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, . [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, . 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,. [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, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 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, . [RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", RFC 9256, DOI 10.17487/RFC9256, July 2022, . 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]