Advertisement of Remote Interface Identifiers for Layer 2 Bundle Members
draft-ietf-lsr-l2-bundle-member-remote-id-02

LSR Working Group                                               L. Gong
Internet Draft                                             China Mobile
Intended status: Standards Track                                 C. Lin
Expires: September 15, 2026                                     M. Chen
                                                   New H3C Technologies
                                                            L. Ginsberg
                                                              P. Psenak
                                                          Cisco Systems
                                                         March 15, 2026

      Advertisement of Remote Interface Identifiers for Layer 2 Bundle
                                 Members
               draft-ietf-lsr-l2-bundle-member-remote-id-02

Abstract

   In networks where Layer 2 (L2) interface bundles (such as a Link
   Aggregation Group (LAG) [IEEE802.1AX]) are deployed, a controller
   may need to collect the connectivity relationships between bundle
   members for traffic engineering (TE) purposes. For example, when
   performing topology management and bidirectional path computation
   for TE, it is essential to know the connectivity relationships among
   bundle members.

   This document describes how OSPF and IS-IS would advertise the
   remote interface identifiers for Layer 2 bundle members. The
   corresponding extension of BGP-LS is also specified.

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 15 September 2026.

Glctgp, et al.       Expires September 15, 2026               [Page 1]
Internet-Draft        L2 Bundle Member Remote ID            March 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/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
   respect to this document.  Code Components extracted from this
   document must include Revised BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Revised BSD License.

Table of Contents

   1. Introduction...................................................2
      1.1. Requirements Language.....................................3
   2. Use Case.......................................................3
   3. Advertising L2 Bundle Member Remote Interface Identifier.......4
   4. OSPF Extension.................................................5
   5. IS-IS Extension................................................5
   6. BGP-LS Extension...............................................6
   7. Acquirement of Remote Interface Identifier.....................7
   8. Security Considerations........................................7
   9. IANA Considerations............................................8
   10. References....................................................8
      10.1. Normative References.....................................8
      10.2. Informational References................................10
   Contributors.....................................................10
   Authors' Addresses...............................................10

1. Introduction

   BGP-LS [RFC9552] is widely used for collecting topology information
   from IGPs. In networks where Layer 2 (L2) interface bundles (such as
   a Link Aggregation Group (LAG) [IEEE802.1AX]) are deployed, a
   controller may need to collect the connectivity relationships
   between bundle members for traffic engineering (TE) purposes. For
   example, when performing topology management and bidirectional path
   computation for TE, it is essential to know the connectivity
   relationships among bundle members.

   When advertising L2 bundles in OSPF [RFC9356] and IS-IS [RFC8668], a
   member link is described by its local interface identifier, also
   referred to as a link local identifier. If the remote interface

Glctgp, et al.       Expires September 15, 2026               [Page 2]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   identifier could be advertised for each member link, the pairing
   relationships between the local and remote interfaces would be
   clear.

   This document describes the mechanism for advertising the remote
   interface identifier for Layer 2 bundle members in OSPF and IS-IS.
   The BGP-LS extension for advertising L2 bundle member interface
   remote identifier is also specified in this document.

1.1. 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. Use Case

   Figure 1 shows a network, in which an L2 bundle is deployed between
   R1 and R2. The controller collects the topology information from R3
   via BGP-LS.

                    +----------+       BGP-LS
                    |Controller|<********************
                    +----------+                    *
                                                    *
                                                    *
                                                    *
       +----+         L2-Bundle          +----+   +----+
       |    |  /-------member 1-------\  |    |   |    |
       |    | /                        \ |    |   |    |
       | R1 +----------member 2----------+ R2 +---+ R3 +
       |    | \                        / |    |   |    |
       |    |  \-------member 3-------/  |    |   |    |
       +----+                            +----+   +----+

                      Figure 1

   The network operator may want to control bidirectional traffic flows
   on the individual member links of the underlying Layer 2 bundle for
   TE purposes. The real-time bandwidth, delay, and link loss might be
   measured for each bundle member at both ends. Labels or SIDs might
   be allocated for each bundle member at both ends. So, there would be
   requirements for the controller to figure out the connectivity
   relationships between bundle members.

