BGP-LS Extension for Inter-AS Topology Retrieval
draft-ietf-idr-bgpls-inter-as-topology-ext-27

IDR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                 H. Chen
Expires: 29 October 2026                                      Individual
                                                           K. Talaulikar
                                                           Cisco Systems
                                                               S. Zhuang
                                                     Huawei Technologies
                                                                  C. Lin
                                                    New H3C Technologies
                                                           27 April 2026

            BGP-LS Extension for Inter-AS Topology Retrieval
             draft-ietf-idr-bgpls-inter-as-topology-ext-27

Abstract

   This document specifies the procedure for distributing Border Gateway
   Protocol-Link State (BGP-LS) key parameters for inter-domain links
   between two Autonomous Systems (ASes).  It defines a new type within
   the BGP-LS Network Layer Reachability Information (NLRI) for a Inter-
   AS Link, as well as three new type-length-values (TLVs) for the BGP-
   LS Inter-AS Link descriptor.  These BGP-LS extensions enable
   Software-Defined Networking (SDN) controllers to retrieve network
   topology across inter-AS environments.

   These extensions and procedures allow network operators to collect
   inter-domain interconnect information and automatically compute the
   end-to-end network topology using information provided by the BGP-LS
   protocol.

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
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   This Internet-Draft will expire on 29 October 2026.

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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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Inter-AS Domain Scenarios . . . . . . . . . . . . . . . . . .   3
   5.  Inter-AS Link NLRI  . . . . . . . . . . . . . . . . . . . . .   4
   6.  Inter-AS Link Descriptor TLVs . . . . . . . . . . . . . . . .   6
     6.1.  Remote AS Number TLV  . . . . . . . . . . . . . . . . . .   7
     6.2.  IPv4 Remote ASBR ID . . . . . . . . . . . . . . . . . . .   7
     6.3.  IPv6 Remote ASBR ID . . . . . . . . . . . . . . . . . . .   8
   7.  Advertisement of IGP Information for Inter-AS Links . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  New BGP-LS NLRI type  . . . . . . . . . . . . . . . . . .  10
     9.2.  New Inter-AS Link Descriptors . . . . . . . . . . . . . .  10
   10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   BGP-LS [RFC9552] describes the use of BGP protocol for advertisement
   of the Link-State topology information.  It enables applications such
   as an SDN controllers to collect the underlay network topology.
   [RFC9552] covers the advertisement of topology information from
   within Interior Gateway Protocol (IGP) domain.  If the network has
   more than one IGP domain, and these domains interconnect with each
   other via inter-AS links, there is no mechanism within the current
   BGP-LS to advertise the interconnect topology information.

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   [RFC9086] defines extensions for exporting BGP peering node topology
   information (including peers, interfaces, and peering ASes) in a way
   that is used to compute efficient BGP Peering Engineering policies
   and strategies.  This information can also be used to compute
   interconnection topology among different IGP domains, but it requires
   every border router to run the BGP-LS protocol and report such
   information to SDN controllers.  Considering there will be several
   border routers on the network boundary, such solution restricts its
   deployment flexibility.

   This document defines the Inter-AS Link NLRI and some new TLVs for
   BGP-LS to cover scenarios where an SDN controller needs to get the
   interconnection topology information between different AS domains
   when sourced from IGPs.

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.  Terminology

   The following terms are defined in this document:

   *  IDCs: Internet Data Centers

   *  MAN: Metro-Area-Network

   *  SDN: Software Defined Network

4.  Inter-AS Domain Scenarios

   Figure 1 illustrates the multi-domain scenarios discussed in this
   document.  Typically, the SDN Controller can retrieve the topology of
   IGP A and IGP B individually via the BGP-LS protocol, but it cannot
   obtain topology connection information between these two IGP domains,
   as IGP protocols are generally not run on the inter-AS links.

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   In Figure 1, S2(in IGP domain A) and T1(in IGP domain B) are
   connected to the IP SDN Controller via BGP-LS, but they can only
   report the topology information among the IGP A and IGP B themselves,
   and can't report the inter-as topology information among them because
   there is no IGP protocol runs on the inter-AS links.  The border
   routers, SB1/SB3 in IGP A and TB2/TB4 in IGP B know the inter-AS
   links among them, and can advertise such information via underlying
   OSPF [RFC5392] or IS-IS [RFC9346], but there is no place in current
   BGP-LS protocol to transfer such information.

