.  Requesting a
   cancellation of a "pending" trigger does not, however, guarantee that
   the corresponding activity will not be started because the uCDN
   cannot control the timing of that activity.  Processing could, for
   example, start after the POST is sent by the uCDN but before that
   request is processed by the dCDN.

   If cancellation of an "active" or "processed" trigger is accepted by
   the dCDN, the dCDN SHOULD stop processing the trigger.  However, as
   with the cancellation of a "pending" trigger, the dCDN does not
   guarantee that the trigger processing doesn't run to completion in
   the meantime.

   If the dCDN cannot stop the trigger processing immediately after
   receiving the request from the uCDN to do so, it MUST set the trigger
   state to "cancelling" and provide this state in the trigger
   representation in its response.  If the trigger processing is stopped
   before its normal completion, the trigger state MUST be set to
   "cancelled".

   Cancellation of a "complete", "failed" or "cancelled" trigger
   requires no processing in the dCDN.  Its state MUST NOT be changed.





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3.4.  Checking Status

   The uCDN has two ways to check the progress of its triggers'
   processing, as described in Section 3.4.1 and Section 3.4.2.

   To enable the uCDN to use client-side caching of the trigger index
   resource, as well as all trigger and trigger collection resources,
   each resource representation sent by the dCDN SHOULD include at least
   one of the following HTTP response headers: "ETag" or "Last-
   Modified".  The dCDN should respond with the HTTP 304 ("Not
   Modified") status code and no response body for conditional resource
   requests using the 'If-None-Match' and/or 'If-Modified-Since'
   headers, as specified in Section 13 of [RFC9110], if it does not have
   a more recent resource representation.

   The dCDN SHOULD also use the cache control headers for responses to
   GET requests for its resources to indicate the frequency at which it
   recommends that the uCDN and/or intermediate proxies should poll for
   change.  If provided, the uCDN should match the frequency of polling
   to the cache control information provided by the dCDN.

3.4.1.  Polling Trigger Collections

   The uCDN MAY fetch the Trigger Collection that contains all of its
   triggers, or one of the collections that filter triggers based on a
   parameter such as state or label.  This makes it possible for the
   uCDN to poll the status of all trigger resources or selected trigger
   subsets.

3.4.1.1.  Extended view representation

   If the dCDN advertises support for extended status, the uCDN MAY
   request the extended trigger collection representation, which embeds
   full representations of trigger resources in the collection resource.
   The extended representation is supported for all trigger collections,
   so it is possible to retrieve all trigger resource representations
   for a specific trigger state (e.g., all triggers in a "pending"
   state).

   The uCDN SHOULD request the extended representation by passing the
   query string parameter "status=extended" when requesting a trigger
   collection resource.  The dCDN SHOULD respond with HTTP Status 200
   ("OK") when such request can be satisfied, 501 ("Not Implemented") if
   the capability has not been implemented or advertised, and 400 ("Bad
   Request") for a malformed query.

   By default, the trigger resources are represented in the trigger
   collection with their resource URI only.



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3.4.2.  Polling Triggers

   The uCDN has a URI provided by the dCDN at the trigger creation time.
   Alternatively, the uCDN MAY discover a trigger resource URI by
   retrieving the trigger index resource, and then the appropriate
   trigger collection referenced in the index.  It may fetch an up-to-
   date representation of the trigger resource at any time using an HTTP
   GET request, including changes in the trigger state, as well as the
   outcome of the trigger processing.

3.5.  Deleting Triggers

   The uCDN MAY request the deletion of trigger resources at any time
   using the HTTP DELETE method, as defined in the CDNI Control
   Interface / Triggers 1st edition [RFC8007],

   Once deleted, the deleted trigger MUST be removed from all trigger
   collections.  Subsequent requests to the trigger resource URI MUST be
   rejected by the dCDN with HTTP error 404 ("Not Found").

   The effect of deletion is similar to cancellation, except that the
   trigger resource becomes unavailable after the deletion is complete.
   For this reason, the uCDN SHOULD cancel triggers rather than delete
   them when it needs to access the trigger status after processing has
   terminated.

   If a "pending" trigger is deleted, the dCDN SHOULD NOT start the
   processing of that activity.  Deleting a "pending" trigger does not,
   however, guarantee that its processing has not started, because the
   uCDN cannot control the timing of that activity.  Processing may, for
   example, start after the DELETE is sent by the uCDN but before that
   request is processed by the dCDN.

   When an "active" or "processed" trigger is deleted, the dCDN SHOULD
   stop processing it.  However, as with the deletion of a "pending"
   trigger, the dCDN does not guarantee this.

   Deletion of a "complete", "cancelled", "cancelling", or "failed"
   trigger MUST result in no further processing by the dCDN.

   The dCDN MUST respond to the trigger deletion request appropriately.
   The dCDN MUST respond with status code 200 (OK) without a response
   body if the trigger has been deleted immediately, 202 (Accepted) if
   the command has been accepted but the trigger has not yet been
   deleted, 404 (Not Found) if the trigger resource does not exist, or
   501 (Not Implemented) if deletion is not supported by the dCDN.





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   The trigger state MUST be set to "cancelling" while the dCDN is
   processing a deletion request asynchronously.

3.6.  Expiry of Triggers

   The dCDN MAY automatically delete trigger resources sometime after
   they reach a terminal state (one of "complete", "processed", "failed"
   or "cancelled").  In this case, after the dCDN has removed such a
   trigger, it MUST respond to subsequent requests for it with the HTTP
   error 404 ("Not Found") and remove it from all trigger collections.

   If the dCDN does remove triggers in a terminal state automatically,
   it MUST report the expiry timeout period, using an attribute
   "staleresourcetime" of the trigger index resource (see Section 4.2
   for details.

   It is RECOMMENDED that the dCDN sets the value of the
   "staleresourcetime" attribute to at least 24 hours.  It is further
   RECOMMENDED that the uCDN sets its trigger polling period to less
   than this period, so it doesn't miss trigger status updates before
   the "complete" or "failed" triggers are expired by the dCDN.

3.7.  Error Handling

   The dCDN MAY reject CI/T interface requests by responding with 4xx or
   5xx HTTP status codes.  For example, the uCDN MAY respond with 400
   ("Bad Request") if the request is malformed, or 403 ("Forbidden") or
   404 ("Not Found") if the request could not be properly authenticated
   or if the uCDN is trying to act on another CDN's resources.

   If any part of the trigger processing fails, the trigger SHOULD be
   reported as "failed" once its activity is complete or if no further
   errors will be reported.  The "errors" property in the trigger will
   be used to enumerate which actions failed and the reasons for
   failure, and can be present while the trigger is still "pending" or
   "active" if the trigger processing is still running for some URLs or
   patterns in the trigger specs.

   Once a request has been accepted, processing errors are reported in
   the trigger using a list of Error.v2 Descriptions.  Each Error.v2
   Description is used to report errors against one or more of the URLs
   or patterns in the trigger specification.

   If a Surrogate affected by a trigger is offline in the dCDN or the
   dCDN is unable to pass a trigger on to any of its cascaded dCDNs:

   *  If the trigger is abandoned by the dCDN, the dCDN SHOULD report an
      error.



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   *  A CI/T "invalidate" command may be reported as "complete" when
      Surrogates that may have the data are offline.  In this case,
      Surrogates MUST NOT use the affected data without first
      revalidating it when they are back online.

   *  CI/T "preposition" and "purge" commands can be reported as
      "processed" if affected caches are offline and the activity will
      complete when they return to service.

   *  Otherwise, the dCDN SHOULD keep the trigger "pending" or "active"
      state until either the trigger is acted upon or the uCDN chooses
      to cancel it.

3.7.1.  Error Propagation

   This subsection explains the mechanism for enabling the uCDN to trace
   an error back to the dCDN in which it occurred.  CDNI triggers may be
   propagated over a chain of downstream CDNs.  For example, an upstream
   CDN A (uCDN-A) that is delegating to a downstream CDN B (dCDN-B) and
   dCDN-B is delegating to a downstream CDN C (dCDN-C).  Triggers sent
   from uCDN-A to dCDN-B may be redistributed from dCDN-B to dCDN-C, and
   errors can occur anywhere along the path.  Therefore, it might be
   essential for uCDN-A which sets the trigger to be able to trace back
   an error to the downstream CDN where it occurred.  This document adds
   a mechanism to propagate the PID of the dCDN where the fault
   occurred, back to the uCDN by adding the PID to the error.v2
   description.  When dCDN-B propagates a trigger further to dCDN-C, it
   MUST also propagate back the errors received in the trigger status
   resource from dCDN-C by adding them to the errors array in its status
   resource to be sent back to the originating uCDN-A.  While
   propagating back the errors dCDN-B MAY also specify the dCDN-C PID,
   indicating to which CDN the error specifically relates.  The trigger-
   originating upstream uCDN-A then receives an array containing the
   errors that occurred across all the downstream CDNs along the
   execution path, where each error MAY include its own CDN identifier.

   Figure 2 below is an example showing the message flow used by uCDN-A
   to trigger activity in dCDN-B, followed by dCDN-C, as well as the
   discovery of the status of that activity, including the Error
   Propagation.

   uCDN-A                         dCDN-B                         dCDN-C
    |                              |                              |
    | (1) POST                     |                              |
    | https://dcdn-b.com           |                              |
    | /cit/uCDN-A                  |                              |
   [ ]--------------------------->[ ]--+                          |
    |                             [ ]  | (2)                      |



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    |                             [ ]<-+                          |
    | (3) HTTP 201 Response.      [ ]                             |
    |<----------------------------[ ]                             |
    | Loc:                        [ ]                             |
    | https://dcdn-b.com          [ ] (4) POST                    |
    | /cit/ucdn-a/123             [ ] https://dcdn-c.com          |
    |                             [ ] /cit/dcdn-b                 | (5)
    |                             [ ]--------------------------->[ ]--+
    |                              |                             [ ]  |
    |                              |                             [ ]<-+
    |                              | (6) HTTP 201 Response.      [ ]
    |                             [ ]<---------------------------[ ]
    |                              |  Loc:                        |
    |                              |  https://dcdn-c.com          |
    |                              |  /cit/dcdn-b/456             |
    |                              |                              |
    |                             [ ]--+                          |
    |                             [ ]  | (7.1)                    |
    |                             [ ]<-+                         [ ]--+
    |                              |                       (7.2) [ ]  |
    |                              |                             [ ]<-+
    |                              |                              |
    .                              .                              .
    .                              .                              .
    .                              .                              .
    |                              | (8) GET                      |
    |                              | https://dcdn-c.com           |
    |                              | /cit/dcdn-b/456              |
    |                             [ ]--------------------------->[ ]
    |                              |                             [ ]
    |                              | (9) HTTP 200                [ ]
    |                              | Trigger resource            [ ]
    |                             [ ]<---------------------------[ ]
    |                              |                              |
    .                              .                              .
    .                              .                              .
    .                              .                              .
    | (10) GET                     |                              |
    | https://dcdn-b.com           |                              |
    | /cit/ucdn-a/123              |                              |
   [ ]--------------------------->[ ]                             |
    |                             [ ]                             |
    | (11) HTTP 200               [ ]                             |
    | Trigger resource            [ ]                             |
   [ ]<---------------------------[ ]                             |

   Figure 2: CDNI Message Flow for Triggers, Including Error Propagation




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   The steps in Figure 2 are as follows:

   1.   uCDN-A creates a trigger in dCDN-B by POSTing a new trigger
        representation to "https://dcdn-b.com/cit/ucdn-a".

   2.   dCDN-B authenticates the request, validates the trigger creation
        request, and, if it accepts the request, creates a new trigger
        resource.

   3.   dCDN-B responds to uCDN-A with an HTTP 201 ("Created") response
        status and the location of the newly created trigger.

   4.   dCDN-B creates a trigger in dCDN-C by POSTing the newly received
        trigger representation to "https://dcdn-c.com/cit/dcdn-b".

   5.   dCDN-C authenticates the request, validates the trigger creation
        request, and, if it accepts the request, creates a new trigger
        resource.

   6.   dCDN-C responds to dCDN-B with an HTTP 201 ("Created") response
        status and the location of the newly created trigger resource.

   7.   dCDN-C acts upon the trigger.  However, the command fails at
        dCDN-C as, for example, the trigger definition contains an
        "action" type that is not supported by dCDN-C.  The dCDN-C's
        action is depicted by 7.2 in the diagram, while 7.1 shows dCDN-B
        acting on its own trigger.

   8.   dCDN-B queries, possibly repeatedly, the trigger resource in
        dCDN-C.

   9.   dCDN-C responds with the trigger resource representation,
        describing the progress or results of the trigger processing.
        In the described flow, the trigger state is "failed", with an
        Error.v2 Description object holding "eunsupported" Error Code
        reflecting the reason.

   10.  uCDN-A queries, possibly repeatedly, the trigger status in dCDN-
        B.












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   11.  dCDN-B responds with the updated trigger resource
        representation, describing the progress or results of trigger
        processing.  In the flow described above, the trigger state is
        "failed", and the "eunsupported" error received in the trigger
        status from dCDN-C is propagated-along with dCDN-C's PID-by
        adding it to the errors array in dCDN-B's status resource, which
        is then sent back to the originating uCDN-A.  The use of dCDN-
        C's PID is OPTIONAL; dCDN-B MAY instead use its own PID, thereby
        obfuscating the identity of dCDN-C from the upstream CDN.

4.  CI/T Object Properties and Encoding

   The Trigger (Section 4.1)>, Trigger Index (Section 4.2), and Trigger
   Collection (Section 4.3) resources and their respective properties
   are encoded in JSON format.  When sending the JSON-based
   representation of these resources, the MIME media type "application/
   cdni" MUST be used, with parameter "ptype" values as defined below
   and in Section 7.1.

   Names in JSON are case-sensitive.  The names and literal values
   specified in the present document MUST always use lowercase.

   JSON types, including "object", "array", "number", and "string", are
   defined in [RFC8259].

   Unrecognized name/value pairs in JSON objects SHOULD NOT be treated
   as an error by either the uCDN or the dCDN.  They SHOULD be ignored
   during processing and passed on by the dCDN to any further dCDNs in a
   cascade.

4.1.  Trigger Resource

   Trigger resource is encoded as a JSON object and MUST use a MIME
   media type of "application/cdni; ptype=ci-trigger.v2".  Please note
   that the dCDN MUST include all existing trigger attributes in the
   trigger resource representation when requested by the uCDN.  The
   trigger resource contains the following name/value pairs:

      Name: action
         Description: Defines the type of the CI/T trigger action.

         Value: Trigger action type, as defined in Section 4.1.1.

         Mandatory-to-Specify: It is optional for trigger updates,
         otherwise mandatory.

      Name: specs




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         Description: Array of trigger specs representing the trigger's
         targets, as described in Section 4.1.2.

         Value: Array of GenericTriggerSpec objects (see
         Section 4.1.2.1).

         Mandatory-to-Specify: It is optional for trigger updates,
         otherwise mandatory.  Furthermore, when mandatory, the list
         MUST NOT be empty.

      Name: extensions
         Description: Array of trigger extensions, as described in
         Section 4.1.3.

         Value: Array of GenericTriggerExtension objects (see
         Section 4.1.3.2).

         Mandatory-to-Specify: No.  The default is no extensions.

      Name: labels
         Description: Array of trigger labels, as described in
         Section 4.1.4.

         Value: Array of trigger labels.  Each label is a key-value
         pair, encoded as a JSON string, with "=" separator.  The label
         key and value parts MUST contain up to 63 characters each, MUST
         begin with a letter or a number, and MAY contain letters,
         numbers, hyphens, dots, and underscores.

         Mandatory-to-Specify: No.  The default is no labels.

      Name: cdn-path
         Description: The chain of CDN PIDs of CDNs that have already
         created this trigger resource.

         Value: Non-empty array of JSON strings, where each string is a
         CDN PID as defined in Section 4.4.3.

         Mandatory-to-Specify: No.  The default is no CDN path.

      Name: ctime
         Description: The time at which the trigger resource was
         received by the dCDN.  The time is determined by the dCDN;
         there is no requirement to synchronize clocks between
         interconnected CDNs.

         Value: Time, as defined in Section 4.3.4 of [RFC8006].




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         Mandatory-to-Specify: The dCDN MUST specify in trigger status
         representations.  It is ignored when included in trigger
         representations sent by the uCDN.

      Name: mtime
         Description: The time at which the trigger resource was last
         modified.  The time is determined by the dCDN; there is no
         requirement to synchronize clocks between interconnected CDNs.

         Value: Time, as defined in Section 4.3.4 of [RFC8006].

         Mandatory-to-Specify: The dCDN MUST specify in trigger status
         representations.  It is ignored when included in trigger
         representations sent by the uCDN.

      Name: etime
         Description: The estimate of the time at which the dCDN expects
         to complete the trigger processing.  Time is determined by the
         dCDN; there is no requirement to synchronize clocks between
         interconnected CDNs.

         Value: Time, as defined in Section 4.3.4 of [RFC8006].

         Mandatory-to-Specify: The dCDN MAY specify in trigger status
         representations.  It is ignored when included in trigger
         representations sent by the uCDN.

      Name: state
         Description: The current trigger state.

         Value: Trigger state, as defined in Section 4.1.5.

