SPRING Working Group C. Li Internet-Draft M. Chen Intended status: Standards Track D. Dhody Expires: April 25, 2019 Z. Li J. Dong Huawei Technologies R. Gandhi Cisco Systems, Inc. October 22, 2018 Path Segment for SRv6 (Segment Routing in IPv6) draft-li-spring-srv6-path-segment-00 Abstract Segment Routing (SR) allows for a flexible definition of end-to-end paths by encoding paths as sequences of topological sub-paths, called "segments". Segment routing architecture can be implemented over an MPLS data plane as well as an IPv6 data plane. Further, Path Segment has been defined to identify an SR path in SR- MPLS networks, and used for various use-cases such as end-to-end SR Path Protection and Performance Measurement (PM) of an SR path. Similar to SR-MPLS, this document defines Path Segment in SRv6 networks to identify an SRv6 path. 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 April 25, 2019. Li, et al. Expires April 25, 2019 [Page 1] Internet-Draft SRv6 Path Segment October 2018 Copyright Notice Copyright (c) 2018 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 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. SRv6 Path Segment . . . . . . . . . . . . . . . . . . . . . . 4 3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 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 MPLS dataplane, called SR-MPLS [I-D.ietf-spring-segment-routing-mpls], a segment is an MPLS label. When segment routing is deployed on IPv6 dataplane, called SRv6 [I-D.ietf-6man-segment-routing-header], a segment is a 128 bit value, and it can be an IPv6 address of a local interface but it does not have to. For supporting SR, an extended header called Segment Routing Header (SRH), which contains a list of SIDs and several needed information such as Segments Left, has been defined in [I-D.ietf-6man-segment-routing-header]. In an SR-MPLS network, when a packet is transmitted along an SR path, the labels in the MPLS label stack will be swapped or popped, so no Li, et al. Expires April 25, 2019 [Page 2] Internet-Draft SRv6 Path Segment October 2018 label or only the last label may be left in the MPLS label stack when the packet reaches the egress node. Thus, the egress node can not determine from which ingress node or SR path the packet comes. For identifying an SR-MPLS path, Path Segment is defined in [I-D.cheng-spring-mpls-path-segment]. Likewise, a path needs to be identified in an SRv6 network for several use cases such as binding bidirectional path [I-D.li-pce-sr-bidir-path] and end-to-end performance measurement [I-D.gandhi-spring-udp-pm]. A SRv6 path can be identified by the full segment list that made up of several SRv6 segments. However, the segment list may not be unique to identify an SRv6 path. This document defines a new SRv6 segment called "SRv6 Path Segment" to identify an SRv6 path. Using of Path Segment as an SRv6 SID (instead of path ID carried by an SRH TLV) will see benefit in performance and also ease of using the same concept in SR, irrespective of SR-MPLS and SRv6 data planes. The Path Segment is inserted as the last segment in the segment list and will not affect the order of the original SID list. 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 DM: Delay Measurement. LM: Loss Measurement. MPLS: Multiprotocol Label Switching. PM: Performance Measurement. PSID: Path Segment ID. SID: Segment ID. SL: Segment List. SR: Segment Routing. SR-MPLS: Segment Routing with MPLS data plane. Li, et al. Expires April 25, 2019 [Page 3] Internet-Draft SRv6 Path Segment October 2018 SRH: Segment Routing Header. PSID: Path Segment ID. PSP: Penultimate Segment Popping. Further, this document makes use of the terms defined in [RFC8402] and [I-D.filsfils-spring-srv6-network-programming]. 2. SRv6 Path Segment As defined in [I-D.filsfils-spring-srv6-network-programming], a SRv6 segment is a 128 bit value, which can be present as LOC:FUNCT. For identifying an SRv6 path, this document defines a new segment called SRv6 Path Segment. A Path Segment (consisted of LOC and FUNCT part) can identify an SRv6 path within an SRv6 domain. Also, the SRv6 Path Segment may be used to identify an SRv6 Policy, its Candidate-path or a SID-List [I-D.ietf-spring-segment-routing-policy] terminating on an egress node depending on the use-case. Note that, based on the use-case, the different SID-Lists of SR Policy may use the same SRv6 Path Segment. 