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PCE Working Group                                               D. Dhody
Internet-Draft                                                  U. Palle
Intended status: Standard              Huawei Technologies India Pvt Ltd
Expires: December 31, 2011                                 June 29, 2011


  Supporting explicit-path per destination in Path Computation Element
           Communication Protocol (PCEP) - P2MP Path Request.
              draft-dhody-pce-pcep-p2mp-per-destination-00

Abstract

   The ability to determine paths of point-to-multipoint (P2MP)
   Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
   Traffic Engineering Label Switched Paths (TE LSPs) is one the key
   requirements for Path Computation Element (PCE).  [RFC 6006] and
   [PCE-P2MP-PROCEDURES] describes these mechanisms for intra and inter
   domain environment.

   Explicit Path in this document refers to the configured list of
   network elements that MUST be traversed or MUST be excluded in the
   final path computation.  This should not be confused with the RSVP
   terminology.  Network elements can further be strict or loose hop.

   This document describes extensions to the PCE communication Protocol
   (PCEP) to define explicit-path per destination in P2MP context.

Status of This Memo

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   This Internet-Draft will expire on December 31, 2011.


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Copyright Notice

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   This Internet-Draft will expire on December 31, 2011.
Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Need to Define Explicit Path Per Destination  . . . . . . . . . 4
   4.  Detailed Description  . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Objective . . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.2.  Request Message Format  . . . . . . . . . . . . . . . . . . 4
     4.3.  Ordering Destinations in END-POINTS Objects . . . . . . . . 5
       4.3.1.  Example . . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   7.  Manageability Considerations  . . . . . . . . . . . . . . . . . 8
     7.1.  Control of Function and Policy  . . . . . . . . . . . . . . 8
     7.2.  Information and Data Models . . . . . . . . . . . . . . . . 9
     7.3.  Liveness Detection and Monitoring . . . . . . . . . . . . . 9
     7.4.  Verify Correct Operations . . . . . . . . . . . . . . . . . 9
     7.5.  Requirements On Other Protocols . . . . . . . . . . . . . . 9
     7.6.  Impact On Network Operations  . . . . . . . . . . . . . . . 9
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 9
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 9























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1.  Introduction

   The Path Computation Element (PCE) architecture is defined in
   [RFC4655].  [RFC 6006] describe a PCE-based path computation
   procedure to compute optimal constrained (G)MPLS P2MP TE LSPs.  It
   also defines the format of path request message used in P2MP, which
   limits explicit path in form of <IRO> / <XRO> to be applied to full
   P2MP tunnel and thus to only the common path to all leaves.

   This document describes the need for supporting explicit-path per
   destination in intra and inter-domain P2MP scenario.  It further
   lists the path request format and mode of operations

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 RFC2119.

2.  Terminology

   The following terminology is used in this document.

   Explicit-Path:  Set of network elements configured by the
      administrator that MUST be traversed or MUST be excluded.

   IRO:  Include Route Object.

   PCC:  Path Computation Client: any client application requesting a
      path computation to be performed by a Path Computation Element.

   PCE:  Path Computation Element.  An entity (component, application,
      or network node) that is capable of computing a network path or
      route based on a network graph and applying computational
      constraints.

   P2MP:  Point-to-Multipoint

   P2P:  Point-to-Point

   RRO:  Record Route Object

   RSVP:  Resource Reservation Protocol

   TE LSP:  Traffic Engineering Label Switched Path.






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   XRO:  Exclude Route Object.

3.  Need to Define Explicit Path Per Destination

   o  [PCE-P2MP-PROCEDURES] defines inter-domain P2MP path computation
      procedure, since different destinations will have different domain
      paths within the domain tree, it requires domain-sequence encoded
      in form of <IRO> to be attached per destination.  It cannot be
      encoded for all destinations.

   o  Administrator at the source can exert stronger control by
      providing explicit path (include, exclude, loose etc) per
      destination.

   o  Compatibility: Basic MPLS TE P2MP Tunnel configurations for
      various operators support the configuration of explicit-path per
      destination.