         Mandatory-to-Specify: The dCDN MUST include trigger state in
         the trigger resource representations it sends.  The trigger
         state defaults to "pending" when a trigger is created and is
         optional in trigger updates sent by the uCDN.

      Name: state-reason
         Description: A human-readable explanation for the object state.

         Value: A JSON string, the human-readable reason.

         Mandatory-to-Specify: No.  The dCDN MAY include the trigger
         reason in the trigger resource representations it sends.

      Name: errors
         Description: Descriptions of errors that have occurred while
         processing the trigger.



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         Value: An array of Error.v2 Descriptions, as defined in
         Section 4.1.6.1.  An empty array is allowed and is equivalent
         to omitting the "errors" attribute from the object.

         Mandatory-to-Specify: No.  The dCDN SHOULD include this
         attribute in the trigger resource representations it sends when
         the trigger is in a "failed" state.

      Name: total-objects-count
         Description: Total aggregate number of objects affected by the
         trigger, e.g., number of objects purged, invalidated or
         prepositioned as a result of trigger processing.  It is
         RECOMMENDED that the dCDN maintains this attribute as a
         cumulative counter across all of its nodes, without de-
         duplicating the same objects processed in multiple nodes.  The
         primary purpose of this attribute is to help the uCDN identify
         abnormal trigger processing results, e.g., a purge or
         preposition trigger that impacted a lower number of objects
         than expected.  The dCDN MAY provide an updated object count as
         the trigger processing progresses in an "active" trigger state.

         Value: Integer.

         Mandatory-to-Specify: No.  This attribute is "optional-to-
         implement".  When supported, the dCDN SHOULD include this
         attribute in the trigger resource representations requested by
         the uCDN.

      Name: total-nodes-count
         Description: The total number of unique dCDN nodes affected by
         the trigger.  The primary purpose of this attribute is to help
         the uCDN validate trigger processing results in combination
         with the cumulative counters "total-objects-count" and "total-
         objects-size".  The dCDN MAY provide an updated nodes count as
         the trigger processing progresses in an "active" trigger state.

         Value: Integer.

         Mandatory-to-Specify: No.  This attribute is "optional-to-
         implement".  When supported, the dCDN SHOULD include this
         attribute in the trigger resource representations requested by
         the uCDN.

      Name: total-objects-size
         Description: Total aggregate size of objects affected by the
         trigger, in bytes.  It is RECOMMENDED that the dCDN maintains
         this attribute as a cumulative counter across all of its nodes,
         without de-duplicating the same objects processed in multiple



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         nodes.  As with "total-objects-count" attribute above, the
         primary purpose of this attribute is to help the uCDN identify
         abnormal trigger processing results.  The dCDN MAY provide an
         updated object size as the trigger processing progresses in
         "active" trigger state.

         Value: Integer.

         Mandatory-to-Specify: No.  This attribute is "optional-to-
         implement".  When supported, the dCDN SHOULD include this
         attribute in the trigger resource representations requested by
         the uCDN.

      Name: objects
         Description: List of objects derived by the dCDN when
         processing the trigger.  When the "content-objectlist" trigger
         specification is used, the trigger MAY include one or more
         manifest files that form a hierarchical structure (e.g., media
         HLS playlists referenced by master HLS playlists, or JSON
         object lists referenced by other JSON object lists).  The
         purpose of this optional attribute is to provide a single,
         flattened list of content objects derived from the input
         trigger.

         Value: An array of ObjectList (Section 4.4.2) objects.  The
         dCDN SHOULD provide the list of objects it used as input for
         processing the trigger with Section 4.1.2.8, provided that the
         dCDN advertised support for extended status (Section 5.5).  An
         empty array is allowed and is equivalent to omitting "objects"
         from the trigger representation.  This field is intended to
         provide the list of all objects used in processing.  The
         objects that failed to process SHOULD be specified using the
         Error.v2 Description resource.

         Mandatory-to-Specify: No.  The dCDN MAY send this attribute in
         its trigger resource representation when available and the
         capability is advertised via FCI as described above.

4.1.1.  Trigger Action

   A trigger action is used in a trigger resource to describe trigger
   actions.  It was initially referred to in [RFC8007] as "Trigger
   Type".

   All trigger actions MUST be registered in the IANA "CDNI CI/T Trigger
   Types" registry (see Section 7.2).





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   The dCDN receiving a request containing a trigger action that it does
   not recognize or does not support MUST reject the request by creating
   a trigger with a "failed" state and the "errors" array containing an
   Error.v2 Description with error "eunsupported" (see Section 4.1.6.2).

   The following trigger actions are defined by this document:

      +=============+===============================================+
      | JSON string | Description                                   |
      +=============+===============================================+
      | preposition | A request for the dCDN to acquire metadata or |
      |             | content.                                      |
      +-------------+-----------------------------------------------+
      | invalidate  | A request for the dCDN to invalidate metadata |
      |             | or content.  After servicing this request,    |
      |             | the dCDN will not use the specified data      |
      |             | without first revalidating it using, for      |
      |             | example, an "If-None-Match" HTTP request.     |
      |             | The dCDN need not erase the associated data.  |
      +-------------+-----------------------------------------------+
      | purge       | A request for the dCDN to erase metadata or   |
      |             | content.  After servicing the request, the    |
      |             | specified data MUST NOT be held on the dCDN   |
      |             | (the dCDN should reacquire the metadata or    |
      |             | content from the uCDN if it needs it).        |
      +-------------+-----------------------------------------------+

                                  Table 2

   The dCDN MUST support at least one of the trigger actions.

4.1.2.  Trigger Specs

   The CDNI Control Interface / Triggers 1st edition [RFC8007] defines a
   set of properties and objects used by the trigger commands to specify
   the targets upon which the trigger is applied.  This document
   modifies the trigger interface objects so that it has a list of
   trigger specs.  Such structure improves the interface's extensibility
   and flexibility.  Furthermore, the document defines a generic trigger
   spec object that acts as a wrapper for managing individual CDNI
   trigger specs in an opaque manner, allowing future extension of the
   interface.

   All trigger specs MUST be registered in the IANA "CDNI CI/T Trigger
   Specs" registry (see Section 7.3).






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   A dCDN receiving a trigger creation request that contains a trigger
   spec it does not recognize or support MUST reject the request by
   creating a trigger resource with a "failed" state and the "errors"
   array containing an Error.v2 Description with the error "espec" (see
   Section 4.1.6.2).

   This document also defines an initial set of trigger spec objects and
   registers them in the IANA "CDNI CI/T Trigger Specs" registry:

      +====================+========================================+
      | JSON string        | Description                            |
      +====================+========================================+
      | urls               | Allowing the specification of trigger  |
      |                    | targets via URLs.                      |
      +--------------------+----------------------------------------+
      | ccids              | Allowing the specification of trigger  |
      |                    | targets via CCIDs content grouping, as |
      |                    | defined in section 4.2.8 [RFC8006].    |
      +--------------------+----------------------------------------+
      | uri-pattern-match  | Allowing the specification of trigger  |
      |                    | targets via [RFC3986] URI patterns.    |
      +--------------------+----------------------------------------+
      | uri-regex-match    | Allowing the specification of trigger  |
      |                    | targets via regexes matching their     |
      |                    | URI, as defined in Section 4.1.2.7.    |
      +--------------------+----------------------------------------+
      | content-objectlist | Allowing the specification of trigger  |
      |                    | targets via an object list and an      |
      |                    | object list type.                      |
      +--------------------+----------------------------------------+

                                  Table 3

   The dCDN MUST support the "urls" trigger spec.  Support for all other
   trigger specs is OPTIONAL.

   Each trigger usually refers to the targets by the target URLs, using
   a "urls" trigger spec object or some aggregating spec such as the
   "url-regex-match".  If content URLs are transformed by a transit CDN
   in a cascade, that transit CDN MUST similarly transform URLs in
   triggers it passes to its dCDNs.

   When processing a trigger, CDNs MUST ignore the URL scheme (HTTP or
   HTTPS) in comparing URLs.  For example, for a CI/T "invalidate" or
   "purge" action, content MUST be invalidated or purged regardless of
   the protocol clients used to request it.





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4.1.2.1.  Generic Spec Object

   A trigger resource, as defined in Section 4.1, includes an array of
   trigger spec objects.  Each trigger spec object contains properties
   that are used as trigger target selection directives for the dCDN
   when processing the trigger, e.g., content URLs or metadata URL
   patterns.  Each such trigger spec is a specialization of a CDNI
   GenericTriggerSpec object.  The GenericTriggerSpec object abstracts
   the basic information required for trigger distribution from the
   specifics of any given property (i.e., property semantics,
   enforcement options, etc.).

   The semantics of the trigger specs list is additive, i.e., the
   trigger applies to any object matching one of the listed specs.

   A GenericSpecObject object is a wrapper for managing individual CDNI
   trigger specs in an opaque manner.

   It is encoded as a JSON object containing the following name/value
   pairs:

      Name: trigger-subject
         Description: Case-insensitive CDNI trigger subject.

         Value: String containing the type of the subject matching the
         "cit-spec-value" property, such as "content" or "metadata" as
         defined in Section 4.1.2.2.

         Mandatory-to-Specify: Yes.

      Name: cit-spec-type
         Description: Case-insensitive CDNI trigger spec type.

         Value: String containing the spec type of the object contained
         in the cit-spec-value property (see table in Section 4.1.2).

         Mandatory-to-Specify: Yes.

      Name: cit-spec-value
         Description: A CDNI trigger spec object.

         Value: Defined by the value of the cit-spec-type property.

         Mandatory-to-Specify: Yes.

   The structure of a JSON-serialized GenericTriggerSpec object,
   containing a specific trigger spec is illustrated below:




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   {
     "cit-spec-type":
        <Type of this trigger spec>,
     "cit-spec-value":
         {
           <properties of this trigger spec object>
         },
      "trigger-subject":
        <Category of this trigger spec subject>

   }

4.1.2.2.  Trigger Subject

   Because the scope of the trigger may relate to either metadata as
   well as content, the "trigger spec object" also specifies the
   trigger's target subject (i.e., metadata or content) against which to
   match.

   All trigger subjects MUST be registered in the IANA "CDNI CI/T
   Trigger Subjects" registry (see Section 7.4).

   The dCDN receiving a trigger creation request containing a trigger
   subject that it does not recognize or does not support MUST reject
   the request by creating a trigger resource with a "failed" state and
   the "errors" array containing an Error.v2 Description with error
   "esubject" (see Section 4.1.6.2).

   This document also defines an initial set of trigger subject values
   and registers them in the IANA "CDNI CI/T Trigger Subjects" registry:

   +=============+====================================================+
   | JSON string | Description                                        |
   +=============+====================================================+
   | metadata    | Indicating the trigger target specification refers |
   |             | to Metadata object(s), as defined at [RFC8006].    |
   +-------------+----------------------------------------------------+
   | content     | Indicating the trigger target specification refers |
   |             | to client-facing content objects.                  |
   +-------------+----------------------------------------------------+

                                 Table 4

   The dCDN MUST support at least one of the trigger subjects.  The dCDN
   MAY advertise separate endpoints for each one of the two trigger
   subjects, using the CI/T Endpoint Capability Object (Section 5.1).





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4.1.2.3.  Spec Constraints

   There are certain constraints on the way the trigger specs can be
   combined with trigger subject and trigger actions:

    +====================+=================+==========================+
    | Trigger spec types | Trigger subject | Trigger action           |
    |                    | ("content" and  | ("preposition", "purge", |
    |                    | "metadata")     | and "invalidate")        |
    +====================+=================+==========================+
    | urls               | Any             | Any                      |
    +--------------------+-----------------+--------------------------+
    | ccids              | "content" only  | "purge" or "invalidate"  |
    +--------------------+-----------------+--------------------------+
    | uri-pattern-match  | Any             | "purge" or "invalidate"  |
    +--------------------+-----------------+--------------------------+
    | uri-regex-match    | Any             | "purge" or "invalidate"  |
    +--------------------+-----------------+--------------------------+
    | content-objectlist | Any             | Any                      |
    +--------------------+-----------------+--------------------------+

                Table 5: Summary of trigger spec constraints

4.1.2.4.  URLs Spec

   The "urls" spec type allows the uCDN to manage uCDN content or
   metadata objects held by the dCDN based on the objects' URLs.  Full
   URLs SHOULD be used to ensure unambiguous identification of the
   referenced objects.

   The URLs spec is encoded as a JSON object containing the following
   name/value pairs:

      Name: urls
         Description: An array of URLs over which the trigger MUST be
         executed.

         Value: A JSON array of URLs, each represented as a JSON string.

         Mandatory-to-Specify: Yes.

      Name: url-type
         Description: Type of URL used.

         Value: URL Type as defined in Section 4.4.1.

         Mandatory-to-Specify: No.  When omitted or empty, the
         "published" URL type is assumed.



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   Below is an example of a JSON-serialized URLs spec object, matching
   the metadata at metadata.example.com/a/b/c.

   {
     "trigger-subject": "metadata",
     "cit-spec-type": "urls",
     "cit-spec-value": {
       "urls": [ "https://metadata.example.com/a/b/c" ],
       "url-type": "published"
     }
   }

4.1.2.5.  CCIDs Spec

   The "ccids" spec type allows the uCDN to specify the Content
   Collection IDentifier (CCID) of content to which the trigger applies.
   The CCID is a grouping of content as defined by [RFC8006].  The
   "ccids" spec type is valid only for the "content" spec subject (see
   Section 4.1.2.2).

   CCIDs spec is encoded as a JSON object containing the following name/
   value pairs:

      Name: ccids
         Description: An array of Content Collection IDentifiers over
         which the trigger MUST be executed.

         Value: A JSON array of strings, where each string is a Content
         Collection IDentifier.

         Mandatory-to-Specify: Yes.

4.1.2.6.  URI Pattern Match Spec

   The "uri-pattern-match" spec type allows the uCDN to manage its
   content or metadata objects held by the dCDN based on the objects'
   URI pattern.  The value is a UriPatternMatch object, as defined in
   Section 4.1.2.6.1.

4.1.2.6.1.  UriPatternMatch

   A UriPatternMatch consists of a string pattern to match against a
   URI, and flags describing the type of match.

   It is encoded as a JSON object containing the following name/value
   pairs:

      Name: pattern



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         Description: A pattern for URI matching.

         Value: The pattern represented as a JSON string.  The pattern
         can contain the wildcards "*" and "?", where "*" matches any
         sequence of [RFC3986] pchar or "/" characters (including the
         empty string) and "?" matches exactly one [RFC3986] pchar
         character.  The three literals "$", "*", and "?"  MUST be
         escaped as "$$", "$*" and "$?" (where "$" is the designated
         escape character).  All other characters are treated as
         literals.

         Mandatory-to-Specify: Yes.

      Name: case-sensitive
         Description: Flag indicating whether or not case-sensitive
         matching should be used.

         Value: A JSON boolean.  When set to "true", matching is case-
         sensitive; when set to "false", matching is case-insensitive.

         Mandatory-to-Specify: No; default is "false", i.e., a case-
         insensitive match.

      Name: match-query-string
         Description: Flag indicating whether to include the query part
         of the URI when compared against the pattern.

         Value: One of the JSON values "true" (the full URI including
         the query part should be compared against the given pattern) or
         "false" (the query part of the URI should be dropped before
         comparison with the given pattern).

         Mandatory-to-Specify: No; default is "false".  The query part
         of the URI should be dropped before comparison with the given
         pattern.

      Name: url-type
         Description: Type of URLs to match.

         Value: URL Type as defined in Section 4.4.1.

         Mandatory-to-Specify: No.  When omitted or empty, "published"
         URL type is assumed.

   Example of case-sensitive prefix match against
   "https://www.example.com/trailers/":





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   {
     "pattern": "https://www.example.com/trailers/*",
     "case-sensitive": true
   }

4.1.2.7.  URI Regex Match Spec

   The "uri-regex-match" spec type allows the uCDN to manage content or
   metadata objects held by the dCDN based on the objects' URI regex.

4.1.2.7.1.  RegexMatch

   A RegexMatch consists of a regular expression string a URI is matched
   against, and flags describing the type of match.  It is encoded as a
   JSON object with the following properties:

      Name: regex
         Description: A regular expression for URI matching.

         Value: A regular expression to match against the URI, i.e.,
         against the path-absolute and the query string parameters
         [RFC3986].  The regular expression string MUST be compatible
         with POSIX [POSIX.1] Section 9 Extended Regular Expressions.
         This regular expression MUST be evaluated in the POSIX locale
         (POSIX [POSIX.1] Section 7.2).

         Note: Because '\' has a special meaning in JSON [RFC8259] as
         the escape character within JSON strings, the regular
         expression character '\' MUST be escaped as '\\'.

         Mandatory-to-Specify: Yes.

      Name: case-sensitive
         Description: Flag indicating whether or not case-sensitive
         matching should be used.

         Value: JSON boolean.  Either "true" (the matching is case-
         sensitive) or "false" (the matching is case insensitive).

         Mandatory-to-Specify: No; default is "false", i.e., a case-
         insensitive match.

      Name: match-query-string
         Description: Flag indicating whether to include the query part
         of the URI when compared against the regex.






