Protocols Applicability for Computing-Aware Traffic Steering (CATS)
draft-yxl-cats-protocols-applicability-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Huijuan Yao , Quan Xiong , Changwang Lin | ||
| Last updated | 2026-01-08 | ||
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draft-yxl-cats-protocols-applicability-00
cats H. Yao
Internet-Draft China Mobile
Intended status: Informational Q. Xiong
Expires: 13 July 2026 ZTE Corporation
C. Lin
New H3C Technologies
9 January 2026
Protocols Applicability for Computing-Aware Traffic Steering (CATS)
draft-yxl-cats-protocols-applicability-00
Abstract
This document analyzes the applicability of protocols related to a
CATS system，and describes how to build a CATS system by extending
existing IETF protocols.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 13 July 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. CATS Applicability Overview . . . . . . . . . . . . . . . . . 3
3.1. Control Plane Applicability Analysis . . . . . . . . . . 3
3.2. Management Plane Applicability Analysis . . . . . . . . . 3
3.3. Data Plane Applicability Analysis . . . . . . . . . . . . 3
4. Protocols Applicability to CATS . . . . . . . . . . . . . . . 4
4.1. IGP/BGP-LS Applicability for Metrics Collection . . . . . 4
4.2. BGP Applicability for Metrics Distribution . . . . . . . 4
4.3. PCEP Applicability for Service-aware Computing . . . . . 5
4.4. BGP-FS Applicability for Service Mapping . . . . . . . . 5
4.5. BGP SR Policy Applicability for Service-aware Candidate
Paths . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.6. Yang Model Applicability for Service Configuration and
Management . . . . . . . . . . . . . . . . . . . . . . . 6
4.7. Data plane Protocols Applicability for Forwarding CATS
Packets . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[I-D.ietf-cats-framework] introduces a framework for Computing-Aware
Traffic Steering (CATS). This document analyzes the corresponding
protocols in control plane, management plane and data plane, and
evaluates how far the existing protocols or be extended to support
CATS such as metrics distribution and their operational requirements.
2. Conventions Used in This Document
2.1. Terminology
The terms defined in [I-D.ietf-cats-framework] can be used in this
document.
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2.2. 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.
3. CATS Applicability Overview
As defined in [I-D.ietf-cats-framework], the CATS framework structure
consists of the C-SMA (responsible for maintaining service metrics),
the C-NMA (responsible for maintaining network metrics), the C-PS
(responsible for maintaining forwarding table entries), and the C-TC
(responsible for traffic classification).
3.1. Control Plane Applicability Analysis
The control plane protocols are used to distribute the CATS metrics
of service,then to chose forwarding paths to the CATS service's
destinatios. Based on [I-D.ietf-cats-framework], various relevant
computing metrics are defined in [I-D.ietf-cats-metric-definition],
which can be used in CATS. However, the protocols and technologies
for distributing metrics from the egress gateway to the ingress
gateway are still under research.Extensible protocols include YANG,
BGP existing attribute, new BGP address family, FlowSpec, or BGP-LS.
In addition, The FlowSpec protocol can be extended to accommodate the
selection of CATS service paths. In addition, the control protocols
are capable of controlling traffic classification include FlowSpec
and YANG model. The FlowSpec is a distributed control method, while
the YANG model is a centralized control method. These two protocol
models can be extended to classify CATS data traffics.
3.2. Management Plane Applicability Analysis
Management plane protocols are used to manage and configure CATS
systems. Existing PING and TRACE protocols may be utilized in CATS
networks. These protocols could be extended to operate on specific
CATS Service Identifiers (CS-IDs). Alternatively, YANG models could
be extended to report statistical information about CATS flows for
monitoring purposes.
3.3. Data Plane Applicability Analysis
The data plane protocols are used to forward the CATS traffiic to the
corresponding destination by existing rotocols IPv4/IPv6 or IPv4/IPv6
over SRv6.
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4. Protocols Applicability to CATS
4.1. IGP/BGP-LS Applicability for Metrics Collection
As defined in [I-D.ietf-cats-framework] section 3.4.3, the CATS
Network Metric Agent (C-NMA) is used to gather information about the
state of the underlay network. The C-NMA could collect the network
metrics leveraging the existing IGP (Interior Gateway Protocol)
(e.g., OSPF-TE[RFC7471] and IS-IS TE [RFC8570]) and advertise them to
the CATS Path Selector (C-PSes) through BGP-LS (Border Gateway
Protocol Link State) [RFC8571].
