Inter-Domain Routing R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 12 April 2025 K. Talaulikar Cisco Systems, Inc. Y. Liu China Mobile L. Changwang New H3C Technologies 9 October 2024 Validity of SR Policy Candidate Path draft-chen-idr-bgp-sr-policy-cp-validity-03 Abstract This document defines extensions to BGP to distribute the validity control parameters of a candidate path for an 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). 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 12 April 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Chen, et al. Expires 12 April 2025 [Page 1] Internet-Draft Validity of SR Policy Candidate Path October 2024 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 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 . . . . . . . . . . . . . . . . . . 2 2. Carrying CP Validity Sub-TLV in BGP . . . . . . . . . . . . . 3 3. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction SR Policy architecture is specified in [RFC9256]. An SR Policy comprises one or more candidate paths (CP) of which at a given time one and only one may be active (i.e., installed in forwarding and usable for steering of traffic). Each CP in turn may have one or more SID-List of which one or more may be active; when multiple SID- List are active then traffic is load balanced over them. [I-D.chen-spring-sr-policy-cp-validity]supplemented candidate path validity criterion in [RFC9256]. It defines three validity control parameters under candidate Path to control the validity judgment of candidate Path. This document defines extensions to BGP to distribute the validity control parameters of a candidate path for an SR Policy. 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. Chen, et al. Expires 12 April 2025 [Page 2] Internet-Draft Validity of SR Policy Candidate Path October 2024 2. Carrying CP Validity Sub-TLV in BGP As defined in [I-D.ietf-idr-sr-policy-safi], a new SAFI is defined (the SR Policy SAFI with codepoint 73) as well as a new NLRI. The NLRI contains the SR Policy candidate path and, according to [I-D.ietf-idr-sr-policy-safi], the content of the SR Policy Candidate Path is encoded in the Tunnel Encapsulation Attribute defined in [RFC9012] using a new Tunnel-Type called SR Policy Type with codepoint 15. This document defines CP Validity Sub-TLV to carry the validity control parameters of a candidate path. The new SR Policy encoding structure with CP Validity Sub-TLV is expressed as below: SR Policy SAFI NLRI: Attributes: Tunnel Encaps Attribute (23) Tunnel Type: SR Policy (15) Binding SID SRv6 Binding SID Preference Priority Policy Name Policy Candidate Path Name Explicit NULL Label Policy (ENLP) CP Validity Segment List Weight Segment Segment ... ... Figure 1 3. CP Validity Sub-TLV The format of the CP Validity Sub-TLV is defined as follows: 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 | valid SL count| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | valid SL weight | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Chen, et al. Expires 12 April 2025 [Page 3] Internet-Draft Validity of SR Policy Candidate Path October 2024 Figure 2 where: Type: to be assigned by IANA. Length: the total length of the value field not including Type and Length fields. The total length must be 6. valid SL count：1-octet field which indicates the minimum number of valid segment Lists under the active candidate path. When the number of valid segment Lists under candidate path is greater than or equal to this field, the candidate path is considered valid. 0 indicates no requirement for SL count. 0xff indicates that the candidate path is considered valid only if all the segment Lists are valid. valid SL weight: 4-octet field which indicates the minimum value of the sum of the weights of the valid segment List under the active candidate Path. When the sum of the weights of the valid segment Lists under the candidate path is greater than or equal to this field, the candidate Path is considered valid. 0 indicates no requirement for weight.0xffffffff indicates that the candidate path is considered valid only if all the segment Lists are valid. 4. Operations The document does not bring new operation beyond the description of operations defined in [I-D.ietf-idr-sr-policy-safi]. The existing operations defined in [I-D.ietf-idr-sr-policy-safi] can apply to this document directly. Typically, but not limit to, the SR policies carrying the validity control parameters of the candidate path are configured by a controller. After configuration, the SR policies carrying the validity control parameters of the candidate path will be advertised by BGP update messages. The operation of advertisement is the same as defined in [I-D.ietf-idr-sr-policy-safi], as well as the reception. 5. IANA Considerations This document defines a new sub-TLV in the registry "BGP Tunnel Encapsulation Attribute sub-TLVs" to be assigned by IANA: Chen, et al. Expires 12 April 2025 [Page 4] Internet-Draft Validity of SR Policy Candidate Path October 2024 Value Description Reference ------- ------------------------- -------------- TBD CP Validity Sub-TLV This document Figure 3 6. Security Considerations The security considerations of BGP [RFC4271] and BGP SR policy [I-D.ietf-idr-sr-policy-safi] apply to the extensions described in this document as well. It does not introduce additional security issues compared to existing SR policy extensions. The CP Validity information is critical to determining the validity of the CP, and a wrong CP Validity information may cause unexpected forwarding actions and results. Implementations need to make sure that the CP Validity information is correct to avoid unexpected forwarding actions and results. Additionally, the distribution of CP validity information from the controller to the ingress router needs to be protected. The security considereations in [I-D.ietf-idr-sr-policy-safi] apply to this distribution procedure. 7. Acknowledgements TBD. 8. Normative References [I-D.chen-spring-sr-policy-cp-validity] Chen, R., Liu, Y., Talaulikar, K., Sidor, S., Zhao, D., Lin, C., and Z. Ali, "Validity of SR Policy Candidate Path", Work in Progress, Internet-Draft, draft-chen- spring-sr-policy-cp-validity-03, 21 July 2024, . [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-09, 3 October 2024, . Chen, et al. Expires 12 April 2025 [Page 5] Internet-Draft Validity of SR Policy Candidate Path October 2024 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder, "The BGP Tunnel Encapsulation Attribute", RFC 9012, DOI 10.17487/RFC9012, April 2021, . [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, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Detao Zhao ZTE Corporation Nanjing China Email: zhao.detao@zte.com.cn Ketan Talaulikar Cisco Systems, Inc. Email: ketant.ietf@gmail.com Chen, et al. Expires 12 April 2025 [Page 6] Internet-Draft Validity of SR Policy Candidate Path October 2024 Yisong Liu China Mobile Beijing China Email: liuyisong@chinamobile.com Changwang Lin New H3C Technologies Beijing China Email: linchangwang.04414@h3c.com Chen, et al. Expires 12 April 2025 [Page 7]