



Network Working Group                                        N.B. Sopher
Internet-Draft                                              O. Finkelman
Obsoletes: 8007 (if approved)                                      Qwilt
Intended status: Standards Track                               S. Mishra
Expires: 16 February 2026                                        Verizon
                                                          J.K. Robertson
                                                                   Qwilt
                                                           A. Arolovitch
                                                                  Viasat
                                                          15 August 2025


  Content Delivery Network Interconnection (CDNI) Control Interface /
                          Triggers 2nd Edition
               draft-ietf-cdni-ci-triggers-rfc8007bis-17

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 16 February 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 Collection  . . . . . . . . . . . . . . . . . . .   8
     2.6.  Session Overview  . . . . . . . . . . . . . . . . . . . .   9
     2.7.  Trigger Processing  . . . . . . . . . . . . . . . . . . .  10
       2.7.1.  Timing and Order  . . . . . . . . . . . . . . . . . .  10
       2.7.2.  Scope . . . . . . . . . . . . . . . . . . . . . . . .  11
       2.7.3.  Results . . . . . . . . . . . . . . . . . . . . . . .  11
     2.8.  Trigger Extensibility . . . . . . . . . . . . . . . . . .  11
     2.9.  Multiple Interconnected CDNs  . . . . . . . . . . . . . .  12
     2.10. Loop Detection and Prevention . . . . . . . . . . . . . .  13
   3.  CDNI Trigger Interface  . . . . . . . . . . . . . . . . . . .  14
     3.1.  Creating Triggers . . . . . . . . . . . . . . . . . . . .  15
     3.2.  Modifying Triggers  . . . . . . . . . . . . . . . . . . .  16
     3.3.  Cancelling Triggers . . . . . . . . . . . . . . . . . . .  17
     3.4.  Checking Status . . . . . . . . . . . . . . . . . . . . .  17
       3.4.1.  Polling Trigger Collections . . . . . . . . . . . . .  18
         3.4.1.1.  Extended view representation  . . . . . . . . . .  18
       3.4.2.  Polling Triggers  . . . . . . . . . . . . . . . . . .  19
     3.5.  Deleting Triggers . . . . . . . . . . . . . . . . . . . .  19
     3.6.  Expiry of Triggers  . . . . . . . . . . . . . . . . . . .  20
     3.7.  Error Handling  . . . . . . . . . . . . . . . . . . . . .  20
       3.7.1.  Error Propagation . . . . . . . . . . . . . . . . . .  21
   4.  CI/T Object Properties and Encoding . . . . . . . . . . . . .  24
     4.1.  Trigger Resource  . . . . . . . . . . . . . . . . . . . .  24
       4.1.1.  Trigger Action  . . . . . . . . . . . . . . . . . . .  28
       4.1.2.  Trigger Specs . . . . . . . . . . . . . . . . . . . .  28
         4.1.2.1.  Generic Spec Object . . . . . . . . . . . . . . .  30
         4.1.2.2.  Trigger Subject . . . . . . . . . . . . . . . . .  31
         4.1.2.3.  Spec Constraints  . . . . . . . . . . . . . . . .  32
         4.1.2.4.  URLs Spec . . . . . . . . . . . . . . . . . . . .  32
         4.1.2.5.  CCIDs Spec  . . . . . . . . . . . . . . . . . . .  33



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         4.1.2.6.  URI Pattern Match Spec  . . . . . . . . . . . . .  33
         4.1.2.7.  URI Regex Match Spec  . . . . . . . . . . . . . .  35
         4.1.2.8.  Object List Spec  . . . . . . . . . . . . . . . .  37
       4.1.3.  Trigger Extensions  . . . . . . . . . . . . . . . . .  37
         4.1.3.1.  Enforcement Options . . . . . . . . . . . . . . .  37
         4.1.3.2.  GenericExtensionObject  . . . . . . . . . . . . .  40
         4.1.3.3.  Trigger Extension Objects . . . . . . . . . . . .  42
       4.1.4.  Trigger Labels  . . . . . . . . . . . . . . . . . . .  49
       4.1.5.  Trigger State . . . . . . . . . . . . . . . . . . . .  50
       4.1.6.  Trigger Errors  . . . . . . . . . . . . . . . . . . .  51
         4.1.6.1.  Error.v2 Description  . . . . . . . . . . . . . .  51
         4.1.6.2.  Error Code  . . . . . . . . . . . . . . . . . . .  54
     4.2.  Trigger Collection Resource . . . . . . . . . . . . . . .  56
       4.2.1.  Filtered Representations  . . . . . . . . . . . . . .  58
     4.3.  Other CI/T Objects and Properties . . . . . . . . . . . .  59
       4.3.1.  URL Type  . . . . . . . . . . . . . . . . . . . . . .  59
       4.3.2.  ObjectList  . . . . . . . . . . . . . . . . . . . . .  60
         4.3.2.1.  ObjectList Type . . . . . . . . . . . . . . . . .  64
         4.3.2.2.  JSON Serialized Object List . . . . . . . . . . .  64
         4.3.2.3.  Text Object List  . . . . . . . . . . . . . . . .  65
         4.3.2.4.  ObjectEntry . . . . . . . . . . . . . . . . . . .  65
       4.3.3.  CDN Provider ID . . . . . . . . . . . . . . . . . . .  66
   5.  Footprint and Capabilities  . . . . . . . . . . . . . . . . .  66
     5.1.  CI/T Endpoint Capability Object . . . . . . . . . . . . .  66
       5.1.1.  CI/T Endpoints Capability Object Serialization  . . .  67
     5.2.  CI/T Trigger Scope Capability Object  . . . . . . . . . .  68
       5.2.1.  CI/T Trigger Scope Capability Object Serialization  .  70
     5.3.  CI/T Object List Type Capability Object . . . . . . . . .  70
       5.3.1.  CI/T Object List Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  71
     5.4.  CI/T Private URL Capability Object  . . . . . . . . . . .  71
       5.4.1.  CI/T Private URL Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  71
     5.5.  CI/T Extended Status Capability Object  . . . . . . . . .  72
       5.5.1.  CI/T Private URL Type Capability Object
               Serialization . . . . . . . . . . . . . . . . . . . .  72
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  73
     6.1.  Creating Triggers . . . . . . . . . . . . . . . . . . . .  73
       6.1.1.  Preposition . . . . . . . . . . . . . . . . . . . . .  73
       6.1.2.  Invalidate  . . . . . . . . . . . . . . . . . . . . .  75
       6.1.3.  Invalidation with Regex . . . . . . . . . . . . . . .  77
       6.1.4.  Preposition with ObjectLists  . . . . . . . . . . . .  79
     6.2.  Changing, Cancelling and Deleting Triggers  . . . . . . .  80
       6.2.1.  Modifying Triggers  . . . . . . . . . . . . . . . . .  80
       6.2.2.  Cancelling Triggers . . . . . . . . . . . . . . . . .  82
       6.2.3.  Deleting Triggers . . . . . . . . . . . . . . . . . .  84
     6.3.  Examining Trigger Status  . . . . . . . . . . . . . . . .  84
       6.3.1.  Collection of All Triggers  . . . . . . . . . . . . .  84



