OSPF Extensions to Advertise Seamless Bidirectional Forwarding Detection (S-BFD) Target Discriminators
draft-ietf-ospf-sbfd-discriminator-06

Internet Engineering Task Force                             C. Pignataro
Internet-Draft                                                     Cisco
Intended status: Standards Track                               M. Bhatia
Expires: October 31, 2016                                 Ionos Networks
                                                               S. Aldrin
                                                     Huawei Technologies
                                                            T. Ranganath
                                                                   Nokia
                                                          April 29, 2016

OSPF Extensions to Advertise Seamless Bidirectional Forwarding Detection
                     (S-BFD) Target Discriminators
                 draft-ietf-ospf-sbfd-discriminator-06

Abstract

   This document defines a new OSPF Router Information (RI) TLV that
   allows OSPF routers to flood the Seamless Bidirectional Forwarding
   Detection (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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 31, 2016.

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Copyright Notice

   Copyright (c) 2016 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
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   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 . . . . . . . . . . .   3
   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  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     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
   Bidirectional Forwarding Detection (BFD) with many negotiations
   eliminated.  This is achieved by using four-octet discriminators,
   unique within an administrative domain, to identify the Network
   Targets.  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 (RI) Link State
   Advertisement (LSA) ([RFC7770]).

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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
   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.

   When multiple S-BFD discriminators are advertised, how a given
   discriminator is mapped to a specific use case is out of scope for
   this document.

2.  Implementation

   This extension makes use of the Router Information (RI) Opaque LSA,
   defined in [RFC7770] , 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 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 union 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)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Type - S-BFD Discriminator TLV Type (TBD [to be filled in by IANA])

   Length - Total length of the discriminator(s) that appear in the
   Value field, in octets.  Each discriminator is 4 octets, so the
   Length is 4 times the number of discriminators included in the TLV.
   There is no optional padding for this field.

   Discriminator(s) - The Value field of the TVL includes the S-BFD
   network target discriminator value or values.

   Routers that do not recognize the S-BFD Discriminator TLV Type will
   ignore the TLV [RFC7770], and therefore will not learn S-BFD
   discriminators via OSPF.

2.2.  Flooding Scope

   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
   [RFC7770].  As such, elements of procedure are inherited from those
   defined in [RFC7770].

   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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   Although the S-BFD discriminators may change when enabling the S-BFD
   functionality or via an explicit configuration event, such changes
   are expected to occur very rarely.  Such a change in the information
   will require S-BFD Discriminator TLV in OSPF to be advertised.

   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 [RFC7770].

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 [RFC7770].  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.

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7.  References

7.1.  Normative References

   [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-09 (work in
              progress), April 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <http://www.rfc-editor.org/info/rfc2328>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <http://www.rfc-editor.org/info/rfc5340>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <http://www.rfc-editor.org/info/rfc7770>.

7.2.  Informative References

   [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
              OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
              July 2008, <http://www.rfc-editor.org/info/rfc5250>.

Authors' Addresses

   Carlos Pignataro
   Cisco Systems, Inc.

   Email: cpignata@cisco.com

   Manav Bhatia
   Ionos Networks

   Email: manav@ionosnetworks.com

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   Sam Aldrin
   Huawei Technologies

   Email: aldrin.ietf@gmail.com

   Trilok Ranganath
   Nokia

   Email: trilok.ranganatha@nokia.com

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