Open Shortest Path First IGP P. Psenak, Ed. Internet-Draft K. Talaulikar Intended status: Standards Track Cisco Systems, Inc. Expires: March 28, 2019 W. Henderickx Nokia P. Pillay-Esnault Huawei September 24, 2018 OSPF LLS Extensions for Local Interface ID Advertisement draft-ietf-ospf-lls-interface-id-06 Abstract Every OSPF interface is assigned an identifier, Interface ID, which uniquely identifies the interface on the router. In some cases it is useful to know the assigned Interface ID on the remote side of the adjacency (Remote Interface ID). This draft describes the extensions to OSPF link-local signalling to advertise the Local Interface Identifier. 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 BCP14 [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." This Internet-Draft will expire on March 28, 2019. Psenak, et al. Expires March 28, 2019 [Page 1] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 Copyright Notice Copyright (c) 2018 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Interface ID Exchange using TE Opaque LSA . . . . . . . . 3 2. Interface ID Exchange using OSPF LLS . . . . . . . . . . . . 3 2.1. Local Interface Identifier TLV . . . . . . . . . . . . . 4 3. Backward Compatibility with RFC 4203 . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Every OSPF interface is assigned an Interface ID, which uniquely identifies the interface on the router. [RFC2328] uses this Interface ID in the Router-LSA Link Data for unnumbered links and uses the value of the MIB-II IfIndex [RFC2863]. [RFC4203] refers to these Interface IDs as the Link Local/Remote Identifiers and defines a way to advertise and use and use them for Generalized Multi- Protocol Label Switching (GMPLS) purposes. [RFC7684] defines a way to advertise Local/Remote Interface IDs in the OSPFv2 Extended Link LSA. There is a known OSPFv2 protocol problem in verifying the bi- directional connectivity with parallel unnumbered links. If there are two parallel unnumbered links between a pair of routers and each link is only advertised from single direction, such two unidirectional parallel links could be considered as a valid single bidirectional link during the OSPF route computation on some other Psenak, et al. Expires March 28, 2019 [Page 2] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 router. If each link is advertised with both its Local and Remote Interface IDs, the advertisement of each link from both sides of adjacency can be verified by cross-checking the Local and Remote Interface IDs of both advertisements. From the perspective of the advertising router, the Local Interface Identifier is a known value, however the Remote Interface Identifier needs to be learnt before it can be advertised. [RFC4203] suggests to use TE Link Local LSA [RFC3630] to communicate the Local Interface Identifier to neighbors on the link. Though such mechanism works, it has some drawbacks. This draft proposes an extension to OSPF link-local signalling [RFC5613] to advertise the Local Interface Identifier. 1.1. Interface ID Exchange using TE Opaque LSA Usage of the Link Local TE Opaque LSA to propagate the Local Interface Identifier to the neighbors on the link is described in [RFC4203]. This mechanism has the following problems: LSAs can only be flooded over an existing adjacency that is in Exchange state or greater. The adjacency state machine progresses independently on each side of the adjacency and, as such, may reach the Full state on one side before the TE Link Opaque LSA arrives. The consequence is that link can be initially advertised without the Remote Interface Identifier. Later, when the TE Link Opaque LSA arrives, the link must be advertised again, this time with the valid Remote Interface Identifier. Implementations may choose to wait before advertising the link, but there is no guarantee that the neighbor will ever advertise the TE Link Opaque LSA with the Interface Identifier. In summary, the existing mechanism does not guarantee that the Remote Interface Identifier is known at the time the link is advertised. The TE Opaque LSA is defined for MPLS Traffic Engineering, but the knowledge of the Remote Interface Identifier is useful also for cases where MPLS TE is not used. One example is the mentioned lack of a valid 2-way connectivity check for parallel point-to- point links between OSPF routers. 