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       6.3.2.  Filtering of Trigger Collection . . . . . . . . . . .  86
       6.3.3.  Individual Trigger Resources  . . . . . . . . . . . .  88
       6.3.4.  Polling for Changes in Status . . . . . . . . . . . .  89
     6.4.  Extensions  . . . . . . . . . . . . . . . . . . . . . . .  92
       6.4.1.  Execution Policy Extension  . . . . . . . . . . . . .  92
       6.4.2.  Extensions with Error Propagation . . . . . . . . . .  96
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 100
     7.1.  CDNI Payload Type Parameter Registrations . . . . . . . . 100
       7.1.1.  CDNI ci-trigger.v2 Payload Type . . . . . . . . . . . 100
       7.1.2.  CDNI ci-trigger-collection.v2 Payload Type  . . . . . 101
       7.1.3.  CDNI FCI CI/T Payload Types . . . . . . . . . . . . . 101
         7.1.3.1.  CDNI FCI CI/T Endpoints Payload Type  . . . . . . 101
         7.1.3.2.  CDNI FCI CI/T Trigger Scope Payload Type  . . . . 101
         7.1.3.3.  CDNI FCI CI/T Object List Type Payload Type . . . 101
     7.2.  "CDNI CI/T Trigger Types" Registry For Trigger Actions  . 101
     7.3.  "CDNI CI/T Trigger Specs" Registry  . . . . . . . . . . . 102
     7.4.  "CDNI CI/T Trigger Subjects" Registry . . . . . . . . . . 102
     7.5.  "CDNI CI/T Object List Types" Registry  . . . . . . . . . 102
     7.6.  "CDNI CI/T Trigger Extensions" Registry . . . . . . . . . 103
     7.7.  "CDNI CI/T Error Codes" Registry  . . . . . . . . . . . . 103
     7.8.  "CDNI CI/T URL Types" Registry  . . . . . . . . . . . . . 104
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . 104
     8.1.  Authentication, Authorization, Confidentiality, Integrity
           Protection  . . . . . . . . . . . . . . . . . . . . . . . 105
     8.2.  Denial of Service . . . . . . . . . . . . . . . . . . . . 106
     8.3.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 106
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 106
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . 106
     9.2.  Informative References  . . . . . . . . . . . . . . . . . 108
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 109
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 109

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.

   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.



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   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 "ci-trigger.v2" object
      representing a trigger resource

   *  The "ci-trigger-collection" object is replaced with "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.

   *  Section 6 contains example messages.






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

   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 uCDN.  Each such trigger is
   identified by a unique Uniform Resource Identifier (URI) is defined
   in Section 4.2 of [RFC9110].

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

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





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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 was used instead.  The HEAD method can
      be used to verify that the target resource exists on the server.

2.3.  Trigger

   To request that an action be carried out by dCDN, uCDN requests to
   create a trigger resource.  If dCDN accepts the request, it creates a
   new trigger resource and returns its unique URI to uCDN.  uCDN MUST
   use this URI for all requests associated with the created trigger
   resource.

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

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

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

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

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




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

   The trigger resource has a "state" attribute.  dCDN creates new
   triggers in the "pending" state.  Once dCDN starts processing a
   trigger, the trigger state is set to "active".  Once the trigger
   processing is complete, the state is set to either "complete" or
   "failed", depending on the processing outcome.

   uCDN MAY request dCDN to cancel a trigger.  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

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

   dCDN MUST be able to associate content objects referenced in a
   trigger created by uCDN with the 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].

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

   Furthermore, dCDN SHOULD reject trigger from uCDN A that seeks to
   preposition the delivery metadata objects, that are in conflict with
   the pre-existing metadata objects belonging to another uCDN B.

2.5.  Trigger Collection

   A trigger collection is a resource that represents all trigger
   resources, belonging to a particular uCDN.  dCDN maintains one
   trigger collection resource for each uCDN.  Each uCDN only has access
   to its own collection resource.  dCDN supports retrieval of multiple
   representations of the trigger collection resource.  The supported
   trigger collection representations are listed in Section 4.2 and
   include filtering of triggers by state and label.  Note that
   additional trigger collection representations can be defined in the
   future.






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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 dCDN and
   for 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 utilies unique UUID identifiers as
   specified in [RFC9562].  Examples of the messages are shown in
   Section 6.

      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.  uCDN requests to create a new trigger resource by POSTing its
       representation to the trigger collection resource with a well-
       known URI "https://dcdn.example/cit/uCDN".

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



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

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

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

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

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

2.7.  Trigger Processing

2.7.1.  Timing and Order

   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 dCDN's control, including the start
   time, pacing of the activity in the network, and order in which dCDN
   chooses to process pending triggers.

   The CI/T "invalidate" and "purge" trigger actions MUST be applied to
   all data acquired before dCDN begins the trigger processing (i.e.,
   enters "active" state).  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.  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 uCDN cannot count on that.

   If uCDN wishes to invalidate or purge content and then immediately
   preposition replacement content at the same URLs, it SHOULD ensure
   that 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



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   it (as a result of the two uCDN requests running in parallel).  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).

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.  The reasons
   for failure, and URLs or patterns affected, SHOULD be made available
   in the trigger state representation.  For more details, 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
   dCDNs located further downstream.

   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
   heve originated.

