IDR C. Lin Internet Draft New H3C Technologies Intended status: Standards Track R. Chen Expires: September 20, 2025 ZTE Corporation March 20 2025 BGP SR Policy Candidate Path State Extend Flags draft-lin-idr-bgp-ls-sr-policy-state-extend-flags-00 Abstract [draft-ietf-idr-bgp-ls-sr-policy]The SR Candidate Path State TLV conveys the operational status and attributes of an SR Policy at the candidate path level. The SR Candidate Path State is frequently extended to carry new attributes and states for CPaths. However, only a few bits remain unassigned in the Flags field of the current implementation. This document addresses the issue of insufficient flag bits in the SR Candidate Path State TLV by defining a variable-length SR Candidate Path State Extend TLV for BGP-LS SR-Policy. This enhancement ensures scalability and flexibility in signaling additional attributes and states for SR Policy candidate paths. 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 September 20, 2025 Lin, idr. Expires September 20, 2025 [Page 1] Internet-Draft SR Candidate Path State Extend TLV March 2025 Copyright Notice Copyright (c) 2025 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...................................................2 1.1. Requirements Language.....................................2 2. Variable-Length SR Candidate Path State Flags TLV..............3 3. Security Considerations........................................3 4. IANA Considerations............................................4 5. References.....................................................4 5.1. Normative References......................................4 5.2. Informative References....................................4 Authors' Addresses................................................5 1. Introduction [draft-ietf-idr-bgp-ls-sr-policy]The SR Candidate Path State TLV conveys the operational status and attributes of an SR Policy at the candidate path level. The SR Candidate Path State is frequently extended to carry new attributes and states for CPaths. However, only a few bits remain unassigned in the Flags field of the current implementation. This document addresses the issue of insufficient flag bits in the SR Candidate Path State TLV by defining a variable-length SR Candidate Path State Extend TLV for BGP-LS SR-Policy. This enhancement ensures scalability and flexibility in signaling additional attributes and states for SR Policy candidate paths. 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 jl, et al. Expires January 9, 2025 [Page 2] Internet-Draft SR Candidate Path State Extend TLV March 2025 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Variable-Length SR Candidate Path State Flags TLV The SR Candidate Path State TLV and The SR Candidate Path State Extend TLV provide the operational status and attributes of the SR Policy at the candidate path level. At most one instance of the SR Candidate Path State Extend TLV is advertised for a given candidate path. If multiple instances are present, then the first valid (i.e., not determined to be malformed as per section 8.2.2 of [RFC9552]) one is used and the rest are ignored. The SR Candidate Path State Extend 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Candidate Path State Flags (Variable) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: o Type: TBD1. o Length: Variable, dependent on the included candidate path Flags. This indicates the length of the value portion in bytes. The length MUST be a multiple of 4 octets. o candidate path Flags: Variable. The extended flag field. This contains a variable number of 32-bit flags. Currently, no bits are defined in this document. Figure 1: SR Candidate Path State Extend TLV 3. Security Considerations The security requirements and mechanisms described in [I-D.ietf-idr- sr-policy-safi] also apply to this document. This document does not introduce any new security consideration. jl, et al. Expires January 9, 2025 [Page 3] Internet-Draft SR Candidate Path State Extend TLV March 2025 4. IANA Considerations IANA maintains a registry called "BGP-LS NLRI and Attribute TLVs" in the "Border Gateway Protocol - Link State (BGP-LS) Parameters" registry group. This document defines a new TLV in the registry "BGP-LS NLRI and Attribute TLVs": Value Description Reference ------------------------------------------------------- TBD1 SR Candidate Path State Extend This document 5. References 5.1. Normative References [I-D.draft-ietf-idr-bgp-ls-sr-policy] S. Previdi, Individual, K. Talaulikar, Ed., Cisco Systems, J. Dong, Huawei Technologies, H. Gredler, RtBrick Inc., J. Tantsura, Nvidia, "Advertisement of Segment Routing Policies using BGP Link-State", Work in Progress, Internet-Draft, draft- ietf-idr-bgp-ls-sr-policy-17, 6 March 2025, . 5.2. Informative References TBD. jl, et al. Expires January 9, 2025 [Page 4] Internet-Draft SR Candidate Path State Extend TLV March 2025 Authors' Addresses Changwang Lin New H3C Technologies China Email: linchangwang.04414@h3c.com Ran Chen ZTE Corporation Email: chen.ran@zte.com.cn jl, et al. Expires January 9, 2025 [Page 5]