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BGP Flow Specification Filtered by Destination-QP
BGP Flow Specification Filtered by Destination-QP
draft-lll-idr-flowspec-filter-qp-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Yisong Liu , Changwang Lin , Jinming Li | ||
| Last updated | 2026-03-01 | ||
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| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-lll-idr-flowspec-filter-qp-00
IDR Working Group Y. Liu
Internet Draft China Mobile
Intended status: Standards Track C. Lin
Expires: September 02, 2026 New H3C Technologies
J. Li
China Mobile
March 02, 2026
BGP Flow Specification Filtered by Destination-QP
draft-lll-idr-flowspec-filter-qp-00
Abstract
BGP Flowspec mechanism (BGP-FS) [RFC8955] [RFC8956] propagates both
traffic Flow Specifications and Traffic Filtering Actions by making
use of the BGP NLRI and the BGP Extended Community encoding formats.
This document specifies a new BGP-FS component type named
Destination-QP(Destination Queue Pair) to support filtering by
Destination-QP.
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 02 September 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
(http://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
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respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction.....................................................2
2. Requirements Language............................................3
3. Terminology......................................................4
4. FlowSpec Fileter by Destination-QP...............................4
5. Use case.........................................................4
6. Security Considerations..........................................7
7. IANA Considerations..............................................7
8. References.......................................................7
8.1. Normative References........................................7
8.2. Informative References......................................8
Authors' Addresses..................................................9
1. Introduction
BGP Flowspec mechanism (BGP-FS) [RFC8955] [RFC8956] propagates both
traffic Flow Specifications and Traffic Filtering Actions by making
use of the BGP NLRI and the BGP Extended Community encoding formats.
In modern AI training clusters, especially those based on RoCEv2 and
RDMA for high-performance inter-GPU communication, traffic exhibits
distinct characteristics that differ significantly from traditional
Internet flows. AI training communication typically consists of
long-lived, high-throughput, and delay-sensitive and jitter-
sensitive flows, such as those generated by collective communication
operations like AllReduce. These flows are often bound to long-term
Queue Pair (QP) [IB-SPEC] instances, with relatively stable five-
tuple fields, making them prone to path polarization and uneven link
utilization when scheduled solely by five-tuple-based hashing. Such
static mapping fails to adapt to the dynamic communication patterns
and strict performance requirements of AI workloads, leading to
localized congestion, degraded training throughput, and reduced
cluster efficiency.
For these reasons, five-tuple-only flow scheduling is no longer
sufficient for AI-oriented lossless networks. Instead, scheduling
mechanisms based on a combination of five-tuple and QP information
have become necessary. By introducing QP-level identification into
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the flow distribution logic, networks can achieve finer-grained
traffic steering, better load balancing across equal-cost multi-path
(ECMP) groups, and improved isolation between communication streams.
As shown in Figure 1, the controller uses BGP Flow-Spec to
distribute QP routes to the Ingress PE according to QP. Based on the
QP value, traffic is redirected to different forwarding paths.
Methods for redirecting traffic to different paths can include
redirection to IP [draft-ietf-idr-flowspec-redirect-ip] or
redirection to SRv6 [draft-ietf0-idr-srv6-flowspec-path-redirect],
among others. Specific methods are beyond the scope of this
document.
At the forwarding level, when the DC sends packets, it carries the
corresponding QP for traffic belonging to the same task.
The Ingress PE looks up the QP routes distributed via BGP Flow-Spec
based on the QP of the traffic and forwards the packets according
to the QP routes.
+---------+
|Controler|
+----+----+
|
|BGP Flow-Spec
|for Destination-QP
|
+----+ +---V----+ +-- Path1--+ +--------+
|DC | |Ingress | | | |Egress |
| +-------+PE +-------+ +------+PE |
+----+ +-+------+ | | +--------+
+-- Path2--+
Figure 1
This document specifies a new BGP-FS component type named
Destination-QP(Destination Queue Pair) to support filtering by
Destination-QP.
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
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BCP 14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when,
they appear in all capitals, as shown here.
