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Versions: (draft-zhang-pce-hierarchy-extensions) 00 01 02 03 04 05 06 07 08 09 10

Network Working Group                                      F. Zhang, Ed.
Internet-Draft                                                   Q. Zhao
Intended status: Experimental                                     Huawei
Expires: February 18, 2014                      O. Gonzalez de Dios, Ed.
                                                          Telefonica I+D
                                                             R. Casellas
                                                                    CTTC
                                                                 D. King
                                                      Old Dog Consulting
                                                         August 18, 2013


Extensions to Path Computation Element Communication Protocol (PCEP) for
              Hierarchical Path Computation Elements (PCE)
                 draft-ietf-pce-hierarchy-extensions-00

Abstract

   The Hierarchical Path Computation Element (H-PCE) architecture,
   defined in the companion framework document [RFC6805], provides a
   mechanism to allow the optimum sequence of domains to be selected,
   and the optimum end-to-end path to be derived through the use of a
   hierarchical relationship between domains.

   This document defines the Path Computation Element Protocol (PCEP)
   extensions for the purpose of implementing Hierarchical PCE
   procedures which are described in the aforementioned document. These
   extensions are experimental and published for examination,
   discussion, implementation, and evaluation.


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."

   This Internet-Draft will expire on January 14, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the


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   document authors.  All rights reserved.

   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
     1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . 4
     1.3.  Requirements Language  . . . . . . . . . . . . . . . . . . 4
   2.  Requirements for H-PCE . . . . . . . . . . . . . . . . . . . . 4
     2.1.  PCEP Requests  . . . . . . . . . . . . . . . . . . . . . . 4
       2.1.1.  Qualification of PCEP Requests . . . . . . . . . . . . 4
       2.1.2.  Multi-domain Objective Functions . . . . . . . . . . . 5
       2.1.3.  Multi-domain Metrics . . . . . . . . . . . . . . . . . 6
     2.2.  Parent PCE Capability Discovery  . . . . . . . . . . . . . 6
     2.3.  PCE Domain and PCE ID Discovery  . . . . . . . . . . . . . 6
   3.  PCEP Extensions (Encoding) . . . . . . . . . . . . . . . . . . 6
     3.1.  OPEN Object  . . . . . . . . . . . . . . . . . . . . . . . 6
       3.1.1.  OF Codes . . . . . . . . . . . . . . . . . . . . . . . 6
       3.1.2.  OPEN Object Flags  . . . . . . . . . . . . . . . . . . 7
       3.1.3.  Domain-ID TLV  . . . . . . . . . . . . . . . . . . . . 7
       3.1.4.  PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 9
     3.2.  RP object  . . . . . . . . . . . . . . . . . . . . . . . . 9
       3.2.1.  RP Object Flags  . . . . . . . . . . . . . . . . . . . 9
       3.2.2.  Domain-ID TLV  . . . . . . . . . . . . . . . . . . . . 9
     3.3.  Metric Object  . . . . . . . . . . . . . . . . . . . . . .10
     3.4.  PCEP-ERROR Object  . . . . . . . . . . . . . . . . . . . .10
       3.4.1.  Hierarchy PCE Error-Type . . . . . . . . . . . . . . .10
     3.5.  NO-PATH Object . . . . . . . . . . . . . . . . . . . . . .10
   4.  H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . .10
     4.1.  OPEN Procedure between Child PCE and Parent PCE  . . . . .11
     4.2.  Procedure to Obtain Domain Sequence  . . . . . . . . . . .11
   5.  Error Handling . . . . . . . . . . . . . . . . . . . . . . . .11
   6.  Manageability Considerations . . . . . . . . . . . . . . . . .12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .12
   9.  Contributing Authors . . . . . . . . . . . . . . . . . . . . .12
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .12
   11. Normative References . . . . . . . . . . . . . . . . . . . . .13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .13

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1.  Introduction

   [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can
   be used for computing end-to-end paths for inter-domain MPLS Traffic
   Engineering (TE) and GMPLS Label Switched Paths (LSPs).

   Within the hierarchical PCE architecture, the parent PCE is used to
   compute a multi-domain path based on the domain connectivity
   information.  A child PCE may be responsible for a single domain or
   multiple domains, it is used to compute the intra-domain path based
   on its domain topology information.

   The H-PCE end-to-end domain path computation procedure is described
   below:

   o  A path computation client (PCC) sends the inter-domain path
      computation requests to the child PCE responsible for its domain;

   o  The child PCE forwards the request to the parent PCE;

   o  The parent PCE computes the likely domain paths from the ingress
      domain to the egress domain;

   o  The parent PCE sends the intra-domain path computation requests
      (between the domain border nodes) to the child PCEs which are
      responsible for the domains along the domain path;

   o  The child PCEs return the intra-domain paths to the parent PCE;

   o  The parent PCE constructs the end-to-end inter-domain path based
      on the intra-domain paths;

   o  The parent PCE returns the inter-domain path to the child PCE;

   o  The child PCE forwards the inter-domain path to the PCC.

   In addition, the parent PCE may be requested to provide only the
   sequence of domains to a child PCE so that alternative inter-domain
   path computation procedures, including Per Domain (PD) [RFC5152] and
   Backwards Recursive Path Computation (BRPC) [RFC5441] may be used.

   This document defines the PCEP extensions for the purpose of
   implementing Hierarchical PCE procedures, which are described in
   [RFC6805].

