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Versions: 00 01 02 03 04 draft-ietf-pce-association-bidir

PCE Working Group                                               C. Barth
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                               R. Gandhi
Expires: November 22, 2017                           Cisco Systems, Inc.
                                                                  B. Wen
                                                                 Comcast
                                                            May 21, 2017


                        PCEP Extensions for
        Associated Bidirectional Label Switched Paths (LSPs)
               draft-barth-pce-association-bidir-02

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.
    The Stateful PCE extensions allow stateful control of Multiprotocol
   Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths
   (LSPs) using PCEP.

   This document defines PCEP extensions for binding two reverse
   unidirectional MPLS TE LSPs into an Associated Bidirectional Label
   Switched Path (LSP) when using a Stateful PCE for both PCE-Initiated
   and PCC-Initiated LSPs as well as when using a Stateless 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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."


Copyright Notice

   Copyright (c) 2017 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  4
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Single-sided Initiation  . . . . . . . . . . . . . . . . .  5
     3.2.  Double-sided Initiation  . . . . . . . . . . . . . . . . .  5
     3.3.  Co-routed Associated Bidirectional LSP . . . . . . . . . .  6
   4.  Protocol Extensions  . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Association Object . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Bidirectional LSP Association Group TLV  . . . . . . . . .  6
   5.  PCEP Procedure . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  PCE Initiated LSPs . . . . . . . . . . . . . . . . . . . .  8
     5.2.  PCC Initiated LSPs . . . . . . . . . . . . . . . . . . . .  8
     5.3.  Stateless PCE  . . . . . . . . . . . . . . . . . . . . . .  8
     5.4.  State Synchronization  . . . . . . . . . . . . . . . . . .  8
     5.5.  Error Handling . . . . . . . . . . . . . . . . . . . . . .  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.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Association Types  . . . . . . . . . . . . . . . . . . . . 10
     8.2.  Bidirectional LSP Association Group TLV  . . . . . . . . . 10
       8.2.1.  Flag Fields in Bidirectional LSP Association Group
               TLV  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.3.  PCEP Errors  . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 14



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   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14


1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol (PCEP) as a
   communication mechanism between a Path Computation Client (PCC) and a
   Path Control Element (PCE), or between PCE and PCC, that enables
   computation of Multiprotocol Label Switching (MPLS) Traffic
   Engineering (TE) Label Switched Paths (LSPs).

   [I-D.ietf-pce-stateful-pce] specifies extensions to PCEP to enable
   stateful control of MPLS TE LSPs.  It describes two modes of
   operation - Passive Stateful PCE and Active Stateful PCE.  In [I-
   D.ietf-pce-stateful-pce], the focus is on Active Stateful PCE where
   LSPs are provisioned on the PCC and control over them is delegated to
   a PCE.  Further, [I-D.ietf-pce-pce-initiated-lsp] describes the
   setup, maintenance and teardown of PCE-Initiated LSPs for the
   Stateful PCE model.

   [I-D.ietf-pce-association] introduces a generic mechanism to create a
   grouping of LSPs which can then be used to define associations
   between a set of LSPs and/or a set of attributes, for example primary
   and secondary LSP associations, and is equally applicable to the
   active and passive modes of a Stateful PCE [I-D.ietf-pce-stateful-
   pce] or a stateless PCE [RFC5440].

   The MPLS Transport Profile (MPLS-TP) requirements document [RFC5654]
   specifies that MPLS-TP MUST support associated bidirectional point-
   to-point LSPs.  [RFC7551] specifies RSVP signaling extensions for
   binding two reverse unidirectional LSPs into an associated
   bidirectional LSP.  The fast reroute (FRR) procedures for associated
   bidirectional LSPs are described in [I-D.ietf-teas-assoc-corouted-
   bidir-frr].

   This document specifies PCEP extensions for binding two reverse
   unidirectional MPLS-TE LSPs into an Associated Bidirectional LSP for
   both single-sided and double-sided initiation cases when using a
   Stateful or Stateless PCE.  The PCEP extensions cover the following
   cases:

   o  A PCE initiates the forward and/ or reverse LSP of a single-sided
      or double-sided bidirectional LSP on a PCC and retains the control
      of the LSP.  The PCE computes the path of the LSP and updates the
      PCC with the information about the path.

   o  A PCC initiates the forward and/ or reverse LSP of a single-sided
      bidirectional LSP and retains the control of the LSP.  The PCC



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      computes the path of the LSP and updates the PCE with the
      information about the path (as long as it controls the LSP).

   o  A PCC initiates the forward and/ or reverse LSP of a single-sided
      bidirectional LSP and delegates the control of the LSP to a
      Stateful PCE.  The PCE may compute the path of the LSP and update
      the PCC with the information about the path (as long as it
      controls the LSP).

   o  A PCC requests co-routed or non co-routed paths for forward and
      reverse LSPs of a bidirectional LSP from a Stateless PCE.


