Inter-Domain Routing                                               Z. Li
Internet-Draft                                                 S. Zhuang
Intended status: Standards Track                                  Huawei
Expires: October 13, 2022                             K. Talaulikar, Ed.
                                                              Arrcus Inc
                                                               S. Aldrin
                                                             Google, Inc
                                                             J. Tantsura
                                                               Microsoft
                                                               G. Mirsky
                                                                Ericsson
                                                          April 11, 2022


               BGP Link-State Extensions for Seamless BFD
                draft-ietf-idr-bgp-ls-sbfd-extensions-07

Abstract

   Seamless Bidirectional Forwarding Detection (S-BFD) defines a
   simplified mechanism to use Bidirectional Forwarding Detection (BFD)
   with large portions of negotiation aspects eliminated, thus providing
   benefits such as quick provisioning as well as improved control and
   flexibility to network nodes initiating the path monitoring.  The
   link-state routing protocols (IS-IS and OSPF) have been extended to
   advertise the Seamless BFD (S-BFD) Discriminators.

   This document defines extensions to the BGP Link-state address-family
   to carry the S-BFD Discriminators' information via BGP.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 13, 2022.





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Copyright Notice

   Copyright (c) 2022 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
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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.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BGP-LS Extensions for S-BFD Discriminator . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Manageability Considerations  . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Seamless Bidirectional Forwarding Detection (S-BFD) [RFC7880] defines
   a simplified mechanism to use Bidirectional Forwarding Detection
   (BFD) [RFC5880] with large portions of negotiation aspects
   eliminated, thus providing benefits such as quick provisioning as
   well as improved control and flexibility to network nodes initiating
   the path monitoring.

   For monitoring of a service path end-to-end via S-BFD, the headend
   node (i.e.  Initiator) needs to know the S-BFD Discriminator of the
   destination/tail-end node (i.e.  Responder) of that service.  The
   link-state routing protocols (IS-IS [RFC7883] and OSPF [RFC7884])
   have been extended to advertise the S-BFD Discriminators.  With this,
   an Initiator can learn the S-BFD discriminator for all Responders
   within its IGP area/level, or optionally within the domain.  With
   networks being divided into multiple IGP domains for scaling and




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   operational considerations, the service endpoints that require end to
   end S-BFD monitoring often span across IGP domains.

   BGP Link-State (BGP-LS) [RFC7752] enables the collection and
   distribution of IGP link-state topology information via BGP sessions
   across IGP areas/levels and domains.  The S-BFD discriminator(s) of a
   node can thus be distributed along with the topology information via
   BGP-LS across IGP domains and even across multiple Autonomous Systems
   (AS) within an administrative domain.

   This document defines extensions to BGP-LS for carrying the S-BFD
   Discriminators information.

1.1.  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 BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Terminology

   This memo makes use of the terms defined in [RFC7880].

3.  BGP-LS Extensions for S-BFD Discriminator

   The BGP-LS [RFC7752] specifies the Node NLRI for the advertisement of
   nodes and their attributes using the BGP-LS Attribute.  The S-BFD
   discriminators of a node are considered a node-level attribute and
   advertised as such.

   This document defines a new BGP-LS Attribute TLV called the S-BFD
   Discriminators TLV and its format is as follows:

















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      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)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: S-BFD Discriminators TLV

     where:

   o  Type: 1032 (early allocation by IANA)

   o  Length: variable.  It MUST be a minimum of 4 octets and increments
      of 4 octets for each additional discriminator.

   o  Discriminator n: 4 octets each, carrying an S-BFD local
      discriminator value of the node.  At least one discriminator MUST
      be included in the TLV.

   The S-BFD Discriminators TLV can be added to the BGP-LS Attribute
   associated with the Node NLRI that originates the corresponding
   underlying IGP TLV/sub-TLV as described below.  This information is
   derived from the protocol specific advertisements as follows:

   o  IS-IS, as defined by the S-BFD Discriminators sub-TLV in
      [RFC7883].

   o  OSPFv2/OSPFv3, as defined by the S-BFD Discriminator TLV in
      [RFC7884].

4.  IANA Considerations

   IANA is requested to permanently allocate the following code-point
   from the "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor,
   and Attribute TLVs" registry.  The column "IS-IS TLV/Sub-TLV" defined
   in the registry does not require any value and should be left empty.







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         +---------------+--------------------------+----------+
         |  Code Point   | Description              | Length   |
         +---------------+--------------------------+----------+
         |     1032      | S-BFD Discriminators TLV | variable |
         +---------------+--------------------------+----------+

          Table 1: S-BFD Discriminators TLV Code-Point Allocation


5.  Manageability Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that was distributed via [RFC7752].
   Procedures and protocol extensions defined in this document do not
   affect the BGP protocol operations and management other than as
   discussed in the Manageability Considerations section of [RFC7752].
   Specifically, the malformed NLRIs attribute tests in the Fault
   Management section of [RFC7752] now encompasses the new TLV for the
   BGP-LS NLRI in this document.

6.  Security Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that can be distributed via
   [RFC7752].  Procedures and protocol extensions defined in this
   document do not affect the BGP security model other than as discussed
   in the Security Considerations section of [RFC7752].  More
   specifically, the aspects related to limiting the nodes and consumers
   with which the topology information is shared via BGP-LS to trusted
   entities within an administrative domain.

   The TLV introduced in this document is used to propagate IGP defined
   information ([RFC7883] and [RFC7883]).  The TLV represents
   information used to set up S-BFD sessions.  The IGP instances
   originating this information are assumed to support any required
   security and authentication mechanisms (as described in [RFC7883] and
   [RFC7883]) to prevent any security issues when propagating the
   information into BGP-LS.

   Advertising the S-BFD Discriminators via BGP-LS makes it possible for
   attackers to initiate S-BFD sessions using the advertised
   information.  The vulnerabilities this poses and how to mitigate them
   are discussed in [RFC7880].








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7.  Acknowledgements

   The authors would like to thank Nan Wu for his contributions to this
   work and Gunter Van De Velde for his review.  The authors would also
   like to thank Jeff Haas for his shepherd review and Alvaro Retana for
   his AD review of this document.

8.  References

8.1.  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>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC7880]  Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
              Pallagatti, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
              <https://www.rfc-editor.org/info/rfc7880>.

   [RFC7883]  Ginsberg, L., Akiya, N., and M. Chen, "Advertising
              Seamless Bidirectional Forwarding Detection (S-BFD)
              Discriminators in IS-IS", RFC 7883, DOI 10.17487/RFC7883,
              July 2016, <https://www.rfc-editor.org/info/rfc7883>.

   [RFC7884]  Pignataro, C., Bhatia, M., Aldrin, S., and T. Ranganath,
              "OSPF Extensions to Advertise Seamless Bidirectional
              Forwarding Detection (S-BFD) Target Discriminators",
              RFC 7884, DOI 10.17487/RFC7884, July 2016,
              <https://www.rfc-editor.org/info/rfc7884>.

   [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>.

8.2.  Informative References

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.




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Authors' Addresses

   Zhenbin Li
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Shunwan Zhuang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: zhuangshunwan@huawei.com


   Ketan Talaulikar (editor)
   Arrcus Inc
   India

   Email: ketant.ietf@gmail.com


   Sam Aldrin
   Google, Inc

   Email: aldrin.ietf@gmail.com


   Jeff Tantsura
   Microsoft

   Email: jefftant.ietf@gmail.com


   Greg Mirsky
   Ericsson

   Email: gregimirsky@gmail.com








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