6man Working Group C. Li Internet-Draft Huawei Technologies Intended status: Standards Track W. Cheng Expires: May 4, 2021 China Mobile Z. Li D. Dhody Huawei Technologies October 31, 2020 Encapsulation of Path Segment in SRv6 draft-li-6man-srv6-path-segment-encap-04 Abstract Segment Routing (SR) allows for a flexible definition of end-to-end paths by encoding an ordered list of instructions, called "segments". The SR architecture can be implemented over an IPv6 data plane, called SRv6. In some use-cases such as end-to-end SR Path Protection and Performance Measurement (PM), an SRv6 path needs to be identified. This document defines the encoding of Path Segment in SRv6 networks. 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 May 4, 2021. Copyright Notice Copyright (c) 2020 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 (https://trustee.ietf.org/license-info) in effect on the date of Li, et al. Expires May 4, 2021 [Page 1] Internet-Draft SRv6 PSID Encap October 2020 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 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Encoding of an SRv6 Path Segment . . . . . . . . . . . . . . 3 2.1. Encapsulation of SRv6 Path Segment . . . . . . . . . . . 3 3. Processing of SRv6 Path Segment . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Segment routing (SR) [RFC8402] is a source routing paradigm that explicitly indicates the forwarding path for packets at the ingress node by inserting an ordered list of instructions, called segments. When segment routing is deployed on an IPv6 data plane, it is called SRv6, and it uses a new IPv6 [RFC8200] Routing Header (EH) called the IPv6 Segment Routing Header (SRH) [RFC8754] to construct an SRv6 path. As per [I-D.ietf-spring-srv6-network-programming], an SRv6 segment identifier is a 128-bit value, which can be represented as LOC:FUNCT, where LOC is the L most significant bits and FUNCT is the 128-L least significant bits. Most often the LOC part of the SID is routable and leads to the node which instantiates that SID. The FUNCT part of the SID is an opaque identification of a local function bound to the SID. In several use cases, such as binding bidirectional path [I-D.ietf-pce-sr-bidir-path] and end-to-end performance measurement [I-D.gandhi-spring-twamp-srpm], the ability to implement path identification is a pre-requisite. In SRv6, it is possible to identify a path by the content of the segment list. However, the segment list may not be a good key, since the length of the segment list may be too long and flexible according to the number of SIDs. Li, et al. Expires May 4, 2021 [Page 2] Internet-Draft SRv6 PSID Encap October 2020 Therefore, [I-D.li-spring-srv6-path-segment] defines an SRv6 Path Segment to identify an SRv6 path. This document defines the encoding of an SRv6 Path Segment in SRv6 networks. 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. 1.2. Terminology PM: Performance Measurement. SID: Segment ID. SL: Segment List. SR: Segment Routing. SRH: Segment Routing Header. PSID: Path Segment Identifier. PSP: Penultimate Segment Popping. Further, this document makes use of the terms defined in [RFC8402] and [I-D.ietf-spring-srv6-network-programming]. 2. Encoding of an SRv6 Path Segment This section will describe the SRH encoding of an SRv6 Path Segment as defined in [I-D.li-spring-srv6-path-segment]. As per [I-D.li-spring-srv6-path-segment], an SRv6 Path Segment is a 128-bits value, which identifies an SRv6 path. 2.1. Encapsulation of SRv6 Path Segment The SRv6 Path Segment MUST appear only once in a SID list, and it MUST appear as the last entry. To indicate the existence of a Path Segment in the SRH, this document defines a P-bit in the SRH flag field. The encapsulation of SRv6 Path Segment is shown below. Li, et al. Expires May 4, 2021 [Page 3] Internet-Draft SRv6 PSID Encap October 2020 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry | Flags |P| Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[0] (128 bits IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | ... | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n-1] (128 bits IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | SRv6 Path Segment (Segment List[n],128 bits IPv6 value) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // // Optional Type Length Value objects (variable) // // // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1. SRv6 Path Segment in SID List o P-bit: set when SRv6 Path Segment is inserted. It MUST be ignored when a node does not support SRv6 Path Segment processing. 3. Processing of SRv6 Path Segment The processing of SRv6 path segment is out of the scope of this document and is defined in [I-D.li-spring-srv6-path-segment]. 4. IANA Considerations This document requests IANA to allocate bit position TBA within the "Segment Routing Header Flags" registry defined in [RFC8402]. Li, et al. Expires May 4, 2021 [Page 4] Internet-Draft SRv6 PSID Encap October 2020 5. Security Considerations TBA 6. Acknowledgements TBA 7. References 7.1. Normative References [I-D.ietf-spring-srv6-network-programming] Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "SRv6 Network Programming", draft-ietf-spring-srv6-network-programming-24 (work in progress), October 2020. [I-D.li-spring-srv6-path-segment] Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi, "Path Segment for SRv6 (Segment Routing in IPv6)", draft- li-spring-srv6-path-segment-06 (work in progress), September 2020. [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, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 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, . [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, . Li, et al. Expires May 4, 2021 [Page 5] Internet-Draft SRv6 PSID Encap October 2020 7.2. Informative References [I-D.gandhi-spring-twamp-srpm] Gandhi, R., Filsfils, C., Voyer, D., Chen, M., and B. Janssens, "Performance Measurement Using TWAMP Light for Segment Routing Networks", draft-gandhi-spring-twamp- srpm-11 (work in progress), October 2020. [I-D.ietf-idr-sr-policy-path-segment] Li, C., Li, Z., Telecom, C., Cheng, W., and K. Talaulikar, "SR Policy Extensions for Path Segment and Bidirectional Path", draft-ietf-idr-sr-policy-path-segment-01 (work in progress), August 2020. [I-D.ietf-pce-sr-bidir-path] Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong, "PCEP Extensions for Associated Bidirectional Segment Routing (SR) Paths", draft-ietf-pce-sr-bidir-path-03 (work in progress), September 2020. [I-D.ietf-pce-sr-path-segment] Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong, "Path Computation Element Communication Protocol (PCEP) Extension for Path Segment in Segment Routing (SR)", draft-ietf-pce-sr-path-segment-01 (work in progress), May 2020. [I-D.ietf-spring-segment-routing-policy] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", draft- ietf-spring-segment-routing-policy-08 (work in progress), July 2020. Authors' Addresses Cheng Li Huawei Technologies Email: c.l@huawei.com Weiqiang Cheng China Mobile Email: chengweiqiang@chinamobile.com Li, et al. Expires May 4, 2021 [Page 6] Internet-Draft SRv6 PSID Encap October 2020 Zhenbin Li Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Dhruv Dhody Huawei Technologies Divyashree Techno Park, Whitefield Bangalore 560066 India Email: dhruv.ietf@gmail.com Li, et al. Expires May 4, 2021 [Page 7]