IDR C. Lin Internet Draft New H3C Technologies Intended status: Standards Track W. Cheng Expires: August 24, 2025 China Mobile Y. Liu ZTE K. Talaulikar Cisco Systems M. Chen New H3C Technologies February 24, 2025 BGP SR Policy Extensions for Segment List Identifier draft-ietf-idr-sr-policy-seglist-id-03 Abstract Segment Routing is a source routing paradigm that explicitly indicates the forwarding path for packets at the ingress node. An SR Policy is a set of candidate paths, each consisting of one or more segment lists. This document defines extensions to BGP SR Policy to specify the identifier of segment list. 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). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on August 24, 2025. Copyright Notice Copyright (c) 2025 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 Lin, et al. Expires August 24, 2025 [Page 1] Internet-Draft BGP SR Policy Segment List Identifier February 2025 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction...................................................2 1.1. Requirements Language.....................................3 2. Segment List Identifier in SR Policy...........................3 2.1. Segment List ID Sub-TLV...................................4 3. Security Considerations........................................5 4. Implementation Status..........................................5 4.1. New H3C Technologies......................................6 4.2. ZTE Corp..................................................6 5. IANA Considerations............................................7 6. References.....................................................7 6.1. Normative References......................................7 6.2. Informative References....................................7 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]. In order to distribute SR policies to the headend, [I-D.ietf-idr-sr- policy-safi] specifies a mechanism by using BGP. However, there is no identifier for segment list in BGP SR Policy, which may cause inconvenience for other mechanisms to designate segment lists distributed by BGP. Consider the case of a network controller distributing SR policies to the headend nodes where the headend nodes need to collect traffic forwarding statistics per segment list. When a headend node reports each statistic to the controller, it needs to specify the segment list which the statistic belongs to. Due to the lack of identifier, the headend node usually reports all SIDs in the associated segment list along with the statistic, and then the controller needs to compare the SIDs one by one to recognize which segment list it is. The advertisement of all SIDs in the segment list consumes a lot of octets, and the comparison of SIDs can be complicated. Lin, et al. Expires August 24, 2025 [Page 2] Internet-Draft BGP SR Policy Segment List Identifier February 2025 Consider a second example where a network controller distributes SR policies using BGP, and then it uses NETCONF to set some configurations of the segment lists which are not suitable to be carried in BGP. The controller needs to specify which segment list these configurations belong to when it issues them. In this case, a simple identifier of segment list can also be helpful. An identifier of segment list may also serve as a user-friendly attribute for debugging and troubleshooting purposes, such as displaying an invalid segment list when its associated BFD session is down. This document defines extensions to BGP SR Policy to specify the identifier of segment list. 1.1. 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. 2. Segment List Identifier in SR Policy As defined in [I-D.ietf-idr-sr-policy-safi], the SR policy encoding structure is as follows: SR Policy SAFI NLRI: Attributes: Tunnel Encaps Attribute (23) Tunnel Type: SR Policy Binding SID SRv6 Binding SID Preference Priority Policy Name Policy Candidate Path Name Explicit NULL Label Policy (ENLP) Segment List Weight Segment Segment ... ... SR policy with segment list identifier is expressed as below: Lin, et al. Expires August 24, 2025 [Page 3] Internet-Draft BGP SR Policy Segment List Identifier February 2025 SR Policy SAFI NLRI: Attributes: Tunnel Encaps Attribute (23) Tunnel Type: SR Policy Binding SID SRv6 Binding SID Preference Priority Policy Name Policy Candidate Path Name Explicit NULL Label Policy (ENLP) Segment List Weight Segment List Identifier Segment Segment ... ... The segment list identifier can be advertised using the Segment List ID sub-TLV, as defined in Section 2.1. When signaling SR Policy by PCEP [I-D.ietf-pce-multipath] (see section 5.2), a segment list is identified by "Path ID", which is