2. Interface ID Exchange using OSPF LLS To address the problems described earlier and to allow the Interface Identifier exchange to be part of the neighbor discovery process, we propose to extend OSPF link-local signalling to advertise the Local Interface Identifier in OSPF Hello and Database Description (DD) packets. Psenak, et al. Expires March 28, 2019 [Page 3] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 2.1. Local Interface Identifier TLV The Local Interface Identifier TLV is a LLS TLV. It has 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: 18 Length: 4 octets Local Interface Identifier: The value of the local Interface Identifier. Local Interface Identifier TLV signalling using LLS is applicable to all OSPF interface types other than virtual links. 3. Backward Compatibility with RFC 4203 If the Local Interface ID signaling via Link Local TE Opaque LSA is supported in addition to the new LLS mechanism, implementations which support Local Interface ID signalling using LLS MUST prefer the Local Interface ID value received through LLS over the value received through the Link Local TE Opaque LSA if both are received from the same OSPF router. Implementations which support Local Interface ID signalling via Link Local TE Opaque LSA MAY continue to do so to ensure backward compatibility. If they also support Local Interface ID signalling using LLS as described herein, they MUST signal the same Local Interface ID via both mechanisms. During the rare conditions, when the Local Interface ID changes, a timing interval may exist, where the received values of the Local Interface ID advertised through LLS and Link Local TE Opaque LSA may differ. Such situation is temporary and received values via both mechanisms should become equal as soon as the next Hello and/or Link Local TE Opaque LSA is re-generated by the originator. Psenak, et al. Expires March 28, 2019 [Page 4] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 4. IANA Considerations This specification allocates a single code point from the "Open Shortest Path First (OSPF) Link Local Signalling (LLS) - Type/Length/ Value Identifiers (TLV)" registry. Following value is allocated: o 18 - Local Interface Identifier TLV 5. Security Considerations The security considerations for "OSPF Link-Local Signaling" [RFC5613] also apply to the Local Interface Identifier TLV described herein. The current usage of a neighbor's Local Interface Identifier is to disambiguate parallel links between OSPF routers. Hence, modification of the advertised Local Interface Identifier TLV may result in the wrong neighbor interface identifier being advertised in the OSPFv2 Extended Link LSA [RFC7684] and could prevent the link from being used. If authentication is being used in the OSPF routing domain [RFC5709], then the Cryptographic Authentication TLV [RFC5613] SHOULD also be used to protect that contents of the Link-Local Signaling (LLS) block. Receiving a malformed LLS Interface Identifier TLV MUST NOT result in a hard router or OSPF process failure. The reception of malformed LLS TLVs or Sub-TLVs SHOULD be logged but such logging MUST be rate- limited to prevent Denial-of-Service (DoS) attacks. 6. Acknowledgements Thanks to Tony Przygienda for his extensive review and useful comments. 7. References 7.1. 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, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . Psenak, et al. Expires March 28, 2019 [Page 5] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, . [RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. Yeung, "OSPF Link-Local Signaling", RFC 5613, DOI 10.17487/RFC5613, August 2009, . [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, . 7.2. Informative References [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, . [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic Authentication", RFC 5709, DOI 10.17487/RFC5709, October 2009, . [RFC8379] Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L. Jalil, "OSPF Graceful Link Shutdown", RFC 8379, DOI 10.17487/RFC8379, May 2018, . Authors' Addresses Psenak, et al. Expires March 28, 2019 [Page 6] Internet-DraftOSPF Link Local Signalling (LLS) Extensions September 2018 Peter Psenak (editor) Cisco Systems, Inc. Apollo Business Center Mlynske nivy 43 Bratislava 821 09 Slovakia Email: ppsenak@cisco.com Ketan Jivan Talaulikar Cisco Systems, Inc. S.No. 154/6, Phase I, Hinjawadi PUNE, MAHARASHTRA 411 057 India Email: ketant@cisco.com Wim Henderickx Nokia Copernicuslaan 50 Antwerp 2018 BE Email: wim.henderickx@nokia.com Padma Pillay-Esnault Huawei 2330 Central Expressway Santa Clara, CA 95050 USA Email: padma@huawei.com Psenak, et al. Expires March 28, 2019 [Page 7]