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         Value: JSON Boolean.  Either "true" (the full URI, including
         the query part, should be compared against the regex) or
         "false" (the query part of the URI should be dropped before
         comparison with the given regex).

         Mandatory-to-Specify: No; default is "false".  The query part
         of the URI MUST be dropped before comparison with the given
         regex.  This makes the regular expression simpler and safer for
         cases in which the query parameters are not relevant to the
         match.

      Name: url-type
         Description: Type of URLs to match against.

         Value: URL Type as defined in Section 4.4.1.

         Mandatory-to-Specify: No.  When omitted or empty, "published"
         URL type is assumed.

   Example of a case-sensitive, no query parameters, regex match against
   is below.

   Please note that some lines in the example are wrapped for clarity.

   "^(https:\/\/video\.example\.com)\/([a-z])\/
    movie1\/([1-7])\/*(index.m3u8|\d{3}.ts)$"

   {
     "regex": "^(https:\\/\\/video\\.example\\.com)\\/([a-z])\\/
              movie1\\/([1-7])\\/*(index.m3u8|\\d{3}.ts)$",
     "case-sensitive": true
   }

   This regex matches URLs of the domain "video.example.com" where the
   path structure is /(single lower case letter)/(name-of-title)/(single
   digit between 1 to 7)/(index.m3u8 or a 3 digit number with ts
   extension).  For example:

    https://video.example.com/d/movie1/5/index.m3u8

   or

    https://video.example.com/k/movie1/4/013.ts








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4.1.2.8.  Object List Spec

   The "objectlist" spec type allows the uCDN to manage content or
   metadata held by the dCDN based on structured object lists.  The
   Object List spec type is valid only for the "content" spec subject
   (see Section 4.1.2.2).

   An object list is encoded as a JSON object with the following
   properties:

      Name: objects
         Description: An array of objects to be used in the trigger

         Value: Array of ObjectList (Section 4.4.2) objects

         Mandatory-to-Specify: Yes.

4.1.3.  Trigger Extensions

   A "trigger" object, as defined in Section 4.1 includes an optional
   array of trigger extension objects.  A trigger extension contains
   properties that are used as directives for the dCDN when executing
   the trigger command, e.g., location policies, time policies, and so
   on.  Each such CDNI trigger extension is a specialization of a CDNI
   GenericTriggerExtension object.  The GenericTriggerExtension object
   abstracts the basic information required for trigger distribution
   from the specifics of any given property (i.e., property semantics,
   enforcement options, etc.).  All trigger extensions are optional, and
   it is thus the responsibility of the extension specification to
   define a consistent default behavior for extensions supported by the
   dCDN when not specified by the uCDN.

4.1.3.1.  Enforcement Options

   The trigger enforcement options concept is in accordance with the
   metadata enforcement options as defined in Section 3.2 of [RFC8006].

   The GenericTriggerExtension object defines the properties contained
   within it as well as whether or not the properties are "mandatory-to-
   enforce".  If the dCDN does not understand or support a mandatory-to-
   enforce property, the dCDN MUST NOT execute the trigger command.  If
   the extension is not mandatory-to-enforce, then that
   GenericTriggerExtension object can be safely ignored and the trigger
   command can be processed in accordance with the rest of the CDNI
   trigger spec.






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   Although a CDN MUST NOT execute a trigger command if a mandatory-to-
   enforce extension cannot be enforced, it could still be safe for a
   transit CDN (tCDN) to redistribute that trigger (the "safe-to-
   redistribute" property) to another CDN without modification, provided
   the tCDN does not need to do trigger processing of its own and only
   pass the trigger to one or more dCDNs.  For example, in the cascaded
   CDN case, a transit CDN (tCDN) could convey mandatory-to-enforce
   trigger extension to the dCDN.  For a trigger extension that does not
   require customization or translation (i.e., trigger extension that is
   safe-to-redistribute), the data representation received off the wire
   MAY be stored and redistributed without being understood or supported
   by tCDN.  However, for a trigger extension that requires translation,
   transparent redistribution of the uCDN trigger values might not be
   appropriate.  Certain trigger extensions can be safely, though
   perhaps not optimally, redistributed unmodified.  For example, a
   preposition command might be executed in suboptimal times for some
   geographies if transparently redistributed, but it might still work.

   Redistribution safety MUST be specified for each
   GenericTriggerExtension listed.  If a CDN does not understand or
   support a given GenericTriggerExtension object that is not safe-to-
   redistribute, the CDN MUST set the "incomprehensible" flag to true
   for that GenericTriggerExtension object before redistributing it.
   The "incomprehensible" flag signals to the dCDN that trigger metadata
   was not properly transformed by the tCDN.  A CDN MUST NOT attempt to
   execute a trigger with an extension that has been marked as
   "incomprehensible" by the uCDN.

   tCDNs MUST NOT change the value of mandatory-to-enforce or safe-to-
   redistribute when propagating a trigger to the dCDN.  Although a tCDN
   can set the value of "incomprehensible" to true, a tCDN MUST NOT
   change the value of "incomprehensible" from true to false.

   Table 6 describes the action to be taken by a tCDN for the different
   combinations of mandatory-to-enforce ("MtE") and safe-to-redistribute
   ("StR") properties when the tCDN either does or does not understand
   the trigger extension object in question:














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     +=======+=======+============+=================================+
     | MtE   | StR   | Extension  | Trigger action                  |
     |       |       | object     |                                 |
     |       |       | understood |                                 |
     |       |       | by tCDN    |                                 |
     +=======+=======+============+=================================+
     | False | True  | True       | Can execute and redistribute.   |
     +-------+-------+------------+---------------------------------+
     | False | True  | False      | Can execute and redistribute.   |
     +-------+-------+------------+---------------------------------+
     | False | False | False      | Can execute.  MUST set          |
     |       |       |            | "incomprehensible" to true when |
     |       |       |            | redistributing.                 |
     +-------+-------+------------+---------------------------------+
     | False | False | True       | Can execute.  Can redistribute  |
     |       |       |            | after transforming the trigger  |
     |       |       |            | extension (if the CDN knows how |
     |       |       |            | to do so safely); otherwise,    |
     |       |       |            | MUST set "incomprehensible" to  |
     |       |       |            | true when redistributing.       |
     +-------+-------+------------+---------------------------------+
     | True  | True  | True       | Can execute and redistribute.   |
     +-------+-------+------------+---------------------------------+
     | True  | True  | False      | MUST NOT execute but can        |
     |       |       |            | redistribute, provided own      |
     |       |       |            | processing is not required.     |
     +-------+-------+------------+---------------------------------+
     | True  | False | True       | Can execute.  Can redistribute  |
     |       |       |            | after transforming the trigger  |
     |       |       |            | extension (if the CDN knows how |
     |       |       |            | to do so safely); otherwise,    |
     |       |       |            | MUST set "incomprehensible" to  |
     |       |       |            | true when redistributing.       |
     +-------+-------+------------+---------------------------------+
     | True  | False | False      | MUST NOT execute.  May          |
     |       |       |            | redistribute, provided own      |
     |       |       |            | processing is not required.     |
     |       |       |            | MUST set "incomprehensible" to  |
     |       |       |            | true when redistributing.       |
     +-------+-------+------------+---------------------------------+

         Table 6: Action to be taken by a tCDN for the different
                  combinations of MtE and StR properties

   Table 7 describes the action to be taken by the dCDN for the
   different combinations of mandatory-to-enforce and "incomprehensible"
   ("Incomp") properties, when the dCDN either does or does not
   understand the trigger extension object in question:



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     +=======+========+==================+==========================+
     | MtE   | Incomp | Extension object | Trigger action           |
     |       |        | understood by    |                          |
     |       |        | the dCDN         |                          |
     +=======+========+==================+==========================+
     | False | False  | True             | Can execute.             |
     +-------+--------+------------------+--------------------------+
     | False | True   | True             | Can execute but MUST NOT |
     |       |        |                  | interpret/apply any      |
     |       |        |                  | trigger extension marked |
     |       |        |                  | as "incomprehensible".   |
     +-------+--------+------------------+--------------------------+
     | False | False  | False            | Can execute.             |
     +-------+--------+------------------+--------------------------+
     | False | True   | False            | Can execute but MUST NOT |
     |       |        |                  | interpret/apply any      |
     |       |        |                  | trigger extension marked |
     |       |        |                  | as "incomprehensible".   |
     +-------+--------+------------------+--------------------------+
     | True  | False  | True             | Can execute.             |
     +-------+--------+------------------+--------------------------+
     | True  | True   | True             | MUST NOT execute.        |
     +-------+--------+------------------+--------------------------+
     | True  | False  | False            | MUST NOT execute.        |
     +-------+--------+------------------+--------------------------+
     | True  | True   | False            | MUST NOT execute.        |
     +-------+--------+------------------+--------------------------+

        Table 7: Action to be taken by the dCDN for the different
                combinations of MtE and Incomp properties

4.1.3.2.  GenericExtensionObject

   A GenericTriggerExtension object is a wrapper for managing individual
   CDNI Trigger extensions in an opaque manner.

   It is encoded as a JSON object containing the following name/value
   pairs:

      Name: cit-extension-type
         Description: Case-insensitive CDNI trigger extension object
         type.

         Value: String containing the CDNI Extension Type [RFC7736] of
         the object contained in the "cit-extension-value" property (see
         table in Section 2.8).

         Mandatory-to-Specify: Yes.



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      Name: cit-extension-value
         Description: CDNI trigger extension object.

         Value: Defined by the value of the "cit-extension-type"
         property above.

         Mandatory-to-Specify: Yes.

      Name: mandatory-to-enforce
         Description: Flag identifying whether or not the enforcement of
         this trigger extension is mandatory.

         Value: Boolean.

         Mandatory-to-Specify: No.  The default is to treat the trigger
         extension as mandatory to enforce (i.e., a value of True).

      Name: safe-to-redistribute
         Description: Flag identifying whether or not this trigger
         extension can be safely redistributed without modification,
         even if the CDN fails to understand the extension.

         Value: Boolean.

         Mandatory-to-Specify: No.  The default is to allow transparent
         redistribution (i.e., a value of True).

      Name: incomprehensible
         Description: Flag identifying whether or not any CDN in the
         chain of delegation has failed to understand and/or failed to
         properly transform this trigger extension object.  Note: This
         flag only applies to trigger extension objects whose "safe-to-
         redistribute" property has a value of False.

         Value: Boolean.

         Mandatory-to-Specify: No.  The default is comprehensible (i.e.,
         a value of False).

   The structure of a JSON-serialized GenericTriggerExtension object
   containing a specific trigger extension object is illustrated below:










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   {
     "cit-extension-type":
        <Type of this trigger extension object>,
     "cit-extension-value":
         {
           <properties of this trigger extension object>
         },
     "mandatory-to-enforce": <bool>,
     "safe-to-redistribute": <bool>,
     "incomprehensible": <bool>
   }

4.1.3.3.  Trigger Extension Objects

   The objects defined below are intended to be used in the
   GenericTriggerExtension object's cit-extension-value field as defined
   in Section 4.1.3.2, and their cit-extension-type property MUST be set
   to the appropriate Extension Type as defined in Section 2.8.

4.1.3.3.1.  LocationPolicy Extension

   A content operation may be relevant for a specific geographical
   region or need to be excluded from a specific region.  In this case,
   the trigger should be applied only to parts of the network that are
   either "included" or "not excluded" by the location policy.  Note
   that the restrictions here are on the cache location rather than the
   client location.

   The LocationPolicy object defines the cache or CDN locations in which
   the trigger is to be executed, thereby constraining the trigger's
   scope to those locations.  Although users are typically proximate to
   the corresponding cache nodes, the policy applies to the caches
   themselves, not to the users' locations.

   Example use cases:

   *  Preposition: Because modern streaming content often includes
      numerous renditions - across resolutions, bitrates, and languages
      - prepositioning all variants can be untenable.  The uCDN MAY
      perform location-aware prepositioning by selecting which content
      renditions to preposition based on the languages prevalent in a
      given region.  For example, only Danish, Norwegian and Swedish
      audio or subtitle renditions might be prepositioned in southern
      Scandinavia.







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   *  Purge: In certain cases, content may have been located on servers
      in regions where the content must not reside.  In such cases, a
      purge operation to remove content specifically from that region is
      required.

   Object specification:

      Name: locations
         Description: An Access List that allows or denies (blocks) the
         trigger execution per cache location.

         Value: Array of LocationRule objects (see Section 4.2.2.1 of
         [RFC8006]).  The LocationRule utilizes Footprint objects to
         define footprints in which the rule is to be applied, as
         defined in Section 4.2.2.2 of [RFC8006] and extended by
         [RFC9388] to support the "subdivisioncode" footprint type.

         Mandatory-to-Specify: Yes.

   If a location policy object is not listed within the trigger command,
   the default behavior is to execute the trigger in all available
   caches and locations of the dCDN.

   The trigger command is allowed or denied for a specific cache
   location according to the action of the first location whose
   footprint matches that cache's location.  The evaluation order is
   implicit and follows the sequence of LocationRule objects as they
   appear in the extension.  If two or more footprints overlap, the
   first footprint that matches against the cache's location determines
   the action a CDN MUST take.

   If the "locations" property is an empty list, or if none of the
   listed footprints match the location of a given cache, the trigger
   MUST be treated as not applicable to that cache - that is, the result
   is equivalent to a "deny" action.

   The following is an example of a JSON-serialized generic trigger
   extension object containing a location policy object that allows the
   trigger execution in the US but blocks its execution in
   Massachussetts.  The execution of the trigger outside of the US is
   blocked implicitly.










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   {
     "cit-extension-type": "location-policy",
     "cit-extension-value": {
       "locations": [
         {
           "action": "allow",
           "footprints": [{
             "footprint-type": "countrycode",
             "footprint-value": [ "us" ]
           }]
         },
         {
           "action": "deny",
           "footprints": [{
             "footprint-type": "subdivisioncode",
             "footprint-value": [ "us-ma" ]
           }]
         }
       ]
     }
   }

4.1.3.3.2.  TimePolicy Extension

   The uCDN may wish to perform content management operations on the
   dCDN on a specific schedule.  The TimePolicy extension allows the
   uCDN to instruct the dCDN to execute the trigger command in a desired
   time window.  For example, a video content provider may wish to pre-
   populate a new episode during off-peak hours so that it is ready on
   caches at prime time when the episode is released for viewing.  A
   scheduled operation enables the uCDN to direct the dCDN in what time
   frame to execute the trigger.

   This specification supports region-by-region time scheduling when
   used in conjunction with the Location Policy defined in
   Section 4.1.3.3.1.  The uCDN can trigger separate commands for
   different geographical regions using a different schedule for each
   region.  This allows the uCDN to control the execution time per
   region.

   Object specification:

      Name: unix-time-window
         Description: A UNIX epoch time window in which the trigger
         SHOULD be executed.

         Value: TimeWindow object using UNIX epoch timestamps (see
         Section 4.2.3.2 of [RFC8006]).



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         Mandatory-to-Specify: No, but exactly one of either
         "unixEpochWindow" or "utcWindow" MUST be present.

      Name: utc-window
         Description: A UTC time window in which the trigger SHOULD be
         executed.

         Value: UTCWindow object as defined in Section 4.1.3.3.2.1.

         Mandatory-to-Specify: No, but exactly one of either
         "unixEpochWindow" or "utcWindow" MUST be present.

   If a time policy object is not listed within the trigger command, the
   default behavior is to execute the trigger in a time frame most
   suitable to the dCDN taking under consideration other constraints and
   / or obligations.

   Example of a JSON-serialized generic trigger extension object
   containing a time policy object that schedules the trigger execution
   to a window between 09:00 01/01/2000 UTC and 17:00 01/01/2000 UTC,
   using the "unix-time-window" property:

   {
      "cit-extension-type": "time-policy",
      "cit-extension-value":
       {
         "unix-time-window": {
            "start": 946717200,
            "end": 946746000
         }
       },
      "mandatory-to-enforce": true,
      "safe-to-redistribute": true,
      "incomprehensible": false
   }

4.1.3.3.2.1.  UTCWindow

   A UTCWindow object describes a time range in UTC or UTC and a zone
   offset that can be applied by a TimePolicy.

   It is encoded as a JSON object containing the following name/value
   pairs:

      Name: start
         Description: The start time of the window.

         Value: Internet date and time as defined in [RFC3339].



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         Mandatory-to-Specify: No. but at least one of "start" or "end"
         MUST be present and non-empty.  If "start" is empty or not
         specified, the time range is considered to begin at an
         arbitrary (unspecified) time.

      Name: end
         Description: The end time of the window.

         Value: Internet date and time as defined in [RFC3339].

         Mandatory-to-Specify: No. but at least one of "start" or "end"
         MUST be present and non-empty.  If "end" is empty or not
         specified, the time range is considered to end at an arbitrary
         (unspecified) time.

   Example JSON-serialized UTCWindow object that describes a time window
   from 02:30 01/01/2000 UTC to 04:30 01/01/2000 UTC:

   {
     "start": "2000-01-01T02:30:00.00Z",
     "end": "2000-01-01T04:30:00.00Z"
   }

   Example JSON-serialized UTCWindow object that describes a time window
   in New York time zone offset UTC-05:00 from 02:30 01/01/2000 to 04:30
   01/01/2000:

   {
     "start": "2000-01-01T02:30:00.00-05:00",
     "end": "2000-01-01T04:30:00.00-05:00"
   }

4.1.3.3.3.  ExecutionPolicy Extension

   Unless specified otherwise, the dCDN is at liberty to decide how to
   choose trigger commands for execution from all pending commands,
   whether to process trigger commands sequentially or in parallel,
   immediately upon acceptance, or with a delay in batches.  The uCDN
   may wish to control trigger processing in more detail, including the
   order of execution, dependencies, and concurrency.

