IDR Working Group C. Lin Internet Draft New H3C Technologies Intended status: Standards Track September 11, 2024 Expires: March 10, 2025 SR Policies Extensions for Headend Behavior in BGP-LS draft-lin-idr-bgpls-sr-policy-headend-behavior-00 Abstract The SRv6 Policy Headend Behaviors are defined in [RFC8986]. This document defines extensions for carrying Headend Behavior when delivering SR Policies using Border Gateway Protocol Link-State (BGP-LS). 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 March 10, 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 (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 Lin, et al. Expires March 10, 2025 [Page 1] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 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...................................................3 1.1. Requirements Language.....................................3 2. Carrying Headend Behavior in BGP-LS............................3 2.1. Headend Behavior TLV......................................3 2.2. L2 Headend Behavior TLV...................................4 3. Security Considerations........................................6 4. IANA Considerations............................................6 5. References.....................................................6 5.1. Normative References......................................6 Authors' Addresses................................................7 Lin, et al. Expires March 10, 2025 [Page 2] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 1. Introduction Segment Routing (SR) [RFC8402] is a source routing paradigm that explicitly indicates the forwarding path for packets at the ingress node. The ingress node steers packets into a specific path according to the Segment Routing Policy (SR Policy) as defined in [RFC9256]. [RFC8986] describes a set of SRv6 Policy Headend [RFC8402] behaviors, primarily including H.Encaps, H.Encaps.Red, H.Encaps.L2, and H.Encaps.L2.Red. [I-D. lin-idr-sr-policy-headend-behavior] defines extensions to BGP SR policy, enabling the distribution of SR policies that carry headend behavior. This allows the headend to be instructed to perform specific behaviors when packets are steered into the SR policy. [I-D.ietf-idr-bgp-ls-sr-policy] describes a mechanism for distributing SR policy information to external components using BGP- LS. This information can be used by external components for tasks such as path computation, re-optimization, service placement, and network visualization. This document defines two new TLVs that enable the headend to report the headend behaviors associated with the SR Policy CP by using BGP- LS. 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 Headend Behavior in BGP-LS 2.1. Headend Behavior TLV A SR Policy CP may be instantiated with a specific headend behavior via a local configuration, PCEP, or BGP SR Policy signaling. Then the state and attributes of the headend behavior associated with the candidate path of SR policy can be distributed to the controller. 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. Lin, et al. Expires March 10, 2025 [Page 3] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 This TLV is optional and only one these TLVs is advertised for a given SR Policy 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]. The Headend Behavior sub-TLV encodes the default headend behavior associated with the candidate path for L3 traffic. When the headend steers L3 packets into that SR Policy and the associated candidate path is active, the specific headend behavior should be performed by default. The 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Headend Behavior | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: o Type: to be assigned by IANA. o Length: 2 octets. The total length of the value field not including Type and Length fields o Headend Behavior: a 2-octet value. The following values are defined. * TBD: H.Encaps. A headend behavior defined in [RFC8986]. * TBD: H.Encaps.Red. A headend behavior defined in [RFC8986]. o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on transmission and MUST be ignored on receipt. 2.2. L2 Headend Behavior TLV A SR Policy CP may be instantiated with a specific L2 Headend behavior via a local configuration, PCEP, or BGP SR Policy signaling. Then the state and attributes of the L2 Headend behavior Lin, et al. Expires March 10, 2025 [Page 4] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 associated with the candidate path of SR policy can be distributed to the controller. 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 these TLVs is advertised for a given SR Policy 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]. The L2 Headend Behavior sub-TLV encodes the default headend behavior associated with the candidate path for L2 traffic. When the headend steers L2 packets into that SR Policy and the associated candidate path is active, the specific L2 headend behavior should be performed by default. The 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | l2 Headend Behavior | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: o Type: to be assigned by IANA. o Length: 2 octets. The total length of the value field not including Type and Length fields o L2 Headend Behavior: a 2-octet value. The following values are defined. * TBD: H.Encaps.L2. A headend behavior defined in [RFC8986]. * TBD: H.Encaps.L2.Red. A headend behavior defined in [RFC8986]. o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on transmission and MUST be ignored on receipt. Lin, et al. Expires March 10, 2025 [Page 5] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 3. 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 [RFC9552]. 4. IANA Considerations IANA maintains a registry group called "Border Gateway Protocol - Link State (BGP-LS) Parameters" with a registry called "BGP-LS NLRI and Attribute TLVs". The following TLV codepoints are suggested for early allocation by IANA): Codepoint Description Reference ---------------------------------------------------------- TBD Headend Behavior This document TBD L2 Headend Behavior This document 5. References 5.1. Normative References [I-D.lin-idr-sr-policy-headend-behavior] Lin, C., Jiang, W., Liu, Y. Chen, M., and Chen, R., "BGP Extensions of SR Policy for Headend Behavior", Work in Progress, Internet-Draft, draft-lin-idr-sr-policy-headend-behavior, 16 May 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . Lin, et al. Expires March 10, 2025 [Page 6] Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986,DOI 10.17487/RFC8986, February 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 Changwang Lin New H3C Technologies China Email: linchangwang.04414@h3c.com Lin, et al. Expires March 10, 2025 [Page 7]