As defined in [I-D.ietf-cats-framework] section 3.4.2, the CATS
Service Metric Agent (C-SMA) is used to gather information about
service sites and server resources, as well as the status of the
different service instances. The C-SMA may collect the service
information through private interfaces associated with multiple
service contact instances and report them to the C-PSes through BGP-
LS extensions for service metrics.
4.2. BGP Applicability for Metrics Distribution
As defined in [I-D.ietf-cats-framework] section 4.2, the C-SMA needs
to collect the computing-related capabilities and metrics, associate
them with a CS-ID and distribute the computing metrics to the C-PSes.
The C-NMA needs to collect the network-related capabilities and
metrics, and distribute the network metrics to the C-PSes. The
C-PSes could use the combination of computing and network metrics to
determine the best Egress CATS-Forwarder to provide access to a
service contact instance and invoke the compute function required by
a service request.
BGP (Border Gateway Protocol) is an inter-Autonomous System (AS)
routing protocol that enables the distribution of routing information
across the networks. It operates between different AS, which are
networks under a single administration to exchange network
reachability information and determine the best paths for data
transmission. The exsiting BGP technology (e.g., [RFC4271] and
[I-D.ietf-idr-bgp4-rfc4271bis]) can be used to distribute the network
metrics from the C-NMA to the C-PSes. The C-SMA may distribute the
computing metrics to the C-PSes through BGP extensions for CATS.
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4.3. PCEP Applicability for Service-aware Computing
As defined in [I-D.ietf-cats-framework] section 3.4.4, C-PSes
determines the best paths to forward traffic after collecting the
computing and network metrics. And a standalone C-PS can be a
functional component of a PCE (Path Computation Element). The Path
Computation Element Protocol (PCEP) as per [RFC5440] is used to
enable computation of the path between a PCE and a Path Computation
Client (PCC) (or other PCE).
The C-PSes which is viewed as a PCE can compute the best path from
ingress CATS-Forwarder (which is viewed as a PCC)to egress CATS-
Forwarder based on the network topology information from C-NMA. But
in CATS, the C-PSes may firstly select the egress CATS-Forwarder and
the related service instances and compute the path associated with
the computing metric information from C-SMA. The C-PSes could also
distribute the best path including the corresponding CS-ID and
possibly CSCI-IDs through PCEP extensions.
4.4. BGP-FS Applicability for Service Mapping
A BGP Flow Specification (BGP-FS) is an n-tuple consisting of several
matching criteria that can be applied to IP traffic such as BGP flow
specification version 1 (FSv1) as per [RFC8955] and version 2 of the
BGP flow specification (FSv2) as per [I-D.ietf-idr-flowspec-v2]. A
service is identified by an prefix as defined in [RFC8955] and
[RFC8956] can be used to steer the traffic in IP networks by L3
traffic filtering rules. The MPLS label filtering rules can be used
to match the traffic in [I-D.ietf-idr-flowspec-mpls-match] and the
MPLS label for a service mapping to a MPLS network can use the Label-
action defined in [I-D.ietf-idr-bgp-flowspec-label]. It also could
use the BGP FlowSpec to steer packets into an SR Policy as per
[I-D.ietf-idr-ts-flowspec-srv6-policy].
As defined in [I-D.ietf-cats-framework] section 3.4.4, a standalone
C-PS can be a functional component of a centralized controller. The
BGP-FS may help the C-PSes to distribute the routes associated with
computing metrics and steer the traffic for CATS services. The CATS
services may be mapped to the corresponding CS-ID or SR Policy
through BGP-FS extensions.
4.5. BGP SR Policy Applicability for Service-aware Candidate Paths
The ingress node can steer the packets into a specific path according
to the Segment Routing Policy (SR Policy) as defined in [RFC9256] and
the BGP SR Policy can be used to distribute SR policies to the
headend as per [RFC9830].
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As per [I-D.ietf-cats-framework] section 3.4.4, a standalone C-PS can
be a functional component of a centralized controller. The C-PS may
distribute SR policies to the CATS Ingress CATS-Router associated
with computing metrics in SR-MPLS and SRv6 networks. The SR policy
may be distributed to carry the identifiers of CATS services in
candidate paths by the BGP SR Policy extensions.
4.6. Yang Model Applicability for Service Configuration and Management
As per [I-D.ietf-cats-framework] section 3.3, the CATS management
plane is responsible for monitoring, configuring, and maintaining
CATS network devices. The CATS data may be required to be maintained
in the management plane and configured to the control plane, data
plane and C-SMA. A YANG data model may be required for the
configuration and management.
The routing data model and ietf-routing YANG model is defined for
configuring and managing a routing subsystem as per [RFC8349]. The
model contains all the basic network-related configuration parameters
to operate the CATS networks. The data model may be required to
augment for the CATS computing information.