   Please note that the uCDN MAY request immediate processing of a
   trigger either by setting its state to "active" at creation time or
   by modifying a pending trigger to set its state to "active".

   Example use cases:





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   *  Priority: The uCDN may have multiple trigger commands in "pending"
      and/or "active" mode.  For example, trigger commands with policy
      constraints, a large number of content objects affected, or other
      dCDN business logic may take a long time to execute.  The uCDN may
      wish to prescribe the order in which the dCDN picks up its trigger
      commands for execution from the "pending" queue, by indicating a
      relative priority of each trigger.  The priority would affect the
      selection of trigger commands specific to the requesting uCDN.
      The dCDN may separately prioritize triggers from multiple uCDNs
      subject to its business logic.  Additionally, the uCDN may wish to
      prescribe the order in which parts of "active" triggers are
      processed.  The priority may affect the order within the same
      trigger and/or multiple triggers that are in "active" state at the
      same time.  Multiple priority-related use cases exist:

      -  The uCDN needs to introduce an urgent "purge" or "invalidate"
         trigger into an existing queue of trigger commands to correct
         wrong versions of content objects published by it

      -  The uCDN needs to indicate which content objects should be
         prepositioned, purged, or invalidated first, for example
         prepositioning newer released content before prepositioning
         updates to an existing catalog

   *  Prerequisite: In some cases, the uCDN may wish to indicate what
      trigger commands should be processed and completed before another
      trigger command is processed.  For example, the uCDN may want to
      rectify incorrectly published content by purging content objects
      and then prepositioning them again.  In this case, the uCDN may
      want the preposition trigger command to be processed only after
      the purge trigger command has been processed because the
      concurrent processing of these triggers may cause the new version
      of these content objects to be purged.  Alternatively, the uCDN
      may wish to condition the execution of purge or invalidation
      triggers upon the completion or cancellation of long-running
      preposition triggers to avoid race conditions that would result
      from processing these in parallel.  The prerequisite requirement
      implies that a previous trigger reaches one of the following
      states:

      -  "complete" or "processed" for successful completion

      -  "failed" for failed processing

      -  "cancelled" for completion of cancellation

   The ExtensionPolicy extension is encoded as a JSON object containing
   the following name/value pairs:



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      Name: priority
         Description: Relative weight of the trigger.  When picking a
         trigger for execution from all pending triggers posted by each
         uCDN, the dCDN MUST choose the trigger with the highest
         priority first.

         Value: Integer from -100 to 100.

         Mandatory-to-Specify: No.  The value defaults to zero if
         omitted.

      Name: depends
         Description: Links to trigger resources that the current
         trigger depends on.  Indicates which triggers should fully
         finish processing before starting execution of the current
         trigger.  The triggers SHOULD be in one of the following states
         to be considered finished: "complete", "processed", "failed" or
         "cancelled".

         Value: A JSON array of zero or more URLs, represented as JSON
         strings.

         Mandatory-to-Specify: No.  In case of a missing or an empty
         list, no dependencies are assumed.

   If the dCDN receives a new trigger with the ExecutionPolicy extension
   that does not reference an existing trigger URL in the "depends"
   extension attribute, the dCDN MUST set the trigger state to "failed",
   set the error to "eextension", and MAY include an optional error
   description.  A trigger modification request that would result in the
   "depends" attribute containing invalid trigger URLs MUST be rejected
   by the dCDN with status code 409 (Conflict).  URL values that
   reference existing finished triggers are allowed but ignored.

   The following is an example of a JSON-serialized generic extension
   trigger object containing an execution policy object that specifies
   trigger priority of 100, and makes its execution dependent on the
   completion of the previously created triggers:













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   {
     "cit-extension-type": "execution-policy",
     "cit-extension-value":
     {
       "priority": 100,
       "depends": [
        "https://dcdn.example/cit/b1467469-3cf3-4613-8629-814cd938f30b",
        "https://dcdn.example/cit/c73a9911-298b-4ee3-bbab-03bce07b7d5c"
       ]
     }
   }

4.1.3.3.4.  Combining Trigger Extensions

   The uCDN MAY combine multiple options in the same trigger command.
   The dCDN determines how to handle an incoming trigger according to
   the following rules:

   1.   When the dCDN receives a request to create a trigger, it MUST
        reject the request if the trigger depends on other pending
        triggers with lower priority in order to prevent deadlocks.

   2.   Otherwise, if the request for new trigger resource creation sets
        its state to "active":

        *  If the trigger has a TimePolicy extension that has a "start"
           attribute set in the future, the dCDN MUST reject the
           request.

        *  Otherwise, if the trigger has an ExecutionPolicy extension,
           with prerequisite triggers that are not finished at the time
           of the request, the dCDN MUST reject the request.

        *  Otherwise, if the trigger has a lower priority than pre-
           existing triggers in "pending" state, the dCDN MUST reject
           the request.  Please note that the trigger has an implicit
           priority of zero if no priority is explicitly specified.

        *  Otherwise, if the trigger has a TimeWindow that ends before
           the start of the TimeWindow of any trigger it depends on, or
           before the start of the TimeWindow of any pending trigger
           with higher priority, the dCDN MUST reject the request.

        *  Otherwise, the dCDN MAY still reject the trigger due to its
           business logic (e.g,, if the dCDN processes triggers at
           specific times during the day).





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        *  Otherwise, the dCDN SHOULD create the trigger in "active"
           state and begin its processing.

        *  In all of the above cases, the dCDN rejects the request by
           creating a trigger in a "failed" state, setting the error to
           "ereject" and optionally providing an error description.

   3.   Otherwise, the dCDN SHOULD create the new trigger resource as
        requested and set its state to "pending".

   4.   The dCDN MAY start the trigger processing at any time after the
        trigger creation, as long as the prerequisites are met, i.e. the
        start of processing is within the TimePolicy window, there are
        no other pending triggers with higher priority, and there are no
        incomplete prerequisite triggers.

   5.   The dCDN SHOULD periodically re-evaluate the pending trigger
        queue for triggers that have a TimePolicy set, to ensure that
        processing of such triggers completes before the corresponding
        TimePolicy window expires.  If during such evaluation a pending
        trigger is deemed to have expired, the dCDN MUST set the trigger
        state to "failed" and the error to "ereject", optionally
        providing the error description.

   6.   Whenever a trigger reaches a terminal state (i.e., "complete",
        "processed", "failed", or "cancelled"), the dCDN SHOULD re-
        evaluate the queue of pending triggers.  If during such
        evaluation a pending trigger is deemed to have expired, the dCDN
        MUST set the trigger state to "failed" and the error to
        "ereject", optionally providing the error description.
        Otherwise, the dCDN MAY start processing triggers that were
        previously dependent on the completed trigger.

   7.   Whenever a pending trigger becomes eligible for processing, the
        dCDN SHOULD re-evaluate the pending trigger queue.  If during
        such evaluation a pending trigger is deemed to have expired, the
        dCDN MUST set the trigger state to "failed" and the error to
        "ereject", optionally providing the error description.
        Otherwise, the dCDN MAY start processing additional triggers
        that could not be processed earlier due to their lower priority
        relative to the active trigger.










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   8.   When the dCDN receives a request to modify the priority and/or
        dependencies and/or TimeWindow of a pending trigger, it MUST
        reject the request with status 409 (Conflict) if the change
        would result in that trigger depending on other triggers with
        lower priority, or its TimeWindow ending before the start of the
        TimeWindow of any trigger it depends on, or before the start of
        the TimeWindow of any trigger with higher priority.

   9.   Otherwise, the dCDN MUST reject the request with status code 409
        (Conflict) if the change would result in the trigger depending
        on other triggers that, directly or indirectly, depend on the
        modified trigger.

   10.  When the dCDN receives a request to modify the TimeWindow
        extension, it MUST reject the request with status code 409
        (Conflict) if the modification would set the "end" time to a
        value in the past.

   11.  Otherwise, the dCDN SHOULD accept the request and evaluate
        whether the modified trigger becomes eligible for processing as
        a result of the change.  If at this time, the modified trigger
        has a TimePolicy "end" time set in the past, the dCDN MUST set
        the trigger state to "failed" and the error to "ereject",
        optionally providing the error description.

   12.  When the dCDN receives a request to change the state of a
        pending trigger to "active", it MUST reject the request with
        status code 409 (Conflict) if, as a result of the change, the
        trigger would depend on incomplete triggers, have lower priority
        than other pending triggers, have a TimeWindow start time in the
        future, or set a new TimeWindow end time in the past.

   13.  Otherwise, the dCDN MAY still reject the request with status
        code 409 (Conflict) if the processing of the trigger could not
        be started immediately due to the dCDN business logic.

   14.  Otherwise, the dCDN MUST set the trigger state to "active" and
        start its processing.

4.1.4.  Trigger Labels

   Trigger labels provide a framework for the uCDN to associate an array
   of key-value pairs with trigger resources.








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   The labels may be used to simplify the management of a large number
   of triggers by grouping related triggers and tracking their status
   using the trigger collection resource associated with the label value
   (see Section 4.3 for more details).  In this case, the label values
   remain fully opaque to the dCDN and serve for trigger grouping
   purposes only.

   Alternatively, trigger labels may be used by the uCDN to pass to the
   dCDN information to be used for the trigger processing.  For example,
   in the case of the uCDN and the dCDN utilizing non-standard
   configuration metadata objects, the uCDN may use trigger labels to
   help the dCDN identify the appropriate configuration section where
   the trigger should be applied.  The uCDN may also use the labels to
   pass to the dCDN freeform content metadata to inform the dCDN cache
   management operations.

4.1.5.  Trigger State

   The trigger state describes the current state of the triggered
   activity.  It MUST be one of the JSON strings in the following table:

       +============+==============================================+
       | JSON       | Description                                  |
       | string     |                                              |
       +============+==============================================+
       | pending    | The trigger has not yet been acted upon.     |
       +------------+----------------------------------------------+
       | active     | The trigger is currently being acted upon.   |
       +------------+----------------------------------------------+
       | complete   | The trigger processing completed             |
       |            | successfully.                                |
       +------------+----------------------------------------------+
       | processed  | The trigger has been created, and no further |
       |            | status update will be made (can be used in   |
       |            | cases where completion cannot be confirmed). |
       +------------+----------------------------------------------+
       | failed     | The trigger processing could not be          |
       |            | completed.                                   |
       +------------+----------------------------------------------+
       | cancelling | The trigger processing is still in progress, |
       |            | but the trigger has been cancelled by the    |
       |            | uCDN.                                        |
       +------------+----------------------------------------------+
       | cancelled  | The trigger was cancelled by the uCDN.       |
       +------------+----------------------------------------------+

                                  Table 8




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   Along with the trigger state, the trigger resource has a state reason
   property, allowing the dCDN to provide additional information for the
   trigger state.  For example, the dCDN may indicate that the trigger
   state is "pending" due to one of the execution prerequisites not
   being fulfilled.  Such a prerequisite may be specified via one of the
   extensions.

4.1.6.  Trigger Errors

4.1.6.1.  Error.v2 Description

   An Error.v2 Description is used to report the failure of a trigger.
   It is encoded as a JSON object with the following name/value pairs:

      Name: error
         Value: Error Code, as defined in Section 4.1.6.2.

         Mandatory-to-Specify: Yes.

      Name: description
         Description: A human-readable description of the error.

         Value: A JSON string, the human-readable description.

         Mandatory-to-Specify: No.

      Name: specs
         Description: Array of trigger spec objects from the
         corresponding "specs" array in the trigger resource.  Only
         those specs to which the error applies are listed.

         Value: Array of trigger specs, as defined in Section 4.1.2,
         where each spec object MUST be exactly as it appears in the
         trigger resource.

         Mandatory-to-Specify: Yes.

      Name: extensions
         Description: Array of trigger extension objects copied from the
         corresponding "extensions" array in the trigger resource.  Only
         those extensions to which the error applies are included, but
         those extensions MUST be exactly as they appear in the trigger
         resource.

         Value: Array of GenericTriggerExtension objects, where each
         extension object is copied from the "extensions" array values
         in the trigger resource.




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         Mandatory-to-Specify: No.  The "extensions" array SHOULD be
         used only if the error relates to extension objects.  Property
         omission should be interpreted as "the error is not related to
         any extension".

      Name: cdn-id
         Description: The CDN PID of the CDN where the error occurred.
         The "cdn-id" property is used by the originating uCDN or by the
         propagating dCDN to distinguish in which CDN the error
         occurred.

         Value: A non-empty JSON string, where the string is a CDN PID
         as defined in Section 4.4.3

         Mandatory-to-Specify: Yes. The dCDN may use its own CDN PID if
         it does not want to expose the PIDs of its dCDNs.

      Name: objects
         Description: List of objects that failed to be processed during
         trigger execution.

         Value: An array of ObjectList (Section 4.4.2) objects.  The
         dCDN SHOULD provide the list of objects that it failed to
         process during trigger execution with Section 4.1.2.8, provided
         that the dCDN advertised support for extended status
         (Section 5.5).

         Mandatory-to-Specify: No.  An empty array is allowed and is
         equivalent to omitting "objects" from the Error.v2 Description.

   Example of a JSON-serialized Error.v2 Description object reporting a
   malformed HLS manifest:



















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   {
     "error": "econtent",
     "description": "Failed to parse HLS object list",
     "specs": [{
       "trigger-subject": "content",
       "cit-spec-type": "content-objectlist",
       "cit-spec-value": {
         "objects": [{
           "href": "https://www.example.com/hls/title/index.m3u8",
           "type": "hls"
         }]
      }}
     ],
     "objects": [{
       "href": "https://www.example.com/hls/title/index.m3u8",
       "type": "hls"
     }],
     "cdn": "AS64500:0"
   }

   Example of a JSON-serialized Error.v2 Description object reporting an
   unsupported extension object:





























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   {
     "errors": [{
       "error": "eextension",
       "description": "unrecognized extension location-policy",
       "specs": [{
         "trigger-subject": "content",
         "cit-spec-type": "urls",
         "cit-spec-value": {
           "urls": [
             "https://www.example.com/a/b/c/1",
             "https://www.example.com/a/b/c/2"
           ]
         }
       }],
       "extensions": [{
         "cit-extension-type": "location-policy",
         "cit-extension-value": {
           "locations": [{
             "action": "deny",
             "footprints": [{
                 "footprint-type": "countrycode",
                 "footprint-value": [ "ca" ]
               }]
             }]
           }
       }],
       "cdn": "AS64500:0"
     }]
   }

4.1.6.2.  Error Code

   This type is used by the dCDN to report failures in trigger
   processing.  All Error Codes MUST be registered in the IANA "CDNI CI/
   T Error Codes" registry (see Section 7.7).  Unknown Error Codes MUST
   be treated as fatal errors, and the request MUST NOT be automatically
   retried without modification.

   The following Error Codes are defined by this document and MUST be
   supported by an implementation of the CI/T v2 interface.











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    +==============+=================================================+
    | Error Code   | Description                                     |
    +==============+=================================================+
    | emeta        | The dCDN was unable to acquire and/or does not  |
    |              | have metadata required to fulfill the request.  |
    +--------------+-------------------------------------------------+
    | econtent     | The dCDN was unable to acquire content (CI/T    |
    |              | "preposition" commands only).                   |
    +--------------+-------------------------------------------------+
    | eperm        | The uCDN does not have permission to create the |
    |              | trigger as requested(for example, the data is   |
    |              | owned by another CDN).                          |
    +--------------+-------------------------------------------------+
    | ereject      | The dCDN is not willing to process the trigger  |
    |              | (for example, a "preposition" request for       |
    |              | content at a time when the dCDN would not       |
    |              | accept Request Routing requests from the uCDN). |
    +--------------+-------------------------------------------------+
    | ecdn         | An internal error in the dCDN or one of its     |
    |              | dCDNs.                                          |
    +--------------+-------------------------------------------------+
    | ecancelled   | The uCDN cancelled the request.                 |
    +--------------+-------------------------------------------------+
    | eunsupported | The trigger resource used an "action type" that |
    |              | is not supported by the dCDN.  No action was    |
    |              | taken by the dCDN other than to create a        |
    |              | trigger in a "failed" state.                    |
    +--------------+-------------------------------------------------+
    | espec        | An error occurred while parsing a generic       |
    |              | trigger spec, or that the specific trigger spec |
    |              | is not supported by the CDN.                    |
    +--------------+-------------------------------------------------+
    | esubject     | An error occurred while parsing a trigger       |
    |              | subject, or that the specific trigger subject   |
    |              | is not supported by the CDN.                    |
    +--------------+-------------------------------------------------+
    | eextension   | An error occurred while parsing a generic       |
    |              | trigger extension, or that the specific         |
    |              | extension is not supported by the CDN.          |
    +--------------+-------------------------------------------------+

                                 Table 9

4.2.  Trigger Index Resource

   As described in Section 2.1, the dCDN maintains RESTful trigger
   resources that represent actions ("triggers") requested by the uCDN
   for execution by the dCDN.