3. Terminology
FS: Flow Specification
QP: Queue Pair
4. FlowSpec Filtered by Destination-QP
[draft-ietf-idr-fsv2-ip-basic] defines the Components in the IP
Basic TLV. This document proposes a new Component for Destination-
QP information.
The following new component type is defined.
* Destination-QP
Type TBD - Destination-QP
Length: variable
Component Value format: [numeric_op, value]+
Each Destination-QP value is 4 octets.
Per section 10 of [RFC8955] , If a receiving BGP speaker cannot
support this new Flow Specification component type, it MUST discard
the NLRI value field that contains such unknown components. Since
the NLRI field encoding (Section 4 of [RFC8955]) is defined in the
form of a 2-tuple <length, NLRI value>, message decoding can skip
over the unknown NLRI value and continue with subsequent remaining
NLRI.
5. Use case
The BGP agent specifies the traditional 5-tuple and new defined Destination-QP
as matching criteria.
As shown in Figure 2, for traffic with a Destination-QP value of 1001, redirect it
to Path1; for traffic with a Destination-QP value of 1001, redirect it to Path2.
BGP-FS Route 1:
FS Filters
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Destination: 203.0.113.0/24
source address: 198.51.100.0/24
protocol: UDP
destination port: 4791 (RoCEv2 protocol)
source port: 10001
Destination-QP value: 1001 (the newly defined in this document.)
FS Action:
Redirect Flow to Path1 (The specific format is not discussed in this
document.)
BGP-FS Route 2:
FS Filters
Destination: 203.0.113.0/24
source address: 198.51.100.0/24
protocol: UDP
destination port: 4791 (RoCEv2 protocol)
source port: 10001
Destination-QP value: 2001 (the newly defined in this document.)
FS Action:
Redirect Flow to Path2 (The specific format is not discussed in this
document.)
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+----------+
|Controller|
+----------+
|BGP FS:
|NLRI Filter
| Destination Prefix
| Source Prefix
| IP Protocol
| Destination Port
| Source Port
| Destination-QP
|
|Action:
| Redirect
|
V
+----------+
|Ingress PE|
+----------+
Figure 2
The Ingress PE receives the Flow-Spec route and installs it into the forwarding
plane. Upon receiving AI data traffic, it redirects the traffic to the
corresponding Path for forwarding based on the traffic 5-tuple and Destination-
QP parameters.
In this document, the example uses QP, destination address, and source address as
filtering criteria for flow-spec to redirect traffic to different paths.
+--------------+-------------------+----------------+-----------+
| Destination | Dest Prefix | Source Preifx |Redirect |
| QP | | | |
+--------------+-------------------+----------------+-----------+
| 1001 | 203.0.113.0/24 | 198.51.100.0/24|Path1 |
+--------------+-------------------+----------------+-----------+
| 2001 | 203.0.113.0/24 | 198.51.100.0/24|Path2 |
+--------------+-------------------+----------------+-----------+
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6. Security Considerations
No new security issues are introduced to the BGP protocol by this
specification.
7. IANA Considerations
[draft-ietf-idr-flowspec-v2-04] defines the Types for IP Filters.
This document requested to assign a new type code point from "Non-IP
Types for IP Filters" registry for Destination-QP.
Non-IP Types for IP Filters SubTLV
type Definition
====== ============
64 - Parts of SID
65 - MPLS Match 1: Label in Label stack
66 - MPLS Match 2: EXP bits in top Label
TBD - Destination-QP This document
67-249 unassigned (reserved for now)
250- Filter Error handling
251-255 Reserved
8. References
8.1. Normative References
[IB-SPEC]InfiniBand Trade Association. InfiniBand Routing and
Forwarding. Architecture Supplement, 2023.
[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://www.ietf.org/archive/id/draft-ietf-idr-flowspec-
v2-04.txt>.
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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/info/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/info/rfc4271>.
[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>.
[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>.
8.2. Informative References
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Authors' Addresses
Yisong Liu
China Mobile
China
Email: liuyisong@chinamobile.com
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
Jinming Li
China Mobile
China
Email: lijinming@chinamobile.com
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