Internet Engineering Task Force                             S. Sivabalan
Internet-Draft                                                 J. Medved
Intended status: Informational                       Cisco Systems, Inc.
Expires: July 30, 2013                                  January 28, 2013


               IGP Extensions for Stateful PCE Discovery
                 draft-sivabalan-pce-disco-stateful-00

Abstract

   When a PCE is a Label Switching Router (LSR) participating in the
   Interior Gateway Protocol (IGP), or even a server participating in
   IGP, its presence and path computation capabilities can be advertised
   using IGP flooding.  Such IGP extensions exist for OSPF and ISIS.
   This document specifies two new PCE capabilities advertised by IGP.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2

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     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  2
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3.  Overview of Protocol Extensions  . . . . . . . . . . . . . . .  3
   4.  Backward Compatibility . . . . . . . . . . . . . . . . . . . .  3
   5.  Management Considerations  . . . . . . . . . . . . . . . . . .  3
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  3
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  3
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  4
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  4
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  4

1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol (PCEP),
   which defines the communication between a Path Computation Client
   (PCC) and a Path Control Element (PCE), or between PCE and PCE,
   enabling computation of Multiprotocol Label Switching (MPLS) for
   Traffic Engineering Label Switched Path (TE LSP) characteristics.

   Stateful PCE [I-D.ietf-pce-stateful-pce] specifies a set of
   extensions to PCEP to enable stateful control of TE LSPs between and
   across PCEP sessions in compliance with [RFC4657].  It includes
   mechanisms to effect LSP state synchronization between PCCs and PCEs,
   delegation of control of LSPs to PCEs, and PCE control of timing and
   sequence of path computations within and across PCEP sessions.  It
   focuses on a model where LSPs are configured on the PCC and the LSP's
   path routing and the timing of its setup is delegated to the PCE. A
   mechanism for instantiating LSPs on a PCC using stateful PCE is
   specified in [I-D.crabbe-pce-pce-initiated-lsp].  Such mechanism is
   considered useful in applications such as Software Defined Networks
   (SDN), demand engineering, etc.

   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.  Such extension to OSPF to
   IS-IS exists in [RFC5088] and [RFC5089], respectively.  Currently,
   the IGP PCE capability does not indicate whether the advertised PCE
   is stateful or capable to actively instantiate LSPs on a PCC.
   Advertising such capabilities would facilitate a PCC to learn about
   available stateful PCEs, as well as about a PCE's capability to
   instantiate LSPs.  A PCC could listen to IGP updates, or use other
   mechanisms that carry IGP information to interested clients, such as
   BGP-LS ([I-D.ietf-idr-ls-distribution]). This document extends the
   IGP capability advertisement mechanism to include stateful PCE and
   PCE-based LSP instantiation capabilities.

1.1.  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]

2.  Terminology


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   The following terminology is used in this document:

   IGP: Interior Gateway Protocol
   IS-IS: Intermediate System to Intermediate System
   LSR: Label Switching Router
   OSPF: Open Shortest Path First
   PCC: Path Computation Client
   PCE: Path Computation Element
   PCEP: Path Computation Element Protocol

3.  Overview of Protocol Extensions

   The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to advertise
   PCE capabilities.  It MAY be present within the PCED sub-TLV carried
   by OSPF or IS-IS. [RFC5088] and [RFC5089] provide the description and
   processing rules for this sub-TLV when carried within OSPF and IS-IS,
   respectively.

   The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array
   of units of 32-bit flags numbered from the most significant as bit 0,
   where each bit represents one PCE capability.

   The PCE-CAP-FLAGS sub-TLV has the following format:

   o  TYPE: 5
   o  LENGTH: Multiple of 4
   o  VALUE: This contains an array of units of 32 bit flags with the
      most significant bit as 0. Each bit represents one PCE capability

   PCE capability bits are defined in [RFC5088].  This document defines
   new capability bits for the stateful PCE as follows:


    Bit         Capability
      9         Support stateful PCE capability
     10         Support PCE-based tunnel instantiation capability

4.  Backward Compatibility

   An LSR that does not support the new IGP PCE capability bits
   specified in this document silently ignores those bits.

5.  Management Considerations

   TBD.

6.  Security Considerations

   Security considerations described in [RFC5088] are applicable to
   stateful PCE capabilities.  No additional security measures are
   required.

7.  IANA Considerations

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   IANA is requested to allocate a new bit in "PCE Capability Flags"
   registry for stateful PCE capability as follows:

      Bit                                   Meaning     Reference
        9                   Stateful PCE capability This document
       10 PCE-based tunnel instantiation capability This document

                                Table 1

8.  References

8.1.  Normative References

   [I-D.crabbe-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", Internet-Draft draft-crabbe-pce-pce-initiated-
              lsp-00, October 2012.

   [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", Internet-Draft draft-ietf-idr-ls-
              distribution-01, October 2012.

   [I-D.ietf-pce-stateful-pce]
              Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
              Extensions for Stateful PCE", Internet-Draft draft-ietf-
              pce-stateful-pce-02, October 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5088]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "OSPF Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5088, January 2008.

   [RFC5089]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "IS-IS Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5089, January 2008.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009.

8.2.  Informative References

   [RFC4657]  Ash, J. and J.L. Le Roux, "Path Computation Element (PCE)
              Communication Protocol Generic Requirements", RFC 4657,
              September 2006.

Authors' Addresses


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   Siva Sivabalan
   Cisco Systems, Inc.
   2000 Innovation Drive
   Kanata, Ontario K2K 3E8
   Canada

   Email: msiva@cisco.com


   Jan Medved
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134
   USA

   Email: jmedved@cisco.com





































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