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PCE Working Group                                               D. Dhody
Internet-Draft                                                  U. Palle
Intended status: Experimental                               V. Kondreddy
Expires: October 18, 2013                  Huawei Technologies India Pvt
                                                                     Ltd
                                                          April 16, 2013


   Supporting explicit inclusion or exclusion of abstract nodes for a
 subset of P2MP destinations in Path Computation Element Communication
                            Protocol (PCEP).
              draft-dhody-pce-pcep-p2mp-per-destination-04

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).  [RFC6006] and
   [PCE-P2MP-PROCEDURES] describes these mechanisms for intra and inter
   domain path computation via PCE.

   This document describes the motivation and PCE communication Protocol
   (PCEP) extension for explicitly specifying abstract nodes for
   inclusion or exclusion for a subset of destinations during the Point
   to Multipoint (P2MP) path computation via PCE.

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 October 18, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
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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.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Domain Sequence Tree in Inter Domain P2MP Path
           Computation  . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Explicit inclusion or exclusion of abstract nodes  . . . .  6
   4.  Detailed Description . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Objective  . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  Request Message Format . . . . . . . . . . . . . . . . . .  7
     4.3.  Backward Compatibility . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Manageability Considerations . . . . . . . . . . . . . . . . .  9
     7.1.  Control of Function and Policy . . . . . . . . . . . . . .  9
     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 . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10















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1.  Introduction

   The Path Computation Element (PCE) architecture is defined in
   [RFC4655].  [RFC5862] lay out the requirements for PCEP to support
   Point-to-Multipoint (P2MP) path computation.  [RFC6006] describe an
   extension to PCEP to compute optimal constrained intra-domain (G)MPLS
   P2MP TE LSPs.  [PCE-P2MP-PROCEDURES] describes the mechanism for
   inter-domain P2MP path computation.

   [RFC6006] describe a PCE-based path computation procedure to compute
   optimal constrained (G)MPLS P2MP TE LSPs.  It describes mechanism to
   specify branch nodes that can or cannot be used via Branch Node
   Capability (BNC) object (which only supports IPv4 and IPv6 prefix
   sub-objects and are applied to all destinations).  This document
   explains the need to add the capability to explicitly specify any
   abstract nodes (not just branch nodes) for inclusion or exclusion for
   a subset of destinations.

   [PCE-P2MP-PROCEDURES] describes the core-tree procedure for computing
   inter-domain P2MP tree.  It assumes that, due to deployment and
   commercial limitations, the sequence of domains for a path (the path
   domain tree) will be known in advance.  For a group of destination
   which belong to a destination domain, the domain-sequence needs to be
   encoded separately as described in [DOMAIN-SEQ].  The mechanism, as
   described in this document, of explicitly specifying abstract nodes
   for inclusion or exclusion for a subset of destinations can be used
   for this purpose, where abstract nodes are domains.

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.

   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.




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   PCEP:  Path Computation Element Protocol.

   P2MP:  Point-to-Multipoint

   P2P:  Point-to-Point

   RRO:  Record Route Object

   RSVP:  Resource Reservation Protocol

   TE LSP:  Traffic Engineering Label Switched Path.

   XRO:  Exclude Route Object.

3.  Motivation

3.1.  Domain Sequence Tree in Inter Domain P2MP Path Computation

   [PCE-P2MP-PROCEDURES] describes the core-tree procedure for inter-
   domain path computation.  The procedure assumes that the sequence of
   domains for a path (the path domain tree) will be known in advance
   due to deployment and commercial limitations (e.g., inter-AS peering
   agreements).

   In the Figure 1 below, D1 is the root domain; D5 and D6 are the
   destination domains.  The ingress is A in domain D1; egresses are X,
   Y in Domain D6 and Z in Domain D5.
