Glctgp, et al.       Expires September 15, 2026               [Page 3]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   This document defines a mechanism for IGP routers to advertise the
   remote interface identifiers for each L2 bundle member, along with
   the corresponding mechanism for the controller to collect such
   information via BGP-LS.

3. Advertising L2 Bundle Member Remote Interface Identifier

   In OSPF, the remote interface identifiers of L2 bundle members are
   advertised as follows.

   OSPFv2 Extended Link TLV, or OSPFv3 Router-Link TLV, for L3 Link:
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #1
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 4)
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #2
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 4)
     ...
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #n
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 4)

   In IS-IS, the remote interface identifiers of L2 bundle members are
   advertised as follows. Note that IS-IS can advertise a set of
   members in a single L2 Bundle Member Attribute Descriptor, so the L2
   Bundle Member Interface Remote Identifier Sub-TLV MUST carry
   multiple remote interface identifiers, one for each of the bundle
   members advertised in the associated L2 Bundle Member Descriptor.

   L2 Bundle Member Attributes TLV:
     Parent L3 Neighbor Descriptor
     Length of L2 Bundle Attribute Descriptor
     Number of L2 Bundle Member Descriptors
     L2 Bundle Member Link Local Identifiers of Member #1,#2,...,#n
     Sub-TLV(s)
     L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
       as defined in Section 5) for Member #1,#2,...,#n

   In BGP-LS, the remote interface identifiers of L2 bundle members are
   advertised as follows.

Glctgp, et al.       Expires September 15, 2026               [Page 4]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   BGP-LS Link NLRI: Peer Adj Link for R1->R2(as described in Section
       5.2 of [RFC9086])
   Link Attributes:
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #1
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 6)
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #2
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 6)
     ...
     L2 Bundle Member Attributes TLV:
       L2 Bundle Member Descriptor of Member #n
       L2 Bundle Member Interface Remote Identifier Sub-TLV (Optional -
         as defined in Section 6)

4. OSPF Extension

   This document defines a new L2 Bundle Member Interface Remote
   Identifier Sub-TLV in both OSPFv2 and OSPFv3. This Sub-TLV is used
   to advertise the remote interface identifier for a L2 bundle member.

   It can be carried as a sub-TLV of the OSPF L2 Bundle Member
   Attributes TLV [RFC9356]. It has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Type (TBA)           |           Length (4)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Remote Interface ID                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o Type: TBA.

   o Length: 4.

   o Remote Interface ID: Remote identifier of interface, 4 octets.

   A remote interface ID with value of zero is not valid and MUST be
   ignored and handled as if the sub-TLV was not present.

5. IS-IS Extension

   This document defines a new L2 Bundle Member Interface Remote
   Identifier Sub-TLV in IS-IS. This Sub-TLV is used to advertise the
   remote interface identifiers for L2 bundle members.

Glctgp, et al.       Expires September 15, 2026               [Page 5]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   It can be carried as a sub-TLV of the IS-IS L2 Bundle Member
   Attributes TLV [RFC8668]. It has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type (TBA)  |     Length    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Remote Interface ID 1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                     ...                                       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Remote Interface ID N                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o Type: TBA.

   o Length: 4 * Number of L2 Bundle Member Descriptors.

   o Remote Interface ID: Remote identifier of interface, 4 octets.

   There MUST be one Remote Interface ID for each of the L2 Bundle
   Members advertised under the associated L2 Bundle Member Attribute
   Descriptor. A remote interface ID with value of zero MUST be ignored
   and handled as if the value was unknown.

   MP-TLV [RFC9885] for the new IS-IS sub-TLV SHOULD be set to "N".

