Interface Index Capability for BGP
draft-lin-idr-interface-index-capability-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Changwang Lin , Kevin Wang | ||
| Last updated | 2026-02-27 | ||
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draft-lin-idr-interface-index-capability-00
IDR Working Group C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track K. Wang
Expires: August 29, 2026 HPE Networking
February 27, 2026
Interface Index Capability for BGP
draft-lin-idr-interface-index-capability-00
Abstract
In some scenarios using unnumbered links, it is necessary for the
BGP protocol to advertise the link's Interface Index and obtain the
peer's Remote Interface Identifier.
This document defines a new BGP capability [RFC 5492] for
advertising local interface indexes and obtaining neighbor interface
indexes.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 29 August 2026.
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Internet-Draft Interface Index Capability for BGP
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Table of Contents
1. Introduction...................................................2
2. Requirements Language..........................................3
3. Terminology....................................................3
4. Interface Index Capability.....................................4
5. IANA Considerations............................................4
6. Security Considerations........................................5
7. Informative References.........................................5
Authors' Addresses................................................6
1. Introduction
Here are several issues that arise when using unnumbered links due
to BGP's lack of support for interface index.
Scenario 1: BGP-LS-SPF
BGP-LS-SPF (RFC 9815) is a solution that leverages both the BGP
protocol [RFC4271] and the BGP-LS extension [RFC9552]. In the BGP
SPF routing domain, BGP Routers collects network-wide topology
information through the BGP-LS-SPF protocol and performs cross-
domain path calculation to compute routes using the SPF algorithm.
This approach aims to achieve intelligent traffic engineering and
automated routing optimization in large-scale data center or carrier
networks.
When an IGP protocol advertises an unnumbered link, it uses the
local interface index and the remote interface index to distinguish
between different unnumbered links.
BGP-LS-SPF reuses the BGP-LS information from the IGP. However,
during the deployment of BGP-LS-SPF, if the remote interface index
is unknown, it may lead to path calculation errors.
Scenario 2: BGP Egress Peer Engineering(EPE)
When deploying EPE, the BGP-LS peer link information in EPE is
defined as follows (see Section 5.2 of RFC 9086):
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Internet-Draft Interface Index Capability for BGP
Link Descriptors MUST include the following TLV, as defined in
[RFC7752]:
o Link Local/Remote Identifiers (TLV 258) contains the 4-octet
Link Local Identifier followed by the 4-octet Link Remote
Identifier. The value 0 is used by default when the link remote
identifier is unknown
Currently, BGP has no mechanism to obtain the peer's Link Remote
Identifier.
Scenario 3: BGP neighbor monitoring
During neighbor monitoring, if displaying bidirectional neighbor
connectivity, without the Link Remote Identifier, the corresponding
neighbor relationships on both sides cannot be matched.
Therefore, fundamentally, in unnumbered BGP scenarios, BGP peer
information should include: local router-id, peer address, peer AS
number, local interface index, and remote interface index.
This document defines a new BGP capability [RFC 5492] for advertising
support of the interface index capability, thereby advertising local
interface indexes and obtaining neighbor interface indexes.
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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when,
they appear in all capitals, as shown here.
3. Terminology
The following terminology is used in this document.
o BGP: Border Gateway Protocol
o EPE: Egress Peer Engineering
o BGP-LS-SPF: BGP Link State Shortest Path First Routing
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4. Interface Index Capability
In the BGP protocol, the OPEN message carries the newly added
Interface Index Capability TLV to exchange interface index
information with neighbors.
When sending an OPEN message, the Interface Index Capability is
included to advertise the Interface Index of the interface used to
establish the neighbor relationship.
When receiving an OPEN message, if it contains the Interface Index
Capability, the peer's Remote Interface Index is saved. If the
Interface Index Capability is not carried, save the Remote Interface
Index as 0.
The format of the Interface Index Capability is shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Cap Code = TBD |Cap Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Index Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Interface Index Capability
5. IANA Considerations
A new BGP Capability named "Interface Index Capability" will be
requested from the "Capability Codes" registry within the "IETF
Review" range [RFC5492].
+----------------+--------------------------------+-------------+
| Code Point | Description | Reference |
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+----------------+--------------------------------+-------------+
| TBD | Interface Index Capability |This document|
+----------------+--------------------------------+-------------+
6. Security Considerations
TBD
7. Informative References
[RFC9815]K. Patel, A. Lindem, Arrcus, Inc., S. Zandi, W. Henderickx,
Nokia, "BGP Link State (BGP-LS) Shortest Path First (SPF)
Routing", RFC9815, July 2025.
[RFC4271]Y. Rekhter, T. Li, Ed., S. Hares, Ed., January 2006, "A
Border Gateway Protocol 4 (BGP-4)", RFC4271, January 2006.
[RFC5492] J. Scudder, Juniper Networks, R. Chandra, Sonoa Systems,
"Capabilities Advertisement with BGP-4", RFC 5492,
[RFC7752] H. Gredler, Ed., Individual Contributor, J. Medved, S.
Previdi, Cisco Systems, Inc., A. Farrel, Juniper Networks,
Inc., S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
March 2016
[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel,
K., Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.
[RFC9552] K. Talaulikar, Ed., Cisco Systems, "Distribution of Link-
State and Traffic Engineering Information Using BGP", RFC
9552, December 2023
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Authors' Addresses
Changwang Lin
New H3C Technologies
Email: linchangwang.04414@h3c.com
Kevin Wang
HPE Networking
Email: kfwang@juniper.net
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