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

   The "diamond" configuration may create configuration consistency
   problems, where dCDN may end up in posession of multiple, potentially
   conflicting metadata obhects belonging to 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 path in the
   "diamond" topology.

   Because of that the "diamond" configuration is considered to be a
   configuration error.  A dCDN that receives identical trigger creation
   requests from multiple 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 dCDN is also acting as 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 dCDNs in a cascade.


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 4.3.3)
   to detect and prevent loops as follows:

   *  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
      dCDN's PID is already present and dCDN is not the CDN initiating
      the trigger, this condition likely indicates a loop.  In such
      case, dCDN MUST reject the trigger, which would result in a
      trigger rejection being returned to the originating uCDN.  If dCDN
      receives a trigger that it itself originated, 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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   *  dCDNs SHOULD advertise their CDN provider ID to uCDNs using the
      "cdn-id" attribute of the trigger collection (Section 4.2)
      resource.

3.  CDNI Trigger Interface

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

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

   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, 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 uCDN and by dCDN.

   The CI/T interface uses a root URI for the retrieval of the trigger
   collection 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.

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

   Once created, the new trigger URI also becomes available via the
   trigger collection resource described in Section 4.2.  Additionally,
   uCDN may discover the URIs of multiple trigger collection
   representations by retrieving the trigger collection 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 uCDN, so dCDNs are free to assign whatever structure
   they desire to the URIs for CI/T resources.  Therefore, uCDNs MUST
   NOT make any assumptions regarding the structure of CI/T URIs or the
   mapping between CI/T objects and their associated URIs.  The URIs



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

   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.

   dCDN validates the trigger resource representation sent by uCDN.  If
   the representation is malformed or uCDN does not have sufficient
   access rights, 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 dCDN processed the trigger immediately.

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

   dCDN SHOULD provide continuous updates of the trigger processing
   progress by responding with updated trigger resource representations
   to 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, dCDN SHOULD also provide an
   estimated completion time for the request by using the trigger
   "etime" property.






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   Otherwise, 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 uCDN, subject to the constraints described below.

3.2.  Modifying Triggers

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

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

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

   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 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.  uCDN MAY request to set the trigger state to
   "active" to prompt dCDN to re-examine the trigger resource and start
   its processing immediately.

   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 dCDN or an appropriate 4xx HTTP
   error code in case of a malformed request.

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



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3.3.  Cancelling Triggers

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

   dCDN MUST respond to the trigger cancellation request appropriately.
   dCDN MUST respond with the HTTP status code 200 ("OK") if the trigger
   processing has been cancelled and the trigger state has been set to
   "cancelled", 202 ("Accepted") if the command has been accepted but
   the trigger processing has not been cancelled yet, 404 ("Not Found")
   when the trigger resource does not exist, or 501 ("Not Implemented")
   if cancellation is not supported by dCDN.

   If cancellation of a "pending" trigger is accepted by dCDN, 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 uCDN cannot
   control the timing of that activity.  Processing could, for example,
   start after the POST is sent by uCDN but before that request is
   processed by dCDN.

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

   If uCDN cannot stop the trigger processing immediately after
   receiving the request from 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 dCDN.  Its state MUST NOT be changed.

3.4.  Checking Status

   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 allow uCDN to use client-side caching of all triggers and trigger
   collections, each resource representation sent by dCDN SHOULD include
   at least one of the following 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



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   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.

   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 uCDN and/or intermediate proxies should poll for
   change.  If provided, uCDN should match the frequency of polling to
   the cache control information provided by dCDN.

3.4.1.  Polling Trigger Collections

   uCDN MAY fetch the trigger collection or one of the filtered
   representations of it.  This makes it possible for uCDN to poll the
   status of all trigger resources or selected trigger subsets, filtered
   by trigger state or by trigger label.  In this way, uCDN can monitor
   trigger state changes by polling the representation of the trigger
   collection filtered by trigger state.

3.4.1.1.  Extended view representation

   If dCDN advertises support for extended status, 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 filtered representations
   of the trigger collection, so it is possible to retrieve all trigger
   resource representations for a specific trigger state (e.g., all
   triggers in a "pending" state).

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

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











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3.4.2.  Polling Triggers

   uCDN has a URI provided by dCDN at the trigger creation time.
   Alternatively, uCDN MAY discover trigger resource URI by retrieving
   the trigger collection resource and/or one of its filtered
   representations.  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

   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
   representations of the trigger collection.  Subsequent requests to
   the trigger resource URI MUST be rejected by 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, uCDN SHOULD cancel triggers rather than delete them
   when uCDN needs to access the trigger status after the trigger
   processing is stopped.

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

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

   Deletion of a "complete", "cancelled" or "failed" trigger no
   processing in dCDN.

   dCDN MUST respond to the trigger deletion request appropriately.
   dCDN MUST respond with the HTTP 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
   been deleted yet.  404 ("Not Found") when the trigger resource does
   not exist, or 501 ("Not Implemented") if deletion is not supported by
   dCDN.



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

3.6.  Expiry of Triggers

   dCDN MAY automatically delete trigger resources sometime after they
   reach a terminal state (one of "complete", "processed", "failed", or
   "cancelled").  In this case, after 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 the trigger collection resource.

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

   It is RECOMMENDED that dCDN sets its staleresourcetime to at least 24
   hours.  It is further RECOMMENDED that 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
   dCDN.

3.7.  Error Handling

   dCDN MAY reject CI/T interface requests by responding with 4xx or 5xx
   HTTP status codes.  For example, 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 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 dCDN
   is unable to pass a trigger on to any of its cascaded dCDNs:

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

3.7.1.  Error Propagation

   This subsection explains the mechanism for enabling uCDN to trace an
   error back to 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 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 the downstream 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 dCDN-C PID,
   indicating to which CDN the error specifically relates.  The trigger
   originating upstream CDN then receives an array built of the errors
   that occurred in all the CDNs along the execution path, where each
   error MAY carry 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.  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.

   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 PID by adding
        it to the errors array in dCDN-B's status resource to be sent
        back to the originating uCDN-A.