                             +-----------------+
                      +------+IP SDN Controller+-----+
                      |      +-----------------+     |
                      |                              |
                      |BGP-LS                        |BGP-LS
                      |                              |
      +---------------+-------+               +------+--------------+
      | +--+         +|-+   +-+-+           +-+-+   +|-+        +--+|
      | |S1+---------+S2+---+SB1+-----------+TB2+---+T1+--------+T2||
      | +-++   N1    +-++   +-+-+           +-+-+   ++++   N2   +-++|
      |   |                   |               |                   | |
      |   |                   |               |                   | |
      | +-++        +-++    +-+-+           +-+-+   ++++        +-++|
      | |S4+--------+S3+----+SB3+-----------+TB4+---+T3+--------+T4||
      | +--+        +--+    +-+-+           +-+-+   ++-+        +--+|
      |                       |               |                     |
      |                       |               |                     |
      |       IGP A           |               |      IGP B          |
      +-----------------------+               +---------------------+

                  Figure 1: Inter-AS Domain Scenarios

5.  Inter-AS Link NLRI

   [RFC9552] defines four NLRI types (Node, Link, IPv4 Topology Prefix,
   and IPv6 Topology Prefix) to transfer the topology and prefix
   information.  For inter-AS link, as the two ends of the link belong
   in different IGP domains and the link does not run an IGP protocol,
   it is not appropriate to advertise their information within the
   existing NLRI types listed above.

   This document defines a new NLRI type 7, see__Section 9) within the
   BGP-LS NLRI, referred to as the Inter-AS Link NLRI.  The Inter-AS
   Link NLRI is encoded in the format shown in Figure 2 as explained
   below:

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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
       +-+-+-+-+-+-+-+-+
       |  Protocol-ID  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Identifier                          |
       |                            (64 bits)                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //              Local Node Descriptors (variable)              //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //           Inter-AS Link Descriptors (variable)              //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: Inter-AS Link NLRI Format

   This document specifies the advertisement of Inter-AS Links using the
   Inter-AS Link NLRI when originating the information from the
   underlying OSPF [RFC5392] and IS-IS [RFC9346] advertisements.

   This section describes the encoding of the Inter-AS Link NLRI while
   the more detailed procedures for sourcing of this information from
   the underlying IGP are described in Section 7.

   The "Protocol-ID" is set to the value indicating the source protocol
   of the Inter-AS Link information, as specified in [RFC9552]
   Section 5.2.  As the information is sourced from OSPF or IS-IS, the
   value MUST correspond to one of IGP values as specified in [RFC9552].

   The semantics of "Identifier" field are the same as defined in
   [RFC9552] and will be set to a value that is identical to the
   "Identifier" value of the IGP domain associated with the ASBR of the
   inter-AS link.  Therefore, the "Identifier" values for the two half-
   links (refer section 5.2.2 of [RFC9552]) of the inter-AS link could
   be different depending on the configuration of Identifiers for the
   two IGP domains.

   The "Local Node Descriptors" field is encoded using the TLV 256
   defined in section 5.2.1.2 of [RFC9552] to identify the ASBR
   associated with the specific half-link of the inter-AS link.  The
   following TLVs MUST be included as the Local Node Descriptors:

   - Autonomous System (TLV 512) [RFC9552].

   - OSPF Area-ID (TLV 514) [RFC9552] to be included only in the case of
   OSPF, when the Inter-AS TE LSA from which information is sourced is
   being flooded with an area-scope.  It is not included when the LSA is
   flooded with AS-scope.

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   - IGP Router ID (TLV 515) encoded for either OSPF or IS-IS, depending
   on the source protocol as specified in section 5.2.1.4 of [RFC9552].

   - One or both of IPv4 and IPv6 Router-ID of the ASBR using TLV 1028
   and/or 1029 [RFC9552], depending on whether the ASBR is configured
   with one or both of the IPv4 and IPv6 TE Router-IDs.  (Note: while
   [RFC9552] introduced these TLVs for use in the BGP-LS attribute, this
   document also leverages the same TLVs for use in the NLRI.)

   Inter-AS Link Descriptors are encoded as TLVs that identify the
   specific half-link of the inter-AS link.  Section 6 of this document
   introduces the TLVs that MUST be included as the Inter-AS Link
   Descriptors:

   - Remote AS Number (TLV 270), and

   - One or both of IPv4 and IPv6 Remote ASBR ID using TLV 271 and/or
   TLV 272, depending on whether the Remote ASBR is configured with one
   or both of the IPv4 and IPv6 TE Router-IDs.

   Additionally, the following TLVs MUST be included as Inter-AS Link
   Descriptors if they are being advertised in the underlying IGP
   advertisement of the inter-AS link as they help identify individual
   links when there are more than one inter-AS links between two ASBRs.

   - Link Local/Remote Identifiers (TLV 258) [RFC9552]

   - IPv4 Interface Address (TLV 259) [RFC9552]

   - IPv4 Neighbor Address (TLV 260) [RFC9552]

   - IPv6 Interface Address (TLV 261) [RFC9552]

   - IPv6 Neighbor Address (TLV 262) [RFC9552]

   Use of any other TLVs as Local Node Descriptors or Inter-AS Link
   Descriptors may cause challenges in the correlation of the two Inter-
   AS Link NLRI half-links when the BGP-LS Producer implementations
   vary.

