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PCE Working Group                                               D. Dhody
Internet-Draft                                                  U. Palle
Intended status: Experimental                               V. Kondreddy
Expires: April 2, 2015                               Huawei Technologies
                                                      September 29, 2014


   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-07

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).  The RFC 6006 and
   RFC 7334 describes these mechanisms for intra and inter domain path
   computation via PCE(s).

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

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
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   This Internet-Draft will expire on April 2, 2015.

Copyright Notice

   Copyright (c) 2014 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Domain Sequence Tree in Inter Domain P2MP Path
           Computation . . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  PCE-sequence  . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Explicit inclusion or exclusion of abstract nodes . . . .   5
   4.  Detailed Description  . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Objective . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Request Message Format  . . . . . . . . . . . . . . . . .   6
     4.3.  Backward Compatibility  . . . . . . . . . . . . . . . . .   7
   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 . . . . . . . . . . . . . . .   8
     7.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   8
     7.4.  Verify Correct Operations . . . . . . . . . . . . . . . .   8
     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

1.  Introduction

   The PCE architecture is defined in [RFC4655].  [RFC5862] lay out the
   requirements for PCEP to support P2MP path computation.  [RFC6006]
   describe an extension to PCEP to compute optimal constrained intra-
   domain (G)MPLS P2MP TE LSPs.  [RFC7334] describes the mechanism for
   inter-domain P2MP path computation.

   Further [RFC6006] describes mechanism to specify a list of nodes that
   can be used as branch nodes or a list of nodes that cannot be used as



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   branch nodes via Branch Node Capability (BNC) object.  The BNC object
   is used to specify which nodes have the capability to act as a branch
   nodes or which nodes lack the capabilty.  It supports IPv4 and IPv6
   prefix sub-objects only.

   This document explains the need to add the capability to explicitly
   specify any abstract nodes (not just nodes with branch node
   capabiltiy) for inclusion or exclusion for a subset of destinations.

   [RFC7334] describes the core-tree procedure to compute 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 particular 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.

   PCEP:  Path Computation Element Protocol.

   P2MP:  Point-to-Multipoint

   P2P:  Point-to-Point

   RRO:  Record Route Object




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   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

   [RFC7334] 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.

                        -----------                      ----------
                       | Domain D3 |                    | Domain D6|
                       |           |                    |***   *** |
                      /|           |                    |*X*   *Y* |
                     / |           |                    |***   *** |
                    /   -----------\                    /----------
                   /                \                  /
                  /                  \                /
                 /                    \              /
    ------------/                      \------------/
   |  Domain D1 |                      |  Domain D4 |
   | ***        |                      |            |
   | *A*        |                      |            |
   | ***        |                      |            |
    ------------\                      /------------\
                 \                    /              \
                  \                  /                \
                   \                /                  \
                    \   -----------/                    \----------
                     \ | Domain D2 |                    | Domain D5|
                      \|           |                    |***       |
                       |           |                    |*Z*       |
                       |           |                    |***       |
                        -----------                      ----------

                     Figure 1: Domain Topology Example





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   In the Figure 2 below, the P2MP tree spans 5 domains.  Destination in
   D6 (X and 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].

3.1.1.  PCE-sequence

   [RFC7334] also mentions PCE-sequence (i.e. list of PCE for each
   domain in the path domain tree).  [RFC5886] specify PCE-ID object
   (used to specify a PCE's IP address) and <pce-list> (list of PCE or
   PCE-sequence).  Like domain-sequence as explained above, PCE-sequence
   will be different for different destinations and thus should be
   encoded per subset of destinations.

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




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   [RFC6006] only allows to encode a list of nodes that have (or have
   not) the branch node capability by using the Branch Node Capability
   (BNC) Object.  This object apply to all destinations (old and new) in
   the P2MP tree.

   For an existing P2MP tree with an overloaded branch node, when adding
   a set of new leaves, administrator may want to exclude that
   particular branch node 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 Ingress can exert stronger control by providing
   explicit inclusion or exclusion of any abstract nodes (not limited to
   specifying nodes with branch node capability) 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 <pce-
   list>, <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, AS 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 <pce-list>, <IRO> and <XRO> is applied for all
   destinations in one such P2MP <END-POINTS> object.

4.2.  Request Message Format

   The format of PCReq message is modified as follows:









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

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

           <pce-list>::=<PCE-ID>[<pce-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-pce-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.

   <pce-list> can be used to specify the Pce-sequence instead of domain-
   sequence.

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].






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5.  IANA Considerations

   There are no new IANA allocation in this document.

6.  Security Considerations

   PCEP security mechanisms as described in [RFC5440], [RFC6006] and
   [RFC7334] 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 [RFC7334] 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.

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].





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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,
   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.

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

   [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.

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.






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

   [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.

   [RFC5886]  Vasseur, JP., Le Roux, JL., and Y. Ikejiri, "A Set of
              Monitoring Tools for Path Computation Element (PCE)-Based
              Architecture", RFC 5886, June 2010.

   [RFC7334]  Zhao, Q., Dhody, D., King, D., Ali, Z., and R. Casellas,
              "PCE-Based Computation Procedure to Compute Shortest
              Constrained Point-to-Multipoint (P2MP) Inter-Domain
              Traffic Engineering Label Switched Paths", RFC 7334,
              August 2014.

   [DOMAIN-SEQ]
              Dhody, D., Palle, U., and R. Casellas, "Standard
              Representation Of Domain Sequence (draft-ietf-pce-pcep-
              domain-sequence)", July 2014.

Authors' Addresses

   Dhruv Dhody
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruv.ietf@gmail.com


   Udayasree Palle
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: udayasree.palle@huawei.com










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

   EMail: venugopalreddyk@huawei.com












































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