3. Operation A Path Segment is a local segment of egress node, it is allocated by the egress node. A Path Segment can be allocated by several ways, such as CLI, BGP [I-D.li-idr-sr-policy-path-segment-distribution], PCEP [I-D.li-pce-sr-path-segment] or other ways. The procedure of Path Segment allocation is out of scope of this document. When the Path Segment is allocated by the egress, it MUST be distributed to the ingress node at minimum. In this case, the transit nodes do not know how to process the Path Segment. A Path Segment is used for path identification and it MUST NOT be copied to the IPv6 destination address. The SRv6 Path Segment MUST be inserted as the last entry in the SID list without affecting the segment left field in the SRH. The last entry field in SRH should be set as the index of the Path Segment, which is the last entry in the SID list. In this case, Path Segment presenting to a transit node is an error condition. Also, PSP of the SRH MUST be disabled. Li, et al. Expires April 25, 2019 [Page 4] Internet-Draft SRv6 Path Segment October 2018 The Path Segment SHOULD appear only once in a SID list, and the one that appears at the last entry in the SID list will be processed while the rests will be ignored. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[0] (128 bits IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | ... | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n-1] (128 bits IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Path Segment(Segment List[n], 128 bits IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1. SRv6 Path Segment in SID List If an egress node supports Path Segment processing and related OAM mechanisms are enabled, the node will inspect the last entry in the SID list to obtain the Path Segment. The behavior of Path Segment related function will be defined in the future version of this draft or related use-case drafts. 4. IANA Considerations This document does not require any IANA actions. 5. Security Considerations This document does not introduce additional security requirements and mechanisms other than the ones described in [RFC8402]. Li, et al. Expires April 25, 2019 [Page 5] Internet-Draft SRv6 Path Segment October 2018 6. Acknowledgements The authors would like to thank Zafar Ali for his valuable comments and suggestions. 7. References 7.1. Normative References [I-D.filsfils-spring-srv6-network-programming] Filsfils, C., Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 Network Programming", draft-filsfils-spring-srv6-network- programming-05 (work in progress), July 2018. [I-D.ietf-6man-segment-routing-header] Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-segment-routing-header-14 (work in progress), June 2018. [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, . 7.2. Informative References [I-D.cheng-spring-mpls-path-segment] Cheng, W., Wang, L., Li, H., Chen, M., Gandhi, R., Zigler, R., and S. Zhan, "Path Segment in MPLS Based Segment Routing Network", draft-cheng-spring-mpls-path-segment-03 (work in progress), October 2018. Li, et al. Expires April 25, 2019 [Page 6] Internet-Draft SRv6 Path Segment October 2018 [I-D.gandhi-spring-udp-pm] Gandhi, R., Filsfils, C., daniel.voyer@bell.ca, d., Salsano, S., Ventre, P., and M. Chen, "UDP Path for In- band Performance Measurement for Segment Routing Networks", draft-gandhi-spring-udp-pm-02 (work in progress), September 2018. [I-D.ietf-spring-segment-routing-mpls] Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing with MPLS data plane", draft-ietf-spring-segment-routing-mpls-14 (work in progress), June 2018. [I-D.ietf-spring-segment-routing-policy] Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., bogdanov@google.com, b., and P. Mattes, "Segment Routing Policy Architecture", draft-ietf-spring-segment-routing- policy-01 (work in progress), June 2018. [I-D.li-idr-sr-policy-path-segment-distribution] Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing Policies for Path Segment and Bi-directional Path", draft- li-idr-sr-policy-path-segment-distribution-00 (work in progress), April 2018. [I-D.li-pce-sr-bidir-path] Li, C., Chen, M., Dhody, D., Cheng, W., Li, Z., Dong, J., and R. Gandhi, "PCEP Extension for Segment Routing (SR) Bi-directional Associated Paths", draft-li-pce-sr-bidir- path-01 (work in progress), September 2018. [I-D.li-pce-sr-path-segment] Li, C., Chen, M., Dhody, D., Cheng, W., Dong, J., Li, Z., and R. Gandhi, "Path Computation Element Communication Protocol (PCEP) Extension for Path Identification in Segment Routing (SR)", draft-li-pce-sr-path-segment-02 (work in progress), September 2018. Authors' Addresses Cheng Li Huawei Technologies Email: chengli13@huawei.com Li, et al. Expires April 25, 2019 [Page 7] Internet-Draft SRv6 Path Segment October 2018 Mach(Guoyi) Chen Huawei Technologies Email: mach.chen@huawei.com Dhruv Dhody Huawei Technologies Divyashree Techno Park, Whitefield Bangalore, Karnataka 560066 India Email: dhruv.ietf@gmail.com Zhenbin Li Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: jie.dong@huawei.com Rakesh Gandhi Cisco Systems, Inc. Canada Email: rgandhi@cisco.com Li, et al. Expires April 25, 2019 [Page 8]