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Versions: (draft-zhuang-idr-bgp-ls-sbfd-extensions) 00 01 02

Inter-Domain Routing                                               Z. Li
Internet-Draft                                                    Huawei
Intended status: Standards Track                               S. Aldrin
Expires: December 31, 2018                                   Google, Inc
                                                             J. Tantsura
                                                          Nuage Networks
                                                               G. Mirsky
                                                               ZTE Corp.
                                                               S. Zhuang
                                                                  Huawei
                                                           K. Talaulikar
                                                           Cisco Systems
                                                           June 29, 2018


               BGP Link-State Extensions for Seamless BFD
                 draft-li-idr-bgp-ls-sbfd-extensions-02

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

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 https://datatracker.ietf.org/drafts/current/.





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   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 December 31, 2018.

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
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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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem and Requirement . . . . . . . . . . . . . . . . . . .   3
   4.  BGP-LS Extensions for S-BFD Discriminator . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Manageability Considerations  . . . . . . . . . . . . . . . .   6
     6.1.  Operational Considerations  . . . . . . . . . . . . . . .   6
     6.2.  Management Considerations . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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.




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   For monitoring of a service path end-to-end via S-BFD, the headend/
   initiator node needs to know the S-BFD Discriminator of the
   destination/tail-end node of that service.  The link-state routing
   protocols (IS-IS, OSPF and OSPFv3) have been extended to advertise
   the S-BFD Discriminators.  With this a initiator node can learn the
   S-BFD discriminator for all nodes within its IGP area/level or
   optionally within the domain.  With networks being divided into
   multiple IGP domains for scaling and 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 draft defines extensions to BGP-LS for carrying the S-BFD
   Discriminators information.

2.  Terminology

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

3.  Problem and Requirement

   Seamless MPLS [I-D.ietf-mpls-seamless-mpls] extends the core domain
   and integrates aggregation and access domains into a single MPLS
   domain.  In a large network, the core and aggregation networks can be
   organized as different ASes.  Although the core and aggregation
   networks are segmented into different ASes, an E2E LSP can be created
   using hierarchical BGP signaled LSPs based on iBGP labeled unicast
   within each AS, and eBGP labeled unicast to extend the LSP across AS
   boundaries.  This provides a seamless MPLS transport connectivity for
   any two service end-points across the entire domain.  In order to
   detect failures for such end to end services and trigger faster
   protection and/or re-routing, S-BFD MAY be used for the Service Layer
   (e.g. for MPLS VPNs, PW, etc. ) or the Transport Layer monitoring.
   This brings up the need for setting up S-BFD session spanning across
   AS domains.

   In a similar Segment Routing (SR) [I-D.ietf-spring-segment-routing]
   multi-domain network, an end to end SR Policy
   [I-D.ietf-spring-segment-routing-policy] path may be provisioned
   between service end-points across domains either via local
   provisioning or by a controller or signalled from a Path Computation




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   Engine (PCE).  Monitoring using S-BFD can similarly be setup for such
   a SR Policy.

   Extending the automatic discovery of S-BFD discriminators of nodes
   from within the IGP domain to across the administrative domain using
   BGP-LS enables setting up of S-BFD sessions on demand across IGP
   domains.  The S-BFD discriminators for service end point nodes MAY be
   learnt by the PCE or a controller via the BGP-LS feed that it gets
   from across IGP domains and it can signal or provision the remote
   S-BFD discriminator on the initiator node on demand when S-BFD
   monitoring is required.  The mechanisms for the signaling of the
   S-BFD discriminator from the PCE/controller to the initiator node and
   setup of the S-BFD session is outside the scope of this document.

   Additionally, the service end-points themselves MAY also learn the
   S-BFD discriminator of the remote nodes themselves by receiving the
   BGP-LS feed via a route reflector (RR) or a centralized BGP Speaker
   that is consolidating the topology information across the domains.
   The initiator node can then itself setup the S-BFD session to the
   remote node without a controller/PCE assistance.

   While this document takes examples of MPLS and SR paths, the S-BFD
   discriminator advertisement mechanism is applicable for any S-BFD
   use-case in general.

4.  BGP-LS Extensions for S-BFD Discriminator

   The BGP-LS [RFC7752] specifies the Node NLRI for advertisement of
   nodes and their attributes using the BGP-LS Attribute.  The S-BFD
   discriminators of a node are considered as its 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: TBD (see IANA Considerations Section 5)

   o  Length: variable.  Minimum of 8 octets and increments of 4 octets
      there on for each additional discriminator

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

   The S-BFD Discriminators TLV can only 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
   below..

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

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

   When the node is not running any of the IGPs but running a protocol
   like BGP, then the locally provisioned S-BFD discriminators of the
   node MAY be originated as part of the BGP-LS attribute within the
   Node NLRI corresponding to the local node.








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5.  IANA Considerations

   This document requests assigning code-points from the registry "BGP-
   LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
   TLVs" based on table below.  The column "IS-IS TLV/Sub-TLV" defined
   in the registry does not require any value and should be left empty.

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


6.  Manageability Considerations

   This section is structured as recommended in [RFC5706].

   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 encompass the new TLVs for the
   BGP-LS NLRI in this document.

6.1.  Operational Considerations

   No additional operation considerations are defined in this document.

6.2.  Management Considerations

   No additional management considerations are defined in this document.

7.  Security 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 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.

   Advertising the S-BFD Discriminators via BGP-LS makes it possible for
   attackers to initiate S-BFD sessions using the advertised



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   information.  The vulnerabilities this poses and how to mitigate them
   are discussed in [RFC7752].

8.  Acknowledgements

   The authors would like to thank Nan Wu for his contributions to this
   work.

9.  References

9.1.  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>.

9.2.  Informative References

   [I-D.ietf-mpls-seamless-mpls]
              Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
              M., and D. Steinberg, "Seamless MPLS Architecture", draft-
              ietf-mpls-seamless-mpls-07 (work in progress), June 2014.






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   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing
              Architecture", draft-ietf-spring-segment-routing-15 (work
              in progress), January 2018.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-01 (work in progress), June 2018.

   [RFC5706]  Harrington, D., "Guidelines for Considering Operations and
              Management of New Protocols and Protocol Extensions",
              RFC 5706, DOI 10.17487/RFC5706, November 2009,
              <https://www.rfc-editor.org/info/rfc5706>.

   [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>.

Authors' Addresses

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

   Email: lizhenbin@huawei.com


   Sam Aldrin
   Google, Inc

   Email: aldrin.ietf@gmail.com


   Jeff Tantsura
   Nuage Networks

   Email: jefftant.ietf@gmail.com


   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com



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

   Email: zhuangshunwan@huawei.com


   Ketan Talaulikar
   Cisco Systems

   Email: ketant@cisco.com






































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