6. BGP-LS Extension

   This document defines a new L2 Bundle Member Interface Remote
   Identifier Sub-TLV in BGP-LS. This Sub-TLV is derived from the
   Remote Interface Identifier Sub-TLV of OSPF (Section 3) and IS-IS
   (Section 4).

   It can be carried as a sub-TLV of the BGP-LS L2 Bundle Member
   Attributes TLV [RFC9085]. It has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Type (TBA)           |           Length (4)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Remote Interface ID                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o Type: TBA.

Glctgp, et al.       Expires September 15, 2026               [Page 6]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   o Length: 4.

   o Remote Interface ID: Remote identifier of interface, 4 octets.

   A remote interface ID with value of zero is not valid and MUST be
   ignored and handled as if the sub-TLV was not present.

7. Acquirement of Remote Interface Identifier

   IGPs have no direct way to exchange L2 bundle member link
   identifiers since the Layer 3 protocol is not operating directly on
   the bundle members. Some L2 protocols may be used to get the remote
   interface identifiers for bundle members. This may be discovered via
   [IEEE802.1AX] when used to form the LAG bundle. A router may also
   run LLDP [802.1AB] on the bundle members to exchange local interface
   identifiers with its neighbor, by using the Port ID TLV.

   How the remote interface identifier is obtained is out of the scope
   of this document.

8. Security Considerations

   This document describes how OSPF, IS-IS and BGP-LS would advertise
   the remote interface identifiers for Layer 2 bundle members. There
   are no new security issues introduced by the extensions in this
   document. The security considerations of [RFC8668], [RFC9356] ,
   [RFC9552],[RFC9085] and [RFC9086] are are applicable to this
   document.

   As always, if the IS-IS protocol is used in an environment where
   unauthorized access to the physical links on which IS-IS Protocol
   Data Units (PDUs) are sent occurs, then attacks are possible.  The
   use of authentication as defined in [RFC5304] and [RFC5310] is
   recommended to prevent such attacks.

   As always, if the OSPF protocol is used in an environment where
   unauthorized access to the physical links on which OSPF packets are
   sent occurs, then attacks are possible.  The use of authentication
   as defined in [RFC5709], [RFC7474], [RFC4552], and [RFC7166] is
   recommended for preventing such attacks.

   The isolation of BGP-LS peering sessions is recommended to ensure
   that BGP-LS topology information (including the newly added remote
   interface identifiers information) is not advertised to an external
   BGP peering session outside the trusted domain [RFC8402].

Glctgp, et al.       Expires September 15, 2026               [Page 7]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

9. IANA Considerations

   This document adds the following new sub-TLV to the "OSPFv2 Extended
   Link TLV Sub-TLVs" registry.

   +------+----------------------------------------------+----+
   | Type | Designation                                  |L2BM|
   +======+==============================================+====+
   | TBA  | L2 Bundle Member Interface Remote Identifier | Y  |
   +------+----------------------------------------------+----+

   This document adds the following new sub-TLV to the "OSPFv3
   Extended-LSA Sub-TLVs" registry.

   +------+----------------------------------------------+----+
   | Type | Description                                  |L2BM|
   +======+==============================================+====+
   | TBA  | L2 Bundle Member Interface Remote Identifier | Y  |
   +------+----------------------------------------------+----+

   This document adds the following new sub-TLV to the "IS-IS Sub-TLVs
   for TLVs Advertising Neighbor Information" registry.

   +------+-----------------------------+---+---+---+---+---+---+---+
   | Type | Description                 | 22| 23| 25|141|222|223| MP|
   +======+=============================+===+===+===+===+===+===+===+
   | TBA  | L2 Bundle Member            | n | n | y | n | n | n | n |
   |      | Interface Remote Identifier |   |   |   |   |   |   |   |
   +------+-----------------------------+---+---+---+---+---+---+---+

   This document adds the following new sub-TLV to the "BGP-LS NLRI and
   Attribute TLVs" registry.