6.  Inter-AS Link Descriptor TLVs

   This document introduces three TLVs for inclusion as Inter-AS Link
   Descriptors within the Inter-AS Link NLRI for the advertisement of
   inter-AS link information via BGP-LS.

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   +-----------+---------------------+--------------+----------------+
   |  TLV Code | Description         |IS-IS/OSPF TLV| Reference      |
   |   Point   |                     |   /Sub-TLV   | (RFC/Section)  |
   +-----------+---------------------+--------------+----------------+
   |    270    |Remote AS Number     |   24/21      | [RFC9346]/3.4.1|
   |           |                     |              | [RFC5392]/3.3.1|
   |    271    |IPv4 Remote ASBR ID  |   25/22      | [RFC9346]/3.4.2|
   |           |                     |              | [RFC5392]/3.3.2|
   |    272    |IPv6 Remote ASBR ID  |   26/24      | [RFC9346]/3.4.3|
   |           |                     |              | [RFC5392]/3.3.3|
   +-----------+---------------------+--------------+----------------+
                Figure 3: Inter-AS Link Descriptor TLVs

   The encoding of these TLVs are aligned with the corresponding
   advertisements in [RFC9346] and [RFC5392], which keeps the BGP-LS
   protocol agnostic to the underly protocol.

6.1.  Remote AS Number TLV

   The Remote AS Number TLV specifies the AS number of the neighboring
   AS to which the advertised link connects.

   The Remote AS Number TLV is TLV Type 270 and is 4 octets in length.
   Its format is as follows:

    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             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote AS Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 4: Remote AS Number TLV Format

   The Remote AS Number field has 4 octets.  When only 2 octets are used
   for the AS number (for example, when such information is advertised
   from OSPF), the left (high-order) 2 octets MUST be set to 0.

6.2.  IPv4 Remote ASBR ID

   The IPv4 Remote ASBR ID TLV specifies the IPv4 identifier of the
   remote ASBR to which the advertised inter-AS link connects.  This can
   be any stable, routable IPv4 address of the remote ASBR.  The use of
   the TE Router ID, as specified in the Traffic Engineering Router ID
   TLV [RFC9346] is RECOMMENDED.

   The IPv4 Remote ASBR ID TLV is TLV Type 271 and is 4 octets in
   length.  Its format is as follows:

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote ASBR ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 5:  IPv4 Remote ASBR ID TLV Format

6.3.  IPv6 Remote ASBR ID

   The IPv6 Remote ASBR ID TLV specifies the IPv6 identifier of the
   remote ASBR to which the advertised inter-AS link connects.  This can
   be any stable, routable IPv6 address of the remote ASBR.  The use of
   the TE Router ID, as specified in the IPv6 Traffic Engineering Router
   ID TLV [RFC9346] is RECOMMENDED.

   The IPv6 Remote ASBR ID TLV is TLV Type 272 and is 16 octets in
   length.  Its format is as follows:

    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             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote ASBR ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote ASBR ID (continued)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote ASBR ID (continued)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Remote ASBR ID (continued)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 6:  IPv6 Remote ASBR ID TLV Format

   The IPv6 Remote ASBR ID TLV MUST be included if the neighboring ASBR
   has an IPv6 address.  If the neighboring ASBR does not have an IPv6
   address, the IPv4 Remote ASBR ID TLV MUST be included instead.  Both
   an IPv4 Remote ASBR ID TLV and an IPv6 Remote ASBR ID TLV MAY be
   present in an inter-AS Link NLRI.

7.  Advertisement of IGP Information for Inter-AS Links

   Advertisement of Inter-AS Links along with their TE information is
   done is done in IGPs as follows:

   - In OSPFv2 via the Inter-AS-TE-v2 LSA [RFC5392]

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   - In OSPFv3 via the Inter-AS-TE-v3 LSA[RFC5392]

   - In IS-IS via the Inter-AS Reachability Information TLV (TLV 141)
   [RFC9346]

   The routers that connect to the SDN controller via the BGP-LS
   protocol within each domain will advertise the information from the
   above IGPs for the inter-AS link.  To retrieval the Inter-AS
   topology, the Autonomous System TLV(TLV 512), Remote AS number, IPv6
   Remote ASBR ID and/or IPv4 Remote ASBR ID MUST be presented within
   the inter-AS Link NLRI of each inter-AS link.

