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Network Working Group                                            J. Dong
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                D. Dhody
Expires: January 4, 2018                             Huawei Technologies
                                                             J. Tantsura
                                                              Individual
                                                               K. Kumaki
                                                        KDDI Corporation
                                                                T. Murai
                                         Furukawa Network Solution Corp.
                                                            July 3, 2017


      BGP Extensions for Path Computation Element (PCE) Discovery
                 draft-dong-pce-discovery-proto-bgp-07

Abstract

   In networks where a Path Computation Element (PCE) is used for path
   computation, it is desirable for the Path Computation Clients (PCCs)
   to discover dynamically and automatically a set of PCEs along with
   certain information relevant for PCE selection.  RFC 5088 and RFC
   5089 define the PCE discovery mechanisms based on Interior Gateway
   Protocols (IGP).  This document defines extensions to BGP for the
   advertisement of PCE Discovery information.  The BGP based PCE
   discovery mechanism is complementary to the existing IGP based
   mechanisms.

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."



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   This Internet-Draft will expire on January 4, 2018.

Copyright Notice

   Copyright (c) 2017 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.  Carrying PCE Discovery Information in BGP . . . . . . . . . .   3
     2.1.  PCE NLRI  . . . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  PCE Descriptors . . . . . . . . . . . . . . . . . . .   4
     2.2.  PCE Attribute TLVs  . . . . . . . . . . . . . . . . . . .   5
       2.2.1.  PCE Domain TLV  . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  Neighbor PCE Domain TLV . . . . . . . . . . . . . . .   6
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   In networks where a Path Computation Element (PCE) is used for path
   computation, it is desirable for the Path Computation Clients (PCCs)
   to discover dynamically and automatically a set of PCEs along with
   certain information relevant for PCE selection.  [RFC5088] and
   [RFC5089] define the PCE discovery mechanisms based on Interior
   Gateway Protocols (IGP).  When PCCs are LSRs participating in the IGP
   (OSPF or IS-IS), and PCEs are either LSRs or servers also
   participating in the IGP, an effective mechanism for PCE discovery
   within an IGP routing domain consists of utilizing IGP
   advertisements.



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   [RFC4674] presents a set of requirements for a PCE discovery
   mechanism.  This includes the discovery by a PCC of a set of one or
   more PCEs which may potentially be in some other domains.  This is a
   desirable function in the case of inter-domain path computation.  For
   example, Backward Recursive Path Computation (BRPC) [RFC5441] can be
   used by cooperating PCEs to compute an inter-AS path, in which case
   the discovery of PCE as well as the domain information is useful.

   BGP has been extended for north-bound distribution of routing and TE
   information to PCE [RFC7752] and [I-D.ietf-idr-te-pm-bgp].  Similary
   this document extends BGP to also carry the PCE discovery
   information.

   This document defines extensions to BGP to allow a PCE to advertise
   its location, along with some information useful to a PCC for the PCE
   selection, so as to satisfy dynamic PCE discovery requirements set
   forth in [RFC4674].

   This specification contains two parts: definition of a new BGP-LS
   NLRI [RFC7752] that describes PCE information and definition of PCE
   Attribute TLVs as part of BGP-LS attributes.

2.  Carrying PCE Discovery Information in BGP

2.1.  PCE NLRI

   The PCE discovery information is advertised in BGP UPDATE messages
   using the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760].
   The "Link- State NLRI" defined in [RFC7752] is extended to carry the
   PCE information.  BGP speakers that wish to exchange PCE discovery
   information MUST use the BGP Multiprotocol Extensions Capability Code
   (1) to advertise the corresponding (AFI, SAFI) pair, as specified in
   [RFC4760].

   The format of "Link-State NLRI" is defined in [RFC7752].  A new "NLRI
   Type" is defined for PCE Information as following:

   o  Type = TBD1: PCE NLRI

   The format of PCE NLRI is shown in the following figure:











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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
      +-+-+-+-+-+-+-+-+
      |  Protocol-ID  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Identifier                          |
      |                            (64 bits)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                  PCE Descriptors (variable)                   ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 1. PCE NLRI

   The 'Protocol-ID' field is defined in [RFC7752], to be set to the
   appropriate value that indicates the source of the PCE information.
   If BGP speaker and PCE are co-located, the Protocol-ID SHOULD be set
   to "Direct".  If PCE information to advertise is configured at the
   BGP speaker, the Protocol-ID SHOULD be set to "Static configuration".

