SPRING Working Group S. Hegde Internet-Draft R. Bonica Intended status: Standards Track Juniper Networks Expires: August 26, 2021 P. Shaofu G. Mirsky Z. Zhang ZTE Corporation B. Decraene Orange February 22, 2021 The SRv6 END.DTM Endpoint Behavior draft-bonica-spring-srv6-end-dtm-04 Abstract This document describes a new SRv6 endpoint behavior, called END.DTM. END.DTM supports inter-working between SRv6 and SR-MPLS. Like any endpoint behavior, END.DTM contains a function and arguments. The function causes the processing node to decapsulate a packet, impose an SR-MPLS label stack and forward the packet. The arguments determine SR-MPLS label stack contents. 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 August 26, 2021. Copyright Notice Copyright (c) 2021 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 Hegde, et al. Expires August 26, 2021 [Page 1] Internet-Draft END.DTM February 2021 (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. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. Use-case . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Processing . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Overview Segment Routing (SR) [RFC8402] allows source nodes to steer packets through SR paths. It can be implemented over IPv6 [RFC8200] or MPLS [RFC3031]. When SR is implemented over IPv6, it is called SRv6 [I-D.ietf-spring-srv6-network-programming]. When SR is implemented over MPLS, it is called SR-MPLS [RFC8660]. This document describes a new SRv6 endpoint behavior, called END.DTM. END.DTM supports inter-working between SRv6 and SR-MPLS. Like any endpoint behavior, END.DTM contains a function and arguments. The function causes the processing node to: o Decapsulate a packet (i.e., remove an IPv6 header and its extensions). o Impose an SR-MPLS label stack. o Forward the packet. The arguments determine MPLS-label stack contents and anything that might be encoded in the MPLS-label stack (e.g., transport class [I-D.hegde-spring-mpls-seamless-sr]) Hegde, et al. Expires August 26, 2021 [Page 2] Internet-Draft END.DTM February 2021 2. 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. 3. Use-case ------ ------ ------ ------ ------ |Node 1| --- |Node 2| --- |Node 3| --- |Node 4| --- |Node 5| ------ ------ ------ ------ ------ Seg. A Seg. B Seg. C Seg. D <-----------SRv6 Part ----------><-------SR-MPLS Part------> Figure 1: END.DTM Use-case Figure 1 depicts an inter-working SR path. The SR path originates on Node 1 and terminates on Node 5. It contains: o An SRv6 part o An SR-MPLS part The SRv6 part includes Nodes 1, 2 and 3. Nodes 1 and 2 MUST be SRv6-capable but are NOT REQUIRED to be SR-MPLS capable. An END.DTM segment is instantiated on Node 3. Therefore, Node 3 MUST be SRv6-capable and SR-MPLS capable. The SRv6 part also includes: o Segment A - An END segment that is instantiated on Node 2. o Segment B - An END.DTM segment that is instantiated on Node 3. The SR-MPLS part includes Nodes 4 and 5. These nodes MUST be SR- MPLS-capable but are NOT REQUIRED to be SRv6 capable. The SR-MPLS part also includes: o Segment C - A prefix segment that is instantiated on Node 4. o Segment D - A prefix segment that is instantiated on Node 5. Hegde, et al. Expires August 26, 2021 [Page 3] Internet-Draft END.DTM February 2021 The following paragraphs describe how a packet traverses this inter- working SR path: Node 1 encapsulates the packet in an SRv6 header. The SRv6 header contains the following Segment Identifiers (SID): o A SID representing Segment A, encoded in the Destination Address field of the IPv6 header. o A SID representing Segment B, encoded in a Segment Routing Header (SRH) [RFC8754]. Node 1 sends the packet to Node 2. When the packet arrives at Node 2, The Destination Address field in the IPv6 header represents a locally instantiated END SID. Node 2 processes the packet as follows: o Decrement the Segments Left field in the SRH o Copy the next SID from the SRH to the