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Versions: (draft-ppsenak-ospf-lls-interface-id) 00 01 02 03 04 05 06 07 08 09

Open Shortest Path First IGP                              P. Psenak, Ed.
Internet-Draft                                             K. Talaulikar
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: April 14, 2019                                    W. Henderickx
                                                                   Nokia
                                                       P. Pillay-Esnault
                                                                  Huawei
                                                        October 11, 2018


        OSPF LLS Extensions for Local Interface ID Advertisement
                  draft-ietf-ospf-lls-interface-id-08

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
   (LLS) 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 April 14, 2019.




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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.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   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



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   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 (LLS)
   [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.



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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: TBD

      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.





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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 TBD - 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.  Acknowledgments

   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,
              <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>.





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   [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 in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  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>.

Authors' Addresses

   Peter Psenak (editor)
   Cisco Systems, Inc.
   Apollo Business Center
   Mlynske nivy 43
   Bratislava  821 09
   Slovakia

   Email: ppsenak@cisco.com






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   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
   Belgium

   Email: wim.henderickx@nokia.com


   Padma Pillay-Esnault
   Huawei
   2330 Central Expressway
   Santa Clara,  CA 95050
   USA

   Email: padma@huawei.com


























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