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 Advertisement of Candidate Path Validity Control Parameters using BGP-LS draft-chen-idr-bgp-ls-sr-policy-cp-validity-02 Abstract This document describes a mechanism to collect the configuration and states of SR policies carrying the validity control parameters of the candidate path by using BGP Link-State (BGP-LS) updates. Such information can be used by external components for path computation, re-optimization, service placement, etc. 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. 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. Chen, et al. Expires 12 April 2025 [Page 1] Internet-Draft Advertisement of CP Validity Control Par October 2024 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. Carrying CP Validity Sub-TLV in BGP-LS . . . . . . . . . . . 3 3. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 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. In many network scenarios, the configuration and state of each TE Policy is required by a controller which allows the network operator to optimize several functions and operations through the use of a controller aware of both topology and state information [I-D.ietf-idr-bgp-ls-sr-policy]. Based on the mechanism defined in [I-D.ietf-idr-bgp-ls-sr-policy], this document defines extensions to BGP-LS to distribute the validity control parameters of a candidate path for an SR Policy. Chen, et al. Expires 12 April 2025 [Page 2] Internet-Draft Advertisement of CP Validity Control Par October 2024 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. Carrying CP Validity Sub-TLV in BGP-LS In order to collect configuration and states of SR policies carrying the validity control parameters of the candidate path, this document defines a new SR Policy state TLV which enable the headend to report the validity control parameters of a candidate path. This TLV is carried in the optional non-transitive BGP Attribute "LINK_STATE Attribute" defined in [RFC9552] associated with the SR Policy CP NLRI type. This TLV is optional and only one this TLV is advertised for a given CP. If multiple TLVs are present, then the first one is considered valid and the rest are ignored as describe in [I-D.ietf-idr-bgp-ls-sr-policy]. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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. Chen, et al. Expires 12 April 2025 [Page 3] Internet-Draft Advertisement of CP Validity Control Par October 2024 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 quantity. 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 operations procedures of [RFC9552] can apply to this document. Typically, but not limit to, the SR policies carrying the validity control parameters of the candidate path can be distributed by the ingress node. 5. IANA Considerations IANA maintains a registry called "Border Gateway Protocol - Link State (BGP-LS) Parameters" with a sub-registry called "Node Anchor, Link Descriptor and Link Attribute TLVs". The following TLV codepoints are suggested (for early allocation by IANA): Value Description Reference ------- ------------------------- -------------- TBD CP Validity Sub-TLV This document 6. Security Considerations Procedures and protocol extensions defined in this document do not affect the base BGP security model. See [RFC6952] for details. The security considerations of the base BGP-LS specification as described in [RFC9552] and BGP-LS SR Policy specification as described in [I-D.ietf-idr-bgp-ls-sr-policy] also apply. 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. Chen, et al. Expires 12 April 2025 [Page 4] Internet-Draft Advertisement of CP Validity Control Par October 2024 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 a router to an controller needs to be protected. The security considereations in [I-D.ietf-idr-bgp-ls-sr-policy] 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-bgp-ls-sr-policy] Previdi, S., Talaulikar, K., Dong, J., Gredler, H., and J. Tantsura, "Advertisement of Segment Routing Policies using BGP Link-State", Work in Progress, Internet-Draft, draft- ietf-idr-bgp-ls-sr-policy-05, 22 July 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of BGP, LDP, PCEP, and MSDP Issues According to the Keying and Authentication for Routing Protocols (KARP) Design Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . Chen, et al. Expires 12 April 2025 [Page 5] Internet-Draft Advertisement of CP Validity Control Par October 2024 [RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and Traffic Engineering Information Using BGP", RFC 9552, DOI 10.17487/RFC9552, December 2023, . 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 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 6]