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                    |  +-------------+                +----------------+
                    |  |D 3          |                |D 6             |
                    |  |         +--+|                |          +--+  |
                    |  |         |J ||                |          |X |  |
                    |  |  +--+   +--+|                |   +--+   +--+  |
                    |  |  |F |       |                |   |U |         |
                    |  |  *--+       |                |   +--+         |
                    |  | /      +--+ |                |          +--+  |
                    |  |/       |K | |                |          |Y |  |
                    |  /        +--+ |                |   +--+   +--+  |
                    | /|  +--+       |+--------------+|   |V |         |
                    |/ |  |G |       ++-+          +-++   +--+         |
     +-------------+/  |  +--+       ||N|          |S||                |
     |             /|  |             ++-+          +-++                |
     |         +--*||  +-------------+|              |+----------------+
     |         |D |||                 |     +--+     |
     |         +--+||                 |     |P |     |
     |    +--+     ||                 |     +--+     |
     |    |B |     ||                 |              |
     |    +--+     ||                 |              |
     |             ||                 |     +--+     |
     |+--+         ||                 |     |Q |     |
     ||A |         ||                 |     +--+     |
     |+--+         ||                 |              |
     |             ||                 |     +--+     |
     |    +--+     ||  +------------+ |     |R |     |+----------------+
     |    |C |     ||  |D 2         +-++    +--+   +-++ D 5            |
     |    +--+     ||  |            |O||           |T||                |
     |             ||  |            +-++           +-++                |
     |         +--+||  |       +--+ | |  D 4         ||   +--+         |
     |         |E |||  |       |L | | +--------------+|   |W |         |
     |         +--*||  |       +--+ |                 |   +--+         |
     |             \|  |            |                 |          +--+  |
     |D 1          |\  |   +--+     |                 |          |Z |  |
     +-------------+|\ |   |H |     |                 |          +--+  |
                    | \|   +--+  +--+                 |                |
                    |  \         |M |                 |                |
                    |  |\        +--+                 |                |
                    |  | \ +--+     |                 |                |
                    |  |  \|I |     |                 |                |
                    |  |   *--+     |                 |                |
                    |  |            |                 |                |
                    |  +------------+                 +----------------+
         As 100     |  AS 200
                    |

                     Figure 1: Domain Topology Example




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   In the Figure 2 below, the P2MP tree spans 5 domains.  Destination in
   D6 (X & Y) would use the domain-sequence: D1-D3-D4-D6; and
   destination in D5 (Z) would use the domain-sequence: D1-D3-D4-D5.


                               D3    D6
                              /  \  /
                             D1   D4
                                    \
                                     D5

                      Figure 2: Domain Sequence Tree

   Since destinations in different destination domain will have
   different domain sequence within the domain tree, it requires
   following encoding-

   o  Destination X and Y: D1-D3-D4-D6

   o  Destination Z : D1-D3-D4-D5

   An extension in P2MP Path Computation request is needed to support
   this.  (Refer Section 4.2)

   The abstract nodes MAY include (but not limited to) domain subobjects
   AS number and IGP Area as described in [DOMAIN-SEQ].

   [PCE-P2MP-PROCEDURES] also mentions PCE-sequence (i.e.  PCE that
   serves each domain in the path domain tree); like domain-sequence as
   explained above, PCE-sequence will be different for different
   destinations and thus should be encoded as such.

3.2.  Explicit inclusion or exclusion of abstract nodes

   [RFC6006] describes four possible types of leaves in a P2MP request
   encoded in P2MP END-POINTS object.

   o  New leaves to add

   o  Old leaves to remove

   o  Old leaves whose path can be modified/reoptimized

   o  Old leaves whose path must be left unchanged

   Currently [RFC6006] only allows a list of nodes that can be used as
   branch nodes or a list of nodes that cannot be used as branch nodes
   by using the Branch Node Capability (BNC) Object, which applies to



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   all leaves (old and new) in the P2MP tree.

   For an existing P2MP tree which may already have a branch node
   through which most of the leaves are connected, but when adding a set
   of new leaves, administrator may want to exclude that node (as it may
   soon be overloaded) and would like to balance the final P2MP tree.
   This cannot be achieved via the BNC object but by explicitly
   excluding a particular node or including a different node, for the
   P2MP END-POINTS object for new leaves only.

   Administrator at the source can exert stronger control by providing
   explicit inclusion or exclusion of any abstract nodes (not limited to
   branch nodes) for a group (subset) of destinations and not all
   destinations.

4.  Detailed Description

4.1.  Objective

   [RFC6006] defines Request Message Format and Objects, along with
   <end-point-rro-pair-list>.  This section introduce the use of <IRO>
   and <XRO> which are added to the <end-point-rro-pair-list>.

   To allow abstract nodes to be explicitly included or excluded for a
   subset of destinations (encoded in one <END-POINTS> object), changes
   are made as shown below.

   The abstract node (encoded as subobject in <IRO> and <XRO>) MAY be an
   absolute hop, IP-Prefix, Autonomous system or IGP Area.  The
   subobjects are described in [RFC3209], [RFC3477], [RFC4874] and
   [DOMAIN-SEQ].

   Note that one P2MP Path request can have multiple <END-POINTS>
   objects and each P2MP <END-POINTS> object may have multiple
   destinations, the <IRO> and <XRO> is applied for all destinations in
   one such P2MP <END-POINTS> object.