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4.  CI/T Object Properties and Encoding

   Trigger, trigger collection and their properties are encoded using
   JSON, as defined in Section 4.1, and Section 4.2, respectively.  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 uCDN or dCDN.  They SHOULD be ignored during
   processing and passed on by 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 dCDN MUST include all existing trigger attributes in the trigger
   resource representation when requested by 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: It is optional for trigger updates, otherwise
         mandatory.

      Name: specs
         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: 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.



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

         Mandatory: 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: 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 4.3.3.

         Mandatory: 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 dCDN; there is
         no requirement to synchronize clocks between interconnected
         CDNs.

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

         Mandatory: dCDN MUST specify in trigger status representations.
         It is ignored when included in trigger representations sent by
         uCDN.

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

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

         Mandatory: dCDN MUST specify in trigger status representations.
         It is ignored when included in trigger representations sent by
         uCDN.



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

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

         Mandatory: dCDN MAY specify in trigger status representations.
         It is ignored when included in trigger representations sent by
         uCDN.

      Name: state
         Description: The current trigger state.

         Value: Trigger state, as defined in Section 4.1.5.

         Mandatory: 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 uCDN.

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

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

         Mandatory: No. 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.

         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 "errors" from the object.

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

      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 dCDN maintains this attribute as a cumulative
         counter across all of its nodes, without de-duplicating the



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         same objects processed in multiple nodes.  The primary purpose
         of this attribute is to help uCDN identify abnormal trigger
         processing results, e.g., a purge or preposition trigger that
         impacted a lower number of objects than expected.  dCDN MAY
         provide an updated object count as the trigger processing
         progresses in an "active" trigger state.

         Value: Integer.

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

      Name: total-objects-size
         Description: Total aggregate size of objects affected by the
         trigger, in bytes.  It is RECOMMENDED that dCDN maintains this
         attribute as a cumulative counter across all of its nodes,
         without de-duplicating the same objects processed in multiple
         nodes.  As with "total-objects-count" attribute above, the
         primary purpose of this attribute is to help uCDN identify
         abnormal trigger processing results.  dCDN MAY provide an
         updated object size as the trigger processing progresses in
         "active" trigger state.

         Value: Integer.

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

      Name: objects
         Description: List of objects derived by dCDN when processing
         the trigger.

         Value: An array of ObjectList (Section 4.3.2) objects.  dCDN
         SHOULD provide the list of objects it used as input for
         processing the trigger with Section 4.1.2.8, provided that 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: No. dCDN MAY send this attribute in its trigger
         resource representation when available and the capability is
         advertised via FCI as described above.




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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).

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

                                 Table 2

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 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



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   interface.

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

   dCDN receiving a trigger creation request containing a trigger spec
   that it does not recognize or does not support MUST reject the
   request by creating a trigger resource with "failed" state and the
   "errors" array containing an Error.v2 Description with 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

   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 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
         generic-trigger-spec-value property, such as "content" or
         "metadata" as defined in Section 4.1.2.2.

         Mandatory: Yes.

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

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

         Mandatory: Yes.

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

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

         Mandatory: Yes.





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

   {
     "generic-trigger-spec-type":
        <Type of this trigger spec>,
     "generic-trigger-spec-value":
         {
           <properties of this trigger spec object>
         },
      "generic-trigger-spec-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).

   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






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4.1.2.3.  Spec Constraints

   There are certain constraints in 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 uCDN to manage uCDN content or metadata
   objects held by dCDN based on the objects' URLs.

   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 represented as JSON strings.

         Mandatory: Yes.

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

         Value: URL Type as defined in Section 4.3.1.





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

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

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

4.1.2.5.  CCIDs Spec

   The "ccids" spec type allows 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: Yes.

4.1.2.6.  URI Pattern Match Spec

   The "uri-pattern-match" spec type allows uCDN to manage uCDN content
   or metadata objects held by 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.





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

      Name: pattern
         Description: A pattern for URI matching.

         Value: A JSON string representing the pattern.  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: Yes.

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

         Value: One of the JSON values "true" (the matching is case
         sensitive) or "false" (the matching is case insensitive).

         Mandatory: 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: 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 4.3.1.

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





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

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

4.1.2.7.  URI Regex Match Spec

   The "uri-regex-match" spec type allows uCDN to manage content or
   metadata objects held by 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: 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: 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: 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 4.3.1.

         Mandatory: 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,
     "match-query-string": false
   }

   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 uCDN to manage content or metadata
   held by 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 4.3.2) objects

         Mandatory: 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 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 dCDN
   when not specified by 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 dCDN does not understand or support a mandatory-to-
   enforce property, 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 needs 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 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 trigger extension that requires translation,
   transparent redistribution of uCDN trigger values might not be
   appropriate.  Certain trigger extensions can be safely, though
   perhaps not optimally, redistributed unmodified.  For example,
   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 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 uCDN.

   tCDNs MUST NOT change the value of mandatory-to-enforce or safe-to-
   redistribute when propagating a trigger to 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 dCDN for the different
   combinations of mandatory-to-enforce and "incomprehensible"
   ("Incomp") properties, when 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    |                          |
     |       |        | 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 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: generic-trigger-extension-type
         Description: Case-insensitive CDNI trigger extension object
         type.

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

         Mandatory: Yes.



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

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

         Mandatory: Yes.

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

         Value: Boolean.

         Mandatory: 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: 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: 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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   {
     "generic-trigger-extension-type":
        <Type of this trigger extension object>,
     "generic-trigger-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 generic-trigger-extension-value
   field as defined in Section 4.1.3.2, and their generic-trigger-
   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 which CDN or cache locations for
   which the trigger command is relevant.

   Example use cases:

   *  Preposition: Certain contracts allow for prepositioning or
      availability of contracts in all regions except for certain
      excluded regions in the world, including caches.  For example,
      some content cannot ever knowingly touch servers in a specific
      country, including cached content.  Therefore, these regions MUST
      be excluded from a prepositioning operation.

   *  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:




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      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]).

         Mandatory: Yes.

      Name: url-type
         Description: Type of URL used in the ObjectList(s).

         Value: URL Type as defined in Section 4.3.1.

