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Internet Engineering Task Force (IETF)                    P. Psenak, Ed.Request for Comments: 8510                                 K. TalaulikarCategory: Standards Track                            Cisco Systems, Inc.ISSN: 2070-1721                                            W. Henderickx                                                                   Nokia                                                       P. Pillay-Esnault                                                              Huawei USA                                                            January 2019OSPF Link-Local Signaling (LLS) Extensions forLocal Interface ID AdvertisementAbstract   Every OSPF interface is assigned an Interface ID that 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 document describes the extensions to OSPF link-local signaling   (LLS) to advertise the Local Interface ID.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttps://www.rfc-editor.org/info/rfc8510.Psenak, et al.               Standards Track                    [Page 1]

RFC 8510          OSPF LLS Extensions for Interface ID      January 2019Copyright Notice   Copyright (c) 2019 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1. Introduction ....................................................31.1. Interface ID Exchange Using Link Local TE Opaque LSA .......41.2. Requirements Language ......................................42. Interface ID Exchange Using OSPF LLS ............................42.1. Local Interface ID TLV .....................................53. Backward Compatibility withRFC 4203 ............................54. IANA Considerations .............................................65. Security Considerations .........................................66. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................7   Acknowledgments ....................................................8   Authors' Addresses .................................................8Psenak, et al.               Standards Track                    [Page 2]

RFC 8510          OSPF LLS Extensions for Interface ID      January 20191.  Introduction   Every OSPF interface is assigned an Interface ID that uniquely   identifies the interface on the router.  [RFC2328] uses this   Interface ID in the Router Link State Advertisement (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 them   for GMPLS purposes.  [RFC8379] defines a way to advertise Local/   Remote Interface IDs in the OSPFv2 Extended Link Opaque LSA.   There is a known OSPFv2 protocol problem in verifying the   bidirectional connectivity with parallel unnumbered links.  If there   are two parallel unnumbered links between a pair of routers and each   link is only advertised from a single direction, such two   unidirectional parallel links could be considered as a valid single   bidirectional link during the OSPF route computation on some other   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   ID is a known value.  However, the Remote Interface ID needs to be   learned before it can be advertised.  [RFC4203] suggests using the TE   Link Local LSA [RFC3630] to communicate the Local Interface ID to   neighbors on the link.  Though such a mechanism works, it has some   drawbacks.   This document proposes an extension to OSPF link-local signaling   (LLS) [RFC5613] to advertise the Local Interface ID.Psenak, et al.               Standards Track                    [Page 3]

RFC 8510          OSPF LLS Extensions for Interface ID      January 20191.1.  Interface ID Exchange Using Link Local TE Opaque LSA   Usage of the Link Local TE Opaque LSA to propagate the Local   Interface ID to the neighbors on the link is described in [RFC4203].   This mechanism has the following problems:   o  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 Link Local TE Opaque      LSA arrives.  The consequence of this is that the link can be      initially advertised without the Remote Interface ID.  Later, when      the Link Local TE Opaque LSA arrives, the link must be advertised      again but this time with the valid Remote Interface ID.      Implementations may choose to wait before advertising the link,      but there is no guarantee that the neighbor will ever advertise      the Link Local TE Opaque LSA with the Interface ID.  In summary,      the existing mechanism does not guarantee that the Remote      Interface ID is known at the time the link is advertised.   o  The Link Local TE Opaque LSA is defined for MPLS Traffic      Engineering, but the knowledge of the Remote Interface ID 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.1.2.  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 inBCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.2.  Interface ID Exchange Using OSPF LLS   To address the problems described earlier and to allow the Interface   ID exchange to be part of the neighbor discovery process, we propose   to extend OSPF link-local signaling to advertise the Local Interface   ID in OSPF Hello and Database Description (DD) packets.Psenak, et al.               Standards Track                    [Page 4]

