



Computing-Aware Traffic Steering(CATS)                        T. Fu, Ed.
Internet-Draft                                             H. Zhang, Ed.
Updates:      China Academy of Information and Communications Technology
         2                                                  J. Wang, Ed.
         0                                                  China Mobile
         2                                                   29 May 2026
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Intended status: Informational                                          
Expires: 30 November 2026


   Computing-Aware Traffic Steering (CATS) Northbound Interface (NBI)
                             Specification
                  draft-ftzhswj-cats-northbound-api-00

Abstract

   In scenarios such as industrial Internet, smart cities, and smart
   hospitals, enterprise customers lease a large amount of computing and
   network resources from operators and need to manage their own
   resources flexibly for agile business operations.  Therefore, these
   customers’ systems require the Computing-Aware Traffic Steering
   (CATS) northbound interface (NBI) to gain greater flexibility in
   business optimization.  The CATS NBI is a standardized set of
   interfaces that governs interactions between the CATS system and
   upper-layer applications, software, and services.  It defines
   interaction protocols, data models, message formats, and procedures.
   Unlike the southbound interface, which carries detailed information,
   the NBI simplifies data structures to deliver streamlined management
   capabilities.  Positioned between the three-layer CATS architecture
   and scenario-specific applications, it is primarily invoked by user



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   management platforms, user business orchestration systems, AI
   inference platforms, and other application services.  However, the
   current lack of a unified standard for the CATS NBI results in
   protocol heterogeneity, incompatible data formats, and inconsistent
   functionalities.  This makes unified management and coordinated
   scheduling of multi-vendor, multi-domain CATS systems difficult,
   hindering large-scale deployment.  A unified NBI specification is
   therefore urgently needed.  This document defines the standard for
   the Computing-Aware Traffic Steering (CATS) Northbound Interface
   (NBI), specifying the interaction protocols, data models, message
   formats, and procedures between the CATS system and upper-layer
   management platforms and application services.  As CATS technology
   may be adopted in future fields including the industrial Internet,
   Internet of Vehicles, and smart cities, enterprises and users require
   a concise, user-friendly, and comprehensive set of invocation
   interfaces.  The core objective of the NBI is to enable standardized
   exposure of capabilities such as CATS resource query, traffic
   steering policy selection, metric subscription, and fault alarming,
   supporting unified management and coordinated scheduling of multi-
   vendor, multi-domain CATS systems.  Based on the IETF CATS framework,
   metric definitions, and use case requirements documents, this
   document focuses on the specifications of NBI functions, protocols,
   and data models, providing a unified standard for CATS northbound
   interoperability.

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 30 November 2026.

Copyright Notice

   Copyright (c) 2026 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.  Backgroud . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   5
   3.  Overall Architecture of the CATS Northbound Interface . . . .   5
     3.1.  Northbound Interface Components . . . . . . . . . . . . .   6
     3.2.  Interaction Relationships . . . . . . . . . . . . . . . .   6
     3.3.  Interface Positioning . . . . . . . . . . . . . . . . . .   6
   4.  Interface Protocol and Transmission Specifications  . . . . .   6
     4.1.  Basic Specifacation . . . . . . . . . . . . . . . . . . .   6
     4.2.  Transmission Security . . . . . . . . . . . . . . . . . .   7
     4.3.  URI Naming Convention . . . . . . . . . . . . . . . . . .   7
     4.4.  Version Compatibility . . . . . . . . . . . . . . . . . .   7
   5.  Data Model Specifications . . . . . . . . . . . . . . . . . .   7
     5.1.  Data Modeling Language  . . . . . . . . . . . . . . . . .   7
     5.2.  Core Data Models  . . . . . . . . . . . . . . . . . . . .   7
   6.  Northbound Interface Functions  . . . . . . . . . . . . . . .   7
     6.1.  Resource Management Module  . . . . . . . . . . . . . . .   8
     6.2.  Policy Management Module  . . . . . . . . . . . . . . . .   8
     6.3.  Metric Subscription Module  . . . . . . . . . . . . . . .   8
     6.4.  Alarm Management Module . . . . . . . . . . . . . . . . .   8
     6.5.  Configuration Management Module . . . . . . . . . . . . .   8
   7.  Message Format and Interaction Procedures . . . . . . . . . .   8
     7.1.  General Message Format  . . . . . . . . . . . . . . . . .   8
     7.2.  8.2 Typical Interaction Procedures  . . . . . . . . . . .   9
   8.  Interface Security Requirements . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     11.2.  Informative References . . . . . . . . . . . . . . . . .   9
   Appendix A.  Appendix 1 . . . . . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  10
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10





