Network Working Group H. Chen Internet-Draft D. Eastlake Intended status: Standards Track Independent Expires: 28 March 2025 A. Wang China Telecom G. Mishra Verizon Inc. Y. Liu China Mobile Y. Fan Casa Systems L. Liu Fujitsu X. Liu Alef Edge 24 September 2024 IGP Extensions for Advertising Link Numbers draft-chen-lsr-adv-lkno-05 Abstract This document describes OSPF and IS-IS extensions for distributing the link numbers assigned to the links originating at a node. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 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." Chen, et al. Expires 28 March 2025 [Page 1] Internet-Draft Advertise Link No September 2024 This Internet-Draft will expire on 28 March 2025. Copyright Notice Copyright (c) 2024 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 2. Extensions to OSPFv2 . . . . . . . . . . . . . . . . . . . . 3 3. Extensions to OSPFv3 . . . . . . . . . . . . . . . . . . . . 4 4. Extensions to IS-IS . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. Normative References . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction When the links originating at each node in a network are numbered from 1 to the number of the such links for that node, an efficient stateless multicast along an explicit P2MP path can be achieved through using the link numbers of the links on the path to represent the path. This document proposes OSPF and IS-IS extensions for distributing the link numbers assigned to the links originating at a node which will support such multicast. After a controller such as PCE as a controller has the link numbers of the links originating at every node, for an explicit P2MP path, the controller can send the ingress the path represented by the link numbers of the links on the path. 1.1. Terminology LSA: Link State Advertisement. Chen, et al. Expires 28 March 2025 [Page 2] Internet-Draft Advertise Link No September 2024 OSPF: Open Shortest Path First. LSP: Link State Protocol data unit. IS-IS: Intermediate System to Intermediate System. MT: Multi-Topology. TE: Traffic Engineering. 2. Extensions to OSPFv2 This section describes extensions to OSPFv2 for distributing the link numbers assigned to the links of a node. [RFC7684] defines the OSPFv2 Extended Link TLV to advertise the information about a link. Multiple Link TLVs for the links of a router are included in the OSPFv2 Extended Link Opaque LSA of the router. The OSPFv2 Extended Link TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (1) | Length (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: OSPFv2 Extended Link TLV Type: 1. Length: Variable, dependent on Sub-TLVs. Link Type, Link ID and Link Data: They are defined in Section A.4.2 of [RFC2328]. Reserved: MUST be set to 0 on transmission and MUST be ignored on reception. Chen, et al. Expires 28 March 2025 [Page 3] Internet-Draft Advertise Link No September 2024 Under the OSPFv2 Extended Link TLV for a link, a Link Number Sub-TLV is defined for distributing the link number assigned to the link by the router originating the LSA. A Link Number Sub-TLV is included in the Link TLV for a link of Link Type Point-to-Point, Broadcast (i.e., link to LAN or Transit Network), or stub (i.e., link to stub network). The Link Number Sub-TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (TBD1) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Link Number Sub-TLV Type: TBD1. (Note this is the Sub-TLV Type, not the Link Type.) Length: 2. Link Number: A 2-octet field carrying the link number assigned to the link when the Link Type of the link in the OSPFv2 Extended Link TLV containing this Sub-TLV is 1 (i.e., Point-to-Point connection to another router), 2 (i.e., connection to a Transit Network or LAN), or 3 (i.e., connection to a stub network). 3. Extensions to OSPFv3 This section describes extensions to OSPFv3 for distributing the link numbers assigned to the links of a node. [RFC8362] defines the OSPFv3 Extended Router LSA, which may include multiple Router-Link TLVs. Chen, et al. Expires 28 March 2025 [Page 4] Internet-Draft Advertise Link No September 2024 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS Age |1|0|1| 0x21 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS Checksum | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0 |N|x|V|E|B| Options | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLVs | : : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Extended Router-LSA A Router-Link TLV defines a single router link. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (1 - Router-Link) | Length (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Type | 0 | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Neighbor Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Neighbor Router ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs | : : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Router-Link TV Under the Router-Link TLV for a link, a Link Number Sub-TLV is defined. This Sub-TLV has the same format as the Link Number Sub-TLV defined above for the OSPFv2 Extended Link TLV. Chen, et al. Expires 28 March 2025 [Page 5] Internet-Draft Advertise Link No September 2024 The Router-Link TLV for a link may include a Link Number Sub-TLV for distributing the link number assigned to the link by the router originating the LSA. 4. Extensions to IS-IS This section describes extensions to IS-IS for distributing the link numbers assigned to the links of a node. The Extended IS Reachability TLV (Type 22) defined in [RFC5305] may contain Sub-TLVs (such as those for TE (Traffic Engineering)) that apply to a link/interface to a neighbor. To encode multiple links or interfaces to neighbors, the structure inside TLV is repeated. The Multi-Topology (MT) Intermediate Systems TLV (Type 222) defined in [RFC5120] may contain Sub-TLVs (such as those for TE) that apply to a link/interface. It is aligned with the Extended IS Reachability TLV (Type 22) but has an additional two bytes in front at the beginning of the TLV for MT-ID. A Link Number Sub-TLV is defined and used in the Extended IS Reachability TLV (Type 22) and/or MT Intermediate Systems TLV (Type 222) to advertise the link numbers assigned to the links of a node. The Link Number Sub-TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (TBD3) | Length | Link Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: IS-IS Link Number Sub-TLV Type: TBD3. Length: 2. Link Number: A 2-octet field carrying the link number assigned to the link. 5. Security Considerations TBD. Chen, et al. Expires 28 March 2025 [Page 6] Internet-Draft Advertise Link No September 2024 6. IANA Considerations Under "OSPFv2 Extended Link TLV Sub-TLVs registry" as defined in [RFC7684], IANA is requested to assign a registry value for Link Number Sub-TLV as follows: +==============+======================+=====================+ | Value | Description | reference | +==============+======================+=====================+ | TBD1 | Link Number | This document | +--------------+----------------------+---------------------+ Under "OSPFv3 Extended-LSA Sub-TLVs registry" as defined in [RFC8362], IANA is requested to assign a registry value for Link Number Sub-TLV as follows: +==============+======================+=====================+ | Value | Description | reference | +==============+======================+=====================+ | TBD2 | Link Number | This document | +--------------+----------------------+---------------------+ Under "Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223" for IS-IS TLV Codepoints, IANA is requested to assign a codepoint for Link Number Sub-TLV as follows: +============+===================+==+==+==+===+===+===+=============+ |Sub-TLV Type|Sub-TLV Name |22|23|25|141|222|223|reference | +============+===================+==+==+==+===+===+===+=============+ | TBD3 |Link Number |y |n |n | n | y | n |This document| +------------+-------------------+--+--+--+---+---+---+-------------+ 7. Acknowledgements TBD. 8. 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, . Chen, et al. Expires 28 March 2025 [Page 7] Internet-Draft Advertise Link No September 2024 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . Authors' Addresses Huaimo Chen Independent Boston, MA, United States of America Email: hchen.ietf@gmail.com Donald E. Eastlake 3rd Independent 2386 Panoramic Circle Apopka, FL, 32703 United States of America Phone: +1-508-333-2270 Email: d3e3e3@gmail.com Chen, et al. Expires 28 March 2025 [Page 8] Internet-Draft Advertise Link No September 2024 Aijun Wang China Telecom Beiqijia Town, Changping District Beijing 102209 China Email: wangaj3@chinatelecom.cn Gyan S. Mishra Verizon Inc. 13101 Columbia Pike Silver Spring, MD 20904 United States of America Phone: 301 502-1347 Email: gyan.s.mishra@verizon.com Yisong Liu China Mobile Email: liuyisong@chinamobile.com Yanhe Fan Casa Systems United States of America Email: yfan@casa-systems.com Lei Liu Fujitsu United States of America Email: liulei.kddi@gmail.com Xufeng Liu Alef Edge United States of America Email: xufeng.liu.ietf@gmail.com Chen, et al. Expires 28 March 2025 [Page 9]