4.  Detailed Description

4.1.  Objective

   [RFC 6006] defines Request Message Format and Objects, along with
   <end-point-rro-pair-list>.  This section introduce the concept of
   <iro-list>, <xro-list> and <metric-list> which are added to the <end-
   point-rro-pair-list> to support 'per destination'.

   Use of <iro-list>, <xro-list> to carry explicit-path per destination.

   Use of <iro-list> to carry domain-sequence per destination in inter-
   domain scenario.

   Use of <metric-list> to carry metric value of each calculated path
   encoded in <rro-list>.

4.2.  Request Message Format

   To carry explicit path for each destination, <END-POINTS> objects
   need to be ordered and grouped in a way such that IRO object, XRO
   object, RRO object and METRIC object can be associated with each
   destination.










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           The format of PCReq message is modified as follows:

           <PCReq Message>::= <Common Header>
                              <request>
           where:
           <request>::= <RP>
                        <end-point-iro-xro-rro-metric-list>
                        [<OF>]
                        [<LSPA>]
                        [<BANDWIDTH>]
                        [<metric-list>]
                        [<IRO>]
                        [<LOAD-BALANCING>]

           where:
           <end-point-iro-xro-rro-metric-list> ::=
                        <END-POINTS>
                        [<IRO-List>]
                        [<XRO-List>]
                        [<RRO-List>]
                        [<metric-list>]
                        [<end-point-iro-xro-rro-metric-list >]


           <RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
           <metric-list>::=<METRIC>[<metric-list>]
           <IRO-List>::=<IRO>[<IRO-List>]
           <XRO-List>::=<XRO>[<XRO-List>]

   From [RFC 6006] usage of <end-point-rro-pair-list> is changed to
   <end-point-iro-xro-rro-metric-list> in this document.

   Note that the new format is backward compatible to [RFC 6006] format.

4.3.  Ordering Destinations in END-POINTS Objects

   Multiple destinations are encoded into a single ENDPOINTS object,
   Each Endpoint maybe followed by multiple lists of IROs, XROs, RROs or
   METRICs.  The first <IRO> object would belong to the first
   destination, the second <IRO> object to the second destination and
   hence forth.  The first <XRO> object would belong to the first
   destination, the second <XRO> object to the second destination and
   hence forth...

   Note that a destination (P2MP tree leaf) MAY have






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   o  both <IRO> and <XRO>

   o  <IRO> only

   o  <XRO> only

   o  No explicit path

   To maintain the ordering between the destination and objects in the
   list, there MAYBE a need to divide a set of destinations into
   multiple ENDPOINTS, this explained in below example.

4.3.1.  Example

   Destination 1 has include IRO1 and exclude XRO1

   Destination 2 has only include IRO2

   Destination 3 has only exclude XRO3

   Destination 4 has only exclude XRO4

   Destination 5 has none

   Here if we try to encode all destinations in one <ENDPOINT> and
   objects in list, we will not map XRO3 to destination 3, the rule is
   to map sequentially and thus XRO3 will belong to destination 2.

   To avoid this we must break the set of destinations into two sets as
   shown below





















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                     +-----------------------------+
                     |           Leaf Type         |
                     +-----------------------------+
                     |           Source IP         |
                     +-----------------------------+
            +------> |         Destination 1       |   <ENDPOINT>
            |        +-----------------------------+
            |    +-> |         Destination 2       |
            |    *   +-----------------------------+
            |    *   |         Destination 5       |
            |    *   +-----------------------------+
            |    *
            |    *   +-----------------------------+
            +----*-> |             IRO1            |
            |    *   +-----------------------------+
            |    *   |            HOPI 1-1         |
            |    *   +-----------------------------+
            |    *   |             ....            |   <IRO-List>
            |    *   +-----------------------------+   with 2 IRO1, IRO2
            |    +-> |              IRO2           |
            |        +-----------------------------+
            |        |            HOPI 2-1         |
            |        +-----------------------------+
            |        |             ....            |
            |        +-----------------------------+
            |
            |        +-----------------------------+
            +----->  |             XRO1            |
                     +-----------------------------+  <XRO-List>
                     |            HOPX 1-1         |  with 1 XRO1
                     +-----------------------------+
                     |             ....            |
                     +-----------------------------+

   ENDPOINT1 carries destination 1, 2 and 5 and corresponding <iro-list>
   and <xro-list>.  Here Destination 1 has IRO1 and XRO1; Destination 2
   has IRO2; and Destination 5 has none.