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   The trigger index resource maintains references to all trigger
   collection resources that can be used to retrieve triggers.  The dCDN
   MUST create the trigger index resource when it first instantiates the
   CI/T interface for a uCDN, before any trigger resources are created.
   The dCDN MUST also create the unfiltered trigger collection
   containing all triggers, as well as trigger collections for each
   trigger state, and include references to these collections in the
   top-level trigger index resource.  The dCDN MUST NOT remove the
   trigger index resource, the unfiltered trigger collection, or the
   state-based trigger collections once they have been created, as long
   as it continues to offer CI/T services to the uCDN.

   The dCDN MUST update both the unfiltered trigger collection and the
   state-based trigger collections when triggers are created, deleted,
   or their state changes.

   If triggers include labels, the dCDN MUST create and maintain a
   trigger collection resource for each label value used in any trigger
   resources, and update the trigger index to keep references to label-
   based trigger collections current.  The dCDN MUST remove a label-
   based trigger collection when no triggers remain that use the
   corresponding label value.

   As a top-level resource, the trigger index also includes global dCDN
   attributes, such as the "staleresourcetime" attribute, which
   regulates the expiration of completed triggers, and the "cdn-id"
   attribute, which indicates the CDN PID of the dCDN.

   The trigger index resource representation MUST use a MIME media type
   of "application/cdni; ptype=ci-trigger-index.v2".

   A trigger index is encoded as a JSON object containing the following
   name/value pairs:

      Name: collections
         Description: Array of Trigger Collection View (Section 4.3.1)
         objects.

         Value: An array of JSON-encoded Trigger Collection View
         objects, one for each existing trigger collection resource.
         This includes the unfiltered trigger collection, per-state
         trigger collections (one for each trigger state as specified in
         Section 4.1.5), and any per-label trigger collections, if they
         exist.

         Mandatory-to-Specify: Yes.

      Name: staleresourcetime



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         Description: The length of time for which the dCDN guarantees
         to keep a completed trigger resource.  After this time, the
         dCDN SHOULD delete the trigger resource and all references to
         it from the collection.

         Value: A JSON number, which must be a positive integer,
         representing time in seconds.

         Mandatory-to-Specify: Yes.

      Name: cdn-id
         Description: The dCDN PID.

         Value: A JSON string, dCDN's PID, as defined in Section 4.4.3.

         Mandatory-to-Specify: No.

4.3.  Trigger Collection Resource

   The collection of trigger resources represents triggers created by
   the dCDN, optionally filtered by a parameter.

   Trigger resources in a collection are usually represented using their
   unique URIs.  Note that the collection may refer to CI/T Resources
   from several versions of CI/T objects, i.e., a subsequent call for
   the retrieval of the relevant trigger resource may provide objects of
   various MIME media types: ci-trigger-status as defined in [RFC8007],
   ci-trigger.v2 defined in this document, or objects of future CI/T
   objects versions, based on the version of the JSON object used to
   create the trigger.

   To allow the uCDN to check the status of multiple triggers in a
   single request, the dCDN MAY maintain optional representations of the
   trigger collection, which contain a subset of all triggers, filtered
   using a parameter.  These filtered collection representations are
   "optional-to-implement", but if they are implemented, the dCDN MUST
   include links to them in the trigger collection resource.

   All trigger collection representations MUST use a MIME media type of
   "application/cdni; ptype=ci-trigger-collection.v2".

   A trigger collection is encoded as a JSON object containing the
   following name/value pairs:

      Name: trigger-urls
         Description: Links to trigger resources in the collection.





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         Value: A JSON array of zero or more URLs, represented as JSON
         strings.

         Mandatory-to-Specify: Yes.

      Name: trigger-objects
         Description: Array of all triggers in the collection.  Should
         be returned only when an extended trigger collection view is
         requested as described in Section 3.4.1.1.

         Value: An array of JSON-encoded trigger resources.

         Mandatory-to-Specify: No.  The "trigger-objects" attribute
         SHOULD only be used by the dCDN that supports and advertises
         the appropriate extended status for trigger collections (see
         Section 5.5 for details).

      Name: filter-type
         Description: Indicates the type of filter applied to select the
         triggers in the collection.

         Value: One of "state" or "label".

         Mandatory-to-Specify: No.  The "filter-type" attribute MUST be
         used only in per-state and per-label trigger collections.  If
         omitted or empty, the trigger collection MUST include all
         existing triggers.

      Name: filter-value
         Description: Specifies the filter value used to select the
         triggers in the collection.

         Value: For per-label trigger collections, this attribute MUST
         contain the corresponding label value.  For per-state trigger
         collections, it MUST contain the trigger state shared by all
         triggers in the collection.

         Mandatory-to-Specify: No.  The "filter-value" attribute MUST be
         used only in per-state and per-label trigger collections.  If
         omitted or empty, the trigger collection MUST include all
         existing triggers.

4.3.1.  Trigger Collection View

   The Trigger Collection View is used to provide a brief description of
   the trigger collection resource within the trigger index.  It is
   encoded as a JSON object containing the following name/value pairs:




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      Name: filter-type
         Description: Indicates the type of filter applied to select the
         triggers in the described trigger collection.

         Value: One of "state" or "label".

         Mandatory-to-Specify: No.  The "filter-type" attribute MUST be
         used to describe only per-state and per-label trigger
         collections.  If omitted or empty, the trigger collection view
         MUST point to the trigger collection of all triggers.

      Name: filter-value
         Description: Specifies the filter value used to select the
         triggers in the collection.

         Value: For per-label trigger collections, this attribute MUST
         contain the corresponding label value.  For per-state trigger
         collections, it MUST contain the trigger state shared by all
         triggers in the collection.

         Mandatory-to-Specify: No.  The "filter-value" attribute MUST be
         used to describe only per-state and per-label trigger
         collections.  If omitted or empty, the trigger collection view
         MUST point to the trigger collection of all triggers.

      Name: collection-uri
         Description: URI of the trigger collection.

         Value: A URI represented as a JSON string.

         Mandatory-to-Specify: Yes.

4.4.  Other CI/T Objects and Properties

   This section describes common CI/T objects, which are used as part of
   the specification of several other CI/T objects, and their encodings.

4.4.1.  URL Type

   This type is used by the uCDN to indicate how to interpret URLs
   referenced by trigger specs that use URLs, such as Section 4.1.2.4,
   Section 4.1.2.6, Section 4.1.2.7, and Section 4.1.2.8.

   One option is for the uCDN to use "published" URLs.  Published URLs
   are the URLs used by end users.  When processing a trigger that uses
   this URL type, the dCDN MUST be able to match the URLs with metadata
   objects provided by the uCDN.  When this is not the case, the dCDN
   MUST return the error code "emeta".



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   When processing published URLs in "preposition" trigger action, the
   dCDN MUST invoke processing of metadata objects it would have invoked
   in content acquisition to satisfy an end-user request, e.g.,
   SourceMetadata (see Section 4.2.1 of [RFC8006]).

   Another type of URL in common use is a "private" URL.  A private URL
   is based on cache keys that are dynamically constructed via
   lightweight processing of various properties of the HTTP request and/
   or response.  As an example, an origin might specify a cache key as a
   value returned in a specific HTTP response header.

   As an example, the uCDN may prefer to use such private URLs in
   "purge" or "invalidate" trigger actions to simplify processing.

   The dCDNs implementing the CI/T interface MUST support the
   "published" URL type.  The dCDN MAY support the additional "private"
   URL type.  In this case, the dCDN SHOULD advertise the private URL
   type support via FCI using Section 5.4.  If the private URL is not
   supported by the dCDN, it SHOULD reject the trigger creation request
   using "eunsupported" Error Code.  If both URL types are supported by
   the dCDN, the uCDN MUST use only one URL type in each trigger.

   The following URL types are defined by this document and MUST be
   supported by the implementation of the CI/T interface:

     +===========+===================================================+
     | URL Type  | Description                                       |
     +===========+===================================================+
     | published | Published URL used by end users to access content |
     +-----------+---------------------------------------------------+
     | private   | Private URLs used by the dCDN to look up content  |
     |           | objects in cache                                  |
     +-----------+---------------------------------------------------+

                                  Table 10

4.4.2.  ObjectList

   ObjectList is a metadata object describing lists of objects that can
   be used in the context of CI/T v2 trigger specs, trigger status
   resources, or other contexts as required.  The ObjectList object can
   either embed the lists of objects or point to external URL(s) that
   hold such lists.  ObjectList allows the specification of an object
   list type, providing instructions on the interpretation of the object
   list format.






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   ObjectLists MAY be recursive, i.e., including references to secondary
   manifests, including references to HLS, MPEG-DASH, or MSS manifests
   as well as additional JSON-encoded ObjectLists, etc.  The party
   consuming the object list MUST parse all recursions based on the
   object list type property.  When doing so, the consuming party SHOULD
   also detect potential loops when the descendant ObjectList points
   back to its parent ObjectList.

   In the case of the uCDN accessing ObjectList objects referencing
   external URLs published by the dCDN, both parties SHOULD comply with
   the CI/T interface security requirements (see Section 8.1 for
   details).  When the dCDN accesses external URLs referenced by
   ObjectLists supplied by the uCDN, for example as part of trigger
   spec, the dCDN MUST match these URLs with source metadata objects,
   published by the uCDN, such as SourceMetadata objects specified in
   Section 4.2.1 of [RFC8006], and use these metadata objects for
   content acquisition if a match was found.

   ObjectLists MAY combine regular objects and secondary ObjectLists in
   the same object.  Please note that when embedding non-JSON object
   lists directly in ObjectList, absolute URLs MUST be provided at all
   times and the text SHOULD be encoded per the JSON grammar
   specification [ECMA404], including explicit newline encoding.  When
   the uCDN accesses ObjectList metadata resources published by the
   dCDN, the same interface authentication and authorization
   requirements would apply, as when accessing the interface itself.

   The ObjectList properties are as follows:

      Name: data
         Description: List of objects in one of the recognized formats.

         Value: JSON string.

         Mandatory-to-Specify: No.  Either "data" or "href" MUST be set.

      Name: href
         Description: URL pointing to an external object list or object
         in one of the recognized formats.

         Value: A URL represented as a JSON string.

         Mandatory-to-Specify: No.  Either "data" or "href" MUST be set.

      Name: type






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         Description: Object list type to be used when parsing and
         interpreting this object list.  By default, each record in the
         list is assumed to represent a content or metadata object that
         does not require additional processing.

         Value: ObjectListType (see Section 4.4.2.1).

         Mandatory-to-Specify: Yes.

   ObjectList is encoded as an array of per-object records in JSON
   format as follows:

   External HLS manifest:

   [
     {
       "href": "https://example.com/hls/a36f764e/index.m3u8",
       "type": "hls"
     }
   ]

   External object list in text format:

   [
     {
       "href": "https://example.com/hls/35cdc008/assets",
       "type": "text"
     }
   ]

   List of external manifests and objects of mixed types:

   [
     {
       "href": "https://example.com/hls/35cdc008/index.m3u8",
       "type": "hls"
     },
     {
       "href": "https://example.com/dash/35cdc008/main.mpd",
       "type": "dash"
     },
     {
       "href": "https://example.com/dash/35cdc008/files.json",
       "type": "json"
     }
   ]

   Embedded JSON-encoded object list:



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   [
     {
       "data": [
         {
           "href": "https://example.com/hls/35cdc008/index.m3u8",
           "type": "hls"
         },
         {
           "href": "https://example.com/dash/35cdc008/main.mpd",
           "type": "dash"
         },
         {
           "href": "https://example.com/img/35cdc008/thumb-l.jpg",
           "size": 10260
         },
         {
           "href": "https://example.com/img/35cdc008/thumb-s.jpg",
           "size": 1453
         }
       ],
       "type": "json"
     }
   ]

   Embedded HLS manifest:

   Please note that some lines in the example are wrapped for clarity.
























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   [
     {
       "data": "#EXTM3U\n
   #EXT-X-STREAM-INF:BANDWIDTH=150000,RESOLUTION=416x234,
     CODECS=\"avc1.42e00a,mp4a.40.2\"\n
   http://example.com/low/index.m3u8\n
   #EXT-X-STREAM-INF:BANDWIDTH=240000,RESOLUTION=416x234,
     CODECS=\"avc1.42e00a,mp4a.40.2\"\n
   http://example.com/lo_mid/index.m3u8\n
   #EXT-X-STREAM-INF:BANDWIDTH=440000,RESOLUTION=416x234,
     CODECS=\"avc1.42e00a,mp4a.40.2\"\n
   http://example.com/hi_mid/index.m3u8\n
   #EXT-X-STREAM-INF:BANDWIDTH=640000,RESOLUTION=640x360,
     CODECS=\"avc1.42e00a,mp4a.40.2\"\n
   http://example.com/high/index.m3u8\n
   #EXT-X-STREAM-INF:BANDWIDTH=64000,
     CODECS=\"mp4a.40.5\"\n
   http://example.com/high/index.m3u8\n",
       "type": "hls"
     }
   ]

4.4.2.1.  ObjectList Type

   ObjectListType objects are used to specify the registered type of
   ObjectList objects (see Section 7.5), used in trigger spec, trigger
   objects, and Error.v2 Description objects.

   The following table defines the initial ObjectListType JSON string
   values





















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   +=============+============================+========================+
   | JSON string | Description                | Protocol               |
   |             |                            | Specification          |
   +=============+============================+========================+
   | hls         | HTTP Live Streaming        | RFC 8216               |
   |             |                            | [RFC8216]              |
   +-------------+----------------------------+------------------------+
   | mss         | Microsoft Smooth Streaming | MSS [MSS]              |
   +-------------+----------------------------+------------------------+
   | dash        | Dynamic Adaptive Streaming | MPEG-DASH              |
   |             | over HTTP (MPEG-DASH)      | [MPEG-DASH]            |
   +-------------+----------------------------+------------------------+
   | json        | JSON-serialized object     | JSON (Section          |
   |             | list                       | 4.4.2.2)               |
   +-------------+----------------------------+------------------------+
   | text        | Object list in text format | Text (Section          |
   |             |                            | 4.4.2.3)               |
   +-------------+----------------------------+------------------------+

                                  Table 11

   If the support for the ObjectList Spec (Section 4.1.2.8) is
   implemented, the dCDN MUST support at least one of the ObjectList
   types.

4.4.2.2.  JSON Serialized Object List

   This ObjectList type specifies a collection of objects encoded in
   JSON format, where each entry is encoded as an ObjectEntry
   (Section 4.4.2.4) object.  The entries in the JSON object list MAY
   have an object list type specified, allowing for a recursive object
   list structure.

4.4.2.3.  Text Object List

   Unlike the JSON Serialized Object List (Section 4.4.2.2), the text-
   based object list will not support a recursive object list structure,
   and every object specified in it SHOULD be acted upon without
   additional processing.

4.4.2.4.  ObjectEntry

   ObjectEntry is a metadata object describing an object and its
   associated metadata, to be used in JSON-encoded ObjectList
   (Section 4.4.2) objects.

   The ObjectEntry properties are as follows:




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      Name: href
         Description: Object URL

         Value: A URL represented as a JSON string.

         Mandatory-to-Specify: Yes.

      Name: type
         Description: ObjectList type to be used when processing this
         object.  By default, the ObjectEntry object is assumed to
         represent an object and does not require additional processing.

         Value: ObjectListType (see Section 4.4.2.1).

         Mandatory-to-Specify: No.

      Name: size
         Description: Object size, in bytes.  Can be used to decide to
         download the object based on size.  For example, the dCDN may
         ignore objects that are too small or too large.

         Value: Integer.

         Mandatory-to-Specify: No.

   The following is an example of JSON-serialized ObjectEntry objects:

   [
     {
       "href": "https://example.com/hls/35cdc008/index.m3u8",
       "type": "hls"
     },
     {
       "href": "https://example.com/dash/35cdc008/main.mpd",
       "type": "dash"
     },
     {
       "href": "https://example.com/img/35cdc008/thumb-l.jpg",
       "size": 102600
     },
     {
       "href": "https://example.com/img/35cdc008/thumb-s.jpg",
       "size": 14535
     }
   ]






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4.4.3.  CDN Provider ID

   The CDN PID consists of the two characters "AS" followed by the CDN
   provider's Autonomous System number [RFC1930], then a colon (":") and
   an additional qualifier that is used to guarantee uniqueness in case
   a particular AS has multiple independent CDNs deployed -- for
   example, "AS64496:0".

   If the CDN provider has multiple ASes, the same AS number SHOULD be
   used in all messages from that CDN provider, unless there are
   multiple distinct CDNs.

   If the CDNI Request Routing Redirection interface (RI) described in
   [RFC7975] is implemented by the dCDN, the CI/T interface and the RI
   SHOULD use the same CDN PID.

5.  Footprint and Capabilities

   This section covers the FCI objects required for the advertisement of
   the specs, extensions, and properties introduced in this document.

5.1.  CI/T Endpoint Capability Object

   The CI/T trigger endpoint capability object is used to advertise one
   or more CI/T interface endpoints along with CI/T interface versions
   supported by these endpoints.  The capability type is
   "FCI.CITEndpoints".  Version 1, as originally defined in [RFC8007],
   is the default if this capability is not explicitly declared.