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1.  Introduction


1.1.  Backgroud

   With the rapid proliferation of low-latency, high-computing services
   such as agent collaboration, edge computing, AR/VR, and intelligent
   transportation, traditional traffic steering mechanisms that rely
   solely on network connectivity fail to adapt to dynamic changes in
   computing resources.  This easily leads to issues including computing
   overload, unbalanced scheduling, and degraded user experience.  As a
   new traffic engineering technology, Computing-Aware Traffic Steering
   (CATS) fundamentally integrates multi-dimensional metrics such as
   computing status, network quality, and service load to dynamically
   select optimal service instances and steer traffic, ensuring service
   Quality of Experience (QoE).  The CATS system consists of core
   components including the C-SMA (CATS Service Metric Agent), C-NMA
   (CATS Network Metric Agent), C-PS (CATS Path Selector), and
   C-Forwarder.  It requires exposing a unified interface to upper-layer
   management platforms and application services to enable resource
   control, policy configuration, metric visualization, and fault
   operation and maintenance.  Currently, there is a lack of a unified
   standard for the CATS northbound interface, resulting in protocol
   heterogeneity, incompatible data formats, and inconsistent
   functionalities.  This may prevent users from gaining sufficient
   capabilities when managing their CATS systems across vendors,
   hindering large-scale deployment.In scenarios such as the industrial
   Internet, smart cities, and smart hospitals, enterprise customers
   lease substantial computing and network resources from operators and
   require flexible resource management to support agile business
   operations.  Therefore, these customers’ systems need the Computing-
   Aware Traffic Steering (CATS) northbound interface to achieve greater
   flexibility in business optimization.  The CATS northbound interface
   is a standardized set of interfaces that governs interactions between
   the CATS system and upper-layer applications, software, and services.
   It defines interaction protocols, data models, message formats, and
   procedures.  Unlike the southbound interface, which carries detailed
   information, it delivers streamlined management capabilities by
   simplifying interface data structures.  Positioned between the three-
   layer CATS architecture and scenario-specific applications, it is
   primarily invoked by user management platforms, user business
   orchestration systems, AI inference platforms, and other application
   services.  However, the current lack of a unified standard interface
   for CATS leads to protocol heterogeneity, incompatible data formats,
   and inconsistent functionalities.  This makes unified management and
   coordinated scheduling of multi-vendor, multi-domain CATS systems
   difficult, restricting large-scale deployment.  A unified northbound
   interface specification is therefore urgently needed.



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1.2.  Requirements Language

   The key words "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.  Definition of Terms

   Computing-Aware Traffic Steering(CATS): A traffic engineering
   technique that dynamically steers traffic by jointly considering
   computing status, network quality, and service load.  Computing-Aware
   Traffic Steering Metric(CATS Metric):A multi-dimensional indicator
   used to evaluate computing resources, network performance, and
   service status for CATS-based traffic decisions.  CATS Service Metric
   Agent(C-SMA):A CATS component responsible for collecting,
   aggregating, and reporting service-related metrics such as load and
   QoE.  CATS Network Metric Agent(C-NMA):A CATS component responsible
   for collecting, aggregating, and reporting network-related metrics
   such as latency, packet loss, and bandwidth.  CATS Path
   Selector(C-PS):A CATS core component that selects optimal service
   instances and forwarding paths based on aggregated CATS metrics.
   CATS Service ID(CS-ID):A unique identifier assigned to a CATS service
   for service-level management and policy binding.  CATS Service
   Contact Instance ID(CSCI-ID):A unique identifier for a specific
   instance of a CATS service, used for instance-level scheduling and
   monitoring.  CATS Northbound Interface(CATS NBI):A standardized
   interface set enabling interaction between the CATS system and upper-
   layer management platforms and applications.  Operations,
   Administration, and Maintenance(OAM):A set of functions for network/
   system monitoring, fault management, performance measurement, and
   maintenance.  Quality of Experience(QoE):A holistic metric reflecting
   the end-user’s perceived quality of a service, considering latency,
   jitter, packet loss, and service availability.  REST
   Configuration(RESTCONF):An HTTP/JSON-based protocol defined by IETF
   RFC 8040 for configuring and retrieving data modeled in YANG.  YANG:
   A data modeling language defined by IETF RFC 7950, used to model
   configuration and operational data for network and service
   management.

3.  Overall Architecture of the CATS Northbound Interface









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3.1.  Northbound Interface Components

   The CATS northbound interface consists of three components, listed
   from top to bottom as follows: Application Adaptation Module:
   Connected to upper-layer management platforms, business orchestration
   systems, and application services (e.g., AR/VR, AI inference
   platforms), acting as the northbound interface callers.  Interface
   Service Module: The core functions of the CATS northbound interface,
   including protocol adaptation, data model parsing, functional logic
   processing, and security control modules, serving as the core of this
   standard.  CATS Adaptation Module: Connected to internal components
   of the CATS system, which receive northbound interface instructions
   and execute scheduling logic.  To simply user's operations, it's
   mainly used by C-SMA.

3.2.  Interaction Relationships

   The interaction modes of the northbound interface are divided into
   synchronous request-response and asynchronous subscription-push:
   Synchronous interaction: The upper layer initiates requests for
   query, configuration, and policy delivery, and the CATS interface
   returns responses synchronously (e.g., resource query, policy
   configuration).  Asynchronous interaction: The upper layer subscribes
   to metrics and alarms, and the CATS interface pushes data in real
   time (e.g., computing load, fault alarms).