a 4-octet identifier. In this document, the segment list identifier is also represented using a 4-octet ID. 2.1. Segment List ID Sub-TLV The Segment List ID sub-TLV specifies the identifier of the segment list by a 4-octet number. The Segment List ID is unique within the context of a Candidate Path. The Segment List ID sub-TLV is optional and it MUST NOT appear more than once inside the Segment List sub-TLV. If multiple instances are present, then the first one is considered valid and the rest are ignored. The Segment List ID sub-TLV has the following format: Lin, et al. Expires August 24, 2025 [Page 4] Internet-Draft BGP SR Policy Segment List Identifier February 2025 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 | Flags | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Segment List ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: o Type: TBD(19). o Length: 6. o Flags: 1 octet of flags. None are defined at this stage. Flags SHOULD be set to zero on transmission and MUST be ignored on receipt. o RESERVED: 1 octet of reserved bits. SHOULD be set to zero on transmission and MUST be ignored on receipt. o Segment List ID: 4 octets which carry a 32-bit unsigned non-zero number that serves as the identifier associated with the segment list. A value of 0 indicates that there is no identifier associated with the Segment List. The scope of this identifier is the SR Policy Candidate path. 3. Security Considerations The security requirements and mechanisms described in [I-D.ietf-idr- sr-policy-safi] also apply to this document. This document does not introduce any new security consideration. 4. Implementation Status [Note to the RFC Editor - remove this section before publication, as well as remove the reference to [RFC7942]. This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not Lin, et al. Expires August 24, 2025 [Page 5] Internet-Draft BGP SR Policy Segment List Identifier February 2025 intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to [RFC7942], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". 4.1. New H3C Technologies * Organization: New H3C Technologies. * Implementation: H3C CR16000, CR19000 series routers implementation. * Description: All sections including all the "MUST" and "SHOULD" clauses have been implemented in above-mentioned New H3C Products(running Version 7.1.099 and above). * Maturity Level: Product * Coverage: All sections. * Version: Draft-03 * Licensing: N/A * Implementation experience: Nothing specific. * Contact: linchangwang.04414@h3c.com * Last updated: February 10, 2025 4.2. ZTE Corp * Organization: ZTE Corporation * Implementation: ZTE's ZXR10 core router * Description: The implementation in lab has been completed. The commercial implementation is under development. * Maturity Level: Product * Coverage: All Lin, et al. Expires August 24, 2025 [Page 6] Internet-Draft BGP SR Policy Segment List Identifier February 2025 * Version: Draft-03 * Licensing: N/A * Implementation experience: Nothing specific. * Contact: feng.jun99@zte.com.cn * Last updated: February 6, 2025 5. IANA Considerations This document defines a new Sub-TLV in the registry "SR Policy Segment List Sub-TLVs" [I-D.ietf-idr-sr-policy-safi]: Value Description Reference ------------------------------------------------------- TBA (19) Segment List ID sub-TLV This document 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, 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, . [I-D.ietf-idr-sr-policy-safi] Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and D. Jain, "Advertising Segment Routing Policies in BGP", Work in Progress, Internet-Draft, draft- ietf-idr-sr-policy-safi-13, 6 February 2025, . 6.2. Informative References [RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", RFC 9256, DOI 10.17487/RFC9256, July 2022, . Lin, et al. Expires August 24, 2025 [Page 7] Internet-Draft BGP SR Policy Segment List Identifier February 2025 [I-D.ietf-pce-multipath] Koldychev, M., Sivabalan, S., Saad, T., Beeram, V. P., Bidgoli, H., Yadav, B., Peng, S., and G. S. Mishra, "PCEP Extensions for Signaling Multipath Information", Work in Progress, Internet-Draft, draft- ietf-pce-multipath-12, 8 October 2024, . Lin, et al. Expires August 24, 2025 [Page 8] Internet-Draft BGP SR Policy Segment List Identifier February 2025 Authors' Addresses Changwang Lin New H3C Technologies China Email: linchangwang.04414@h3c.com Weiqiang Cheng China Mobile China Email: chengweiqiang@chinamobile.com Yao Liu ZTE China Email: liu.yao71@zte.com.cn Ketan Talaulikar Cisco Systems India Email: ketant.ietf@gmail.com Mengxiao Chen New H3C Technologies China Email: chen.mengxiao@h3c.com Lin, et al. Expires August 24, 2025 [Page 9]