   As defined in [RFC7752], the 64-Bit 'Identifier' field is used to
   identify the "routing universe" where the PCE belongs.

2.1.1.  PCE Descriptors

   The PCE Descriptor field is a set of Type/Length/Value (TLV)
   triplets.  The format of each TLV is as per Section 3.1 of [RFC7752].
   The PCE Descriptor TLVs uniquely identify a PCE.  The following PCE
   descriptor are defined -

      +-----------+-----------------------+----------+
      | Codepoint |       Descriptor TLV  | Length   |
      +-----------+-----------------------+----------+
      |  TBD2     | IPv4 PCE Address      |   4      |
      |  TBD3     | IPv6 PCE Address      |   16     |
      +-----------+-----------------------+----------+
                     Table 1: PCE Descriptors

   The PCE address TLVs specifies an IP address that can be used to
   reach the PCE.  The PCE-ADDRESS Sub-TLV defined in [RFC5088] and
   [RFC5089] is used in the OSPF and IS-IS respectively.  The format of
   the PCE address TLV are -









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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=TBD2        |             Length=4          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         IPv4 PCE Address                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       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=TBD3        |             Length=16         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                         IPv6 PCE Address                      |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          Figure 2. PCE Address TLVs

   When the PCE has both an IPv4 and IPv6 address, both the TLVs MAY be
   included.

2.2.  PCE Attribute TLVs

   PCE Attribute TLVs are TLVs that may be encoded in the BGP-LS
   attribute [RFC7752] with a PCE NLRI.  The format of each TLV is as
   per Section 3.1 of [RFC7752].  The format and semantics of the Value
   fields in some PCE Attribute TLVs correspond to the format and
   semantics of the Value fields in IS-IS PCED Sub-TLV, defined in
   [RFC5089].  Other PCE Attribute TLVs are defined in this document.

   The following PCE Attribute TLVs are valid in the BGP-LS attribute
   with a PCE NLRI:

   +-----------+---------------------+--------------+------------------+
   |  TLV Code | Description         |  IS-IS TLV   | Reference        |
   |   Point   |                     |   /Sub-TLV   | (RFC/Section)    |
   +-----------+---------------------+--------------+------------------+
   |    TBD4   | Path Scope          |       5/2    | [RFC5089]/4.2    |
   |    TBD5   | PCE Domain          |       -      |       -          |
   |    TBD6   | Neighbor PCE        |       -      |       -          |
   |           | Domain              |              |                  |
   |    TBD7   | PCE Capability      |       5/5    | [RFC5089]/4.5    |
   +-----------+---------------------+--------------+------------------+
                        Table 2: PCE Attribute TLVs





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   The format and semantics of Path Scope and PCE capability is as per
   [RFC5089].  The Path Scope TLV is mandatory.

2.2.1.  PCE Domain TLV

   The PCE Domain TLV specifies a PCE-Domain (IGP area and/or AS) where
   the PCE has topology visibility and through which the PCE can compute
   paths.

    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=TBD5        |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                       Domain Sub-TLVs (variable)            //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The length of this TLV is variable.  The value contains one or more
   domain sub-TLVs as listed below -

          +--------------------+-------------------+----------+
          | Sub-TLV Code Point | Description       |   Length |
          +--------------------+-------------------+----------+
          |        512         | Autonomous System |        4 |
          |        514         | OSPF Area-ID      |        4 |
          |        1027        | IS-IS Area        | Variable |
          |                    | Identifier        |          |
          +--------------------+-------------------+----------+

   Multiple sub-TLVs MAY be included, when the PCE has visibility into
   multiple PCE-Domains.

2.2.2.  Neighbor PCE Domain TLV

   The Neighbor PCE Domain TLV specifies a neighbor PCE-Domain (IGP area
   and/or AS) toward which a PCE can compute paths.