4.2.  Request Message Format













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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-pair-list>
                                  [<OF>]
                                  [<LSPA>]
                                  [<BANDWIDTH>]
                                  [<metric-list>]
                                  [<IRO>]
                                  [<LOAD-BALANCING>]

          where:

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

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

   From [RFC6006] usage of <end-point-rro-pair-list> is changed to <end-
   point-iro-xro-rro-pair-list> in this document.

   [RFC6006] describes Branch Node Capability (BNC) Object which is
   different from the use of <IRO> and <XRO> to specify inclusion/
   exclusion of abstract nodes for a subset of destinations as described
   here.

4.3.  Backward Compatibility

   A legacy implementation that does not support explicit inclusion or
   exclusion of abstract nodes for a subset of P2MP destinations will
   act according to the procedures set out in [RFC5440], that is it will
   find the P2MP Path Request message out of order with respect to the
   format specified in [RFC6006].

5.  IANA Considerations

   There are no new IANA allocation in this document.






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6.  Security Considerations

   PCEP security mechanisms as described in [RFC5440], [RFC6006] and
   [PCE-P2MP-PROCEDURES] are applicable for this document.

   The new explicit inclusion or exclusion of abstract nodes for a
   subset of P2MP destination defined in this document allow finer and
   more specific control of the path computed by a PCE.  Such control
   increases the risk if a PCEP message is intercepted, modified, or
   spoofed because it allows the attacker to exert control over the path
   that the PCE will compute or to make the path computation impossible.
   Therefore, the security techniques described in [RFC5440], [RFC6006]
   and [PCE-P2MP-PROCEDURES] are considered more important.

   Note, however, that the route exclusion mechanisms also provide the
   operator with the ability to route around vulnerable parts of the
   network and may be used to increase overall network security.

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].

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].




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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,
   Daniel King 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", BCP 14,
                          RFC 2119, March 1997.

9.2.  Informative References

   [RFC3209]              Awduche, D., Berger, L., Gan, D., Li, T.,
                          Srinivasan, V., and G. Swallow, "RSVP-TE:
                          Extensions to RSVP for LSP Tunnels", RFC 3209,
                          December 2001.

   [RFC3477]              Kompella, K. and Y. Rekhter, "Signalling
                          Unnumbered Links in Resource ReSerVation
                          Protocol - Traffic Engineering (RSVP-TE)",
                          RFC 3477, January 2003.

   [RFC4655]              Farrel, A., Vasseur, J., and J. Ash, "A Path
                          Computation Element (PCE)-Based Architecture",
                          RFC 4655, August 2006.

   [RFC4874]              Lee, CY., Farrel, A., and S. De Cnodder,
                          "Exclude Routes - Extension to Resource
                          ReserVation Protocol-Traffic Engineering
                          (RSVP-TE)", RFC 4874, April 2007.

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

   [RFC5862]              Yasukawa, S. and A. Farrel, "Path Computation
                          Clients (PCC) - Path Computation Element (PCE)
                          Requirements for Point-to-Multipoint MPLS-TE",
                          RFC 5862, June 2010.



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   [RFC6006]              Zhao, Q., King, D., Verhaeghe, F., Takeda, T.,
                          Ali, Z., and J. Meuric, "Extensions to the
                          Path Computation Element Communication
                          Protocol (PCEP) for Point-to-Multipoint
                          Traffic Engineering Label Switched Paths",
                          RFC 6006, September 2010.

   [PCE-P2MP-PROCEDURES]  Zhao, Q., Dhody, D., Ali, Z., Saad,, T.,
                          Sivabalan,, S., and R. Casellas, "PCE-based
                          Computation Procedure To Compute Shortest
                          Constrained P2MP Inter-domain Traffic
                          Engineering Label Switched Paths (draft-ietf-
                          pce-pcep-inter-domain-p2mp-procedures-03)",
                          Feb 2013.

   [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
                          (draft-zhao-pce-pcep-p2mp-mib-05)",
                          August 2012.

   [DOMAIN-SEQ]           Dhody, D., Palle, U., and R. Casellas,
                          "Standard Representation Of Domain Sequence
                          (draft-ietf-pce-pcep-domain-sequence-03)",
                          March 2013.

Authors' Addresses

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

   EMail: dhruv.dhody@huawei.com


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

   EMail: udayasree.palle@huawei.com






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   Venugopal Reddy Kondreddy
   Huawei Technologies India Pvt Ltd
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: venugopalreddyk@huawei.com












































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