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

   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 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.  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 specific cache location, then 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 Canada:


















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   {
     "generic-trigger-extension-type": "location-policy",
     "generic-trigger-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,
     "incomprehensible": false
   }

4.1.3.3.2.  TimePolicy Extension

   uCDN may wish to perform content management operations on dCDN on a
   specific schedule.  The TimePolicy extension allows uCDN to instruct
   dCDN to execute the trigger command in a desired time window.  For
   example, a content provider may wish to pre-populate a new episode at
   off-peak time so that it would be ready on caches at prime time when
   the episode is released for viewing.  A scheduled operation enables
   uCDN to direct 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. uCDN can trigger separate commands for different
   geographical regions using a different schedule for each region.
   This allows 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.





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

         Mandatory: 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: 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 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:

   {
      "generic-trigger-extension-type": "time-policy",
      "generic-trigger-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



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         Description: The start time of the window.

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

         Mandatory: No. but at least one of either "start" or "end" MUST
         be present and non-empty.

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

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

         Mandatory: No. but at least one of either "start" or "end" MUST
         be present and non-empty.

   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, 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. uCDN may
   wish to control trigger processing in more detail, including the
   order of execution, dependencies, and concurrency.

   Example use cases:

   *  Priority: 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.  uCDN may
      wish to prescribe the order in which dCDN picks up its trigger



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      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.
      dCDN may separately prioritize triggers from multiple uCDNs
      subject to its business logic.  Multiple priority-related use
      cases exist:

      -  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

      -  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, uCDN may wish to indicate what
      trigger commands should be processed and completed before another
      trigger command is processed.  For example, uCDN may want to
      rectify incorrectly published content by purging content objects
      and then prepositioning them again.  In this case, 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, 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

   *  Urgency: uCDN may wish to indicate that dCDN should process a
      trigger command without delay.  This requirement is separate and
      additional to priority, as priority indicates the order in which
      triggers should be processed, yet does not prescribe how soon each
      trigger should be executed.  dCDN MAY reject such requests for
      urgent processing using "ereject" error code.  This can happen due
      to dCDN's internal business logic (e.g., batch-driven purge and
      invalidation), or due to dependencies on other triggers that could
      not be completed by dCDN immediately.  In such a case uCDN should
      either modify the request by removing prerequisites or cancel such
      pending triggers before re-trying the request.



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   uCDN may combine multiple options in the same trigger command. dCDN
   should consider the following when processing such commands:

   *  dCDN MUST reject triggers that are dependent on other pending
      triggers with lower priority to prevent deadlocks.

   *  When introducing an urgent trigger uCDN SHOULD indicate a priority
      that is equal to or higher than the highest priority among the
      pending triggers that belong to the same uCDN. dCDN MUST reject
      urgent triggers that have lower priority than other pending
      triggers of the same uCDN.

   *  dCDN MUST reject an urgent trigger that has pending triggers as
      its prerequisite. dCDN MAY reject an urgent trigger that has
      triggers in an "active" or "cancelling" state as its prerequisite,
      such as when such triggers are deemed to take a long time to
      complete or cancel.

   When combining ExtensionPolicy with Section 4.1.3.3.2, TimePolicy
   governs the time window when the trigger can execute, while
   ExecutionPolicy controls the order of trigger execution within their
   respective windows.  The following error conditions should be
   considered by dCDN:

   *  When a trigger is marked urgent, but its TimePolicy extension
      doesn't allow immediate processing, it should be rejected by dCDN.

   *  When a trigger has a TimePolicy extension and is also dependent on
      another trigger with a TimePolicy extension, that specifies an
      execution window (directly or via a chain of dependency) that
      doesn't start until after the depending trigger's execution window
      ends, such a trigger should be rejected.

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

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

         Value: Integer from -100 to 100.

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

      Name: depends




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

      Name: urgent
         Description: Indicates whether the trigger should be
         immediately moved to the "active" state upon acceptance.  In
         the absence of this flag, dCDN is at liberty to choose the time
         for trigger execution, e.g., batch processing.

         Value: Boolean.

         Mandatory: No.  The default is to handle the trigger as not
         urgent.

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

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

4.1.4.  Trigger Labels

   Trigger labels provide a framework for 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 label-based filtering of the trigger collection resource (see
   Section 4.2 for more details).  In this case the label values remain
   fully opaque to dCDN and serve for trigger grouping purposes only.

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

                                  Table 8

   Along with the trigger state, the trigger resource has a state reason
   property, allowing dCDN to provide additional information for the
   trigger state.  For example, dCDN may indicate that the trigger state



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   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: Yes.

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

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

         Mandatory: 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: 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: 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 4.3.3

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

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

         Value: An array of ObjectList (Section 4.3.2) objects. dCDN
         SHOULD provide the list of objects that it failed to process
         during trigger execution with Section 4.1.2.8, provided that
         dCDN advertised support for extended status (Section 5.5).

         Mandatory: 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 object list :




















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   {
     "error": "econtent",
     "description": "Failed to parse HLS object list",
     "specs": [{
       "trigger-subject": "content",
       "generic-trigger-spec-type": "content-objectlist",
       "generic-trigger-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",
         "generic-trigger-spec-type": "urls",
         "generic-trigger-spec-value": {
           "urls": [
             "https://www.example.com/a/b/c/1",
             "https://www.example.com/a/b/c/2"
           ]
         }
       }],
       "extensions": [{
         "generic-trigger-extension-type": "location-policy",
         "generic-trigger-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 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.

     +==============+================================+==============+
     | Error Code   | Description                    | Registration |
     +==============+================================+==============+
     | emeta        | dCDN was unable to acquire     | RFCthis      |
     |              | and/or does not have metadata  |              |
     |              | required to fulfill the        |              |
     |              | request.                       |              |



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




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                                 Table 9

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

4.2.  Trigger Collection Resource

   As described in Section 2.1, dCDN maintains RESTful trigger resources
   that represent an action ("trigger") uCDN requests dCDN to carry out.

   A collection of trigger resources represents all triggers created by
   the dCDN at the request of a uCDN, and is by itself a RESTful
   resource.  dCDN MUST make the trigger collection resource available
   to each uCDN, and MUST maintain it, adding and removing triggers from
   the collection as the triggers are created (Section 3.1) by uCDN and
   are either deleted (Section 3.5) by uCDN or expire (Section 3.6).
   When dCDN first instantiates the CI/T interface for a uCDN, the
   trigger collection resource is empty.

   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 request the creation of a new trigger resource, uCDN POSTs the new
   trigger representation to the trigger collection resource.