   +------+----------------------------------------------+
   | Type | Description                                  |
   +======+==============================================+
   | TBA  | L2 Bundle Member Interface Remote Identifier |
   +------+----------------------------------------------+

10. References

10.1. Normative References

   [IEEE802.1AX]
             IEEE, "IEEE Standard for Local and Metropolitan Area
             Networks--Link Aggregation", IEEE Std 802.1AX, DOI
             10.1109/IEEESTD.2020.9105034, May 2020,
             <https://doi.org/10.1109/IEEESTD.2020.9105034>.

Glctgp, et al.       Expires September 15, 2026               [Page 8]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
             for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
             <https://www.rfc-editor.org/info/rfc4552>.

   [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
             Authentication", RFC 5304, DOI 10.17487/RFC5304, October
             2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
             and M. Fanto, "IS-IS Generic Cryptographic
             Authentication", RFC 5310, DOI 10.17487/RFC5310, February
             2009, <https://www.rfc-editor.org/info/rfc5310>.

   [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
             Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
             Authentication", RFC 5709, DOI 10.17487/RFC5709, October
             2009, <https://www.rfc-editor.org/info/rfc5709>.

   [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
             Authentication Trailer for OSPFv3", RFC 7166,DOI
             10.17487/RFC7166, March 2014, <https://www.rfc-
             editor.org/info/rfc7166>.

   [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
             "Security Extension for OSPFv2 When Using Manual Key
             Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
             <https://www.rfc-editor.org/info/rfc7474>.

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, May 2017.

   [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/info/rfc8402>.

   [RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
             M., and E. Aries, "Advertising Layer 2 Bundle Member Link
             Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
             December 2019, <https://www.rfc-editor.org/info/rfc8668>.

Glctgp, et al.       Expires September 15, 2026               [Page 9]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   [RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
             H., and M. Chen, "Border Gateway Protocol - Link State
             (BGP-LS) Extensions for Segment Routing", RFC 9085, DOI
             10.17487/RFC9085, August 2021, <https://www.rfc-
             editor.org/info/rfc9085>.

   [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>.

   [RFC9356] Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
             Member Link Attributes in OSPF", RFC 9356, January 2023,
             <https://www.rfc-editor.org/info/rfc9356>.

   [RFC9885] P. Kaneriya, T. Li, A. Przygienda, S. Hegde and L.
             GinsbergK. , "Multi-Part TLVs in IS-IS", RFC 9885, October
             2025, <https://www.rfc-editor.org/info/rfc9885>.

10.2. Informational References

   [802.1AB] "IEEE Standard for Local and metropolitan area networks-
             Station and Media Access Control Connectivity Discovery",
             IEEE Std 802.1AB-2016, 29 January 2016.

   [RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
             Traffic Engineering Information Using BGP", RFC 9552, DOI
             10.17487/RFC9552, December 2023, <https://www.rfc-
             editor.org/info/rfc9552>.

Contributors

   Ketan Talaulikar
   Cisco Systems
   India
   Email: ketant.ietf@gmail.com
Authors' Addresses

   Liyan Gong
   China Mobile
   China
   Email: gongliyan@chinamobile.com

Glctgp, et al.       Expires September 15, 2026              [Page 10]
Internet-Draft        L2 Bundle Member Remote ID            March 2026

   Changwang Lin
   New H3C Technologies
   China
   Email: linchangwang.04414@h3c.com

   Mengxiao Chen
   New H3C Technologies
   China
   Email: chen.mengxiao@h3c.com

   Les Ginsberg
   Cisco Systems
   United States of America
   Email: ginsberg@cisco.com

   Peter Psenak
   Cisco Systems
   Apollo Business Center
   Mlynske nivy 43
   Bratislava 821 09
   Slovakia
   Email: ppsenak@cisco.com

Glctgp, et al.       Expires September 15, 2026              [Page 11]