2.  Conventions Used in This Document

2.1.  Key Word Definitions

   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].

2.2.  Terminology

   The reader is assumed to be familiar with the terminology defined in
   [RFC5440] and [RFC7551].


3.  Overview

   As shown in Figure 1, two reverse unidirectional LSPs can be
   associated to form an associated bidirectional LSP.  There are two
   methods of initiating the bidirectional LSP association, single-sided
   and double-sided as described in the following sections.


               LSP1 -->          LSP1 -->          LSP1 -->
      +-----+           +-----+           +-----+           +-----+
      |  A  +-----------+  B  +-----------+  C  +-----------+  D  |
      +-----+           +--+--+           +--+--+           +-----+
               <-- LSP2    |                 |     <-- LSP2
                           |                 |
                           |                 |
                        +--+--+           +--+--+
                        |  E  +-----------+  F  |
                        +-----+           +-----+
                                 <-- LSP2

           Figure 1: Example of Associated Bidirectional LSP



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3.1.  Single-sided Initiation

   As specified in [RFC7551], in the single-sided initiation case, the
   bidirectional tunnel is signaled only by one endpoint node (PCC) of
   the tunnel.  Both forward and reverse LSPs of this tunnel are
   initiated with the Association Type set to "Single-sided
   Bidirectional LSP Association" on the originating endpoint node.  The
   forward and reverse LSPs are identified in the Bidirectional LSP
   Association Group TLV of their PCEP Association Objects.

   The originating endpoint node signals the properties for the revere
   LSP in the RSVP REVERSE_LSP Object [RFC7551] of the forward LSP Path
   message.  The remote endpoint then creates the corresponding reverse
   tunnel and signals the reverse LSP in response to the received RSVP
   Path message.

   The two unidirectional reverse LSPs on the originating endpoint node
   are bound together using the PCEP Association Object and on the
   remote endpoint node by the RSVP signaled Association Object.

   As shown in Figure 1, both the forward LSP LSP1 and the reverse LSP
   LSP2 are initiated on the originating endpoint node A, either by the
   PCE or the PCC.  The creation of reverse LSP2 on the remote endpoint
   node D is triggered by the RSVP signaled LSP1.

   As specified in [I-D.ietf-teas-assoc-corouted-bidir-frr], for fast-
   reroute bypass tunnel assignment, the LSP starting from the
   originating node is identified as the forward LSP of the single-sided
   initiated bidirectional LSP.

3.2.  Double-sided Initiation

   As specified in [RFC7551], in the double-sided initiation case, the
   bidirectional LSP is signaled by the both endpoint nodes (PCCs) of
   the tunnel.  The forward and reverse LSPs of this tunnel are
   initiated with the Association Type set to "Double-sided
   Bidirectional LSP Association" on both endpoint nodes.  The forward
   and reverse LSPs are identified in the Bidirectional LSP Association
   Group TLV of their Association Objects.

   The two reverse unidirectional LSPs on both the endpoint nodes are
   bound together by using the PCEP Association Object.

   As shown in Figure 1, LSP1 is initiated on the endpoint node A and
   LSP2 is initiated on the endpoint node D, both by the PCE.

   As specified in [I-D.ietf-teas-assoc-corouted-bidir-frr], for fast-
   reroute bypass tunnel assignment, the LSP with the higher source



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   address is identified as the forward LSP of the double-sided
   initiated bidirectional LSP.

3.3.  Co-routed Associated Bidirectional LSP

   In both single-sided and double-sided initiation cases, forward and
   reverse LSPs may be co-routed as shown in Figure 2, where both
   forward and reverse LSPs follow the same congruent path.


               LSP3 -->          LSP3 -->          LSP3 -->
      +-----+           +-----+           +-----+           +-----+
      |  A  +-----------+  B  +-----------+  C  +-----------+  D  |
      +-----+           +-----+           +-----+           +-----+
              <-- LSP4          <-- LSP4          <-- LSP4

      Figure 2: Example of Co-routed Associated Bidirectional LSP


4.  Protocol Extensions

4.1.  Association Object

   As per [I-D.ietf-pce-association], LSPs are associated by adding them
   to a common association group.  This document defines two new
   Bidirectional LSP Association Groups to be used by the associated
   bidirectional LSPs.  A member of the Bidirectional LSP Association
   Group can take the role of a forward or reverse LSP.  The reverse LSP
   source address MUST be the destination address of the forward LSP and
   the reverse LSP destination address MUST be the source address of the
   forward LSP within a bidirectional LSP association group.  An LSP can
   not be part of more than one Bidirectional LSP Association Group.

