Computing-Aware Traffic Steering (CATS) Northbound Interface (NBI) Specification
draft-ftzhswj-cats-northbound-api-00
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| Document | Type | Active Internet-Draft (individual) | |
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| Authors | Tao Fu , Zhang Hengsheng , Jing Wang | ||
| Last updated | 2026-05-29 | ||
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draft-ftzhswj-cats-northbound-api-00
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
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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
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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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