IDR C. Lin Internet Draft New H3C Technologies Intended status: Standards Track W. Cheng Expires: February 3, 2024 China Mobile Y. Liu ZTE K. Talaulikar Cisco Systems M. Chen New H3C Technologies August 2, 2023 BGP SR Policy Extensions for Segment List Identifier draft-lin-idr-sr-policy-seglist-id-04 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), 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 February 2, 2024. Lin, et al. Expires February 3, 2024 [Page 1] Internet-Draft BGP SR Policy Segment List Identifier August 2023 Copyright Notice Copyright (c) 2023 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 ................................................ 3 1.1. Requirements Language .................................. 3 2. Segment List Identifier in SR Policy ........................ 4 2.1. Segment List ID Sub-TLV ................................ 5 3. Security Considerations ..................................... 5 4. IANA Considerations ......................................... 6 5. References .................................................. 6 5.1. Normative References ................................... 6 5.2. Informative References ................................. 6 Authors' Addresses ............................................. 7 Lin, et al. Expires February 3, 2024 [Page 2] Internet-Draft BGP SR Policy Segment List Identifier August 2023 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- segment-routing-te-policy] 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. For example, a network controller distributes SR policies to the headend nodes, and the headend nodes 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 the controller needs to distinguish the segment list by comparing the SIDs one by one. The advertisement of all SIDs in the segment list consumes a lot of octets, and the comparison of SIDs can be complicated. For another example, 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. So, the controller needs to specify the segment list which the configurations belong to. 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 a 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. Lin, et al. Expires February 3, 2024 [Page 3] Internet-Draft BGP SR Policy Segment List Identifier August 2023 2. Segment List Identifier in SR Policy As defined in [I-D.ietf-idr-segment-routing-te-policy], 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: 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. Lin, et al. Expires February 3, 2024 [Page 4] Internet-Draft BGP SR Policy Segment List Identifier August 2023 When signaling SR Policy by PCEP [I-D.ietf-pce-multipath], a segment list is identified by "Path ID", which is a 4-octet identifier. In this document, the segment list identifier is provided to achieve greater flexibility. 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. The Segment List ID sub-TLV has the following format: 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. 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 octet of ID for the segment list. 3. Security Considerations The security requirements and mechanisms described in [I-D.ietf-idr- segment-routing-te-policy] also apply to this document. This document does not introduce any new security consideration. Lin, et al. Expires February 3, 2024 [Page 5] Internet-Draft BGP SR Policy Segment List Identifier August 2023 4. IANA Considerations This document defines a new Sub-TLVs in registries "SR Policy Segment List Sub-TLVs" [I-D.ietf-idr-segment-routing-te-policy]: Value Description Reference ------------------------------------------------------- TBA Segment List ID sub-TLV This document 5. References 5.1. 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-segment-routing-te-policy] Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., Rosen, E., Jain, D., and S. Lin, "Advertising Segment Routing Policies in BGP", Work in Progress, Internet- Draft, draft-ietf-idr-segment- routing-te-policy-23, 25 July 2023, . 5.2. 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, . [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-09, 24 July 2023, . Lin, et al. Expires February 3, 2024 [Page 6] Internet-Draft BGP SR Policy Segment List Identifier August 2023 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 February 3, 2024 [Page 7]