   This document defines two new Association Types for the Association
   Object as follows:

   o  Association Type (TBD1) = Single-sided Bidirectional LSP
      Association Group

   o  Association Type (TBD2) = Double-sided Bidirectional LSP
      Association Group

   The Association ID, Association Source, optional Global Association
   Source and optional Extended Association ID in the Bidirectional LSP
   Association Group Object are populated using the procedures defined
   in [RFC7551].

4.2.  Bidirectional LSP Association Group TLV



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   The Bidirectional LSP Association Group TLV is an optional TLV for
   use with the Single-sided and Double-sided Bidirectional LSP
   Association Group Object Types.

   o  The Bidirectional LSP Association Group TLV follows the PCEP TLV
      format from [RFC5440].

   o  The Type (16 bits) of the TLV is TBD3, to be assigned by IANA.

   o  The Length is 4 Bytes.

   o  The value comprises of a single field, the Bidirectional LSP
      Association Flags (32 bits), where each bit represents a flag
      option.

   o  If the Bidirectional LSP Association Group TLV is missing, it
      means the LSP is the forward LSP.

   o  The Bidirectional LSP Association Group TLV MUST NOT be present
      more than once.  If it appears more than once, only the first
      occurrence is processed and any others MUST be ignored.

   The format of the Bidirectional LSP Association Group TLV is shown in
   Figure 3:


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Type = TBD3           |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Reserved                          |C|R|F|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 3: Bidirectional LSP Association Group TLV format

   Bidirectional LSP Association Flags are defined as following.

   F (Forward LSP, 1 bit) - Indicates whether the LSP associated is the
     forward LSP of the bidirectional LSP.  If this flag is set, the LSP
     is a forward LSP.

   R (Reverse LSP, 1 bit) - Indicates whether the LSP associated is the
     reverse LSP of the bidirectional LSP.  If this flag is set, the LSP
     is a reverse LSP.

   C (Co-routed LSP, 1 bit) - Indicates whether the bidirectional LSP is
     co-routed.  If this flag is set, the associated bidirectional LSP



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     is co-routed.  This flag MUST be set for both the forward and
     reverse LSPs of a co-routed bidirectional LSP.

   The Reserved flags MUST be set to 0 when sent and MUST be ignore when
   received.

   When an associated bidirectional LSP is delegated to a Stateful PCE,
   the C flag is used by the PCE to compute paths of the forward and
   reverse LSPs.


5.  PCEP Procedure

5.1.  PCE Initiated LSPs

   As specified in [I-D.ietf-pce-association], Association Groups can be
   created by both Stateful PCE and PCC.

   A Stateful PCE can create and update the forward and reverse LSPs
   independently for both Single-sided and Double-sided bidirectional
   LSP association groups.

5.2.  PCC Initiated LSPs

   A PCC can associate or remove an LSP under its control from the
   bidirectional LSP association group.  The PCC must report the change
   in association to Stateful PCE via PCRpt message.

5.3.  Stateless PCE

   A PCC can request co-routed or non co-routed forward and reverse
   direction paths from a stateless PCE for the bidirectional LSP
   association group.

5.4.  State Synchronization

   During state synchronization, a PCC MUST report all the existing
   bidirectional LSP association groups to the Stateful PCE.  After the
   state synchronization, the PCE MUST remove all stale associations.

5.5.  Error Handling

   The reverse LSP in the bidirectional LSP association group MUST have
   the source address matching the destination address of the forward
   LSP and destination address matching the source address of the
   forward LSP.  If a PCE attempts to add an LSP to a bidirectional LSP
   association group not complying to this rule, the PCC for the single-
   sided initiation case MUST send PCErr with Error-Type= TBD4



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   (Bidirectional LSP Association Error) and Error-Value = 1 (Endpoints
   mismatch).  Similarly, if a PCC attempts to add an LSP to a
   bidirectional LSP association group at PCE not complying to this
   rule, the PCE for both single-sided and double-sided initiated
   bidirectional LSPs MUST send this PCErr.


6.  Security Considerations

   This document introduces two new Association Types for the
   Association Object, Double-sided Bidirectional LSP Association Group
   and Single-sided Associated Bidirectional LSP Group.  These types, by
   themselves, introduce no additional security concerns beyond those
   discussed in [RFC5440], [I-D.ietf-pce-stateful-pce], and [I-D.ietf-
   pce-association].


7.  Manageability Considerations

7.1.  Control of Function and Policy

   An operator MUST be allowed to provision the bidirectional LSP
   association parameters at PCEP peers.

