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Versions: (draft-bhatia-ospf-sbfd-discriminator) 00 01 02 03 04 05 06 RFC 7884

Internet Engineering Task Force                                M. Bhatia
Internet-Draft                                            Ionos Networks
Intended status: Standards Track                            C. Pignataro
Expires: March 27, 2016                                    Cisco Systems
                                                               S. Aldrin
                                                     Huawei Technologies
                                                            T. Ranganath
                                                          Alcatel-Lucent
                                                      September 24, 2015


        OSPF extensions to advertise S-BFD Target Discriminator
                 draft-ietf-ospf-sbfd-discriminator-02

Abstract

   This document defines a new OSPF Router Information (RI) TLV that
   allows OSPF routers to flood the S-BFD discriminator values
   associated with a target network identifier.  This mechanism is
   applicable to both OSPFv2 and OSPFv3.

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 RFC 2119 [RFC2119].

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 http://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 27, 2016.








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Copyright Notice

   Copyright (c) 2015 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
   (http://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
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   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.  Relationship between OSPF and S-BFD . . . . . . . . . . .   2
   2.  Implementation  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  S-BFD Discriminator TLV . . . . . . . . . . . . . . . . .   3
     2.2.  Flooding Scope  . . . . . . . . . . . . . . . . . . . . .   4
   3.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Seamless Bidirectional Forwarding Detection (S-BFD), specified in
   [I-D.ietf-bfd-seamless-base], is a simplified mechanism for using BFD
   with many negotiations eliminated.  This is achieved by using unique
   network-wide discriminators to identify the Network Targets (e.g., IP
   addresses).  These S-BFD discriminators can be advertised by the
   IGPs, and this document concerns itself with OSPF.  Specifically,
   this document defines a new TLV (named the S-BFD Discriminator TLV)
   to be carried within the OSPF Router Information LSA ([RFC4970]).

1.1.  Relationship between OSPF and S-BFD

   This document, implicitly, defines a relationship between OSPF and
   S-BFD.  S-BFD assigns one or more Discriminators to each S-BFD
   reflector node.  OSPF, in turn, learns about these from S-BFD, and
   floods them in the newly defined TLV.  After this information is



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   flooded, it is stored in all the OSPF nodes such that S-BFD
   initiators can map out target nodes to target Discriminators, and can
   therefore construct the S-BFD probe.

2.  Implementation

   This extension makes use of the Router Information (RI) Opaque LSA,
   defined in [RFC4970] , for both OSPFv2 [RFC2328] and OSPFv3
   [RFC5340], by defining a new OSPF Router Information (RI) TLV: the
   S-BFD Discriminator TLV.

   The S-BFD Discriminator TLV is OPTIONAL.  Upon receipt of the TLV, a
   router may decide to ignore this TLV or install the S-BFD
   discriminator in BFD Target Identifier Table.

   In the presence of multiple instances of the OSPF/OSPFv3 RI LSA, the
   S-BFD Discriminators for an OSPF router are the superset of all
   Discriminators advertised in all instances of the S-BFD Discriminator
   TLV (see Section 2.1) in all advertised non-MaxAge OSPF RI LSAs.

2.1.  S-BFD Discriminator TLV

   The format of the S-BFD Discriminator TLV is as follows:

        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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Discriminator 1                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Discriminator 2 (Optional)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               ...                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Discriminator n (Optional)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type - S-BFD Discriminator TLV Type

   Length - Total length of the discriminator (Value field) in octets,
   not including the optional padding.  The Length is a multiple of 4
   octets, and consequently specifies how many Discriminators are
   included in the TLV.

   Value - S-BFD network target discriminator value or values.





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   Routers that do not recognize the S-BFD Discriminator TLV Type MUST
   ignore the TLV.  S-BFD discriminator is associated with the BFD
   Target Identifier type, that allows demultiplexing to a specific task
   or service.

2.2.  Flooding Scope

   The flooding scope for S-BFD Discriminator information advertised
   through OSPF can be limited to one or more OSPF areas, or can be
   extended across the entire OSPF routing domain.

