IDR X. Yi, Ed.
Internet-Draft M. Han, Ed.
Intended status: Standards Track China Unicom
Expires: 17 May 2026 G. Zeng, Ed.
Huawei Technologies
13 November 2025
Distribution of Service Metadata in BGP FlowSpec
draft-yi-idr-bgp-fs-edge-service-metadata-05
Abstract
In edge computing and distributed cloud environments, a service may
be deployed on multiple instances across one or more sites, referred
to as edge service. The edge service is typically associated with an
ANYCAST IP address. With the emergence of Computing-Aware Traffic
Steering (CATS) requirements, there is a growing need to consider
both network and computing metrics when making traffic steering
decisions. Traditional routing protocols lack the capability to
convey compute-related information, necessitating extensions to
existing protocols.
This draft defines a mechanism to distribute service routes along
with computing-related metadata using BGP FlowSpec. The service
metadata, including compute resource status and performance metrics,
can be collected by a central controller, processed, and then
distributed to ingress routers using BGP FlowSpec extensions. This
enables ingress routers to make path selections based not only on
routing cost but also on the running environment and resource
availability of edge services, thereby optimizing Quality of
Experience (QoE).
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."
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This Internet-Draft will expire on 17 May 2026.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. BGP FlowSpec Extension for Service Metadata . . . . . . . . . 3
2.1. Metadata Path Attribute TLV . . . . . . . . . . . . . . . 4
2.2. Aggregated Metric Path Attribute TLV . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Normative References . . . . . . . . . . . . . . . . . . . . 5
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The proliferation of edge computing and multi-cloud deployments has
led to services being distributed across numerous geographically
dispersed sites. These deployments support applications such as VR/
AR, intelligent transportation, and distributed AI workloads, which
require low latency and high reliability. In such environments,
multiple service instances are replicated across various sites to
ensure sufficient capacity and maintain the required QoE.
Computing-Aware Traffic Steering (CATS)
[I-D.ietf-idr-5g-edge-service-metadata] has been proposed as a
traffic engineering approach that optimizes traffic steering to
service instances by considering both network and compute resources.
However, existing routing protocols like BGP focus primarily on
network-layer metrics (e.g., AS paths, hop count) and lack the
ability to convey compute-related information such as CPU
utilization, memory capacity, or service load.
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This gap creates a critical challenge: without compute-aware metrics,
networks cannot make optimal steering decisions. For example, a user
might be routed to the nearest site based on network latency, only to
find it overloaded, while a lighter-loaded site with slightly higher
latency could provide better overall QoE. To address this, there is
a need to extend BGP FlowSpec to carry both service routes and
compute-related metadata, enabling ingress routers to make informed
decisions based on a holistic view of network and compute resources.
This document defines an extension to BGP FlowSpec that allows the
distribution of service metadata alongside service routes. The
extension leverages the metrics framework defined in
[I-D.ietf-cats-metric-definition], particularly the Level 2 (L2)
normalized metrics, to provide a scalable and efficient way to convey
compute-related information.
1.1. Terminology
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. BGP FlowSpec Extension for Service Metadata
The goal of the BGP FlowSpec extension is to distribute the
information of the service route and metadata. A service is
identified by an prefix and this information is carried using the
existing Destination Prefix Component specified in [RFC8955] and
[RFC8956]. [I-D.ietf-idr-ts-flowspec-srv6-policy] defines that the
Color Extended Community and BGP Prefix-SID attribute is carried in
the context of the FlowSpec NLRI.
In addition to that, this document proposes to carry the service
metadata attribute(See Figure 1). The ingress router can compare the
compute metric of different sites and steer the traffic into the best
one using the SR policy. The metadata can be original values defined
in [I-D.ietf-idr-5g-edge-service-metadata] or an aggregated one
calculated using original values.
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+------------+
| BGP FS |
| Controller |
+------------+
| FlowSpec route to Ingress:
| NLRI: Destination Prefix
| Redirect to IPv6 Nexthop: Egress's Address
| Policy Color: C1
| PrefixSID: End.X1
| Service Metadata: Compute metric
| .-----.
| ( )
V .--( )--.
+-------+ ( ) +------+ +---------+
| |_( SRv6 Core Network )_| | (End.X1) | |
|Ingress| ( ================> ) |Egress|----------| Site |
+-------+ (SR List<S1,S2,S3>) +------+ +---------+
'--( )--'
( )
'-----'
Figure 1: Example of using BGP FlowSpec to distribute the service
route and metadata
2.1. Metadata Path Attribute TLV
The Metadata Path Attribute TLV is the same as defined in
[I-D.ietf-idr-5g-edge-service-metadata], including the following
three sub-TLVs:
1. Site Preference Index sub-TLV indicates the preference to choose
the site.
2. Capacity Index sub-TLV indicates the capability of a site. One
Edge Site can be in full capacity, reduced capacity, or
completely out of service.
3. Load Measurement sub-TLV indicates the load level of the site.
2.2. Aggregated Metric Path Attribute TLV
To align with the metrics framework defined in
[I-D.ietf-cats-metric-definition], this document introduces an
Aggregated Metric Path Attribute TLV(See Figure 2) that carries a
Level 2 (L2) normalized metric. The L2 metric is a single normalized
value that represents the overall performance of a service instance,
derived from lower-level metrics (L0 or L1) using aggregation and
normalization functions.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Aggregated Metadata Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Aggregated Metric Value (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Aggregated Metric Path Attribute TLV format
* Type: identify the Aggregated Metadata Attribute, to be assigned
by IANA.
* Length: the total number of the octets of the value field.
* Value: value of Aggregated Computing metric.
3. Security Considerations
TBD
4. IANA Considerations
This document requires IANA to assign the following code points from
the registry called "BGP Path Attributes":
+=======+==========================+=============+
| Value | Description | Reference |
+=======+==========================+=============+
| TBD1 | Aggregated Metadata Type | Section 2.2 |
+-------+--------------------------+-------------+
Table 1
5. Normative References
[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/info/rfc8955>.
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[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/info/rfc8956>.
[I-D.ietf-idr-5g-edge-service-metadata]
Dunbar, L., Majumdar, K., Li, C., Mishra, G. S., and Z.
Du, "BGP Extension for 5G Edge Service Metadata", Work in
Progress, Internet-Draft, draft-ietf-idr-5g-edge-service-
metadata-30, 18 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-5g-
edge-service-metadata-30>.
[I-D.ietf-cats-metric-definition]
Yao, K., Li, C., Contreras, L. M., Ros-Giralt, J., and H.
Shi, "CATS Metrics Definition", Work in Progress,
Internet-Draft, draft-ietf-cats-metric-definition-04, 20
October 2025, <https://datatracker.ietf.org/doc/html/
draft-ietf-cats-metric-definition-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>.
[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>.
[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>.
Contributors
Tao He
China Unicom
Email: het21@chinaunicom.cn
Hang Shi
Huawei Technologies
Email: shihang9@huawei.com
Cheng Li (editor)
Huawei Technologies
Email: c.l@huawei.com
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Xiangfeng Ding
Huawei Technologies
Email: dingxiangfeng@huawei.com
Haibo Wang
Huawei Technologies
Email: rainsword.wang@huawei.com
Authors' Addresses
Xinxin Yi (editor)
China Unicom
Beijing
China
Email: yixx3@chinaunicom.cn
Mengyao Han (editor)
China Unicom
Beijing
China
Email: hanmy12@chinaunicom.cn
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Guanming Zeng (editor)
Huawei Technologies
Beijing
China
Email: zengguanming@huawei.com
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