Destination Address field of the IPv6 header. o Forward the packet to Node 3. When the packet arrives at Node 3, The Destination Address field in the IPv6 header represents a locally instantiated END.DTM SID. Node 3 processes the packet as follows: o Decapsulate the packet (i.e., remove the IPv6 header and its extensions, including the SRH) o Push two SR-MPLS label stack entries, representing Segments D and C. Set the MPLS Traffic Class and TTL values to reflect the Traffic Class and Hop count values received in the IPv6 header. o Forward the packet to Node 4. When the packet arrives at Node 4, it is encapsulated in an SR-MPLS label stack. Node 4 processes the packet as described in SR-MPLS [RFC8660]. 4. Processing The End.DTM SID MUST be the last segment in a SR Policy. Its arguments are associated with an SR-MPLS label stack. When Node N receives a packet destined to S and S is a locally instantiated End.DTM SID, Node N executes the following procedure: Hegde, et al. Expires August 26, 2021 [Page 4] Internet-Draft END.DTM February 2021 S01. When an IPv6 Routing Header is processed { S02. If (Segments Left != 0) { S03. Send an ICMP Parameter Problem to the Source Address, Code 0 (Erroneous header field encountered), Pointer set to the Segments Left field, interrupt packet processing and discard the packet. S04. } S05. Proceed to process the next header in the packet S06. } When processing the Upper-layer header of a packet matching a FIB entry locally instantiated as an End.DTM SID, N executes the following procedure: S01. Decapsulate the packet (i.e., remove the outer IPv6 Header and all its extension headers) S02. Push the SR-MPLS label stack that is associated with the END.DTM arguments. Set the MPLS Traffic Class and TTL values to reflect the Traffic Class and Hop count values received in the IPv6 header. S03. Submit the packet to the MPLS FIB lookup for transmission to the new destination 5. IANA Considerations This document requires no IANA action. The authors will request an early allocation from the "SRv6 Endpoint Behaviors" sub-registry of the "Segment Routing Parameters" registry. 6. Security Considerations Because SR inter-working requires co-operation between inter-working domains, this document introduces no security consideration beyond those addressed in [RFC8402], [RFC8754] and [I-D.ietf-spring-srv6-network-programming]. 7. Acknowledgements Thanks to Melchior Aelmans, Bruno Decraene, Takuya Miyasaka and Jeff Tantsura for their comments. 8. References Hegde, et al. Expires August 26, 2021 [Page 5] Internet-Draft END.DTM February 2021 8.1. 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-28 (work in progress), December 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, . [RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing with the MPLS Data Plane", RFC 8660, DOI 10.17487/RFC8660, 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, . 8.2. Informative References [I-D.hegde-spring-mpls-seamless-sr] Hegde, S., Bowers, C., Xu, X., Gulko, A., Bogdanov, A., Uttaro, J., Jalil, L., Khaddam, M., and A. Alston, "Seamless Segment Routing", draft-hegde-spring-mpls- seamless-sr-04 (work in progress), January 2021. Hegde, et al. Expires August 26, 2021 [Page 6] Internet-Draft END.DTM February 2021 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001, . Authors' Addresses Shraddha Hegde Juniper Networks Embassy Business Park Bangalore, KA 560093 India Email: shraddha@juniper.net Ron Bonica Juniper Networks Herndon, Virginia 20171 USA Email: rbonica@juniper.net Peng Shaofu ZTE Corporation Peoples Republic of China Email: peng.shaofu@zte.com.cn Greg Mirsky ZTE Corporation USA Email: gregimirsky@gmail.com Zheng Zhang ZTE Corporation Peoples Republic of China Email: zhang.zheng@zte.com.cn Hegde, et al. Expires August 26, 2021 [Page 7] Internet-Draft END.DTM February 2021 Bruno Decraene Orange France Email: bruno.decraene@orange.com Hegde, et al. Expires August 26, 2021 [Page 8]