3.3.  Interface Positioning

   Unique Entry Point for NBI: All upper-layer CATS-related operations
   access the system through the northbound interface, enabling unified
   management and control.  Stateless Interaction: Interface
   interactions are session-independent, supporting high availability
   and load balancing.  Cross-Domain Interoperability: It supports
   unified northbound access for both single-domain and multi-domain
   CATS systems, adapting to diverse scenarios of carriers and
   enterprises.

4.  Interface Protocol and Transmission Specifications


4.1.  Basic Specifacation

   The CATS northbound interface mandatorily adopts the RESTCONF
   protocol (IETF RFC 8040), transmitted over HTTP with a unified JSON
   data format and compatibility with YANG data models.






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4.2.  Transmission Security

   Interface transmission mandatorily uses TLS 1.3 encryption; plaintext
   HTTP transmission is prohibited.  Port: Default port 443, with
   support for custom ports.  Certificate: X.509 certificates are used
   for mutual authentication to ensure the authenticity of both
   communicating parties

4.3.  URI Naming Convention

   The northbound interface URI follows a hierarchical naming rule.

4.4.  Version Compatibility

   Interface versions adopt path-based versioning (v1/v2) to support
   backward compatibility: Legacy interface versions remain available,
   while new features in later versions use independent paths.  When
   extending data models, newly added fields are optional by default and
   do not affect parsing of older versions.

5.  Data Model Specifications


5.1.  Data Modeling Language

   The core data models are defined using YANG 1.1 (IETF RFC 7950),
   supporting JSON format mapping.  They reuse the IETF CATS metric
   model (draft-ietf-cats-metric-definition) and add northbound-specific
   fields.

5.2.  Core Data Models

   6.2.1 CATS Resource Model (cats-resource.yang) TBA.
   6.2.2 CATS Policy Model (cats-policy.yang) TBA.
   6.2.3 CATS Metric Model Adopts the three-level CATS metric model
   defined in draft-ietf-cats-metric-definition.
   6.2.4 CATS Alarm Model (cats-alarm.yang) TBA.

6.  Northbound Interface Functions












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6.1.  Resource Management Module

   Provides query capabilities for CATS sites, service instances, and
   computing/network resources:
   a.  Shall support querying the list and status of all service sites
   within user permissions.
   b.  Shall support querying computing resources (CPU/GPU/utilization,
   computing score) and network resources (latency/packet loss/
   bandwidth, network score) of a specified site.
   c.  Shall support querying the status, load, and QoE score of a
   service instance identified by a specified CS-ID/CSCI-ID.
   d.  May support querying global Level 2 aggregated metrics of CATS.
   e.  TBD.

6.2.  Policy Management Module

   Supports querying, selecting, modifying, deleting, enabling/disabling
   traffic steering policies for each CATS service:
   a.  Shall support creating static/dynamic/hybrid steering policies
   (binding CS-ID, priority, trigger threshold, target instance).
   b.  Shall support querying all policies or details of a specified
   policy.
   c.  Shall support updating policy trigger conditions, priority, and
   target instances.
   d.  Shall support enabling/disabling a specified policy.
   e.  Shall support deleting invalid policies.
   f.TBD.

6.3.  Metric Subscription Module

   TBD.

6.4.  Alarm Management Module

   TBD.

6.5.  Configuration Management Module

   TBA.

7.  Message Format and Interaction Procedures


7.1.  General Message Format

   8.1.1 Success Response (JSON) TBA.





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7.2.  8.2 Typical Interaction Procedures

   8.2.1 Resource Query (Synchronous GET) TBA.
   8.2.2 Policy Provisioning (Synchronous POST) TBA.
   8.2.3 Metric Subscription (Asynchronous POST) TBA.
   8.2.4 Alarm Subscription (Asynchronous POST) The procedure is the
   same as metric subscription.  Alarm data is pushed in real time upon
   successful subscription.

8.  Interface Security Requirements

   TBA.

9.  IANA Considerations

   This memo includes no request to IANA.

10.  Security Considerations

   This document should not affect the security of the Internet.

11.  References

11.1.  Normative References

   [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>.

11.2.  Informative References

   [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>.

   [exampleRefMin]
              Surname, Initials., "Title", 2006.

   [exampleRefOrg]
              Organization, "Title", 1984, <http://www.example.com/>.

Appendix A.  Appendix 1

   TBD.






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Acknowledgements

   TBD.

Contributors

   Thanks to all of the contributors.

Authors' Addresses

   Fu Tao (editor)
   China Academy of Information and Communications Technology
   Huayuanbei No.52
   beijing
   beijing, 100191
   China
   Email: futao@caict.ac.cn


   Zhang Hengsheng (editor)
   China Academy of Information and Communications Technology
   Huayuanbei No.52
   beijing
   beijing, 100191
   China
   Email: zhanghengsheng@caict.ac.cn


   Wang Jing (editor)
   China Mobile
   beijing
   beijing, 100191
   China
   Email: wangjingjc@chinamobile.com

















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