SPRING Working Group R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 6 January 2024 L. Changwang New H3C Technologies 5 July 2023 Validity of SR Policy Candidate Path draft-chen-spring-sr-policy-cp-validity-00 Abstract 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. However, a candidate path is valid when at least one SID-List is active. This candidate path validity criterion cannot meet the needs of some scenarios. This document defines the new candidate path validity criterion. 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 8 January 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. Chen, et al. Expires 8 January 2024 [Page 1] Internet-Draft Validity of SR Policy Candidate Path July 2023 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 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2 4. Validity of a Candidate Path . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 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. However, a candidate path is valid when at least one SID-List is active. This candidate path validity criterion cannot meet the needs of some scenarios. This document defines the new candidate path validity criterion. 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]. 3. Motivation The candidate path validity criterion defined in [RFC9256] can't meet the needs of the following scenarios: Chen, et al. Expires 8 January 2024 [Page 2] Internet-Draft Validity of SR Policy Candidate Path July 2023 +----------------------+ +---------| SL1(Weight 1, 100MB) | +----------------+ | +----------------------+ | CP1 (200MB) |------+ +----------------+ | +----------------------+ +---------| SL2(Weight 1, 100MB) | +----------------------+ Figure 1 The SR Policy POL1 has two candidate paths: CP1 and CP2, and CP1 is the active candidate path (it is valid and has the highest Preference). The two segment lists (SL1 and SL2) of CP1 are installed as the forwarding instantiation of SR Policy POL1. The CP1 carries a total of 200MB of traffic. Within the POL1, the flow-based hashing over its each SL with a ratio 50%, that is each SL carry 100MB of traffic. At this time, if one of the Segment Lists is invalids, the remaining Segment List cannot carry 200MB of traffic. However, the CP1 is still active. 4. Validity of a Candidate Path A headend may be informed about the validity control parameters of a candidate path for an SR Policy by various means including: via configuration, PCEP, or BGP. The detailed protocol extension will be described in a separate document. This document defines the following validity control parameters under candidate Path to control the validity judgment of candidate Path: * valid SL quantity: 8-bit value, The value is 1-0xff. 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. 0xff indicates that the candidate path is considered valid only if all the segment Lists are valid. * valid SL weight: 32-bit value, The value is 0-0xffffffff. Indicates the minimum value of the sum of the weights of the valid segment List under the active candidate Path. Chen, et al. Expires 8 January 2024 [Page 3] Internet-Draft Validity of SR Policy Candidate Path July 2023 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: 8-bit value, The value is 0-100. 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. Indicates the minimum proportion WTV/WTA. 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. Candidate path is considered valid only when all three validity control parameters are satisfied. 5. IANA Considerations TBD. 6. Security Considerations TBD. 7. Acknowledgements TBD. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Chen, et al. Expires 8 January 2024 [Page 4] Internet-Draft Validity of SR Policy Candidate Path July 2023 [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 Changwang Lin New H3C Technologies Beijing China Email: linchangwang.04414@h3c.com Chen, et al. Expires 8 January 2024 [Page 5]