   Note that the S-BFD session may be required to pan multiple areas, in
   which case the flooding scope may comprise these areas.  This could
   be the case for an ABR, for instance, advertising the S-BFD
   Discriminator information within the backbone area and/or a subset of
   its attached IGP area(s).

   The S-BFD Discriminator TLV is advertised within OSPFv2 Router
   Information LSAs (Opaque type of 4 and Opaque ID of 0) or OSPFv3
   Router Information LSAs (function code of 12), which are defined in
   [RFC4970].  As such, elements of procedure are inherited from those
   defined in [RFC4970].

   In OSPFv2, the flooding scope is controlled by the opaque LSA type
   (as defined in [RFC5250]) and in OSPFv3, by the S1/S2 bits (as
   defined in [RFC5340]).  If the flooding scope is area local, then the
   S-BFD Discriminator TLV MUST be carried within an OSPFv2 type 10
   router information LSA or an OSPFV3 Router Information LSA with the
   S1 bit set and the S2 bit clear.  If the flooding scope is the entire
   IGP domain, then the S-BFD Discriminator TLV MUST be carried within
   an OSPFv2 type 11 Router Information LSA or OSPFv3 Router Information
   LSA with the S1 bit clear and the S2 bit set.

   When the S-BFD Reflector is deactivated, the OSPF speaker advertising
   this S-BFD Discriminator MUST originate a new Router Information LSA
   that no longer includes the corresponding S-BFD Discriminator TLV,
   provided there are other TLVs in the LSA.  If there are no other TLVs
   in the LSA, it MUST either send an empty Router Information LSA or
   purge it by prematurely ageing it.

   For intra-area reachability, the S-BFD Discriminator TLV information
   regarding a specific target identifier is only considered current and
   useable when the router advertising this information is itself
   reachable via OSPF calculated paths in the same area of the LSA in
   which the S-BFD Discriminator TLV appears.  In the case of domain-
   wide flooding, i.e., where the originator is sitting in a remote
   area, the mechanism described in section 5 of [RFC5250] should be
   used.



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   A change in information in the S-BFD Discriminator TLV MUST NOT
   trigger any SPF computation at a receiving router.

3.  Backward Compatibility

   The S-BFD Discriminator TLV defined in this document does not
   introduce any interoperability issues.

   A router not supporting the S-BFD Discriminator TLV will just
   silently ignore the TLV as specified in [RFC4970].

4.  Security Considerations

   This document defines OSPF extensions to distribute the S-BFD
   discriminator within an administrative domain.  Hence the security of
   the S-BFD discriminator distribution relies on the security of OSPF.

   OSPF provides no encryption mechanism for protecting the privacy of
   LSAs and, in particular, the privacy of the S-BFD discriminator
   advertisement information.  This however is not a concern as there
   isn't any need to hide the discriminator value that can be used to
   reach the Reflectors.

5.  IANA Considerations

   IANA has defined a registry for TLVs carried in the Router
   Information LSA defined in [RFC4970].  IANA needs to assign a new TLV
   codepoint for the S-BFD Discriminator TLV carried within the Router
   Information LSA.

        Value      TLV Name                 Reference
        -----      --------                 ----------
        TBD        S-BFD                    (this document)
                   Discriminator

6.  Acknowledgements

   The authors would like to thank Nobo Akiya, Les Ginsberg, Mach Chen
   and Peter Psenak for insightful comments and useful suggestions.

7.  References

7.1.  Normative References








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   [I-D.ietf-bfd-seamless-base]
              Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
              Networks, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", draft-ietf-bfd-seamless-base-04 (work in
              progress), January 2015.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC4970]  Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
              Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 4970, July 2007.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.

7.2.  Informative References

   [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
              OSPF Opaque LSA Option", RFC 5250, July 2008.

Authors' Addresses

   Manav Bhatia
   Ionos Networks

   Email: manav@ionosnetworks.com


   Carlos Pignataro
   Cisco Systems

   Email: cpignata@cisco.com


   Sam Aldrin
   Huawei Technologies

   Email: aldrin.ietf@gmail.com


   Trilok Ranganath
   Alcatel-Lucent

   Email: trilok.ranganatha@alcatel-lucent.com




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