IDR Working Group C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track Y. Liu
Expires: December 28, 2025 China Mobile
Ran.Chen
ZTE
June 26, 2025
Advertisement of SR Policy Administative Flags using BGP Link-State draft-lin-idr-bgp-ls-sr-policy-admin-flag-01Abstract
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.
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Table of Contents1. 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
Authors' Addresses................................................6
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 [I-D.ietf-idr-sr-policy-safi] [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.
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.
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2. TerminologyThe 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 [I-D.ietf-idr-bgp-ls-sr-policy], 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.
- N-Flag(Bit TBD): Indicates the endpoint node SID is included in
installing SID list(s) of the Candidate Path (CP) when set.
- 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 [I-D.ietf-idr-bgp-ls-sr-policy],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. OperationsThe document does not bring new operation beyond the description of operations defined in Section 6 of [I-D.ietf-idr-bgp-ls-sr-policy]. The existing operations defined in [I-D.ietf-idr-bgp-ls-sr-policy] 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[I-D.ietf-idr-bgp-ls-sr-policy] Previdi, S., Talaulikar, K., Dong,
J., Gredler, H., and Tantsura, J., "Advertisement of Segment Routing Policies using BGP Link-State", draft- ietf-idr-bgp-ls-sr-policy-17 (work in progress), March 2025.
[I-D.ietf-idr-sr-policy-safi] Previdi, S., Filsfils, C., Talaulikar,
K., Mattes, P., and Jain, D., "Advertising Segment Routing Policies in BGP", draft-ietf-idr-sr-policy-safi-13 (work in progress), February 2025.
[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>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC2119 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
9. Acknowledgments
The authors would like to thank the following for their valuable contributions of this document:
TBD
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Authors' AddressesChangwang 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
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