   A CI/T Endpoints capability object is encoded as an array of JSON
   objects containing the following name/value pairs:

      Name: trigger-endpoint-uri
         Description: CI/T endpoint URI

         Value: A URL represented as a JSON string.

         Mandatory-to-Specify: Yes.

      Name: trigger-versions
         Description: A list of CI/T versions supported by the trigger
         endpoint.

         Value: An array of JSON strings.  Valid values include "v2",
         corresponding to this version of the interface, and "v1",
         corresponding to [RFC8007].

         Mandatory-to-Specify: Yes.



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      Name: trigger-subjects
         Description: Array of trigger subjects supported by the trigger
         endpoint.

         Value: An array of Strings containing the type of the subject
         matching the cit-spec-value property, such as "content" or
         "metadata" as defined in Section 4.1.2.2.

         Mandatory-to-Specify: No.  A missing or empty "trigger-
         subjects" list means that all trigger subjects are supported by
         the endpoint.  The dCDN SHOULD advertise only one endpoint for
         every trigger subject and CI/T interface version pair.  If more
         than one interface endpoint supports the same trigger subject
         and CI/T interface version (e.g., CI/T version 2 interface for
         content objects), the uCDN SHOULD be able to use any of the
         advertised CI/T interface endpoints interchangeably.

5.1.1.  CI/T Endpoints Capability Object Serialization

   The following example shows the serialization of a CI/T Endpoints
   Capability object for a dCDN that supports version 2 of the CI/T
   interface for content trigger subjects and version 1 for metadata
   trigger subjects, with one metadata endpoint for both the US and
   Brazil, and two separate content endpoints for the two countries.



























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   {
     "capabilities": [
       {
         "capability-type": "FCI.CITEndpoints",
         "capability-value": {
           "trigger-endpoint-uri":
             "https://dcdn.example/configuration/",
           "trigger-versions": [ "v1" ],
           "trigger-subjects": "metadata"
         },
         "footprints": {
           "footprint-type": "countrycode",
           "footprint-value": [ "us", "br" ]
         }
       },
       {
         "capability-type": "FCI.CITEndpoints",
         "capability-value": {
           "trigger-endpoint-uri":
             "https://dcdn.example/cache-management-us/",
           "trigger-versions": [ "v2" ],
           "trigger-subjects": "content"
         },
         "footprints": {
           "footprint-type": "countrycode",
           "footprint-value": [ "us" ]
         }
       },
       {
         "capability-type": "FCI.CITEndpoints",
         "capability-value": {
           "trigger-endpoint-uri":
             "https://dcdn.example/cache-management-br/",
           "trigger-versions": [ "v2" ],
           "trigger-subjects": "content"
         },
         "footprints": {
           "footprint-type": "countrycode",
           "footprint-value": [ "br" ]
         }
       }
     ]
   }








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5.2.  CI/T Trigger Scope Capability Object

   The CI/T supports several trigger actions for different trigger
   subjects as defined in Section 4.1.1 and Section 4.1.2.2.  Additional
   actions, as well as subjects, may be defined in the future.  The
   trigger scope capability object is used to indicate support for a
   trigger action for a subject.  It further specifies the trigger
   generic spec types that may be used for selecting the targets to
   which the triggers apply, along with the supported trigger generic
   extension types.

   All supported combinations of trigger actions and trigger subjects
   MUST be explicitly advertised, with one FCI.CITScope object provided
   for each combination.

   The "trigger-scope-capability" object matches the "FCI.CITScope"
   capability type and is encoded as a JSON object containing the
   following name/value pairs:

      Name: trigger-action
         Description: The supported CDNI CI/T trigger action.

         Value: A string corresponding to an entry from the "CDNI CI/T
         Trigger Types" registry Section 7.2, which corresponds to a
         CDNI CI/T trigger action.

         Mandatory-to-Specify: Yes.

      Name: trigger-subject
         Description: The supported CDNI CI/T trigger subject.

         Value: A string corresponding to an entry from the "CDNI CI/T
         Trigger Subjects" registry Section 7.4, which corresponds to a
         CDNI CI/T trigger subject.

         Mandatory-to-Specify: Yes.

      Name: trigger-specs
         Description: A list of supported CDNI CI/T GenericSpecObject
         types for trigger action and subject.

         Value: List of JSON strings corresponding to entries from the
         "CDNI CI/T Trigger Specs" registry Section 7.3, which
         correspond to CDNI CI/T GenericSpecObject objects.







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         Mandatory-to-Specify: No.  The default in case of a missing or
         an empty list MUST be interpreted as "no GenericSpecObject
         types supported".  A non-empty list MUST be interpreted as
         containing "the only GenericSpecObject types that are
         supported".

      Name: trigger-extensions
         Description: A list of supported CDNI CI/T
         GenericExtensionObject types for trigger action and subject.

         Value: List of JSON strings corresponding to entries from the
         "CDNI CI/T Trigger Extension" registry Section 7.6, which
         corresponds to a CDNI CI/T GenericExtensionObject object.

         Mandatory-to-Specify: No.  The default in case of a missing or
         an empty list MUST be interpreted as "no GenericExtensionObject
         types are supported".  A non-empty list MUST be interpreted as
         containing "the only GenericExtensionObject types that are
         supported".

5.2.1.  CI/T Trigger Scope Capability Object Serialization

   The following shows an example of a JSON-serialized CI/T Trigger
   Scope Capability objects serialization for the dCDN that supports the
   preposition and invalidation of content, using "urls" and "ccids"
   generic spec types, with "time-policy" but only for the "preposition"
   action.  Note that in this example, purge is not supported, and no
   actions involving metadata are supported either.























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   {
        "capabilities": [
           {
             "capability-type": "FCI.CITScope",
             "capability-value": {
                "trigger-action": "preposition",
                "trigger-subject": "content",
                "trigger-specs": [ "urls", "ccids" ],
                "trigger-extensions": [ "time-policy" ]
             },
             "footprints": {
               "footprint-type": "countrycode",
               "footprint-value": [ "us" ]
            }
          },
          {
             "capability-type": "FCI.CITScope",
             "capability-value": {
                "trigger-action": "invalidate",
                "trigger-subject": "content",
                "trigger-specs": [ "urls", "ccids" ]
             },
             "footprints": {
               "footprint-type": "countrycode",
               "footprint-value": [ "us" ]
             }
          }
       ]
   }
   }

5.3.  CI/T Object List Type Capability Object

   Given an object list being supported by the dCDN, the CI/T Object
   List Type capability object is used to indicate support for one or
   more Object List types listed in Section 7.5 by the type property of
   the "ObjectList" object.  The capability type is
   "FCI.CITObjectListType".

      Name: object-list-types
         Description: A list of supported ObjectList types.

         Value: An array of JSON strings representing ObjectListTypes
         (Section 4.4.2.1).

         Mandatory-to-Specify: No.  A missing or an empty list MUST be
         interpreted as no ObjectList types are supported.




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5.3.1.  CI/T Object List Type Capability Object Serialization

   The following shows an example of a JSON-serialized CI/T Object List
   Type Capability object serialization for the dCDN that supports
   "hls", "dash", and "json", in the US only.

   {
     "capabilities": [{
       "capability-type": "FCI.CITObjectListType",
       "capability-value": {
         "object-list-types": [ "hls", "dash", "json" ]
       },
       "footprints": {
         "footprint-type": "countrycode",
         "footprint-value": [ "us" ]
       }
     }]
   }

5.4.  CI/T Private URL Capability Object

   The CI/T Private URL capability object is used to indicate support
   for operations on private URLs (see Section 4.4.1 for details).  The
   capability type is "FCI.CITPrivateUrlType".

      Name: private-url-type-support
         Description: Indicate whether private URL type is supported by
         the dCDN.

         Value: Boolean.

         Mandatory-to-Specify: No.  A missing or an empty attribute MUST
         be interpreted as no support for private URLs.

5.4.1.  CI/T Private URL Type Capability Object Serialization

   The following shows an example of a JSON-serialized CI/T Private URL
   Type Capability object serialization for the dCDN that supports the
   private URL type in URL-based trigger spec types.












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   {
     "capabilities": [{
       "capability-type": "FCI.CITPrivateUrlType",
       "capability-value": { "private-url-type-support": true },
       "footprints": {
         "footprint-type": "countrycode",
         "footprint-value": [ "us" ]
       }
     }]
   }

5.5.  CI/T Extended Status Capability Object

   The CI/T extended trigger status capability object is used to
   indicate support for extended trigger status.  The extended trigger
   status is returned upon the uCDN request and includes:

   *  "objects" attribute in the trigger object

   *  "objects" attribute in Error.v2 description object

   *  "trigger-objects" attribute in the trigger collection object

   The capability type is "FCI.CITExtendedStatus".

      Name: extended-status-objects
         Description: List of CI/T objects that support extended
         attributes.

         Value: An array of JSON strings listing CI/T objects.

         Mandatory-to-Specify: No.  By default, in case of a missing or
         an empty list, no extended attribute objects are supported.

5.5.1.  CI/T Private URL Type Capability Object Serialization

   The following shows an example of a JSON-serialized CI/T Extended
   Status Type Capability object serialization for the dCDN that
   supports extended status in trigger, Error.v2 description, and
   trigger collections objects.











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   {
     "capabilities": [{
       "capability-type": "FCI.CITExtendedStatus",
       "capability-value": {
         "extended-status-objects": [
           "trigger-state",
           "error-v2-description",
           "trigger-collection"
         ]
       },
       "footprints": {
         "footprint-type": "countrycode",
         "footprint-value": [ "us" ]
       }
     }]
   }

6.  Examples

   This section provides examples of using the CI/T interface and its
   features.

   The discovery of the CI/T interface is out of the scope of this
   document.  In an implementation, all CI/T URLs are under the control
   of the dCDN.  The uCDN MUST NOT attempt to ascribe any meaning to
   individual elements of the path.

   In examples in this section, the root URI "https://dcdn.example/cit/"
   is used as the location of the trigger collection resource, and the
   PID of the uCDN is "AS64496:1".

6.1.  Creating Triggers

6.1.1.  Preposition

   Below is an example of a "preposition" trigger creation.  The uCDN
   sends HTTP POST request to the trigger collection URI with the
   trigger representation in the request body.

   Note that pattern-based or label-based specs like "uri-pattern-
   match", "uri-regex-match" and "ccids" are not allowed to be used with
   "preposition" trigger action, where the dCDN MUST have a clear list
   of objects to obtain.








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 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 622

 {
   "action": "preposition",
   "specs": [
     {
       "trigger-subject": "metadata",
       "cit-spec-type": "urls",
       "cit-spec-value": {
       "urls": [ "https://metadata.example.com/a/b/c" ]
            }
     },
     {
       "trigger-subject": "content",
       "cit-spec-type": "urls",
       "cit-spec-value": {
         "urls": [
           "https://www.example.com/a/b/c/1",
           "https://www.example.com/a/b/c/2",
           "https://www.example.com/a/b/c/3",
           "https://www.example.com/a/b/c/4"
         ]
       }
     }
   ],
   "cdn-path": [ "AS64496:1" ]
 }


 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:10 GMT
 Content-Length: 710
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/3f2d259d-a980-4742-beeb-9392a58129f5
 Server: example-server/0.1

 {
   "ctime": 1730119690,
   "etime": 1730119750,



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   "mtime": 1730119690,
   "state": "pending",
   "action": "preposition",
   "specs": [
     {
       "trigger-subject": "metadata",
       "cit-spec-type": "urls",
       "cit-spec-value": {
         "urls": [ "https://metadata.example.com/a/b/c" ]
       }
     },
     {
       "trigger-subject": "content",
       "cit-spec-type": "urls",
       "cit-spec-value": {
         "urls": [
           "https://www.example.com/a/b/c/1",
           "https://www.example.com/a/b/c/2",
           "https://www.example.com/a/b/c/3",
           "https://www.example.com/a/b/c/4"
         ]
       }
     }
   ],
   "cdn-path": [ "AS64496:1" ]
 }

6.1.2.  Invalidate

   Below is an example of a CI/T "invalidate" trigger creation.  This
   trigger instructs the dCDN to revalidate:

   *  the metadata objects with URLs prefixed by
      "https://metadata.example.com/a/b/" using case-insensitive
      matching

   *  a single content object identified by the URL
      "https://www.example.com/a/index.html"

   *  the content objects with URLs prefixed by
      "https://www.example.com/a/b/" using case-sensitive matching

 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*



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 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 783

 {
   "action": "invalidate",
   "specs": [
      {
         "trigger-subject": "metadata",
         "cit-spec-type": "uri-pattern-match",
         "cit-spec-value": {
            "pattern": "https://metadata.example.com/a/b/*"
         }
      },
      {
         "trigger-subject": "content",
         "cit-spec-type": "urls",
         "cit-spec-value": {
            "urls": [
               "https://www.example.com/a/index.html"
            ]
         }
      },
      {
         "trigger-subject": "content",
         "cit-spec-type": "uri-pattern-match",
         "cit-spec-value": {
            "pattern": "https://www.example.com/a/b/*",
            "case-sensitive": true
         }
      }
   ],
   "cdn-path": [ "AS64496:1" ]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:11 GMT
 Content-Length: 807
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/327df5b8-1df8-4cff-92f8-fda27774c171
 Server: example-server/0.1

 {
   "ctime": 1730119691,
   "etime": 1730119751,
   "mtime": 1730119691,
   "state": "pending",



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   "action": "invalidate",
   "specs": [
     {
       "trigger-subject": "metadata",
       "cit-spec-type": "uri-pattern-match",
       "cit-spec-value": {
         "pattern": "https://metadata.example.com/a/b/*"
       }
     },
     {
       "trigger-subject": "content",
       "cit-spec-type": "urls",
       "cit-spec-value": {
         "urls": [ "https://www.example.com/a/index.html" ]
       }
     },
     {
       "trigger-subject": "content",
       "cit-spec-type": "uri-pattern-match",
       "cit-spec-value": {
         "pattern": "https://www.example.com/a/b/*",
         "case-sensitive": true
       }
     }
   ],
   "cdn-path": [ "AS64496:1" ]
 }

6.1.3.  Invalidation with Regex

   In the following example, a CI/T "invalidate" trigger uses the Regex
   property to specify the range of content objects for invalidation,
   the trigger is rejected by the dCDN due to regex complexity, and an
   appropriate error is reflected in the response.

   Please note that some lines in the example are wrapped for clarity.

 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 392

 {
   "action": "invalidate",



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   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "uri-regex-match",
     "cit-spec-value": {
       "regex": "^(https:\\/\\/video\\.example\\.com)\\/
         ([a-z])\\/movie1\\/([1-7])\\/*(index.m3u8|\\d{3}.ts)$",
       "case-sensitive": true,
       "match-query-string": false
     }
   }],
   "cdn-path": [ "AS64496:0" ]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:12 GMT
 Content-Length: 960
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/991b9fb9-d0be-4d05-be06-64c0e5c5a5f9
 Server: example-server/0.1

 {
   "errors": [{
     "specs": [{
       "trigger-subject": "content",
       "cit-spec-type": "uri-regex-match",
       "cit-spec-value": {
       "regex": "^(https:\\/\\/video\\.example\\.com)\\/([a-z])\
         \/movie1\\/([1-7])\\/*(index.m3u8|\\d{3}.ts)$",
         "case-sensitive": true,
         "match-query-string": false
       }
     }],
     "description": "The dCDN rejected a regex due to complexity",
     "error": "ereject",
     "cdn": "AS64500:0"
   }],
   "ctime": 1730119692,
   "etime": 1730119692,
   "mtime": 1730119692,
   "state": "failed",
   "action": "invalidate",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "uri-regex-match",
     "cit-spec-value": {
       "regex": "^(https:\\/\\/video\\.example\\.com)\\/([a-z])\



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         \/movie1\\/([1-7])\\/*(index.m3u8|\\d{3}.ts)$",
       "case-sensitive": true,
       "match-query-string": false
     }
   }],
   "cdn-path": [ "AS64496:0" ]
 }

6.1.4.  Preposition with ObjectLists

   In the following example, a CI/T "preposition" trigger uses the
   ObjectList property to specify the full media library of a specific
   content.  The command fails due to object list parse error and an
   appropriate error is reflected in the response.

 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 328

 {
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "cdn-path": [ "AS64496:0" ]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:13 GMT
 Content-Length: 829
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/86633e6e-d2da-4185-a285-b3d087a5d711
 Server: example-server/0.1




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 {
   "errors": [{
     "specs": [{
       "trigger-subject": "content",
       "cit-spec-type": "content-objectlist",
       "cit-spec-value": {
         "objects": [{
           "href": "https://www.example.com/hls/title/index.m3u8",
           "type": "hls"
         }}
     }],
     "description": "The dCDN was not able to parse the object list",
     "error": "econtent",
     "cdn": "AS64500:0"
   }],
   "ctime": 1730119693,
   "etime": 1730119693,
   "mtime": 1730119693,
   "state": "failed",
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
     }
   }],
   "cdn-path": [ "AS64496:0" ]
 }

6.2.  Changing, Cancelling and Deleting Triggers

6.2.1.  Modifying Triggers

   The uCDN can modify triggers while they are in a "pending" state.
   One example of this might be to adjust a trigger's "specs" and/or
   "labels" attributes.  In the below example, the uCDN updates a
   trigger created earlier by removing the metadata portion of the
   trigger spec and adding trigger labels.  The dCDN responds with a 200
   ("OK") response containing the updated trigger representation.








