SPRING WG W. Cheng Internet-Draft China Mobile Intended status: Standards Track R. Chen Expires: August 19, 2020 A. Liu G. Mirsk ZTE Corporation February 16, 2020 Shorter SRv6 SID Requirements draft-cheng-shorter-srv6-sid-requirement-00 Abstract This document describes a list of requirement for Shorter SRv6 SID. 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 19, 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 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. Cheng, et al. Expires August 19, 2020 [Page 1] Internet-Draft Shorter SRv6 SID Requirements February 2020 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements: . . . . . . . . . . . . . . . . . . . . . . . . 2 3. The proposal solutions of shorter SRv6 SID . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Segment Routing [RFC8402]leverages the source routing paradigm. An ingress node steers a packet through an ordered list of instructions, called segments. A segment can be encoded as a Multi-Protocol Label Switching (MPLS) label, IPv4 address, or IPv6 address. Segment Routing can be deployed on MPLS data plane by encoding 20-bits SIDs in MPLS label stack [I-D.ietf-spring-segment-routing-mpls]. It also can be deployed on the IPv6 data plane by encoding a list of 128-bits SIDs in IPv6 Segment Routing Extension Header (SRH)[I-D.ietf-6man-segment-routing-header]. The SRv6 Network Programming [I-D.ietf-spring-srv6-network-programming]specifies the base set of SRv6 behaviors that enables the creation of interoperable overlays with underlay optimization. However, the size of the IPv6 segment identifier (SID) presents a scaling challenge to use topological instructions that define a strict explicitly routed path in combination with service-based instructions. At the same time, the size of the SRH/SID may be a challenge for some data plane processors and traffic overhead. Meanwhile, SR-MPLS currently, more often than SRv6, is used in metro networks. With the gradual deployment of SRv6 in the core networks, it becomes necessary to support interworking between SR-MPLS and SRv6 and upgrading to SRv6 from SR-MPLS.It requires some solutions to resolve these problems. 2. Requirements: This section list the suggested requirements for Shorter SRv6 SID, which have been used to help the WG evaluate against the proposed solutions: Cheng, et al. Expires August 19, 2020 [Page 2] Internet-Draft Shorter SRv6 SID Requirements February 2020 REQ#1:The Shorter SRv6 solution MUST align with the basic SRv6. There are three basic Segment Routing over the IPv6 data-plane (SRv6) documents: o The Segment Routing (SR) architecture is defined [RFC8402]. o The IPv6 Segment Routing Header (SRH) is defined [I-D.ietf-6man-segment-routing-header]. o SRv6 Network Programming is defined [I-D.ietf-spring-srv6-network-programming]. The Shorter SRv6 SID solution MUST align with above basic SRv6 documents. REQ#2:The Shorter SRv6 SID solution MUST support Efficient SRv6 header compression. When SRv6 is deployed, the SRv6 header overhead must be considered, as the size of the SRH may affect the forwarding performance. The solution MUST reduce the SRv6 SID size effectively. REQ#3:The Shorter SRv6 SID solution MUST be easy to implement and hardware-friendly The Shorter SRv6 SID solution MUST be simple and easy to implement and MUST use the mature hardware capabilities REQ#4:The Shorter SRv6 SID solution MUST be compatible with SRv6 header(SRH). For support of SRv6 network, Segment Routing Header (SRH) has been defined in [I-D.ietf-6man-segment-routing-header]. The Shorter SRv6 SID solution MUST be compatible with SRH. REQ#5:The Shorter SRv6 SID solution MUST support Compressed SRv6 Network Programming. In a SR domain,there will be such the scenario in which some nodes support Compressed SRv6 while others only support SRv6, the proposed solution must support this scenario. REQ#6:The Shorter SRv6 SID solution MUST support super-large-scale networking and address planning. Note:The operator suggest to reuse the current address assignment and planning, thus minimizing the impact on the network. Cheng, et al. Expires August 19, 2020 [Page 3] Internet-Draft Shorter SRv6 SID Requirements February 2020 REQ#7:The Shorter SRv6 SID solution MUST have the ability to upgrade smooth from SR-MPLS to SRv6. 2G/3G/4G backhaul networks widely deploy MPLS to connect wireless services. Many operators are already deploying 5G networks. To optimize the operation of the network, many operators intent to adopt the segment routing. Currently, given maturity of SR-MPLS, it has been deployed on a large scale. Meanwhile the requirements of 5G super-large-scale number of connections accelerate the deployment of IPv6 networks. Thus, logically, operators consider SRv6 solution to fulfill the 5G backhaul requirement. But the backhaul network could not deploy SRv6 in one day, especially if it has already been using MPLS and SR-MPLS. It might be reasonable to upgrade from MPLS to SR- MPLS and then to SRv6 REQ#8:The Shorter SRv6 SID solution MUST support interworking between SRv6 and SR-MPLS domains in the network. SR-MPLS currently, more often than SRv6, is used in metro networks. With the gradual deployment of SRv6 in the core networks, it becomes necessary to support interworking between SR-MPLS and SRv6. 