SPRING Working Group K. Salih Internet-Draft S. Hegde Intended status: Standards Track M. Rajesh Expires: January 11, 2022 R. Bonica Juniper Networks July 10, 2021 SRv6 inter-domain mapping SIDs draft-salih-spring-srv6-inter-domain-sids-00 Abstract This document describes three new SRv6 end point behaviors, named END.REPLACE, END.REPLACEB6 and END.DB6. These SIDs are used in distributed inter-domain solutions for connecting SRv6 domains. This behavior is normally executed on border routers between different domains. These SIDs can also be used to provide multiple intent based paths across these domains. 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 January 11, 2022. 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 (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 Salih, et al. Expires January 11, 2022 [Page 1] Internet-Draft SRv6 interdomain SIDs July 2021 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 . . . . . . . . . . . . . . . . . . . . 2 3. Usecases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. usecase 1 . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. usecase 2 . . . . . . . . . . . . . . . . . . . . . . . . 3 4. SRv6 SID behaviors . . . . . . . . . . . . . . . . . . . . . 4 4.1. END.REPLACE . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. END.REPLACEB6 . . . . . . . . . . . . . . . . . . . . . . 5 4.3. END.DB6 . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 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 [RFC8986]. This document describes three new SRv6 endpoint behaviors, named END.REPLACE, END.REPLACEB6 and END.DB6. These SIDs help in building paths over different SRv6 domans in a distributed manner. These extensions will aid in end to end SRv6 intent based path stitching as well. 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. Salih, et al. Expires January 11, 2022 [Page 2] Internet-Draft SRv6 interdomain SIDs July 2021 3. Usecases The document [I-D.hegde-spring-mpls-seamless-sr] describes different models of topology applicable for the use-cases mentioned in this document. 3.1. usecase 1 This requirement is mentioned in the document [I-D.hegde-spring-mpls-seamless-sr] under the section 4.1.1. ---IBGP------EBGP----IBGP------EBGP-----IBGP--- | | | | | | +-----------+ +-----------+ +-----------+ | | | | | | | ASBR1+--+ASBR2 ASBR3+--+ASBR4 | PE1+ AS1 | X | AS2 | X | AS3 +PE2 | ASBR5+--+ASBR6 ASBR7+--+ASBR8 | | | | | | | +-----+-----+ +-----------+ +-----------+ PE3 |---SRv6---| |---SRv6---| |---SRv6---| Figure 1: Multiple ASes connected with E-BGP The above diagram Figure 1 has three different ASes (AS1, AS2 and AS3). All the three domains are having SRv6. BGP is used for getting option C [RFC4364] style connectivity end to end from PE1 to PE2. 3.2. usecase 2 Salih, et al. Expires January 11, 2022 [Page 3] Internet-Draft SRv6 interdomain SIDs July 2021 +-----------+ +------------+ / \ / \ | ABR1 | | | | PE1+ AS1 + AS2 +PE2 | | | | ABR2 | \ /\ / +------------+ +-----------+ Figure 2: Single AS with Multiple IGP domains The above diagram Figure 2 shows two different SRv6 domains, AS1 and AS2. Services are running between PE1 and PE2 in option B [RFC4364] style. The requirement here is to avoid service route lookup on ABR1 and ABR2 to provide option B style end to end connectivity. 4. SRv6 SID behaviors Here we will describe the new SRv6 SID behaviors 4.1. END.REPLACE For the use-case mentioned under Section 3.1 END.REPLACE SID is applicable The End.REPLACE SID cannot be the last segment in SRH or SR Policy. Any SID instance of this behavior is associated with a set, J, of one or more L3 adjacencies of immediate BGP neighbors When Node N receives a packet destined to S and S is a locally instantiated End.REPLACE SID, Node N executes the following procedure: Salih, et al. Expires January 11, 2022 [Page 4] Internet-Draft SRv6 interdomain SIDs July 2021 S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard packet S07. } S08. Decrement IPv6 Hop Limit by 1 S09. Update IPv6 DA with new destination address(SID) mapped with END.REPLACE SID. S10. Submit the packet to the IPv6 module for transmission to the new destination via a member of J. S11. } 4.2. END.REPLACEB6 For the use-case mentioned under Section 3.1 END.REPLACEB6 SID is applicable The End.REPLACEB6 SID cannot be the last segment in a SRH or SR Policy. Node N is configured with an IPv6 address T (e.g., assigned to its loopback). When Node N receives a packet destined to S and S is a locally instantiated End.REPLACEB6 SID, Node N executes the following procedure: Salih, et al. Expires January 11, 2022 [Page 5] Internet-Draft SRv6 interdomain SIDs July 2021 S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard packet S07. } S08. Decrement IPv6 Hop Limit by 1 S09. Update IPv6 DA with new destination address(SID) mapped with END.REPLACEB6. S10. Push an IPv6 header with an SRH. S11. Set outer IPv6 SA = T and outer IPv6 DA to the first SID in the segment list S12. Set outer Payload Length, Traffic Class, Hop Limit, and Flow Label fields S13. Set the outer Next Header value S14. Submit the packet to the IPv6 module for transmission to the First SID. S15. } 4.3. END.DB6 For the use-case mentioned under Section 3.2 END.DB6 SID is applicable. The End.DB6 SID MUST be the last segment in SRH or SR Policy. Node N is configured with an IPv6 address T (e.g., assigned to its loopback). When Node N receives a packet destined to S and S is a locally instantiated End.DB6 SID, Node N executes the following procedure: S01. When an SRH 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. Remove the outer IPv6 header with all its extension headers. S06. Push the new IPv6 header with the SRv6 SIDs associated with the END.DB6 sid in an SRH. S07. Set outer IPv6 SA = T and outer IPv6 DA to the first SID in the segment list. S08. Set outer Payload Length, Traffic Class, Hop Limit, and Flow Label fields S09. Set the outer Next Header value S10. Submit the packet to the IPv6 module for transmission to First SID. S11. } Salih, et al. Expires January 11, 2022 [Page 6] Internet-Draft SRv6 interdomain SIDs July 2021 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 [RFC8986]. 7. Contributors Swamy SRK Juniper Networks Email: swamys@juniper.net G. Sri Karthik Goud Juniper Networks Email: gkarthik@juniper.net 8. Acknowledgements Thanks to Ram Santhanakrishnan, Srihari Sangli, Rajendra Prasad Bollam and Kiran Kushalad for their valuable comments. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Salih, et al. Expires January 11, 2022 [Page 7] Internet-Draft SRv6 interdomain SIDs July 2021 [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, . [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, . 9.2. 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., Alston, A., and L. M. Contreras, "Seamless SR Problem Statement", draft-hegde- spring-mpls-seamless-sr-05 (work in progress), February 2021. [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001, . Authors' Addresses Salih K A Juniper Networks Embassy Business Park Bangalore, KA 560093 India Email: salih@juniper.net Salih, et al. Expires January 11, 2022 [Page 8] Internet-Draft SRv6 interdomain SIDs July 2021 Shraddha Hegde Juniper Networks Embassy Business Park Bangalore, KA 560093 India Email: shraddha@juniper.net Rajesh Juniper Networks Embassy Business Park Bangalore, KA 560093 India Email: mrajesh@juniper.net Ron Bonica Juniper Networks Herndon, Virginia 20171 USA Email: rbonica@juniper.net Salih, et al. Expires January 11, 2022 [Page 9]