   When advertising these Inter-AS Links from the IGPs into BGP-LS as
   Inter-AS Links, the sourcing of information for the Inter-AS Link
   NLRI except for the Inter-AS Link Descriptors follows the same
   procedures as specified in [RFC9552].  The information about the
   Remote AS Number and the IPv4/IPv6 Remote ASBR IDs specified in
   Section 6 are derived from the Remote AS Number and IPv4/IPv6 Remote
   ASBR ID TLVs specified for OSPF and IS-IS in [RFC5392] and [RFC9346]
   respectively.  The rest of the Inter-AS Link Descriptor TLVs of the
   Inter-AS Link NLRI are sourced from the base OSPF/ISIS TE TLVs that
   were originally introduced for normal IGP links and which are also
   encoded for the inter-AS TE links as specified in [RFC5392] and
   [RFC9346]; their procedures are therefore same as in [RFC9552].

   The OSPF/ISIS Inter-AS Link advertisements also include various link
   properties (e.g., TE metric, Admin Groups, SRLGs, etc.) which are
   encoded using the same TLVs as for normal IGP links.  These link
   properties are advertised using their corresponding BGP-LS TLVs as
   specified in [RFC9552] and other BGP-LS extensions in the BGP-LS
   Attribute associated with the Inter-AS Link NLRI of that specific
   link.

8.  Security Considerations

   BGP-LS security is specified in [RFC9552].  This extension to BGP-LS
   focuses on scenarios where a single entity-operated network includes
   multiple IGP domains composed of its backbone network, several Metro-
   Area Networks (MANs), and Internet Data Centers (IDCs).  The
   configuration of these networks, operated by a single administrative
   entity, creates a "walled garden".  Within this single administrative
   domain, the network operator needs to monitor and engineer traffic
   flows traversing a network that spans multiple Autonomous Systems
   (ASes).  The network operator can obtain this inter-AS topology
   information via the procedure described in this document.

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   A single administrative domain consisting of two ASes that passes
   information about Inter-AS Link characteristics does not cause issues
   within a "walled garden".  However, the Inter-AS Link NLRI and its
   characteristics (Link/Local Identifier, IPv4 Interface Address, IPv4
   Neighbor Address, IPv6 Interface Address, IPv6 Neighbor Address,
   Multi-Topology Identifier, Remote-AS Number, IPv4 Remote ASBR ID, and
   IPv6 Remote ASBR ID) constitute critical network information.  As
   such, operators SHOULD handle this critical information in a manner
   that restricts it to the walled garden.

9.  IANA Considerations

   This document requests IANA to update the allocated codepoints from
   under the "Border Gateway Protocol - Link State (BGP-LS) Parameters"
   registry group as follows:

9.1.  New BGP-LS NLRI type

   IANA has allocated codepoint for the Inter-AS Link NLRI type from the
   "BGP-LS NLRI Types" registry in the “Border Gateway Protocol – Link
   State (BGP-LS) Parameter” Group:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type       |   NLRI Type       |        Reference          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       7       | Inter-AS Link NLRI|      This document        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 7:  Inter-AS Link NLRI Codepoint

9.2.  New Inter-AS Link Descriptors

   IANA has allocated codepoints for the following TLVs from "BGP-LS
   NLRI and Attribute TLVs" registry in the “Border Gateway Protocol –
   Link State (BGP-LS) Parameter” Group:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV Code Point  |   Description         |      Reference        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      270          | Remote AS Number      |     This document     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      271          |  IPv4 Remote ASBR ID  |     This document     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      272          |  IPv6 Remote ASBR ID  |     This document     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 8:  BGP-LS Link Descriptors TLV

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10.  Acknowledgement

   The author would like to thank Susan Hares, Acee Lindem, Jie Dong,
   Shaowen Ma, Jeff Tantsura and Dhruv Dhody for their valuable comments
   and suggestions.

11.  References

11.1.  Normative References

   [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>.

   [RFC5392]  Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
              January 2009, <https://www.rfc-editor.org/info/rfc5392>.

   [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>.

   [RFC9346]  Chen, M., Ginsberg, L., Previdi, S., and D. Xiaodong, "IS-
              IS Extensions in Support of Inter-Autonomous System (AS)
              MPLS and GMPLS Traffic Engineering", RFC 9346,
              DOI 10.17487/RFC9346, February 2023,
              <https://www.rfc-editor.org/info/rfc9346>.

   [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>.

11.2.  Informative References

   [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>.

Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District

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   Beijing
   Beijing, 102209
   China
   Email: wangaj3@chinatelecom.cn

   Huaimo Chen
   Individual
   Boston, MA
   United States of America
   Email: hchen.ietf@gmail.com

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

   Shunwan Zhuang
   Huawei Technologies
   Huawei Building, No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: zhuangshunwan@huawei.com

   Changwang Lin
   New H3C Technologies
   Huawei Building, No.156 Beiqing Rd.
   Beijing
   China
   Email: linchangwang.04414@h3c.com

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