Inter-Domain Routing R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 11 January 2024 10 July 2023 Advertisement of Candidate Path Validity Control Parameters using BGP-LS draft-chen-idr-bgp-ls-sr-policy-cp-validity-00 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/. 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Chen & Zhao Expires 11 January 2024 [Page 1] Internet-Draft Advertisement of CP Validity Control Par July 2023 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 3. Carrying CP Validity Sub-TLV in BGP-LS . . . . . . . . . . . 3 4. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3 5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction SR Policy architecture are 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-te-lsp-distribution]. Based on the mechanism defined in [I-D.ietf-idr-te-lsp-distribution], this document defines extensions to BGP-LS to distribute the validity control parameters of a candidate path for an SR Policy. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Chen & Zhao Expires 11 January 2024 [Page 2] Internet-Draft Advertisement of CP Validity Control Par July 2023 3. 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 [RFC7752] 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]. 4. 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 qty |valid SL weight| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | valid SL weight ratio | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 where: Type: to be assigned by IANA. Length: the total length of the value field not including Type and Length fields. valid SL quantity：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. Chen & Zhao Expires 11 January 2024 [Page 3] Internet-Draft Advertisement of CP Validity Control Par July 2023 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. valid SL weight ratio: 1-octet field which indicates the minimum proportion WTV/WTA. WTV: The sum weights of the valid segment list under the active CP. WTA: The sum weights of all the segment lists under the active CP. When WTV/WTA is greater than or equal to this field, the candidate Path is considered valid. 0 indicates no requirement on weight proportion.100 indicates that the candidate path is considered valid only if all the segment lists are valid. 5. Operations The operations procedures of [RFC7752] 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. 6. 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 Figure 2 Chen & Zhao Expires 11 January 2024 [Page 4] Internet-Draft Advertisement of CP Validity Control Par July 2023 7. Security Considerations Procedures and protocol extensions defined in this document do not affect the BGP security model. See the "Security Considerations"section of [RFC4271] for a discussion of BGP security. Security considerations for acquiring and distributing BGP-LS information are discussed in [RFC7752]. 8. Acknowledgements TBD. 9. Normative References [I-D.chen-spring-sr-policy-cp-validity] Chen, R., Zhao, D., and C. Lin, "Validity of SR Policy Candidate Path", Work in Progress, Internet-Draft, draft- chen-spring-sr-policy-cp-validity-00, 5 July 2023, . [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-00, 9 March 2023, . [I-D.ietf-idr-te-lsp-distribution] Previdi, S., Talaulikar, K., Dong, J., Chen, M., Gredler, H., and J. Tantsura, "Distribution of Traffic Engineering (TE) Policies and State using BGP-LS", Work in Progress, Internet-Draft, draft-ietf-idr-te-lsp-distribution-19, 24 January 2023, . [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, . Chen & Zhao Expires 11 January 2024 [Page 5] Internet-Draft Advertisement of CP Validity Control Par July 2023 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016, . [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 Chen & Zhao Expires 11 January 2024 [Page 6]