7.2.  Information and Data Models

   A Management Information Base (MIB) module for modeling PCEP is
   described in [RFC7420].  However, one may prefer the mechanism for
   configuration using YANG data model [I-D.ietf-pce-pcep-yang].  These
   SHOULD be enhanced to provide controls and indicators for support of
   the associated bidirectional LSP feature.  Support for various
   configuration parameters as well as counters of messages
   sent/received containing the TLVs defined in this document SHOULD be
   added.

7.3.  Liveness Detection and Monitoring

   The mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC5440].

7.4.  Verify Correct Operations

   The mechanisms defined in this document do not imply any new
   operation verification requirements in addition to those already
   listed in [RFC5440].

7.5.  Requirements On Other Protocols



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   The mechanisms defined in this document do not add any new
   requirements on other protocols.

7.6.  Impact On Network Operations

   The mechanisms defined in this document do not have any new impact on
   network operations.


8.  IANA Considerations

8.1.  Association Types

   This document defines the following Association Types for the
   Association Object defined [I-D.ietf-pce-association].

   Value Name                                            Reference
   ---------------------------------------------------------------------
   TBD1 Single-sided Bidirectional LSP Association Group [This document]
   TBD2 Double-sided Bidirectional LSP Association Group [This document]

8.2.  Bidirectional LSP Association Group TLV

   This document defines a new TLV for carrying additional LSP
   information for the Bidirectional LSP Association Group TLV as
   following:

   TLV-Type  Name                                      Reference
   -------------------------------------------------------------------
    TBD3     Bidirectional LSP Association Group TLV   [This document]

8.2.1.  Flag Fields in Bidirectional LSP Association Group TLV

   This document requests that a new sub-registry, named "Bidirectional
   LSP Association Group TLV Flag Field", is created within the "Path
   Computation Element Protocol (PCEP) Numbers" registry to manage the
   Flag field in the Bidirectional LSP Association Group TLV.

   New values are to be assigned by Standards Action [RFC5226].  Each
   bit should be tracked with the following qualities:

      o  Bit number (counting from bit 0 as the most significant bit)

      o  Capability description

      o  Defining RFC





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   The following values are defined in this document for the Flag field.

   Bit No.     Description                   Reference
   ---------------------------------------------------------
    31         F - Forward LSP               [This document]
    30         R - Reverse LSP               [This document]
    29         C - Co-routed LSP             [This document]

8.3.  PCEP Errors

   IANA is requested to allocate new Error-Type and Error-Value within
   the " PCEP-ERROR Object Error Types and Values" sub-registry of the
   PCEP Numbers registry, as follows:

   Error-Type  Description                           Reference
   -----------------------------------------------------------------
    TBD4       Bidirectional LSP Association Error   [This document]

               Error-value=1: Endpoints mismatch     [This document]
































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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.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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

   [RFC7551]  Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
              Extensions for Associated Bidirectional LSPs", RFC 7551,
              May 2015.

   [I-D.ietf-pce-association]  Minei, I., Crabbe, E., Sivabalan, S.,
              Ananthakrishnan, H., Zhang, X., and Y. Tanaka, "PCEP
              Extensions for Establishing Relationships Between Sets of
              LSPs", draft-ietf-pce-association-group (work in
              progress).

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

   [I-D.ietf-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", draft-ietf-pce-pce-
              initiated-lsp (work in progress).

   [I-D.ietf-teas-assoc-corouted-bidir-frr]  Gandhi, R., Ed., Shah, H.,
              and J. Whittaker, "Fast Reroute Procedures for Associated
              Bidirectional Label Switched Paths", draft-ietf-teas-
              assoc-corouted-bidir-frr (work-in-progress).

9.2.  Informative References

   [RFC5654]  Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
              Sprecher, N., and S. Ueno, "Requirements of an MPLS
              Transport Profile", RFC 5654, September 2009.

   [RFC7420]  Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
              Hardwick, "Path Computation Element Communication Protocol
              (PCEP) Management Information Base (MIB) Module", RFC



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              7420, December 2014.

   [I-D.ietf-pce-pcep-yang]  Dhody, D., Hardwick, J., Beeram, V., and J.
              Tantsura, "A YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", draft-ietf-pce-pcep-yang
              (work in progress).













































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Acknowledgments

   TBA.


Authors' Addresses

   Colby Barth
   Juniper Networks

   Email: cbarth@juniper.net


   Rakesh Gandhi
   Cisco Systems, Inc.

   Email: rgandhi@cisco.com


   Bin Wen
   Comcast

   Email: Bin_Wen@cable.comcast.com




























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