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   REQUEST:

   POST /cit/3f2d259d-a980-4742-beeb-9392a58129f5 HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*
   Content-Type: application/cdni; ptype=ci-trigger.v2
   Content-Length: 401

   {
     "specs": [
       {
         "trigger-subject": "content",
         "cit-spec-type": "urls",
         "cit-spec-value": {
           "urls": [
             "https://www.example.com/d/e/f/1",
             "https://www.example.com/d/e/f/2",
             "https://www.example.com/d/e/f/3",
             "https://www.example.com/d/e/f/4"
           ]
         }
       }
     ],
     "labels": [
       "type=video"
     ]
   }

   RESPONSE:

   HTTP/1.1 200 OK
   Date: Sun, 27 Oct 2024 08:48:14 GMT
   Content-Length: 520
   Content-Type: application/cdni; ptype=ci-trigger.v2
   Server: example-server/0.1

   {
     "ctime": 1730119694,
     "etime": 1730119754,
     "mtime": 1730119694,
     "state": "pending",
     "action": "preposition",

     "specs": [
       {
         "trigger-subject": "content",
         "cit-spec-type": "urls",



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         "cit-spec-value": {
           "urls": [
             "https://www.example.com/d/e/f/1",
             "https://www.example.com/d/e/f/2",
             "https://www.example.com/d/e/f/3",
             "https://www.example.com/d/e/f/4"
           ]
         }
       }
     ],
     "labels": [
       "type=video"
     ]
   }

6.2.2.  Cancelling Triggers

   The uCDN can cancel triggers that are not in a terminal state by
   requesting to update the trigger state to "cancelled".  In case of
   asynchronous processing, the dCDN will respond by setting the trigger
   state to "cancelling" and update it "cancelled" when the cancellation
   is complete.





























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   REQUEST:

   POST /cit/3f2d259d-a980-4742-beeb-9392a58129f5 HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*
   Content-Type: application/cdni; ptype=ci-trigger.v2
   Content-Length: 27

   {
     "state": "cancelled"
   }

   RESPONSE:

   HTTP/1.1 200 OK
   Date: Sun, 27 Oct 2024 08:48:15 GMT
   Content-Length: 523
   Content-Type: application/cdni; ptype=ci-trigger.v2
   Server: example-server/0.1

   {
     "ctime": 1730119695,
     "etime": 1730119755,
     "mtime": 1730119695,
     "state": "cancelling",
     "action": "preposition",

     "specs": [
       {
         "trigger-subject": "content",
         "cit-spec-type": "urls",
         "cit-spec-value": {
           "urls": [
             "https://www.example.com/d/e/f/1",
             "https://www.example.com/d/e/f/2",
             "https://www.example.com/d/e/f/3",
             "https://www.example.com/d/e/f/4"
           ]
         }
       }
     ],
     "labels": [
       "type=video"
     ]
   }





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6.2.3.  Deleting Triggers

   The uCDN can delete completed and failed triggers to reduce the size
   of the collections, as described in Section 3.5.  For example, to
   delete the "preposition" trigger from earlier examples:

   REQUEST:

   DELETE /cit/3f2d259d-a980-4742-beeb-9392a58129f5 HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 204 No Content
   Date: Sun, 27 Oct 2024 08:48:16 GMT
   Content-Length: 0
   Content-Type: text/html; charset=UTF-8
   Server: example-server/0.1

6.3.  Examining Trigger Status

   Once triggers have been created, the uCDN can check their status as
   shown in the following examples.

6.3.1.  Trigger Index

   The uCDN can fetch all active trigger collections, representing all
   existing trigger resources.

   REQUEST:

   GET /cit HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 341
   Expires: Sun, 27 Oct 2024 08:49:18 GMT
   Server: example-server/0.1
   ETag: "936094426920308378"
   Last-Modified: Sun, 27 Oct 2024 08:40:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:18 GMT



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   Content-Type: application/cdni; ptype=ci-trigger-index.v2

   {
     "cdn-id": "AS64496:0",
     "staleresourcetime": 86400,
     "collections": [
       {
         "uri": "/cit/all"
       },
       {
         "filter-type": "state",
         "filter-value": "pending",
         "uri": "/cit/state/pending"
       },
       {
         "filter-type": "state",
         "filter-value": "active",
         "uri": "/cit/state/active"
       },
       {
         "filter-type": "state",
         "filter-value": "complete",
         "uri": "/cit/state/complete"
       },
       {
         "filter-type": "state",
         "filter-value": "processed",
         "uri": "/cit/state/processed"
       },
       {
         "filter-type": "state",
         "filter-value": "failed",
         "uri": "/cit/state/failed"
       },
       {
         "filter-type": "state",
         "filter-value": "cancelling",
         "uri": "/cit/state/cancelling"
       },
       {
         "filter-type": "state",
         "filter-value": "cancelled",
         "uri": "/cit/state/cancelled"
       },
       {
         "filter-type": "label",
         "filter-value": "type=video",
         "uri": "/cit/labels/type=video"



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       }
     ]
   }

6.3.2.  Trigger Collection

   Before the dCDN starts processing the remaining trigger shown above,
   it will appear in the collection of pending triggers.  For example:

   REQUEST:

   GET /cit/state/pending HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 123
   Expires: Sun, 27 Oct 2024 08:49:19 GMT
   Server: example-server/0.1
   ETag: "4331492443626270781"
   Last-Modified: Sun, 27 Oct 2024 08:40:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:19 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2
   327df5b8-1df8-4cff-92f8-fda27774c171
   {
     "trigger-urls": [
       "https://dcdn.example/cit/327df5b8-1df8-4cff-92f8-fda27774c171"
     ]
   }

   At this point, if no other triggers had been created, the trigger
   collection for failed triggers would hold the two failed triggers
   shown above while other trigger collecions would be empty.  For
   example:













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   REQUEST:

   GET /cit/state/complete HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 51
   Expires: Sun, 27 Oct 2024 08:49:20 GMT
   Server: example-server/0.1
   ETag: "7958041393922269003"
   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:20 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   {
     "trigger-urls": []
   }





























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   REQUEST:

   GET /cit/state/failed HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 191
   Expires: Sun, 27 Oct 2024 08:49:21 GMT
   Server: example-server/0.1
   ETag: "4331492443626270781"
   Last-Modified: Sun, 27 Oct 2024 08:48:13 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:19 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   {
     "trigger-urls": [
       "https://dcdn.example/cit/991b9fb9-d0be-4d05-be06-64c0e5c5a5f9"
       "https://dcdn.example/cit/86633e6e-d2da-4185-a285-b3d087a5d711"
     ]
   }


6.3.3.  Individual Trigger Resources

   The uCDN can also examine individual triggers:

   REQUEST:

   GET /cit/327df5b8-1df8-4cff-92f8-fda27774c171 HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 545
   Expires: Sun, 27 Oct 2024 08:49:22 GMT
   Server: example-server/0.1
   ETag: "554385204989405469"
   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:22 GMT



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   Content-Type: application/cdni; ptype=ci-trigger.v2

   {
     "ctime": 1730119691,
     "etime": 1730119751,
     "mtime": 1730119691,
     "state": "pending",
     "action": "invalidate",
     "specs": [
       {
         "trigger-subject": "metadata",
         "cit-spec-type": "uri-pattern-match",
         "cit-spec-value": {
           "pattern": "https://metadata.example.com/a/b/*"
         }
       },
       {
         "trigger-subject": "content",
         "cit-spec-type": "urls",
         "cit-spec-value": {
           "urls": [ "https://www.example.com/a/index.html" ]
         }
       },
       {
         "trigger-subject": "content",
         "cit-spec-type": "uri-pattern-match",
         "cit-spec-value": {
           "pattern": "https://www.example.com/a/b/*",
           "case-sensitive": true
         }
       }
     ]
   }

6.3.4.  Polling for Changes in Status

   The uCDN SHOULD use the ETags and/or Last-Modified headers when
   polling for changes in trigger collections or the status of
   individual triggers, as shown in the following examples:












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   REQUEST:

   GET /cit/state/pending HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*
   If-None-Match: "4331492443626270781"
   If-Modified-Since: Sun, 27 Oct 2024 08:40:23 GMT

   RESPONSE:
   HTTP/1.1 304 Not Modified
   Content-Length: 0
   Expires: Sun, 27 Oct 2024 08:49:21 GMT
   Server: example-server/0.1
   ETag: "4331492443626270781"
   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:23 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   REQUEST:

   GET /cit/327df5b8-1df8-4cff-92f8-fda27774c171 HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*
   If-None-Match: "6990548174277557683"
   If-Modified-Since: Sun, 27 Oct 2024 08:49:10 GMT

   RESPONSE:

   HTTP/1.1 304 Not Modified
   Content-Length: 0
   Expires: Sun, 27 Oct 2024 08:49:24 GMT
   Server: example-server/0.1
   ETag: "554385204989405469"
   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:24 GMT
   Content-Type: application/cdni; ptype=ci-trigger.v2











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   When the trigger processing is complete, the contents of the filtered
   collections will be updated.  The dCDN SHOULD also update the "ETag"
   and/or "Last-Modified" response headers - whichever was previously
   sent - when delivering the updated collection representations.  The
   dCDN SHOULD also use cache control headers, such as "Expires" and
   "Cache-Control", to indicate how caching of the resource
   representation should happen by the uCDN and intermediate proxies.
   For example, when the two example triggers are complete, the
   collections of pending and complete triggers look as follows:

   REQUEST:

   GET /cit/state/pending HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 51
   Expires: Sun, 27 Oct 2024 08:49:25 GMT
   Server: example-server/0.1
   ETag: "1337503181677633762"
   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:25 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   {
     "staleresourcetime": 86400,
     "triggers": []
   }

   REQUEST:

   GET /cit/state/complete HTTP/1.1
   User-Agent: example-user-agent/0.1
   Host: dcdn.example
   Accept: */*

   RESPONSE:

   HTTP/1.1 200 OK
   Content-Length: 193
   Expires: Sun, 27 Oct 2024 08:49:26 GMT
   Server: example-server/0.1
   ETag: "4481489539378529796"



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   Last-Modified: Sun, 27 Oct 2024 08:48:17 GMT
   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:26 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   {
     "staleresourcetime": 86400,
     "triggers": [
       "https://dcdn.example/cit/327df5b8-1df8-4cff-92f8-fda27774c171"
     ]
   }

6.4.  Extensions

6.4.1.  Execution Policy Extension

   This subsection illustrates the uses of the Execution Policy
   extension.  The uCDN can create a dependency between triggers.  For
   example, a preposition trigger should only be processed by the dCDN
   after a previous purge trigger has been completed.

 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 294

 {
   "action": "purge",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/1a910c8e/index.m3u8",
         "type": "hls"
       }]
      }
   }]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:27 GMT



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 Content-Length: 385
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/564cc45e-9099-4a37-b95e-60342f2647ba
 Server: example-server/0.1

 {
   "ctime": 1730119707,
   "etime": 1730119767,
   "mtime": 1730119707,
   "state": "pending",
   "action": "purge",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/1a910c8e/index.m3u8",
         "type": "hls"
       }]
      }
   }]
 }


 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 527

 {
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/09000b67/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "cit-extension-type": "execution-policy",
     "cit-extension-value": {



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       "depends": [
         "https://dcdn.example/cit/564cc45e-9099-4a37-b95e-60342f2647ba"
       ]
     }
   ]
 }


 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:28 GMT
 Content-Length: 467
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/f6dde35f-703f-49e9-bb80-4964dff3bca5
 Server: example-server/0.1

 {
   "ctime": 1730119708,
   "etime": 1730119768,
   "mtime": 1730119708,
   "state": "pending",
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/09000b67/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "cit-extension-type": "execution-policy",
     "cit-extension-value": {
       "depends": [
         "https://dcdn.example/cit/564cc45e-9099-4a37-b95e-60342f2647ba"
       ]
     }
   ]
 }

   The uCDN can also stagger long-running triggers to control processing
   order.  In the following example, the uCDN creates a preposition
   trigger with higher priority, which dCDN should pick up for execution
   before the earlier triggers.




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 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2

 {
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/b89d49df/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "cit-extension-type": "execution-policy",
     "cit-extension-value": { "priority": 100 }
    ]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:30 GMT
 Content-Length: 526
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/e5483c4a-7c8e-4820-91c8-3c0a9f2edba8
 Server: example-server/0.1

 {
   "ctime": 1730119710,
   "etime": 1730119770,
   "mtime": 1730119710,
   "state": "pending",
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/b89d49df/index.m3u8",
         "type": "hls"



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       }]
      }
   }],
   "extensions": [
     "cit-extension-type": "execution-policy",
     "cit-extension-value": { "priority": 100 }
    ]
 }

6.4.2.  Extensions with Error Propagation

   In the following example, a CI/T "preposition" command uses two
   extensions to control the way the trigger is executed.  In this
   example, the receiving dCDN, identified as "AS64500:0", does not
   support the first extension in the extensions array.  The dCDN
   "AS64500:0" further distributes this trigger to another downstream
   CDN that is identified as "AS64501:0", which does not support the
   second extension in the extensions array.  The error is propagated
   from "AS64501:0" to "AS64500:0" and the errors.v2 array reflects both
   errors.

 REQUEST:

 POST /cit HTTP/1.1
 User-Agent: example-user-agent/0.1
 Host: dcdn.example
 Accept: */*
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Content-Length: 1249

 {
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",
     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
     }
   }],
   "extensions": [
     {
       "cit-extension-type": "location-policy",
       "cit-extension-value": {
         "locations": [
           {



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             "action": "allow",
             "footprints": [{
                 "footprint-type": "countrycode",
                 "footprint-value": [ "us" ]
             }]
           },
           {
             "action": "deny",
             "footprints": [{
                "footprint-type": "countrycode",
                "footprint-value": [ "ca" ]
             }]
           }
         ]
       },
       "mandatory-to-enforce": true,
       "safe-to-redistribute": true
     },
     {
       "cit-extension-type": "time-policy",
       "cit-extension-value": {
         "unix-time-window": {
           "start": 1730174400,
           "end": 1730260800
         }
       },
       "mandatory-to-enforce": true,
       "safe-to-redistribute": true
     }
   ],
   "cdn-path": [ "AS64496:0" ]
 }

 RESPONSE:

 HTTP/1.1 201 Created
 Date: Sun, 27 Oct 2024 08:48:31 GMT
 Content-Length: 2595
 Content-Type: application/cdni; ptype=ci-trigger.v2
 Location: https://dcdn.example/cit/bcca1cde-ddf0-47db-b859-6a2c043baaa9
 Server: example-server/0.1

 {
   "errors": [
     {
       "extensions": [{
         "cit-extension-type": "location-policy",
         "cit-extension-value": {



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           "locations": [
             {
               "action": "allow",
               "footprints": [{
                   "footprint-type": "countrycode",
                   "footprint-value": [ "us" ]
                 }]
             },
             {
               "action": "deny",
               "footprints": [{
                   "footprint-type": "countrycode",
                   "footprint-value": [ "ca" ]
                 }]
             }
           ]
         },
         "mandatory-to-enforce": true,
         "safe-to-redistribute": true
       }],
       "description": "unrecognized extension type",
       "error": "eextension",
       "cdn": "AS64500:0"
     },
     {
       "extensions": [{
         "cit-extension-type": "time-policy",
         "cit-extension-value": {
           "unix-time-window": {
             "start": 1730174400,
             "end": 1730260800
           }
         },
         "mandatory-to-enforce": true,
         "safe-to-redistribute": true
       }],
       "description": "unrecognized extension type",
       "error": "eextension",
       "cdn": "AS64501:0"
     }
   ],
   "ctime": 1730119691,
   "etime": 1730119691,
   "mtime": 1730119691,
   "state": "failed",
   "action": "preposition",
   "specs": [{
     "trigger-subject": "content",



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     "cit-spec-type": "content-objectlist",
     "cit-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
     }
   }],
   "extensions": [
     {
       "cit-extension-type": "location-policy",
       "cit-extension-value": {
         "locations": [
           {
             "action": "allow",
             "footprints": [{
               "footprint-type": "countrycode",
               "footprint-value": [ "us" ]
             }]
           },
           {
             "action": "deny",
             "footprints": [{
               "footprint-type": "countrycode",
               "footprint-value": [ "ca" ]
             }]
           }
         ]
       },
       "mandatory-to-enforce": true,
       "safe-to-redistribute": true
     },
     {
       "cit-extension-type": "time-policy",
       "cit-extension-value": {
         "unix-time-window": {
           "start": 1730174400,
           "end": 1730260800
         }
       },
       "mandatory-to-enforce": true,
       "safe-to-redistribute": true
     }
   ],
   "cdn-path": [ "AS64496:0" ]
 }





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7.  IANA Considerations

7.1.  CDNI Payload Type Parameter Registrations

   All references to RFC 8007 in the IANA registries should be replaced
   with references to this document, apart from references associated
   with the following registrations:

                 +=======================+===============+
                 | Payload Type          | Specification |
                 +=======================+===============+
                 | ci-trigger-command    | RFC 8007      |
                 +-----------------------+---------------+
                 | ci-trigger-status     | RFC 8007      |
                 +-----------------------+---------------+
                 | ci-trigger-collection | RFC 8007      |
                 +-----------------------+---------------+

                                  Table 12

   The IANA is requested to register the following new Payload Types in
   the "CDNI Payload Types" registry defined by [RFC7736], for use with
   the "application/cdni" MIME media type.

