6MAN D. Steinberg, Ed. Internet-Draft Lapishills Consulting Limited Intended status: Informational W. Henderickx Expires: December 31, 2020 Nokia Z. Li Huawei Technologies W. Cheng China Mobile D. Voyer Bell Canada June 29, 2020 SR-MPLS over IPv6 satisfies CRH requirements draft-steinberg-6man-crh-vs-sr-mpls-00 Abstract SR-MPLS is a mature solution that provides highly scalable traffic engineering capabilities in MPLS networks. This document analyzes how SR-MPLS over IP exceeds the capabilities of the CRH, making the latter redundant. 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 December 31, 2020. 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 Steinberg, et al. Expires December 31, 2020 [Page 1] Internet-DraftSR-MPLS over IPv6 satisfies CRH requirements June 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 2. A Label by any Other Name . . . . . . . . . . . . . . . . . . 2 3. An Endpoint is an Endpoint . . . . . . . . . . . . . . . . . 3 4. All Roads Lead to Rome . . . . . . . . . . . . . . . . . . . 3 5. You Can't Manage What You Can't Measure . . . . . . . . . . . 3 6. MTU Overhead . . . . . . . . . . . . . . . . . . . . . . . . 3 7. Services . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 4 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 9.1. Normative References . . . . . . . . . . . . . . . . . . 4 9.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction SR-MPLS [RFC8660] is a mature solution that provides highly scalable traffic engineering capabilities in MPLS networks. By encapsulating the MPLS label stack in an IPv4 or IPv6 [RFC4023], or IP+UDP [RFC7510] header, an SR-MPLS policy can seamlessly traverse IP-only routers in a network [RFC8663]. The SR-MPLS control plane can run on top of IPv4 or IPv6. The latter is reminded in [I-D.filsfils-spring-sr-mpls-ipv6-control-plane]. This document analyzes how SR-MPLS over IP provides all the capabilities of CRH [I-D.bonica-6man-comp-rtg-hdr], making CRH redundant. The analysis shows that the capabilities provided by CRH are in fact a subset of the capabilities provided by SR-MPLS over IPv6. 2. A Label by any Other Name [I-D.bonica-6man-comp-rtg-hdr] specifies the encoding of identifiers in 16- or 32-bit values and places them in the CRH. The CRH is to be inspected at each node represented by an identifier. Steinberg, et al. Expires December 31, 2020 [Page 2] Internet-DraftSR-MPLS over IPv6 satisfies CRH requirements June 2020 SR-MPLS over IP encodes identifiers in 20-bit values within 32 bit labels and places them in an in the SR-MPLS or UDP header. Because these encodings must translate into an action and a location (IPv6 address) there is really no difference between these encodings, in the end a 32-bit label is just a label that can identify anything at an endpoint. 3. An Endpoint is an Endpoint A node transmitting a packet containing a set of identifiers placed within a CRH writes the IPv6 address of the first segment endpoint into the destination address of the IPv6 header. The same is true for SR-MPLS over IP, the source node writes the IPv6 address of the first segment endpoint into the destination address of the IPv6 header. There is no functional difference between the SR-MPLS over IP endpoint vs the CRH endpoint, both receive a packet destined to their interface and process the next segment. 4. All Roads Lead to Rome At a segment endpoint the router receives the packet destined to it, processes the next segment (MPLS label or CRH segment ID) and rewrites the outer IPv6 header with a new destination address. The CRH calls this table that maps labels to behavior and a destination address a SFIB, however this is identical to the SR-MPLS label table. Ultimately, the packet is received at the final destination within the domain and the packets payload is processed. All roads do indeed lead to Rome. 5. You Can't Manage What You Can't Measure IP ping and traceroute just work for either SR-MPLS over IP or CRH. SR-MPLS has a rich set of OAM mechanisms ([RFC8287]), and these mechanisms are available for SR-MPLS over IP deployments. CRH has no OAM defined for its labels. 6. MTU Overhead Both SR-MPLS over IPv6 and CRH require an IPv6 header. However, due to the overhead required for extension headers, CRH always results in greater overhead in its 32 bit flavor vs SR-MPLS over IP. For the Steinberg, et al. Expires December 31, 2020 [Page 3] Internet-DraftSR-MPLS over IPv6 satisfies CRH requirements June 2020 CRH 16 bit flavor, SR-MPLS over IP still has a lower overhead for up to 5 labels. 7. Services MPLS has a rich set of services that are defined and translate into MPLS labels. Protocols and SDN mechanisms to distribute these service labelse are well known. CRH has no service support, it is simply a transport header carrying transport identifiers. It relies on other headers and identifiers to provide services. 8. Conclusion This analysis shows that CRH and the identifiers it carries do not provide any demonstrable benefit beyond what SR-MPLS over IPv6 provides, in fact it can only support a subset of what SR-MPLS over IPv6 is capable of. Furthermore, OAM is fully defined for SR-MPLS and the control planes supporting SR-MPLS are mature and well defined. The conclusion is that there is no value in defining another header to map labels to behaviors and IPv6 addresses within a domain. This exists and it is SR-MPLS over IPv6. 9. References 9.1. Normative References [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, . [RFC8663] Xu, X., Bryant, S., Farrel, A., Hassan, S., Henderickx, W., and Z. Li, "MPLS Segment Routing over IP", RFC 8663, DOI 10.17487/RFC8663, December 2019, . 9.2. Informative References [I-D.bonica-6man-comp-rtg-hdr] Bonica, R., Kamite, Y., Niwa, T., Alston, A., and L. Jalil, "The IPv6 Compact Routing Header (CRH)", draft- bonica-6man-comp-rtg-hdr-22 (work in progress), May 2020. Steinberg, et al. Expires December 31, 2020 [Page 4] Internet-DraftSR-MPLS over IPv6 satisfies CRH requirements June 2020 [I-D.filsfils-spring-sr-mpls-ipv6-control-plane] Filsfils, C., Clad, F., and K. Talaulikar, "SR-MPLS Data Plane with IPv6 Control Plane", draft-filsfils-spring-sr- mpls-ipv6-control-plane-02 (work in progress), May 2020. [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed., "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005, . [RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black, "Encapsulating MPLS in UDP", RFC 7510, DOI 10.17487/RFC7510, April 2015, . [RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya, N., Kini, S., and M. Chen, "Label Switched Path (LSP) Ping/Traceroute for Segment Routing (SR) IGP-Prefix and IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017, . Authors' Addresses Dirk Steinberg (editor) Lapishills Consulting Limited Cyprus Email: dirk@lapishills.com Wim Henderickx Nokia Belgium Email: wim.henderickx@nokia.com Zhenbin Li Huawei Technologies China Email: lizhenbin@huawei.com Steinberg, et al. Expires December 31, 2020 [Page 5] Internet-DraftSR-MPLS over IPv6 satisfies CRH requirements June 2020 Weiqiang Cheng China Mobile China Email: chengweiqiang@chinamobile.com Daniel Voyer Bell Canada Canada Email: daniel.voyer@bell.ca Steinberg, et al. Expires December 31, 2020 [Page 6]