Network Working Group                                          S. Zhuang
Internet-Draft                                                     Z. Li
Intended status: Standards Track                              Sam aldrin
Expires: February 22, 2015                           Huawei Technologies
                                                             J. Tantsura
                                                               G. Mirsky
                                                                Ericsson
                                                         August 21, 2014


               BGP Link-State Extensions for Seamless BFD
               draft-zhuang-idr-bgp-ls-sbfd-extensions-00

Abstract

   [I-D.ietf-bfd-seamless-base] 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, OSPF and OSPFv3) 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 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 February 22, 2015.



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Copyright Notice

   Copyright (c) 2014 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
   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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem and Requirement . . . . . . . . . . . . . . . . . . .   3
   4.  BGP-LS Extensions for S-BFD Discriminators Exchanging . . . .   3
   5.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [I-D.ietf-bfd-seamless-base] 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.

   [I-D.ginsberg-isis-sbfd-discriminator] defines a mean of advertising
   one or more S-BFD Discriminators using the IS-IS Router Capability
   TLV.  [I-D.bhatia-ospf-sbfd-discriminator] 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.

   The link-state routing protocols (IS-IS, OSPF and OSPFv3) have been
   extended to advertise the S-BFD Discriminators.  But flooding based
   propagation of the S-BFD Discriminators using IGPs is limited by the



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   perimeter of the IGP domain.  For advertising the S-BFD
   Discriminators which span across IGP domains (e.g. multiple ASes),
   the Border Gateway Protocol (BGP) is better suited as its propagation
   perimeter is not limited like the IGPs.

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

2.  Terminology

   This memo makes use of the terms defined in [I-D.ietf-bfd-seamless-
   base].

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 autonomous systems.  Although the core and
   aggregation networks are segmented into different autonomous systems,
   but an E2E LSP will be created using hierarchical-labeled BGP LSPs
   based on iBGP-labeled unicast within each AS, and eBGP-labeled
   unicast to extend the LSP across AS boundaries.  Meanwhile, the
   customer will see only two service-end points in the Seamless MPLS
   network.  In order to detect the possible failure quickly and protect
   the network/trigger re-routing, BFD MAY be used for the Service Layer
   (e.g. for MPLS VPNs, PW ) and the Transport Layer, so the need arises
   that the BFD session has to span across AS domain.

   The link-state routing protocols (IS-IS, OSPF and OSPFv3) have been
   extended to advertise the S-BFD Discriminators.  But flooding based
   propagation of the S-BFD Discriminators using IGPs is limited by the
   perimeter of the IGP domain.  For advertising the S-BFD
   Discriminators which span across IGP domains (e.g. multiple ASes),
   the Border Gateway Protocol (BGP) is better suited as its propagation
   perimeter is not limited like the IGPs.  This draft defines
   extensions requirement to the BGP Link-state address-family to carry
   the S-BFD Discriminators information via BGP.

4.  BGP-LS Extensions for S-BFD Discriminators Exchanging

   The BGP-LS NLRI can be a node NLRI, a link NLRI or a prefix NLRI.
   The corresponding BGP-LS attribute is a node attribute, a link
   attribute or a prefix attribute.  BGP-LS [I-D.ietf-idr-ls-
   distribution] defines the TLVs that map link-state information to
   BGP-LS NLRI and BGP-LS attribute.  This document adds additional BGP-
   LS attribute TLVs to encode the S-BFD Discriminators information.




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   [I-D.ginsberg-isis-sbfd-discriminator] defines the following TLVs to
   encode the S-BFD Discriminators information.

   The ISIS Router CAPABILITY TLV as defined in [RFC4971] will be used
   to advertise S-BFD discriminators.  A new Sub-TLV is defined as
   described below.  S-BFD Discriminators Sub-TLV is formatted as
   specified in [RFC5305].

                                             No. of octets
            +-----------------------------+
            | Type (to be assigned by     |     1
            | IANA - suggested value 19)  |
            +-----------------------------+
            | Length (multiple of 4)      |     1
            +-----------------------------+
            | Discriminator Value(s)      |     4/Discriminator
            :                             :
            +-----------------------------+
            Figure 1: S-BFD Discriminators Sub-TLV


   [I-D.bhatia-ospf-sbfd-discriminator] defines the following TLVs to
   encode the S-BFD Discriminators information.  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)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 2: S-BFD Discriminators Sub-TLV


   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.




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

   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, which allows de-multiplexing to a specific
   task or service.

   These TLVs are mapped to BGP-LS attribute TLVs in the following way.
   The new information in the Link-State NLRIs and attributes is encoded
   in Type/Length/Value triplets.