4.7. Data plane Protocols Applicability for Forwarding CATS Packets
As per [I-D.ietf-cats-framework] section 3.3, the CATS data plane is
responsible for computing-aware steering the packets along the paths
to the service contact instances. It needs to classify and forward
the packets in routing networks such as IPv6, SR-MPLS and SRv6
networks. The ingress CATS-Router needs to encapsulate the
corresponding headers from itself to the egress CATS-Router. It is
required to indicate the interface associated to a specific service
contact instance which connected to the egress CATS-Router.
5. Security Considerations
The security considerations described in [I-D.ietf-cats-framework]
and related routing protocols are applicable to this document. This
document analyzed the applicability for some protocols which do not
introduce any new extensions and new security considerations.
6. IANA Considerations
Currently this document does not make an IANA requests.
7. References
7.1. Normative References
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[I-D.ietf-cats-framework]
Li, C., Du, Z., Boucadair, M., Contreras, L. M., and J.
Drake, "A Framework for Computing-Aware Traffic Steering
(CATS)", Work in Progress, Internet-Draft, draft-ietf-
cats-framework-19, 20 November 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-cats-
framework-19>.
7.2. Informative References
[I-D.ietf-idr-bgp-flowspec-label]
liangqiandeng, Hares, S., You, J., Raszuk, R., and D. Ma,
"Carrying Label Information for BGP FlowSpec", Work in
Progress, Internet-Draft, draft-ietf-idr-bgp-flowspec-
label-02, 20 October 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
flowspec-label-02>.
[I-D.ietf-idr-bgp4-rfc4271bis]
Rekhter, Y., Li, T., Hares, S., and J. Scudder, "A Border
Gateway Protocol 4 (BGP-4)", Work in Progress, Internet-
Draft, draft-ietf-idr-bgp4-rfc4271bis-00, 14 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
bgp4-rfc4271bis-00>.
[I-D.ietf-idr-flowspec-mpls-match]
Yong, L., Hares, S., liangqiandeng, and J. You, "BGP Flow
Specification Filter for MPLS Label", Work in Progress,
Internet-Draft, draft-ietf-idr-flowspec-mpls-match-02, 20
October 2022, <https://datatracker.ietf.org/doc/html/
draft-ietf-idr-flowspec-mpls-match-02>.
[I-D.ietf-idr-flowspec-v2]
Hares, S., Eastlake, D. E., Yadlapalli, C., and S.
Maduschke, "BGP Flow Specification Version 2", Work in
Progress, Internet-Draft, draft-ietf-idr-flowspec-v2-04,
28 April 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-idr-flowspec-v2-04>.
[I-D.ietf-idr-ts-flowspec-srv6-policy]
Wenying, J., Liu, Y., Zhuang, S., Mishra, G. S., and S.
Chen, "Traffic Steering using BGP FlowSpec with SR
Policy", Work in Progress, Internet-Draft, draft-ietf-idr-
ts-flowspec-srv6-policy-07, 4 August 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-ts-
flowspec-srv6-policy-07>.
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[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/rfc/rfc2119>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/rfc/rfc4271>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/rfc/rfc5440>.
[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/rfc/rfc7471>.
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/rfc/rfc768>.
[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/rfc/rfc8174>.
[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/rfc/rfc8349>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/rfc/rfc8402>.
[RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
2019, <https://www.rfc-editor.org/rfc/rfc8570>.
[RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
IGP Traffic Engineering Performance Metric Extensions",
RFC 8571, DOI 10.17487/RFC8571, March 2019,
<https://www.rfc-editor.org/rfc/rfc8571>.
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[RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
RFC 8955, DOI 10.17487/RFC8955, December 2020,
<https://www.rfc-editor.org/rfc/rfc8955>.
[RFC8956] Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed.,
"Dissemination of Flow Specification Rules for IPv6",
RFC 8956, DOI 10.17487/RFC8956, December 2020,
<https://www.rfc-editor.org/rfc/rfc8956>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/rfc/rfc9256>.
[RFC9830] Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
P., and D. Jain, "Advertising Segment Routing Policies in
BGP", RFC 9830, DOI 10.17487/RFC9830, September 2025,
<https://www.rfc-editor.org/rfc/rfc9830>.
Contributors
The following people have substantially contributed to this document:
Peng Liu
China Mobile
Email: liupengyjy@chinamobile.com
Authors' Addresses
Huijuan Yao
China Mobile
Email: yaohuijuan@chinamobile.com
Quan Xiong
ZTE Corporation
Email: xiong.quan@zte.com.cn
Changwang Lin
New H3C Technologies
Email: linchangwang.04414@h3c.com
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