Advertisement of SR Policy Operational States using BGP Link-State
draft-ietf-idr-bgp-ls-sr-policy-admin-flags-00

IDR Working Group                                           C. Lin, Ed.
Internet Draft                                     New H3C Technologies
Intended status: Standards Track                            Z. Ali, Ed.
Expires: January 20, 2027                           Cisco Systems, Inc.
                                                                Y. Liu
                                                           China Mobile
                                                               Ran.Chen
                                                                    ZTE
                                                            A. Karboubi
                                                                  Ciena
                                                          July 19, 2026

     Advertisement of SR Policy Operational States using BGP Link-State
               draft-ietf-idr-bgp-ls-sr-policy-admin-flags-00

Abstract

   This document defines the extension of BGP Link-State to advertise
   the operational 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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on January 29, 2027.

Lin, et al.           Expires January 20, 2027                [Page 1]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 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
   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. Terminology....................................................3
   3. Extension of SR Candidate Path State...........................3
   4. Extension of SR Segment List TLV...............................3
   5. Operations.....................................................4
   6. Security Considerations........................................4
   7. IANA Considerations............................................4
   8. References.....................................................5
      8.1. Normative References......................................5
      8.2. Informative References....................................6
   9. Acknowledgments................................................7
   Appendix A. Cross WG Information..................................8
      A.1. Link to Spring WG.........................................8
      A.2. Interaction with PCE WG...................................8
      A.3. Interaction with SRV6ops Recommendations..................8
   Authors' Addresses................................................9

  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 operational state of the candidate path or
   the segment list, facilitating the operation and maintenance of the
   SR Policy.

Lin, et al.           Expires January 20, 2027                [Page 2]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

   This document defines extensions to BGP-LS to advertise defines the
   extension of BGP Link-State to advertise the operational 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. ietf-spring-sr-policy-
       eligibility].

     - IFN-flag (Bit TBD) (Install Final Node-sid flag) as defined in
       [I-D. ietf-spring-srv6-policy-sid-list-opt]: indicate the
       endpoint node SID is included in installing SID list(s) of the
       Candidate Path (CP) when set. If set to 1, the endpoint node SID
       MUST be included when installing the SR Policy SID list(s) used
       to carry the data traffic. If set to 0, the endpoint node SID
       MUST NOT be included when installing the SR Policy SID list(s)
       used to carry the data traffic.

  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.

   Two New bits in Flags field of the SR Segment List TLV is defined:

Lin, et al.           Expires January 20, 2027                [Page 3]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

     - 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).

  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. Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the security considerations discussed in [RFC9857].

   This document defines new bits in the Flags field of the SR
   Candidate Path State TLV to indicate the operational state of the
   candidate path. Similarly, new bits in the Flags field of the SR
   Segment List TLV are defined to report the operational state of the
   segment list. The values of these bits determine the state of the
   candidate path or segment list within the SR policy and may
   consequently affect packet forwarding in the network. Therefore,
   when configuring, querying, or reporting these administrative flags
   in the BGP control plane, appropriate measures MUST be taken to
   protect such mission-critical or commercially sensitive information.

  7. IANA Considerations

   This document requests four bits in the flag field of "SR Candidate
   Path State TLV" [RFC9857] under the "BGP-LS Node Descriptor, Link
   Descriptor, Prefix Descriptor, and Attribute TLVs" registry.

Lin, et al.           Expires January 20, 2027                [Page 4]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

   Bit     Description                                Reference
   -----------------------------------------------------------------
   TBA     S-Flag: The CP is configured               This document
           as "backup ineligible"
   -----------------------------------------------------------------
   TBA     IS-Flag: The CP is configured              This document
           as "Ignore service route's Prefix SID"
   -----------------------------------------------------------------
   TBA     PE-Flag: The CP is configured              This document
           as "candidate path eligible"
   -----------------------------------------------------------------
   TBA     IFN-flag: The CP is configured             This document
           as "Install Final Node-sid"
   -----------------------------------------------------------------

   This document requests two bits in the flag field of "SR Segment
   List TLV" [RFC9857] under the "BGP-LS Node Descriptor, Link
   Descriptor, Prefix Descriptor, and Attribute TLVs" registry.

   Bit     Description                                  Reference
   ------------------------------------------------------------------
   TBA     S-Flag: Indicates that the CP is in an       This document
           administrative shut state when set and not
           in an administrative shut state when clear.
   ------------------------------------------------------------------
   TBA     PE-Flag: Indicates the Segment List is in    This document
           an eligible state (capable of forwarding
           traffic) when set and not in an eligible
           state when clear.
   ------------------------------------------------------------------
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>.

Lin, et al.           Expires January 20, 2027                [Page 5]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

   [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. ietf-spring-sr-policy-eligibility] Karboubi, A., Shah, H.,
             Sivalaban, S., Stone, A. and Schmutz, C., "Eligibility
             Concept in Segment Routing Policies", draft-ietf-spring-
             sr-policy-eligibility-00 (work in progress), January 2026.

   [I-D. draft-ietf-spring-srv6-policy-sid-list-opt] Z. Ali, C. Lin, Y.
             Liu, R. Chen and C. Li, "SRv6 Policy SID List
             Optimization", Work in Progress, Internet-Draft, draft-
             ietf-spring-srv6-policy-sid-list-opt, 25 November
             2025,<https://datatracker.ietf.org/doc/html/draft-ietf-
             spring-srv6-policy-sid-list-opt-00>.

   [I-D. draft-all-pce-srv6-policy-sid-list-optimization] Z. Ali, C.
             Lin, Y. Liu, R. Chen and C. Li, "Path Computation Element
             Communication Protocol (PCEP) extensions for SRv6 Policy
             SID List Optimization", Work in Progress, Internet-Draft,
             draft-all-pce-srv6-policy-sid-list-optimization, 02 March
             2026, <https://datatracker.ietf.org/doc/html/draft-all-
             pce-srv6-policy-sid-list-optimization-04>.

   [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>.

   [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

Lin, et al.           Expires January 20, 2027                [Page 6]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

  9. Acknowledgments

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

   TBD

Lin, et al.           Expires January 20, 2027                [Page 7]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

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], Section 8.2 of [RFC9256], and
   Section 3.2 of [I-D.draft-ietf-spring-srv6-policy-sid-list-opt] via
   BGP-LS. These SPRING features require the implementation of this
   document.

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].

   The optimization feature implemented in BGP by this document also
   could be implemented in PCEP according to Section 3.1 of [I-D.
   draft-ietf-spring-srv6-policy-sid-list-opt]. [I-D. draft-all-pce-
   srv6-policy-sid-list-optimization] specifies a PCEP extension to
   indicate whether the endpoint's node SID needs to be included or
   excluded when installing the SRv6 Policy.

A.3. Interaction with SRV6ops Recommendations

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

Lin, et al.           Expires January 20, 2027                [Page 8]
Internet-Draft    BGP-LS for SR Policy Admin Flags            July 2026

Authors' Addresses

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

   Zafar Ali (editor)
   Cisco Systems, Inc.
   Email: zali@cisco.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

Lin, et al.           Expires January 20, 2027                [Page 9]