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                     +-----------------------------+
                     |           Leaf Type         |
                     +-----------------------------+
                     |           Source IP         |
                     +-----------------------------+
            +------> |         Destination 3       |   <ENDPOINT>
            |        +-----------------------------+
            |    +-> |         Destination 4       |
            |    *   +-----------------------------+
            |    *
            |    *   +-----------------------------+
            +----*-> |             XRO3            |
                 *   +-----------------------------+
                 *   |            HOPX 3-1         |
                 *   +-----------------------------+
                 *   |             ....            |   <XRO-List>
                 *   +-----------------------------+   with 2 XRO3, XRO4
                 +-> |              XRO4           |
                     +-----------------------------+
                     |            HOPX 4-1         |
                     +-----------------------------+
                     |             ....            |
                     +-----------------------------+

   ENDPOINT2 carries destination 3 and 4 and corresponding <xro-list>
   only.  Here destination 3 maps to XRO3 and Destination 4 to XRO4.

5.  IANA Considerations

   TBD

6.  Security Considerations

   PCEP security mechanisms as described in [RFC6006] and [PCE-P2MP-
   PROCEDURES] are applicable for this document.  This document does not
   add any new security threat.

7.  Manageability Considerations

7.1.  Control of Function and Policy

   Mechanisms defined in this document do not add any new control
   function/policy requirements in addition to those already listed in
   [RFC6006].







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7.2.  Information and Data Models

   Mechanisms defined in this document do not imply any new MIB
   requirements in addition to those already listed in [PCE-P2MP-MIB].

7.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC6006].

7.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC6006].

7.5.  Requirements On Other Protocols

   Mechanisms defined in this document do not imply any requirements on
   other protocols in addition to those already listed in [RFC6006].

7.6.  Impact On Network Operations

   Mechanisms defined in this document do not have any impact on network
   operations in addition to those already listed in [RFC6006].

8.  Acknowledgments

   We would like to thank Pradeep Shastry, Suresh babu, Quintin Zhao and
   Chen Huaimo for their useful comments and suggestions.

9.  References

9.1.  Normative References

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

9.2.  Informative References

   [PCE-P2MP-MIB]         Zhao, Q., Dhody, D., Palle, U., and D. King,
                          "Management Information Base for the PCE
                          Communications Protocol (PCEP) When Requesting
                          Point-to-Multipoint Services", March 2011.

   [PCE-P2MP-PROCEDURES]  Zhao, Q., Ali, Z., Saad,, T., and D. King,
                          "PCE-based Computation Procedure To Compute



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                          Shortest Constrained P2MP Inter-domain Traffic
                          Engineering Label Switched Paths",
                          January 2011.

   [RFC4655]              Farrel, A., Vasseur, J., and J. Ash, "A Path
                          Computation Element (PCE)-Based Architecture",
                          August 2006.

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

   [RFC5440]              Ayyangar, A ., Farrel, A ., Oki, E., Atlas,
                          A., Dolganow, A., Ikejiri, Y., Kumaki, K.,
                          Vasseur, J., and J. Roux, "Path Computation
                          Element (PCE) communication Protocol (PCEP)",
                          March 2009.

   [RFC6006]              Zhao, Q., Verhaeghe, F., Takeda, T., Ali, Z.,
                          Meuric , J., and D. King, "Extensions to the
                          Path Computation Element Communication
                          Protocol (PCEP) for Point-to-Multipoint
                          Traffic Engineering Label Switched Paths",
                          September 2010.

Authors' Addresses

    Dhruv Dhody
   Huawei Technologies India Pvt Ltd
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruvd@huawei.com


   Udayasree Palle
   Huawei Technologies India Pvt Ltd
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: udayasreepalle@huawei.com








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