PCE Working Group C. Lin Internet-Draft New H3C Technologies Intended status: Standards Track R. Chen Expires: May 15, 2025 ZTE Corporation November 13, 2024 PCEP Extensions of SR Policy for Headend Behavior draft-lin-pce-sr-policy-headend-behavior-00 Abstract A Segment Routing (SR) Policy [RFC9256] is a non-empty set of SR Candidate Paths, that share the same tuple. [I-D.draft-ietf-pce-segment-routing-policy-cp] extends [RFC8664] to fully support the SR Policy construct. The header of a packet steered in an SR Policy is augmented with an ordered list of segments associated with that SR Policy. [RFC8986] defines H. Encaps behavior, H. Encaps.Red behavior, H. Encaps.L2 behavior, and H. Encaps.L2.Red behavior for SR policy. This document defines extensions to PCEP to distribute SR policies carrying headend behavior. 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 May 15 2025. lin, et al. Expire May, 2025 [Page 1] Internet-Draft PCEP SR Policy Headend Behavior November 2024 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 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.....................................3 2. PCEP Extensions................................................3 2.1. SRPOLICY-CPATH-HEADEND-BEHAVIOR Sub-TLV...................4 2.2. SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR Sub-TLV................5 3. IANA Considerations............................................6 4. Security Considerations........................................6 5. References.....................................................7 5.1. Normative References......................................7 5.2. Informative References....................................8 Acknowledgments...................................................8 Authors' Addresses................................................8 1. Introduction Segment Routing (SR) [RFC8402] allows a headend node to steer a packet flow along any path. Intermediate per-path states are eliminated thanks to source routing. The headend node is said to steer a flow into an SR Policy [RFC8402]. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy. PCEP Extensions for Segment Routing [RFC8664] specifies extensions that allow PCEP to work with basic SR-TE paths. PCEP extension to support Segment Routing Policy Candidate Paths.[I-D.ietf-pce- segment-routing-policy-cp] specifies extensions that allow PCEP to signal additional attributes of an SR Policy, which are not covered by [RFC8664]. SR Policy is modeled in PCEP as an Association and the SR Candidate Paths are the members of that Association. Thus lin, et al. Expires May, 2025 [Page 2] Internet-Draft PCEP SR Policy Headend Behavior November 2024 the PCE can take computation and control decisions about the Candidate Paths, with the additional knowledge that these Candidate Paths belong to the same SR Policy. [RFC8986] defines End.B6.Encaps behavior and End.B6.Encaps.Red behavior for SRv6 BSID. When receiving packets with an active SID matching a local BSID of these kinds, the headend will perform corresponding behaviors. Different BSID behaviors are suitable for different scenarios. For example, comparing with End.B6.Encaps, End.B6.Encaps.Red reduces the size of the SRH by excluding the first SID, which can be useful for the devices with lower capacity of SID depths, like the switches in data center network. The SRv6 Binding SID sub-TLV is defined in [RFC9604] to signal the SRv6 BSID information along with SR Policies. It enables the specified SRv6 BSID behavior to be instantiated on the headend node. However, if the packets are steering into an SR Policy in some other way than using BSID, the headend behavior is not specified during the distributing of SR Policy by PCEP. The network operator has to use additional tools, like NETCONF, to signal the headend behavior. [RFC8986] defines H. Encaps behavior, H. Encaps.Red behavior, H. Encaps.L2 behavior, and H. Encaps.L2.Red behavior for SR policy. This document defines extensions to PCEP to distribute SR policies that carry headend behavior, so that the headend can be instructed to perform specific behaviors when packets are steered into the SR policy without a BSID. 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. PCEP Extensions In accordance with [RFC8697], TE LSPs are associated by adding them to a common association group by a PCEP peer. [I-D.ietf-pce-segment- routing-policy-cp] defines the SR Policy Association (SRPA), where the SR Candidate Paths are members of this association. To specify the Headend behavior that the candidate path of an SR policy is associated with, two new sub-TLVs, named "SRPOLICY-CPATH- HEADEND-BEHAVIOR" and "SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR," are defined within the SRPA object. lin, et al. Expires May, 2025 [Page 3] Internet-Draft PCEP SR Policy Headend Behavior November 2024 2.1. SRPOLICY-CPATH-HEADEND-BEHAVIOR Sub-TLV The SRPOLICY-CPATH-HEADEND-BEHAVIOR 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. In the case of BSID steering, the behavior defined by the BSID overrides the default headend behavior. The SRPOLICY-CPATH-HEADEND-BEHAVIOR TLV is an