      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                        Value (variable)                     //
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 3: BGP-LS TLV format


   The 2 octet Type field values are defined in Table 1.  The next 2
   octet Length field encodes length of the rest of the TLV.  The Value
   portion of the TLV is variable and is equal to the corresponding
   Value portion of the TLV defined in [I-D.ginsberg-isis-sbfd-
   discriminator] and [I-D.bhatia-ospf-sbfd-discriminator].

   The following 'Node Attribute' TLVs are defined:

 +---------------+-------------------------+----------+----------------+
 |    TLV Code   | Description             | Length   |      ISIS/OSPF |
 |     Point     |                         |          |    TLV/Sub-TLV |
 +---------------+-------------------------+----------+----------------+
 |      TBD      | S-BFD Discriminators    | variable |            TBD |
 |      ...      | ...                     | ...      |            ... |
 +---------------+-------------------------+----------+----------------+
                         Table 1: Node Attribute TLVs


5.  Operation

   In an inter-as VPN network as follows, ASBR1 and ASBR2 establish a
   BGP-LS session for exchanging S-BFD Discriminators information.








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         |-------------------|                |-----------------|
         |     AS1           |                |   AS2           |
   ----- |  ------           |                |                 |
   |CE1|--- |PE1 |------|    |                |                 |
   ----- |  ------      |    |                |                 |
         |              |    | S-BFD          |                 |
         |              |    | Discriminators |                 |
         |              |    | Exchanging via |                 |
         |              |    | BGP-LS         |                 |
         |          -------- | <---------->   | --------  ----- | -----
         |     |----| ASBR1|--------------------| ASBR2|--|PE3|---|CE3|
         |     |    -------- |                | --------  ----- | -----
   ----- |  ------           |                |                 |
   |CE2|--- |PE2 |           |                |                 |
   ----- |  ------           |                |                 |
         |                   |                |                 |
         |-------------------|                |-----------------|

            |<-----------S-BFD Connectivity Test----------->|
            PE1/PE2                                       PE3



   Step 1: ASBR1 learns all the S-BFD Discriminators information within
   AS1 by the mean defines in [I-D.ginsberg-isis-sbfd-discriminator] or
   [I-D.bhatia-ospf-sbfd-discriminator].

   Step 2: ASBR1 sends AS1's S-BFD Discriminators information to AS2's
   ASBR2 via the BGP-LS session.

   Step 3: ASBR2 injects the AS1's S-BFD Discriminators information
   receiving from ASBR1 into IGP (IS-IS or OSPF or OSPFv3), then flood
   them within the domain of the AS2 via IGP, So the nodes of AS2 can
   learn all the S-BFD Discriminators information originating from AS1.

   Likewise, the nodes of AS1 can learn all the S-BFD Discriminators
   information originating from AS2.

   At this point, we can use S-BFD Procedures defines in [I-D.ietf-bfd-
   seamless-base] between the PEs which belong to different AS.

6.  IANA Considerations

   TBD.







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7.  Security Considerations

   This document does not introduce any new security risk.

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, March 1997.

9.2.  Informative References

   [I-D.bhatia-ospf-sbfd-discriminator]
              Bhatia, M., Ranganath, T., Pignataro, C., and S. Aldrin,
              "OSPF extensions to advertise S-BFD Target Discriminator",
              draft-bhatia-ospf-sbfd-discriminator-00 (work in
              progress), May 2014.

   [I-D.ginsberg-isis-sbfd-discriminator]
              Ginsberg, L., Akiya, N., and M. Chen, "Advertising S-BFD
              Discriminators in IS-IS", draft-ginsberg-isis-sbfd-
              discriminator-00 (work in progress), May 2014.

   [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-02 (work in
              progress), August 2014.

   [I-D.ietf-idr-ls-distribution]
              Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
              Ray, "North-Bound Distribution of Link-State and TE
              Information using BGP", draft-ietf-idr-ls-distribution-05
              (work in progress), May 2014.

   [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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   [RFC4971]  Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
              System to Intermediate System (IS-IS) Extensions for
              Advertising Router Information", RFC 4971, July 2007.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.

Authors' Addresses

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

   Email: zhuangshunwan@huawei.com


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

   Email: lizhenbin@huawei.com


   Sam Aldrin
   Huawei Technologies
   2330 Central Expressway
   Santa Clara  CA 95051

   Email: sam.aldrin@huawei.com


   Jeff Tantsura
   Ericsson
   200 Holger Way
   San Jose  CA 95134
   USA

   Email: jeff.tantsura@ericsson.com









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   Greg Mirsky
   Ericsson
   300 Holger Way
   San Jose  CA 95134
   USA

   Email: gregory.mirsky@ericsson.com












































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