               +==========================+===============+
               | Payload Type             | Specification |
               +==========================+===============+
               | ci-trigger.v2            | RFCthis       |
               +--------------------------+---------------+
               | ci-trigger-index.v2      | RFCthis       |
               +--------------------------+---------------+
               | ci-trigger-collection.v2 | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITScope             | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITObjectListType    | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITEndpoints         | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITExtendedStatus    | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITPrivateUrlType    | RFCthis       |
               +--------------------------+---------------+

                                 Table 13

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]



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7.1.1.  CDNI ci-trigger.v2 Payload Type

   Purpose: The purpose of this payload type is to define a new CI/T
   trigger object (and any associated capability advertisement)

   Interface: CI/T

   Encoding: see Section 4.1

7.1.2.  CDNI ci-trigger-index.v2 Payload Type

   Purpose: The purpose of this payload type is to define a new CI/T
   trigger index object (and any associated capability advertisement)

   Interface: CI/T

   Encoding: see Section 4.2

7.1.3.  CDNI ci-trigger-collection.v2 Payload Type

   Purpose: The purpose of this payload type is to define a new CI/T
   trigger collection object (and any associated capability
   advertisement)

   Interface: CI/T

   Encoding: see Section 4.3

7.1.4.  CDNI FCI CI/T Payload Types

7.1.4.1.  CDNI FCI CI/T Endpoints Payload Type

   Purpose: The purpose of this payload type is to distinguish FCI
   advertisement objects for CI/T Endpoints objects

   Interface: FCI

   Value: "FCI.CITEndpoints"

   Encoding: see Section 5.1

7.1.4.2.  CDNI FCI CI/T Trigger Scope Payload Type

   Purpose: The purpose of this payload type is to distinguish FCI
   advertisement objects for CI/T trigger scope

   Interface: FCI




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   Value: "FCI.CITScope"

   Encoding: see Section 5.2

7.1.4.3.  CDNI FCI CI/T Object List Type Payload Type

   Purpose: The purpose of this payload type is to distinguish FCI
   advertisement objects for CI/T Object List Type objects

   Interface: FCI

   Value: "FCI.CITObjectListType"

   Encoding: see Section 5.3

7.1.4.4.  CDNI FCI CI/T Private URL Type Payload Type

   Purpose: The purpose of this payload type is to distinguish FCI
   advertisement objects for CI/T Private URL Type objects

   Interface: FCI

   Value: "FCI.CITPrivateUrlType"

   Encoding: see Section 5.4

7.1.4.5.  CDNI FCI CI/T Extended Status Payload Type

   Purpose: The purpose of this payload type is to distinguish FCI
   advertisement objects for CI/T Extended Status objects

   Interface: FCI

   Value: "FCI.CITExtendedStatus"

   Encoding: see Section 5.5

7.2.  "CDNI CI/T Trigger Types" Registry For Trigger Actions

   In [RFC8007] the IANA was requested to create a new "CDNI CI/T
   Trigger Types" registry under the "Content Delivery Network
   Interconnection (CDNI) Parameters" registry group.

   Additions to the "CDNI CI/T Trigger Types" registry are made via the
   RFC Required policy as defined in [RFC8126].






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   In this second edition of the interface, trigger types are referred
   to as "trigger actions".  The "Trigger Types" registry is used for
   action definitions.  Furthermore, this document, and specifically
   Section 4.1.1, reuses the definition of "trigger types" as defined in
   [RFC8007] as trigger actions, and provide their specifications, with
   no modification compared to [RFC8007].

7.3.  "CDNI CI/T Trigger Specs" Registry

   The IANA is requested to create a new "CDNI CI/T Trigger Specs"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry group.  The "CDNI CI/T Trigger Specs" namespace
   defines the valid trigger targets' spec values in Section 4.1.2, used
   by the trigger spec object.

   Additions to the "CDNI CI/T Trigger Specs" registry are made via the
   RFC Required policy as defined in [RFC8126].

   The initial contents of the "CDNI CI/T Trigger Specs" registry
   consist of the names and descriptions listed in Section 4.1.2, with
   this document serving as their specification.

7.4.  "CDNI CI/T Trigger Subjects" Registry

   The IANA is requested to create a new "CDNI CI/T Trigger Subjects"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry group.  The "CDNI CI/T Trigger Subjects"
   namespace defines the valid trigger targets' subject values in
   Section 4.1.2.2, used by the trigger spec object.

   Additions to the "CDNI CI/T Trigger Subjects" registry are made via
   the RFC Required policy as defined in [RFC8126].

   The initial contents of the "CDNI CI/T Trigger Subjects" registry
   consist of the names and descriptions listed in Section 4.1.2.2, with
   this document serving as their specification.

7.5.  "CDNI CI/T Object List Types" Registry

   The IANA is requested to create a new "CDNI CI/T Object List Types"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry group.  The "CDNI CI/T Object List Types"
   namespace defines the valid object list type values in
   Section 4.4.2.1, used by the Object List object.

   Additions to the "CDNI CI/T Object List Types" registry are made via
   the Specification Required policy as defined in [RFC8126].




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   The initial contents of the "CDNI CI/T Object List Types" registry
   consist of the names and descriptions listed in Section 4.4.2.1, with
   this document serving as their specification.

7.6.  "CDNI CI/T Trigger Extensions" Registry

   The IANA is requested to create a new "CDNI CI/T Trigger Extensions"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry group.  The "CDNI CI/T Trigger Extensions"
   namespace defines the valid trigger targets' extension values in
   Section 2.8, used by the trigger spec object.

   Additions to the "CDNI CI/T Trigger Extensions" registry are made via
   the Specification Required policy as defined in [RFC8126].

   The initial contents of the "CDNI CI/T Trigger Extensions" registry
   consist of the names and descriptions listed in Section 2.8, with
   this document serving as their specification.

7.7.  "CDNI CI/T Error Codes" Registry

   In [RFC8007] the IANA was requested to create a new "CDNI CI/T Error
   Codes" registry under the "Content Delivery Network Interconnection
   (CDNI) Parameters" registry group.

   Additions to the "CDNI CI/T Error Codes" registry are made via the
   Specification Required policy as defined in [RFC8126].  The
   Designated Expert will verify that new Error Code registrations do
   not duplicate existing Error Code definitions (in name or
   functionality), prevent gratuitous additions to the namespace, and
   prevent any additions to the namespace that would impair the
   interoperability of CDNI implementations.

   In this second edition of the interface, the definitions of the Error
   Codes from [RFC8007] are without change.  Additionally, the IANA is
   requested to register three additional error codes, "espec",
   "esubject", and "eextension", with the specification as defined in
   Section 4.1.6.2.

7.8.  "CDNI CI/T URL Types" Registry

   The IANA is requested to create a new "CDNI CI/T URL types" registry
   in the "Content Delivery Networks Interconnection (CDNI) Parameters"
   registry group.  The "CDNI CI/T URL Types" namespace defines the
   valid URL type values in Section 4.4.1, used by Section 4.1.2.4,
   Section 4.1.2.6, Section 4.1.2.7, and Section 4.1.2.8.





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   The initial contents of the "CDNI CI/T Trigger Extensions" registry
   consist of the names and descriptions listed in Section 4.4.1, with
   this document serving as their specification.

8.  Security Considerations

   The CI/T interface provides a mechanism to allow the uCDN to generate
   requests into the dCDN and to inspect its own CI/T requests and their
   current states.  The CI/T interface does not allow access to, or
   modification of, the uCDN or the dCDN metadata relating to content
   delivery or to the content itself.  It can only control the presence
   of that metadata in the dCDN and the processing work and network
   utilization involved in ensuring that presence.

   By examining "preposition" requests to the dCDN, and correctly
   interpreting content and metadata URLs, an attacker could learn the
   uCDN's or content owner's predictions for future content popularity.
   By examining "invalidate" or "purge" requests, an attacker could
   learn about changes in the content owner's catalog.

   An attacker or misbehaving uCDN could inject CI/T triggers to
   generate processing workload in both the dCDN and uCDN.  Similarly, a
   man-in-the-middle attacker could modify valid trigger requests from
   the uCDN to achieve the same effect.  In both cases, that would
   decrease the dCDN's caching efficiency by causing it to unnecessarily
   acquire or reacquire content metadata and/or content.

   The dCDN implementation of CI/T MUST restrict the actions of the uCDN
   to the data corresponding to that uCDN.  Failure to do so would allow
   the uCDNs to detrimentally affect each other's efficiency by
   generating unnecessary acquisition or reacquisition load.

   An origin that chooses to delegate its delivery to a CDN is trusting
   that CDN to deliver content on its behalf; the interconnection of
   CDNs is an extension of that trust to the dCDNs.  That trust
   relationship is a commercial arrangement, outside the scope of the
   CDNI protocols.  So, while a malicious CDN could deliberately
   generate load on the dCDN using the CI/T interface, the protocol does
   not otherwise attempt to address malicious behavior between
   interconnected CDNs.

8.1.  Authentication, Authorization, Confidentiality, Integrity
      Protection

   A CI/T implementation MUST support Transport Layer Security (TLS)
   transport for HTTP (HTTPS) as per [RFC9110].





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   TLS MUST be used by the server side (dCDN) and the client side (uCDN)
   of the CI/T interface, including the authentication of the remote
   end, unless alternate methods are used to ensure the security of the
   information in the CI/T interface requests and responses (such as
   setting up an IPsec tunnel between the two CDNs or using a physically
   secured internal network between two CDNs that are owned by the same
   corporate entity).

   The use of TLS for transport of the CI/T interface allows the dCDN
   and the uCDN to authenticate each other using TLS client
   authentication and TLS server authentication.

   Once the dCDN and the uCDN have mutually authenticated each other,
   TLS allows:

   *  The dCDN and the uCDN to authorize each other (to ensure that they
      are receiving trigger requests from, or responding to, an
      authorized CDN).

   *  CDNI commands and responses to be transmitted with
      confidentiality.

   *  Protection of the integrity of CDNI commands and responses.

   When TLS is used, the general TLS usage guidance in [RFC9325] MUST be
   followed.

   The mechanisms for access control are dCDN-specific and are not
   standardized as part of this CI/T specification.

   HTTP requests that attempt to access or operate on CI/T data
   belonging to another CDN MUST be rejected using, for example, HTTP
   403 ("Forbidden") or 404 ("Not Found").  This is intended to prevent
   unauthorized users from generating unnecessary load in the dCDNs or
   the uCDNs due to revalidation, reacquisition, or unnecessary
   acquisition.

   When deploying a network of interconnected CDNs, the possible
   inefficiencies related to the diamond configuration discussed in
   Section 2.9 should be considered.











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8.2.  Denial of Service

   This document does not define a specific mechanism to protect against
   Denial-of-Service (DoS) attacks on the CI/T interface.  However, CI/T
   endpoints can be protected against DoS attacks through the use of TLS
   transport and/or via mechanisms outside the scope of the CI/T
   interface, such as firewalling or the use of Virtual Private Networks
   (VPNs).

   Depending on the implementation, triggered activity may consume
   significant processing and bandwidth in the dCDN.  A malicious or
   faulty uCDN could use this to generate unnecessary load in the dCDN.
   The dCDN should consider mechanisms to avoid overload -- for example,
   by rate-limiting acceptance or processing of triggers, or by
   performing batch processing.

8.3.  Privacy

   The CI/T protocol does not carry any information about individual end
   users of a CDN; there are no privacy concerns for end users.

   The CI/T protocol does carry information that could be considered
   commercially sensitive by CDN operators and content owners.  The use
   of mutually authenticated TLS to establish a secure session for the
   transport of CI/T data, as discussed in Section 8.1, provides
   confidentiality while the CI/T data is in transit and prevents
   parties other than the authorized dCDN from gaining access to that
   data.  The dCDN MUST ensure that it only exposes CI/T data related to
   the uCDN to clients it has authenticated as belonging to that uCDN.

9.  References

9.1.  Normative References

   [RFC1930]  Hawkinson, J. and T. Bates, "Guidelines for creation,
              selection, and registration of an Autonomous System (AS)",
              BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,
              <https://www.rfc-editor.org/info/rfc1930>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.




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   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC8006]  Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
              "Content Delivery Network Interconnection (CDNI)
              Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
              <https://www.rfc-editor.org/info/rfc8006>.

   [RFC8007]  Murray, R. and B. Niven-Jenkins, "Content Delivery Network
              Interconnection (CDNI) Control Interface / Triggers",
              RFC 8007, DOI 10.17487/RFC8007, December 2016,
              <https://www.rfc-editor.org/info/rfc8007>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/info/rfc9110>.

   [RFC9112]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP/1.1", STD 99, RFC 9112, DOI 10.17487/RFC9112,
              June 2022, <https://www.rfc-editor.org/info/rfc9112>.

   [RFC9325]  Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/info/rfc9325>.








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   [RFC9388]  Sopher, N. and S. Mishra, "Content Delivery Network
              Interconnection (CDNI) Footprint Types: Country
              Subdivision Code and Footprint Union", RFC 9388,
              DOI 10.17487/RFC9388, July 2023,
              <https://www.rfc-editor.org/info/rfc9388>.

   [RFC9562]  Davis, K., Peabody, B., and P. Leach, "Universally Unique
              IDentifiers (UUIDs)", RFC 9562, DOI 10.17487/RFC9562, May
              2024, <https://www.rfc-editor.org/info/rfc9562>.

9.2.  Informative References

   [ECMA404]  ECMA International, "ECMA-404 - The JSON data interchange
              syntax", Edition 2, December 2017, <https://ecma-
              international.org/publications-and-standards/standards/
              ecma-404/>.

   [MPEG-DASH]
              ISO, "Information technology -- Dynamic adaptive streaming
              over HTTP (DASH) -- Part 1: Media presentation description
              and segment format", ISO/IEC 23009-1:2014, Edition 2, May
              2014, <https://www.iso.org/standard/65274.html>.

   [MSS]      Microsoft, "[MS-SSTR]: Smooth Streaming Protocol",
              Protocol Revision 8.0, September 2017,
              <https://msdn.microsoft.com/en-us/library/ff469518.aspx>.

   [POSIX.1]  "The Open Group Base Specifications Issue 7", IEEE
              Std 1003.1 2018 Edition, 31 January 2018,
              <http://pubs.opengroup.org/onlinepubs/9699919799/>.

   [REST]     Fielding, R., "Architectural Styles and the Design of
              Network-based Software Architectures", Ph.D. Dissertation,
              University of California, Irvine , 2000.

   [RFC6707]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", RFC 6707, DOI 10.17487/RFC6707, September
              2012, <https://www.rfc-editor.org/info/rfc6707>.

   [RFC7336]  Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
              "Framework for Content Distribution Network
              Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
              August 2014, <https://www.rfc-editor.org/info/rfc7336>.







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   [RFC7337]  Leung, K., Ed. and Y. Lee, Ed., "Content Distribution
              Network Interconnection (CDNI) Requirements", RFC 7337,
              DOI 10.17487/RFC7337, August 2014,
              <https://www.rfc-editor.org/info/rfc7337>.

   [RFC7736]  Ma, K., "Content Delivery Network Interconnection (CDNI)
              Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
              December 2015, <https://www.rfc-editor.org/info/rfc7736>.

   [RFC7975]  Niven-Jenkins, B., Ed. and R. van Brandenburg, Ed.,
              "Request Routing Redirection Interface for Content
              Delivery Network (CDN) Interconnection", RFC 7975,
              DOI 10.17487/RFC7975, October 2016,
              <https://www.rfc-editor.org/info/rfc7975>.

   [RFC8216]  Pantos, R., Ed. and W. May, "HTTP Live Streaming",
              RFC 8216, DOI 10.17487/RFC8216, August 2017,
              <https://www.rfc-editor.org/info/rfc8216>.

Acknowledgments

   The authors thank Kevin Ma for his input, and Carsten Bormann for his
   review and formalization of the JSON data.

Authors' Addresses

   Nir B. Sopher
   Qwilt
   6, Ha'harash
   Hod HaSharon 4524079
   Israel
   Email: nir@apache.org


   Ori Finkelman
   Qwilt
   6, Ha'harash
   Hod HaSharon 4524079
   Israel
   Email: ori.finkelman.ietf@gmail.com


   Sanjay Mishra
   Verizon
   13100 Columbia Pike
   Silver Spring, MD 20904
   United States of America
   Email: sanjay.mishra@verizon.com



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   Jay K. Robertson
   Qwilt
   275 Shoreline Dr Ste 510
   Redwood City, CA 94065
   United States of America
   Email: jayrobertson@acm.org


   Alan Arolovitch
   Viasat
   1295 Beacon Street Unit 249
   Brookline, MA 02446
   United States of America
   Email: alan.arolovitch@gmail.com





































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