RFC 8510          OSPF LLS Extensions for Interface ID      January 20192.1.  Local Interface ID TLV   The Local Interface ID TLV is an LLS TLV.  It 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             |             Length            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                   Local Interface ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Type: 18      Length: 4 octets      Local Interface ID: The value of the Local Interface ID.   Local Interface ID TLV signaling using LLS is applicable to all OSPF   interface types other than virtual links.3.  Backward Compatibility withRFC 4203   If the Local Interface ID signaling via the Link Local TE Opaque LSA   is supported in addition to the new LLS mechanism, implementations   that support Local Interface ID signaling 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 that support Local Interface ID signaling via the   Link Local TE Opaque LSA MAY continue to do so to ensure backward   compatibility.  If they also support Local Interface ID signaling   using LLS as described in the document, they MUST signal the same   Local Interface ID via both mechanisms.   During the rare conditions in which the Local Interface ID changes, a   timing interval may exist where the received values of the Local   Interface ID advertised through LLS and the Link Local TE Opaque LSA   may differ.  Such a 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 regenerated by the originator.Psenak, et al.               Standards Track                    [Page 5]

RFC 8510          OSPF LLS Extensions for Interface ID      January 20194.  IANA Considerations   IANA has allocated the following code point in the "Link Local   Signalling TLV Identifiers (LLS Types)" subregistry of the "Open   Shortest Path First (OSPF) Link Local Signalling (LLS) - Type/Length/   Value Identifiers (TLV)" registry.   18 - Local Interface ID TLV5.  Security Considerations   The security considerations for "OSPF Link-Local Signaling" [RFC5613]   also apply to the Local Interface ID TLV described in this document.   The current usage of a neighbor's Local Interface ID is to   disambiguate parallel links between OSPF routers.  Hence,   modification of the advertised Local Interface ID TLV may result in   the wrong neighbor Interface ID being advertised in the OSPFv2   Extended Link Opaque LSA [RFC7684] and could prevent the link from   being used.  If authentication is being used in the OSPF routing   domain [RFC5709][RFC7474], then the Cryptographic Authentication TLV   [RFC5613] SHOULD also be used to protect the contents of the LLS   block.   Receiving a malformed LLS Local Interface ID 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.   The Interface ID is assigned by the advertising OSPF router as a   locally unique identifier and need not be unique in any broader   context; it is not expected to contain any information about the   device owner or traffic transiting the device, so there are no   privacy concerns associated with its advertisement.6.  References6.1.  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,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC2328]  Moy, J., "OSPF Version 2", STD 54,RFC 2328,              DOI 10.17487/RFC2328, April 1998,              <https://www.rfc-editor.org/info/rfc2328>.Psenak, et al.               Standards Track                    [Page 6]

RFC 8510          OSPF LLS Extensions for Interface ID      January 2019   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering              (TE) Extensions to OSPF Version 2",RFC 3630,              DOI 10.17487/RFC3630, September 2003,              <https://www.rfc-editor.org/info/rfc3630>.   [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,              <https://www.rfc-editor.org/info/rfc4203>.   [RFC5613]  Zinin, A., Roy, A., Nguyen, L., Friedman, B., and              D. Yeung, "OSPF Link-Local Signaling",RFC 5613,              DOI 10.17487/RFC5613, August 2009,              <https://www.rfc-editor.org/info/rfc5613>.   [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, <https://www.rfc-editor.org/info/rfc7684>.   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.   [RFC8379]  Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and              L. Jalil, "OSPF Graceful Link Shutdown",RFC 8379,              DOI 10.17487/RFC8379, May 2018,              <https://www.rfc-editor.org/info/rfc8379>.6.2.  Informative References   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group              MIB",RFC 2863, DOI 10.17487/RFC2863, June 2000,              <https://www.rfc-editor.org/info/rfc2863>.   [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, <https://www.rfc-editor.org/info/rfc5709>.   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,              "Security Extension for OSPFv2 When Using Manual Key              Management",RFC 7474, DOI 10.17487/RFC7474, April 2015,              <https://www.rfc-editor.org/info/rfc7474>.Psenak, et al.               Standards Track                    [Page 7]

RFC 8510          OSPF LLS Extensions for Interface ID      January 2019Acknowledgments   Thanks to Tony Przygienda for his extensive review and useful   comments.Authors' Addresses   Peter Psenak (editor)   Cisco Systems, Inc.   Apollo Business Center   Mlynske nivy 43   Bratislava  821 09   Slovakia   Email: ppsenak@cisco.com   Ketan 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   Belgium   Email: wim.henderickx@nokia.com   Padma Pillay-Esnault   Huawei USA   2330 Central Expressway   Santa Clara,  CA 95050   United States of America   Email: padma@huawei.comPsenak, et al.               Standards Track                    [Page 8]