3. The proposal solutions of shorter SRv6 SID As we know, there are a number of proposals in the called 'shorter SRv6 SID' topic. This document tries to summarize these proposals here. Then we can discuss whether all the proposals can meet the requirements. And then we can look at merits and costs of each solution. After that, we will possibly refine them, possibly converge on a single one, and probably drop multiples. Here are the solutions that have been proposed: o [I-D.mirsky-6man-unified-id-sr]extends the use the flag of the SRH to unified identifiers encoded as shorter SID (such as 32-bits). It can be interworking with SR-MPLS. It is the earliest one, simple, and compatible well with original SRH. o [I-D.filsfils-spring-net-pgm-extension-srv6-usid] extends SRv6 Network Programming with a new type of SRv6 SID behavior. A uSID carrier can be encoded in the Destination Address of an IPv6 header or at any position in the Segment List of an SRH. o [I-D.decraene-spring-srv6-vlsid]extends SRH and SRv6 Network Programming to allow for SIDs of variable length, from 1 up to 128 bits. It is required to extend the control plane to advertise the SID length. Cheng, et al. Expires August 19, 2020 [Page 4] Internet-Draft Shorter SRv6 SID Requirements February 2020 o [I-D.bonica-6man-comp-rtg-hdr]defines two new Routing header types. Collectively, they are called the Compressed Routing Headers (CRH). Individually,they are called CRH-16 and CRH-32. In the CRH, the Type-specific data field contains a list of Segment Identifiers (SIDs)(16bits/32bits). o [I-D.cl-spring-generalized-srv6-np]proposes Generalized Segment Routing over IPv6 (G-SRv6) Networking Programming, which supports to encode multiple types of Segments in a SRH, called Generalized SRH (G-SRH). These Segments can be called Generalized Segment, and the ID can be Generalized Segment Identifier (G-SID), which may include an SRv6 SID(128 bits),C-SIDs, MPLS labels, or IPv4 tunnel information. 4. IANA Considerations This document has no requests to IANA. 5. Security Considerations This document does not change the security considerations of SRv6, please refers to [RFC8402], [I-D.ietf-6man-segment-routing-header] and [I-D.ietf-spring-srv6-network-programming]. 6. Normative References [I-D.bonica-6man-comp-rtg-hdr] Bonica, R., Kamite, Y., Niwa, T., Alston, A., and N. So, "The IPv6 Compressed Routing Header (CRH)", draft-bonica- 6man-comp-rtg-hdr-11 (work in progress), February 2020. [I-D.cl-spring-generalized-srv6-np] Cheng, W., Li, Z., Li, C., Xie, C., Cong, L., Tian, H., and F. Zhao, "Generalized SRv6 Network Programming", draft-cl-spring-generalized-srv6-np-00 (work in progress), February 2020. [I-D.decraene-spring-srv6-vlsid] Decraene, B. and R. Raszuk, "SRv6 vSID: Network Programming extension for variable length SIDs", draft- decraene-spring-srv6-vlsid-02 (work in progress), February 2020. Cheng, et al. Expires August 19, 2020 [Page 5] Internet-Draft Shorter SRv6 SID Requirements February 2020 [I-D.filsfils-spring-net-pgm-extension-srv6-usid] Filsfils, C., Camarillo, P., Cai, D., Voyer, D., Meilik, I., Patel, K., Henderickx, W., Jonnalagadda, P., and D. Melman, "Network Programming extension: SRv6 uSID instruction", draft-filsfils-spring-net-pgm-extension- srv6-usid-03 (work in progress), February 2020. [I-D.ietf-6man-segment-routing-header] Filsfils, C., Dukes, D., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-segment-routing-header-26 (work in progress), October 2019. [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-22 (work in progress), May 2019. [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-09 (work in progress), February 2020. [I-D.mirsky-6man-unified-id-sr] Cheng, W., Mirsky, G., Peng, S., Aihua, L., Wan, X., Wei, C., and S. Shay, "Unified Identifier in IPv6 Segment Routing Networks", draft-mirsky-6man-unified-id-sr-04 (work in progress), November 2019. [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, . Cheng, et al. Expires August 19, 2020 [Page 6] Internet-Draft Shorter SRv6 SID Requirements February 2020 [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, . Authors' Addresses Weiqiang Cheng China Mobile Email: chengweiqiang@chinamobile.com Ran Chen ZTE Corporation Email: chen.ran@zte.com.cn Aihua Liu ZTE Corporation Email: liu.aihua@zte.com.cn Greg Mirsk ZTE Corporation Email: gregimirsky@gmail.com Cheng, et al. Expires August 19, 2020 [Page 7]