optional TLV for the SRPA object and MUST NOT appear more than once in the SR policy encoding. If the SRPOLICY-CPATH-HEADEND-BEHAVIOR sub-TLV appears more than once, only the first instance of the TLV SHOULD be interpreted, and subsequent instances SHOULD be ignored. The SRPOLICY-CPATH-HEADEND-BEHAVIOR 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Headend Behavior | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: The SRPOLICY-CPATH-HEADEND-BEHAVIOR TLV where: o Type: to be assigned by IANA. o Length: 4. o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on transmission and MUST be ignored on receipt. o Headend Behavior: a 2-octet value. The following values are defined. * TBD: Headend Behavior = 0 Indicates it is of H. Encaps type. A headend behavior defined in [RFC8986]. * TBD: Headend Behavior = 1 Indicates it is of H.Encaps.Red type. A headend behavior defined in [RFC8986]. lin, et al. Expires May, 2025 [Page 4] Internet-Draft PCEP SR Policy Headend Behavior November 2024 * TBD: Headend Behavior = 2 Indicates it is of H.Insert type. A headend behavior defined in [I-D.filsfils-spring-srv6-net- pgm-insertion]. * TBD: Headend Behavior = 3 Indicates it is of H.Insert.Red type. A headend behavior defined in [I-D.filsfils-spring- srv6-net-pgm-insertion]. 2.2. SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR Sub-TLV The SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR 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 headend behavior should be performed by default. In the case of BSID steering, the behavior defined by the BSID overrides the default headend behavior. The SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR TLV is an optional TLV for the SRPA object, and MUST NOT appear more than once in the SR Policy encoding. If the SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR sub-TLV appears more than once, only the first instance of the TLV SHOULD be interpreted and subsequent instances SHOULD be ignored. The SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | L2 Headend Behavior | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: The SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR TLV where: o Type: to be assigned by IANA. o Length: 4. lin, et al. Expires May, 2025 [Page 5] Internet-Draft PCEP SR Policy Headend Behavior November 2024 o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on transmission and MUST be ignored on receipt. o L2 Headend Behavior: a 2-octet value. The following values are defined. * TBD: L2 Headend Behavior = 0: H.Encaps.L2. A headend behavior defined in [RFC8986]. * TBD: L2 Headend Behavior = 1: H.Encaps.L2.Red. A headend behavior defined in [RFC8986]. 3. IANA Considerations This document defines the new TLV for carrying additional information about SR Policy and SR Candidate Paths. IANA is requested to make the assignment of a new value for the existing "PCEP TLV Type Indicators" registry as follows: +-------+-------------------------------------+---------------+ |Value | Description | Reference | +=======+=====================================+===============+ | TBA | SRPOLICY-CPATH-HEADEND-BEHAVIOR | This document | +-------+-------------------------------------+---------------+ | TBA | SRPOLICY-CPATH-L2-HEADEND-BEHAVIOR | This document | +-------+-------------------------------------+---------------+ 4. Security Considerations [RFC8754] defines the notion of an SR domain and use of SRH within the SR domain. Procedures for securing an SR domain are defined the section 5.1 and section 7 of [RFC8754]. This document does not impose any additional security challenges to be considered beyond security threats described in [RFC8754], [RFC8679] and [RFC8986]. Procedures and protocol extensions defined in this document do not affect the security considerations discussed in [I-D.ietf-pce- segment-routing-policy-cp]. lin, et al. Expires May, 2025 [Page 6] Internet-Draft PCEP SR Policy Headend Behavior November 2024 5. References 5.1. Normative References [I-D.ietf-pce-segment-routing-policy-cp] Koldychev, M., Sivabalan, S., Barth, C., Peng, S., and H.Bidgoli, "PCEP extension to support Segment Routing Policy Candidate Paths", Work in Progress, Internet-Draft, draft-ietf-pce-segment-routing- policy-cp-11, 20 June 2023,. [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, . [RFC8679] Shen, Y., Jeganathan, M., Decraene, B., Gredler, H., Michel, C., and H. Chen, "MPLS Egress Protection Framework", RFC 8679, DOI 10.17487/RFC8679, December 2019, . [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, . [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, . [RFC9604] Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S., and C. Li, "Carrying Binding Label/Segment Identifier (SID) in PCE-based Networks.", RFC 9604, DOI 10.17487/RFC9604 16 August 2024, . lin, et al. Expires May, 2025 [Page 7] Internet-Draft PCEP SR Policy Headend Behavior November 2024 5.2. Informative References TBD Acknowledgments TBD Authors' Addresses Changwang Lin New H3C Technologies Email: linchangwang.04414@h3c.com Ran Chen ZTE Corporation China Email: chen.ran@zte.com.cn lin, et al. Expires May, 2025 [Page 8]