   To allow uCDN to check the status of multiple triggers in a single
   request, 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, dCDN MUST include links
   to them in the trigger collection resource.

   dCDN MAY provide filtered representations of the trigger collection
   per trigger state (Section 4.1.5).  If implemented, dCDN SHOULD
   provide a separate filtered collection representation for every
   trigger state, and advertise these representations in the trigger
   collection.

   dCDN MAY further provide filtered collection representations per
   trigger label, as specified by uCDN when creating a trigger resource
   (Section 4.1).  If implemented, dCDN SHOULD provide a separate
   filtered collection representation for every unique trigger label in



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   use by the uCDN, and advertise these representations in the
   collection of all trigger resources.  dCDN MUST update the filtered
   label representations as trigger labels are added or removed by uCDN.

   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: triggers
         Description: Links to triggers in the collection.

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

         Mandatory: Yes.

      Name: staleresourcetime
         Description: The length of time for which dCDN guarantees to
         keep a completed trigger resource.  After this time, 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: Yes, in the collection of all triggers if dCDN
         deletes stale entries.  If the property is present in the
         filtered collection representation, it MUST have the same value
         as in the collection of all triggers.

      Name: coll-state
         Description: Array of Section 4.2.1 objects.

         Value: An array of JSON-encoded filtered collection
         representation objects, with one entry for each trigger state,
         as specified in Section 4.1.5.

         Mandatory: Mandatory in the trigger collection resources, if
         dCDN implements the per-state filtered representations of the
         triggers collection.  Otherwise, optional.

      Name: coll-label
         Description: Array of Section 4.2.1 objects.






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         Value: An array of JSON-encoded filtered collection
         representation objects, with one entry for each unique label
         key-value, as specified by uCDN, using the "labels" attribute
         of a trigger resource (see Section 4.1 for details).

         Mandatory: Mandatory in the trigger collection resources, if
         dCDN implements the per-label filtered representations of the
         triggers collection.  Otherwise, optional.

      Name: all-triggers
         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 triggers.

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

      Name: cdn-id
         Description: The CDN PID of dCDN.

         Value: A JSON string, dCDN's CDN PID, as defined in
         Section 4.3.3.

         Mandatory: No.

4.2.1.  Filtered Representations

   The filtered representation object describes a particular filtered
   representation of triggers.  Currently, it supports filtering by
   trigger state and trigger label.  In the future, further filtering
   capabilities may be added.  It is encoded as a JSON object containing
   the following name/value pairs:

      Name: state
         Description: Trigger state matching the filtered collection
         representation.

         Value: A trigger state, as defined in Section 4.1.5.

         Mandatory: One of the "state" or "label" should be present.

      Name: label
         Description: Trigger label matching the filtered collection.

         Value: A trigger label, as defined in Section 4.1.



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         Mandatory: One of the "state" or "label" should be present.

      Name: uri
         Description: URI of the filtered collection representation
         matching the filtering parameters.

         Value: A URI represented as a JSON string.

         Mandatory: Yes.

4.3.  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.

4.3.1.  URL Type

   This type is used by 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 for uCDN to use in triggers is published URLs, which are
   used by end users.  When using this URL type, uCDN MUST provide
   configuration metadata objects related to these URLs before creating
   a trigger option referencing these URLs.  When this is not the case,
   dCDN MUST return the error code "emeta".

   When processing published URLs in "preposition" trigger action, 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, which 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, uCDN may prefer to use such private URLs in "purge" or
   "invalidate" trigger actions to simplify processing.

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



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

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

                                  Table 10

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

4.3.2.  ObjectList

   ObjectList is a metadata object describing lists of objects that can
   be used in the context of CI/T v2 trigger spec, trigger status
   resources, and 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.

   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 the parent ObjectList.

   In the case of uCDN accessing ObjectList objects referencing external
   URLs published by dCDN, both parties SHOULD comply with the CI/T
   interface security requirements (see Section 8.1 for details).  When
   dCDN accesses external URLs referenced by ObjectLists supplied by
   uCDN, for example as part of trigger spec, dCDN MUST match these URLs
   with source metadata objects, published by 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.






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   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
   uCDN accesses ObjectList metadata resources published by uCDN, the
   same interface authentication and authorization requirements would
   apply, as when accessing the interface itself.

   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"
     }
   ]

   The ObjectList properties are as follows:

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

         Value: JSON String.

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

      Name: type
         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 an object that does not require
         additional processing.

         Value: ObjectListType (see Section 4.3.2).

         Mandatory: Yes.



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4.3.2.1.  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

       +========+==================+===============+===============+
       | JSON   | Description      | Specification | Protocol      |
       | string |                  |               | Specification |
       +========+==================+===============+===============+
       | hls    | HTTP Live        | RFCthis       | RFC 8216      |
       |        | Streaming        |               | [RFC8216]     |
       +--------+------------------+---------------+---------------+
       | mss    | Microsoft Smooth | RFCthis       | MSS [MSS]     |
       |        | Streaming        |               |               |
       +--------+------------------+---------------+---------------+
       | dash   | Dynamic Adaptive | RFCthis       | MPEG-DASH     |
       |        | Streaming over   |               | [MPEG-DASH]   |
       |        | HTTP (MPEG-DASH) |               |               |
       +--------+------------------+---------------+---------------+
       | json   | JSON-serialized  | RFCthis       | JSON (Section |
       |        | object list      |               | 4.3.2.2)      |
       +--------+------------------+---------------+---------------+
       | text   | Object list in   | RFCthis       | Text (Section |
       |        | text format      |               | 4.3.2.3)      |
       +--------+------------------+---------------+---------------+

                                  Table 11

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

4.3.2.2.  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 4.3.2.4) object.  The entries in the JSON object list MAY
   have an object list type specified, allowing for a recursive object
   list structure.









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4.3.2.3.  Text Object List

   Unlike the JSON Serialized Object List (Section 4.3.2.2), 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.

4.3.2.4.  ObjectEntry

   ObjectEntry is a metadata object describing an object and its
   associated metadata, to be used in JSON-encoded ObjectList
   (Section 4.3.2) objects.

   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
     }
   ]

   The ObjectEntry properties are as follows:

      Name: href
         Description: Object URL

         Value: A URL represented as a JSON string.