    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=TBD6        |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                       Domain Sub-TLVs (variable)            //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   The length of this TLV is variable.  The value contains one or more
   domain sub-TLVs as listed above.  Multiple sub-TLVs MAY be included,
   when the PCE can compute paths towards several neighbor PCE-Domains.

3.  Operational Considerations

   Existing BGP-LS operational procedures apply to the advertisement of
   PCE information as per [RFC7752].  This information is treated as
   pure application level data which has no immediate impact on
   forwarding states.  The PCE information SHOULD be advertised only to
   the domains where such information is allowed to be used.  This can
   be achieved by policy control on the ASBRs.

   The PCE information is considered relatively stable and does not
   change frequently, thus this information will not bring significant
   impact on the amount of BGP updates in the network.

4.  IANA Considerations

   IANA needs to assign a new NLRI Type for 'PCE NLRI' from the "BGP-LS
   NLRI-Types" registry.

   IANA needs to assign new TLV code point as per Table 1 and 2 from the
   "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and
   Attribute TLVs" registry.

   [Editor's Note - Check if name of the registry should be changes with
   following instructions - Further IANA is requested to rename the
   registry as "BGP-LS Node Descriptor, Link Descriptor, Prefix
   Descriptor, PCE Descriptor, and Attribute TLVs".]

5.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the BGP security model.  See the 'Security Considerations'
   section of [RFC4271] for a discussion of BGP security.  Also refer to
   [RFC4272] and [RFC6952] for analysis of security issues for BGP.

   Existing BGP-LS security considerations as per [RFC7752] continue to
   apply.

6.  Contributors

   The following individuals gave significant contributions to this
   document:






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   Takuya Miyasaka
   KDDI Corporation
   ta-miyasaka@kddi.com

7.  Acknowledgements

   The authors would like to thank Zhenbin Li, Hannes Gredler, Jan
   Medved, Adrian Farrel, Julien Meuric and Jonathan Hardwick for the
   valuable discussion and comments.

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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <http://www.rfc-editor.org/info/rfc4760>.

   [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "OSPF Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
              January 2008, <http://www.rfc-editor.org/info/rfc5088>.

   [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "IS-IS Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
              January 2008, <http://www.rfc-editor.org/info/rfc5089>.

   [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,
              <http://www.rfc-editor.org/info/rfc7752>.







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8.2.  Informative References

   [I-D.ietf-idr-te-pm-bgp]
              Previdi, S., Wu, Q., Gredler, H., Ray, S.,
              jefftant@gmail.com, j., Filsfils, C., and L. Ginsberg,
              "BGP-LS Advertisement of IGP Traffic Engineering
              Performance Metric Extensions", draft-ietf-idr-te-pm-
              bgp-06 (work in progress), June 2017.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <http://www.rfc-editor.org/info/rfc4272>.

   [RFC4674]  Le Roux, J., Ed., "Requirements for Path Computation
              Element (PCE) Discovery", RFC 4674, DOI 10.17487/RFC4674,
              October 2006, <http://www.rfc-editor.org/info/rfc4674>.

   [RFC5441]  Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
              "A Backward-Recursive PCE-Based Computation (BRPC)
              Procedure to Compute Shortest Constrained Inter-Domain
              Traffic Engineering Label Switched Paths", RFC 5441,
              DOI 10.17487/RFC5441, April 2009,
              <http://www.rfc-editor.org/info/rfc5441>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <http://www.rfc-editor.org/info/rfc6952>.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: jie.dong@huawei.com


   Mach(Guoyi) Chen
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: mach.chen@huawei.com



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   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: dhruv.ietf@gmail.com


   Jeff Tantsura
   Individual
   US

   Email: jefftant.ietf@gmail.com


   Kenji Kumaki
   KDDI Corporation
   Garden Air Tower, Iidabashi, Chiyoda-ku
   Tokyo  102-8460
   Japan

   Email: ke-kumaki@kddi.com


   Tomoki Murai
   Furukawa Network Solution Corp.
   5-1-9, Higashi-Yawata, Hiratsuka
   Kanagawa  254-0016
   Japan

   Email: murai@fnsc.co.jp



















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