Advertisement of SR Policy Administative Flags using BGP Link-State
draft-lin-idr-bgp-ls-sr-policy-admin-flag-03

IDR Working Group                                                C. Lin
Internet Draft                                     New H3C Technologies
Intended status: Standards Track                                 Y. Liu
Expires: December 08, 2026                                 China Mobile
                                                               Ran.Chen
                                                                    ZTE
                                                            A. Karboubi
                                                                  Ciena
                                                           June 6, 2026

    Advertisement of SR Policy Administative Flags using BGP Link-State
               draft-lin-idr-bgp-ls-sr-policy-admin-flag-03

Abstract

   This document defines the extension of BGP Link-State to advertise
   the administrative state of the candidate path or segment list,
   facilitating the operation and maintenance of the SR Policy.

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 December 08, 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
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   warranty as described in the Simplified BSD License.

Table of Contents

   1. Introduction...................................................2
   2. Terminology....................................................3
   3. Extension of SR Candidate Path State...........................3
   4. Extension of SR Segment List TLV...............................3
   5. Operations.....................................................4
   6. IANA Considerations............................................4
   7. Security Considerations........................................4
   8. References.....................................................4
      8.1. Normative References......................................4
      8.2. Informative References....................................5
   9. Acknowledgments................................................5
   Appendix A. Cross WG Information..................................6
      A.1. Link to Spring WG.........................................6
      A.2. Interaction with PCE WG...................................6
      A.3. Interaction with SRV6ops Recommendations..................6
   Authors' Addresses................................................7

  1. Introduction

   Segment routing (SR) [RFC8402] is a source routing paradigm that
   explicitly indicates the forwarding path for packets at the ingress
   node. The ingress node steers packets into a specific path according
   to the Segment Routing Policy (SR Policy) as defined in [RFC9256].
   An SR Policy may have multiple candidate paths that are provisioned
   or signaled [RFC9830] [RFC8664] from one of more sources.

   [I-D.lin-idr-sr-policy-admin-flags] proposes an extension to the BGP
   SR Policy that sets the management state of the candidate path or
   the segment list, facilitating the operation and maintenance of the
   SR Policy.

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   This document defines extensions to BGP-LS to advertise defines the
   extension of BGP Link-State to advertise the administrative state of
   the candidate path or segment list.

  2. Terminology

   The definitions of the basic terms are identical to those found in
   Segment Routing Policy Architecture [RFC9256].

  3. Extension of SR Candidate Path State

   As defined in [RFC9857], the SR Candidate Path State TLV provides
   the operational status and attributes of the SR Policy at the
   candidate path level.

   New bits in Flags field of the SR Candidate Path State TLV are
   defined:

     -           BI-Flag (Bit TBD): Indicates the CP is configured as "backup
       ineligible".

     -           IS-Flag(Bit TBD): Indicates the CP is configured as "Ignore
       service route's Prefix SID". It allows traffic to a BGP service
       route to be steered over an SR policy without imposing the
       service route's prefix label or SRv6 Service SID.

     -           PE-Flag (Bit TBD): Indicates that the CP is set to 'candidate
       path eligible' as defined in [I-D.karboubi-spring-sr-policy-
       eligibility].

  4. Extension of SR Segment List TLV

   As defined in [RFC9857],The SR Segment List TLV is used to report a
   single SID-List of a candidate path.  Multiple instances of this TLV
   may be used to report multiple SID-Lists of a candidate path.

   A New bit in Flags field of the SR Segment List TLV is defined:

     -           S-Flag(Bit TBD): Indicates the SR Segment is in an administrative
       shut state when set and not in administrative shut state when
       clear.

     -           PE-Flag(Bit TBD): When set, indicates the Segment List is in an
       eligible state (capable of forwarding traffic).
       When cleared, indicates the Segment List is ineligible (cannot
       forward traffic).

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  5. Operations

   The document does not bring new operation beyond the description of
   operations defined in Section 6 of [RFC9857]. The existing
   operations defined in [RFC9857] can apply to this document directly.

  6. IANA Considerations

   TBD

  7. Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the BGP security model.

8. References

  8.1. Normative References

   [RFC9857] Previdi, S., Talaulikar, K., Dong, J., Gredler, H., and
             Tantsura, J., "Advertisement of Segment Routing Policies
             using BGP Link-State", RFC 9857, DOI 10.17487/RFC9857,
             October 2025, <https://www.rfc-editor.org/info/rfc9857>.

   [RFC9830] Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
             D. Jain, "Advertising Segment Routing Policies in BGP",
             RFC 9830, DOI 10.17487/RFC9830, September 2025,
             <https://www.rfc-editor.org/info/rfc9830>.

   [I-D. lin-idr-sr-policy-admin-flags] Lin, C., Li, J., and Chen, R.,
             "BGP SR Policy Extensions for Administrative Flags",
             draft-lin-idr-sr-policy-admin-flags (work in progress),
             February 2025.

   [I-D. karboubi-spring-sr-policy-eligibility] Karboubi, A., Shah, H.,
             Sivalaban, S., Stone, A. and Schmutz, C., "Eligibility
             Concept in Segment Routing Policies", draft-karboubi-
             spring-sr-policy-eligibility-01 (work in progress),
             February 2025.

   [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>.

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   [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>.

   [RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
             P. Mattes, "Segment Routing Policy Architecture", RFC
             9256, DOI 10.17487/RFC9256, July 2022, <https://www.rfc-
             editor.org/info/rfc9256>.

  8.2. Informative References

   TBD

  9. Acknowledgments

   The authors would like to thank the following for their valuable
   contributions of this document:

   TBD

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Appendix A. Cross WG Information

   This section describes cross-working group information for use
   during the IETF review process. This section will be removed by the
   RFC editor prior to publication.

A.1. Link to Spring WG

   This document implements the features defined in Section 4 of [I-D.
   ietf-spring-sr-policy-eligibility] and Section 8.2 of [RFC9256] via
   BGP-LS. This spring features require this document to be
   implemented.

A.2. Interaction with PCE WG

   The BGP extension defined by this document also may be implemented
   by a new TLV of PCEP according to Section 4.3 of [I-D. draft-
   karboubi-spring-sidlist-optimized-cs-sr].

A.3. Interaction with SRV6ops Recommendations

   This optimization feature could be distributed to external
   components using BGP-LS extension defined in this document.

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Authors' Addresses

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

   Yisong Liu
   China Mobile
   32 Xuanwumen West Street
   Beijing
   Xicheng District, 100053
   China
   Email: liuyisong@chinamobile.com

   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn

   Amal Karboubi
   Ciena
   Email: akarboub@ciena.com

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