         Mandatory: 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.




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         Value: ObjectListType (see Section 4.3.2.1).

         Mandatory: No.

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

         Value: Integer.

         Mandatory: No.

4.3.3.  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 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




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         Value: A URL represented as a JSON string.

         Mandatory: Yes.

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

         Value: An array of JSON strings.

         Mandatory: Yes.

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

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

         Mandatory: No.  A missing or empty "trigger-subject" list means
         that all trigger subjects are supported by the endpoint.  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),
         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 shows an example of the CI/T Endpoints Capability
   object serialization for dCDN that supports versions 2 and 2.1 of the
   CI/T interface.

















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   {
     "capabilities": [
       {
         "capability-type": "FCI.CITEndpoints",
         "capability-value": {
           "trigger-endpoint-uri":
             "https://dcdn.example/configuration/",
           "trigger-versions": [ "1" ],
           "trigger-subjects": "metadata"
         },
         "footprints": {
           "footprint-type": "countrycode",
           "footprint-value": [ "us" ]
         }
       },
       {
         "capability-type": "FCI.CITEndpoints",
         "capability-value": {
           "trigger-endpoint-uri":
             "https://dcdn.example/cache-management/",
           "trigger-versions": [ "2", "2.1" ],
           "trigger-subjects": "content"
         },
         "footprints": {
           "footprint-type": "countrycode",
           "footprint-value": [ "us" ]
         }
       }
     ]
   }

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 the
   triggers are applied on, along with the supported trigger generic
   extension types.

   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.



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         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: 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: Yes.

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

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

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










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5.2.1.  CI/T Trigger Scope Capability Object Serialization

   The following shows an example of a JSON-serialized CI/T Trigger
   Scope Capability object serialization for 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.

   {
     "capabilities": [{
       "capability-type": "FCI.CITScope",
       "capability-value": {
         "trigger-scope-capabilities": [
           {
             "trigger-action": "preposition",
             "trigger-subject": "content",
             "trigger-specs": [ "urls", "ccids" ],
             "trigger-extensions": [ "time-policy" ]
           },
           {
             "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 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 Section 4.3.2.1.

         Mandatory: No.  In case of 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 dCDN that supports "hls" and
   "dash".

   {
     "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 4.3.1 for details).  The
   capability type is "FCI.CITPrivateUrlType".

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

         Value: Boolean.

         Mandatory: No.  In case of 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 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 uCDN request and includes:

   *  "objects" attribute in the trigger object

   *  "objects" attribute in Error.v2 description object

   *  "all-triggers" 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: 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 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.  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
   CDN PID of uCDN is "AS64496:1".

6.1.  Creating Triggers

6.1.1.  Preposition

   Below is an example of a "preposition" trigger creation.  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 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",
       "generic-trigger-spec-type": "urls",
       "generic-trigger-spec-value": {
       "urls": [ "https://metadata.example.com/a/b/c" ]
            }
     },
     {
       "trigger-subject": "content",
       "generic-trigger-spec-type": "urls",
       "generic-trigger-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",
       "generic-trigger-spec-type": "urls",
       "generic-trigger-spec-value": {
         "urls": [ "https://metadata.example.com/a/b/c" ]
       }
     },
     {
       "trigger-subject": "content",
       "generic-trigger-spec-type": "urls",
       "generic-trigger-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",
         "generic-trigger-spec-type": "uri-pattern-match",
         "generic-trigger-spec-value": {
            "pattern": "https://metadata.example.com/a/b/*"
         }
      },
      {
         "trigger-subject": "content",
         "generic-trigger-spec-type": "urls",
         "generic-trigger-spec-value": {
            "urls": [
               "https://www.example.com/a/index.html"
            ]
         }
      },
      {
         "trigger-subject": "content",
         "generic-trigger-spec-type": "uri-pattern-match",
         "generic-trigger-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",
       "generic-trigger-spec-type": "uri-pattern-match",
       "generic-trigger-spec-value": {
         "pattern": "https://metadata.example.com/a/b/*"
       }
     },
     {
       "trigger-subject": "content",
       "generic-trigger-spec-type": "urls",
       "generic-trigger-spec-value": {
         "urls": [ "https://www.example.com/a/index.html" ]
       }
     },
     {
       "trigger-subject": "content",
       "generic-trigger-spec-type": "uri-pattern-match",
       "generic-trigger-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 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",
     "generic-trigger-spec-type": "uri-regex-match",
     "generic-trigger-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",
       "generic-trigger-spec-type": "uri-regex-match",
       "generic-trigger-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": "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",
     "generic-trigger-spec-type": "uri-regex-match",
     "generic-trigger-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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-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",
       "generic-trigger-spec-type": "content-objectlist",
       "generic-trigger-spec-value": {
         "objects": [{
           "href": "https://www.example.com/hls/title/index.m3u8",
           "type": "hls"
         }}
     }],
     "description": "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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-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

   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, uCDN updates a trigger
   created earlier by removing the metadata portion of the trigger spec
   and adding trigger labels. 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",
         "generic-trigger-spec-type": "urls",
         "generic-trigger-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",
         "generic-trigger-spec-type": "urls",



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         "generic-trigger-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

   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, 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",
         "generic-trigger-spec-type": "urls",
         "generic-trigger-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

   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, uCDN can check their status as shown
   in the following examples.

