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PCE Working Group                                           S. Sivabalan
Internet-Draft                                                 J. Medved
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: July 13, 2014                                          X. Zhang
                                                     Huawei Technologies
                                                        January 13, 2014


               IGP Extensions for Stateful PCE Discovery
                 draft-sivabalan-pce-disco-stateful-03

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.

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
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   This Internet-Draft will expire on July 13, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  IGP Extensions for Stateful PCE Capabilities  . . . . . . . . . 4
   4.  Backward Compatibility  . . . . . . . . . . . . . . . . . . . . 5
   5.  Management Considerations . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6

































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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.

   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.  Advertising active and passive stateful PCE
   capabilities would facilitate a PCC to learn about available stateful
   PCEs, as well as about a PCE's capability to modify LSP parameters.
   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]) where IGP PCE capability
   advertisements can be carried in the Opaque Prefix Attribute defined
   in Section 3.3.3.6.  This document extends the IGP PCE capability
   advertisement mechanism to include active and passive stateful PCEs.

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

   The following terminology is used in this document:

   IGP:  Interior Gateway Protocol






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   IS-IS:  Intermediate System to Intermediate System

   LSR:  Label Switching Router

   OSPF:  Open Shortest Path First

   PCC:  Path Computation Client

   PCE:  Path Computation Client

   PCEP:  Path Computation Client


3.  IGP Extensions for Stateful PCE Capabilities

   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 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
     11         Active Stateful PCE capability
     12         Passive Stateful PCE capability

   Note that while active and passive stateful PCE capabilities may be
   advertised during discovery, PCEP Speakers that wish to use stateful
   PCEP MUST negotiate stateful PCEP capabilities during PCEP session
   setup, as specified in Section 7.1.1 in [I-D.ietf-pce-stateful-pce].
   A PCC MAY initiate stateful PCEP capability negotiation at PCEP
   session setup even if it did not receive any IGP PCE capability
   advertisements.







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4.  Backward Compatibility

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

   IGP extensions defined in this document do not introduce any new
   interoperability issues.


5.  Management Considerations

   A configuration option may be provided for advertising and
   withdrawing Stateful PCE IGP capability on a PCE.


6.  Security Considerations

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


7.  IANA Considerations

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

             Bit                           Meaning             Reference
              11    Active stateful PCE capability         This document
              12   Passive stateful PCE capability         This document


8.  References

8.1.  Normative References

   [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-04
              (work in progress), November 2013.

   [I-D.ietf-pce-stateful-pce]
              Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
              Extensions for Stateful PCE",
              draft-ietf-pce-stateful-pce-07 (work in progress),
              December 2013.




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   [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. Le Roux, "Path Computation Element (PCE)
              Communication Protocol Generic Requirements", RFC 4657,
              September 2006.


Authors' Addresses

   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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   Xian Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P.R.China

   Email: zhang.xian@huawei.com












































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