6.3.1.  Collection of All Triggers

   uCDN can fetch the collection of all triggers it has created that
   have not yet been deleted or expired.  After the trigger operations
   described in Section 6.1 and Section 6.2 above, this collection might
   look as follows:

   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



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   Cache-Control: max-age=60
   Date: Sun, 27 Oct 2024 08:48:18 GMT
   Content-Type: application/cdni; ptype=ci-trigger-collection.v2

   {
     "cdn-id": "AS64496:0",
     "coll-state": [
       {
         "state": "pending",
         "uri": "/cit/state/pending"
       },
       {
         "state": "active",
         "uri": "/cit/state/active"
       },
       {
         "state": "complete",
         "uri": "/cit/state/complete"
       },
       {
         "state": "processed",
         "uri": "/cit/state/processed"
       },
       {
         "state": "failed",
         "uri": "/cit/state/failed"
       },
       {
         "state": "cancelling",
         "uri": "/cit/state/cancelling"
       },
       {
         "state": "cancelled",
         "uri": "/cit/state/cancelled"
       }
     ],
     "coll-label": [
       {
         "label": "type=video",
         "uri": "/cit/labels/type=video"
       }
     ],
     "staleresourcetime": 86400,
     "triggers": [
       "https://dcdn.example/cit/327df5b8-1df8-4cff-92f8-fda27774c171",
       "https://dcdn.example/cit/991b9fb9-d0be-4d05-be06-64c0e5c5a5f9",
       "https://dcdn.example/cit/86633e6e-d2da-4185-a285-b3d087a5d711"
     ]



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   }

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

   At this point, if no other triggers had been created, the filtered
   collection for failed triggers would hold the two failed triggers
   shown above while other filtered representations 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

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




























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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

   {
     "staleresourcetime": 86400,
     "triggers": [
       "https://dcdn.example/cit/991b9fb9-d0be-4d05-be06-64c0e5c5a5f9"
       "https://dcdn.example/cit/86633e6e-d2da-4185-a285-b3d087a5d711"
     ]
   }


6.3.3.  Individual Trigger Resources

   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



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   Date: Sun, 27 Oct 2024 08:48:22 GMT
   Content-Type: application/cdni; ptype=ci-trigger.v2

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

6.3.4.  Polling for Changes in Status

   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.  dCDN SHOULD also update the "ETag" and/
   or "Last-Modified" response headers - whichever was previously sent -
   when delivering the updated collection representations.  dCDN SHOULD
   also use cache control headers, like "Expires" and "Cache-Control",
   to indicate how caching of the resource representation should happen
   by 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.  uCDN can create a dependency between triggers.  For
   example, a preposition trigger should only be processed by 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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/09000b67/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "generic-trigger-extension-type": "execution-policy",
     "generic-trigger-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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/09000b67/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "generic-trigger-extension-type": "execution-policy",
     "generic-trigger-extension-value": {
       "depends": [
         "https://dcdn.example/cit/564cc45e-9099-4a37-b95e-60342f2647ba"
       ]
     }
   ]
 }

   uCDN can also stagger long-running triggers to control processing
   order.  In the following example, 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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/b89d49df/index.m3u8",
         "type": "hls"
       }]
      }
   }],
   "extensions": [
     "generic-trigger-extension-type": "execution-policy",
     "generic-trigger-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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/b89d49df/index.m3u8",
         "type": "hls"



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       }]
      }
   }],
   "extensions": [
     "generic-trigger-extension-type": "execution-policy",
     "generic-trigger-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. 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",
     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
     }
   }],
   "extensions": [
     {
       "generic-trigger-extension-type": "location-policy",
       "generic-trigger-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
     },
     {
       "generic-trigger-extension-type": "time-policy",
       "generic-trigger-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": [{
         "generic-trigger-extension-type": "location-policy",
         "generic-trigger-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": [{
         "generic-trigger-extension-type": "time-policy",
         "generic-trigger-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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     "generic-trigger-spec-type": "content-objectlist",
     "generic-trigger-spec-value": {
       "objects": [{
         "href": "https://www.example.com/hls/title/index.m3u8",
         "type": "hls"
       }]
     }
   }],
   "extensions": [
     {
       "generic-trigger-extension-type": "location-policy",
       "generic-trigger-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
     },
     {
       "generic-trigger-extension-type": "time-policy",
       "generic-trigger-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-collection.v2 | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITObjectsVersion    | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITScope             | RFCthis       |
               +--------------------------+---------------+
               | FCI.CITObjectListType    | RFCthis       |
               +--------------------------+---------------+

                                 Table 13

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

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)




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   Interface: CI/T

   Encoding: see Section 4.1

7.1.2.  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 4.2

7.1.3.  CDNI FCI CI/T Payload Types

7.1.3.1.  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

   Encoding: see Section 5.1

7.1.3.2.  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

   Encoding: see Section 5.2.1

7.1.3.3.  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

   Encoding: see Section 5.3

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.



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

   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
   comprise the names and descriptions listed in Section 4.1.2, with
   this document acting as the 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
   comprise the names and descriptions listed in Section 4.1.2.2, with
   this document acting as the 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 4.3.2.1, used by the Object List object.




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

   The initial contents of the "CDNI CI/T Object List Types" registry
   comprise the names and descriptions listed in Section 4.3.2.1, with
   this document acting as the 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 RFC Required policy as defined in [RFC8126].

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










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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 4.3.1, used by Section 4.1.2.4,
   Section 4.1.2.6, Section 4.1.2.7, and Section 4.1.2.8.

   The initial contents of the "CDNI CI/T Trigger Extensions" registry
   comprise the names and descriptions listed in Section 4.3.1, with
   this document acting as the specification.

8.  Security Considerations

   The CI/T interface provides a mechanism to allow uCDN to generate
   requests into 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, uCDN or dCDN metadata relating to content delivery
   or to the content itself.  It can only control the presence of that
   metadata in dCDN, and the processing work and network utilization
   involved in ensuring that presence.

   By examining "preposition" requests to 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.

   By injecting CI/T triggers, an attacker or a misbehaving uCDN would
   generate work in dCDN and uCDN as they process those requests.  So
   would a man-in-the-middle attacker modify valid trigger requests
   generated by uCDN.  In both cases, that would decrease dCDN's caching
   efficiency by causing it to unnecessarily acquire or reacquire
   content metadata and/or content.

   dCDN implementation of CI/T MUST restrict the actions of uCDN to the
   data corresponding to that uCDN.  Failure to do so would allow 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 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 dCDN
   using the CI/T interface, the protocol does not otherwise attempt to
   address malicious behavior between interconnected CDNs.




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8.1.  Authentication, Authorization, Confidentiality, Integrity
      Protection

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

   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 dCDN and
   uCDN to authenticate each other using the TLS client authentication
   and TLS server authentication.

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

   *  dCDN and 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 dCDNs or 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 dCDN.  A malicious or faulty
   uCDN could use this to generate unnecessary load in dCDN.  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. dCDN MUST ensure that it only exposes CI/T data related to 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>.

   [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>.




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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>.

   [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>.








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   [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


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




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













































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