1.1.  Scope



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   The following functions are out of scope of this document.

   o  Finding end point addresses;

   o  Parent Traffic Engineering Database (TED) methods;

   o  Domain connectivity;

   The document also uses a number of [editor notes] to describe options
   and alternative solutions.  These options and notes will be removed
   before publication once agreement is reached.

1.2.  Terminology

   This document uses the terminology defined in [RFC4655], [RFC5440]
   and the additional terms defined in section 1.4 of [RFC6805].

1.3.  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.  Requirements for H-PCE

   This section compiles the set of requirements of the PCEP protocol to
   support the H-PCE architecture and procedures.

   [RFC6805] identifies high-level requirements of PCEP extensions
   required to support the hierarchical PCE model.

2.1.  PCEP Requests

   The PCReq messages are used by a PCC or PCE to make a path
   computation request to a PCE.  In order to achieve the full
   functionality of the H-PCE procedures, the PCReq message needs to
   include:

   o  Qualification of PCE Requests.

   o  Multi-domain Objective Functions (OF).

   o  Multi-domain Metrics.

2.1.1.  Qualification of PCEP Requests

   As described in section 4.8.1 of [RFC6805], the H-PCE architecture
   introduces new request qualifications, which are:

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   o  It MUST be possible for a child PCE to indicate that a request it
      sends to a parent PCE should be satisfied by a domain sequence
      only, that is, not by a full end-to-end path.  This allows the
      child PCE to initiate a per-domain (PD) [RFC5152] or a backward
      recursive path computation (BRPC) [RFC5441].

   o  As stated in [RFC6805], section 4.5, if a PCC knows the egress
      domain, it can supply this information as the path computation
      request.  It SHOULD be possible to specify the destination domain
      information in a PCEP request, if it is known.

2.1.2.  Multi-domain Objective Functions

   For inter-domain path computation, there are two new objective
   functions which are defined in section 1.3.1 and 4.1 of [RFC6805]:

   o  Minimize the number of domains crossed.  A domain can be either an
      Autonomous System (AS) or an Internal Gateway Protocol (IGP) area
      depending on the type of multi-domain network hierarchical PCE is
      applied to.

   o  Disallow domain re-entry.[Editor's note: Disallow domain re-entry
      may not be an objective function, but an option in the request].

   During the PCEP session establishment procedure, the parent PCE needs
   to be capable of indicating the Objective Functions (OF) capability
   in the Open message.  This capability information may then be
   announced by child PCEs, and used for selecting the PCE when a PCC
   wants a path that satisfies one or multiple inter-domain objective
   functions.

   When a PCC requests a PCE to compute an inter-domain path, the PCC
   needs also to be capable of indicating the new objective functions
   for inter-domain path.  Note that a given child PCE may also act as a
   parent PCE.

   For the reasons described previously, new OF codes need to be defined
   for the new inter-domain objective functions.  Then the PCE can
   notify its new inter-domain objective functions to the PCC by
   carrying them in the OF-list TLV which is carried in the OPEN object.
   The PCC can specify which objective function code to use, which is
   carried in the OF object when requesting a PCE to compute an inter-
   domain path.

   The proposed solution may need to differentiate between the OF code
   that is requested at the parent level, and the OF code that is
   requested at the intra-domain (child domain).



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   A parent PCE MUST be capable of ensuring homogeneity, across domains,
   when applying OF codes for strict OF intra-domain requests.

2.1.3.  Multi-domain Metrics

   For inter-domain path computation, there are several path metrics of
   interest [Editor's note: Current framework only mentions metric
   objectives.  The metric itself should be also defined]:

   o  Domain count (number of domains crossed).

   o  Border Node count.

   A PCC may be able to limit the number of domains crossed by applying
   a limit on these metrics.

2.2.  Parent PCE Capability Discovery

   Parent and child PCE relationships are likely to be configured.
   However, as mentioned in [RFC6805], it would assist network operators
   if the child and parent PCE could indicate their H-PCE capabilities.

   During the PCEP session establishment procedure, the child PCE needs
   to be capable of indicating to the parent PCE whether it requests the
   parent PCE capability or not.  Also, during the PCEP session
   establishment procedure, the parent PCE needs to be capable of
   indicating whether its parent capability can be provided or not.

2.3.  PCE Domain and PCE ID Discovery

   A PCE domain is a single domain with an associated PCE.  Although it
   is possible for a PCE to manage multiple domains.  The PCE domain may
   be an IGP area or AS.

   The PCE ID is an IPv4 and/or IPv6 address that is used to reach the
   parent/child PCE.  It is RECOMMENDED to use an address that is always
   reachable if there is any connectivity to the PCE.

   The PCE ID information and PCE domain identifiers may be provided
   during the PCEP session establishment procedure or the domain
   connectivity information collection procedure.


3.  PCEP Extensions (Encoding)

3.1.  OPEN object

3.1.1.  OF Codes


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   This H-PCE experiment will be carried out using the following OF
   codes:

   o  MTD

      *  Name: Minimize the number of Transit Domains.

      *  Objective Function Code.

      *  Description: Find a path P such that it passes through the
         lnumber of transit domains.

   o  MBN

      *  Name: Minimize the number of border nodes.

      *  Objective Function Code.

      *  Description: Find a path P such that it passes through the
         least number of border nodes.

   o  DDR

      *  Name: Disallow Domain Re-entry (DDR)

      *  Objective Function Code.

      *  Description: Find a path P such that does not entry a domain
         more than once.

3.1.2.  OPEN Object Flags

   This H-PCE experiment will also require two OPEN object flags:

   o  Parent PCE Request bit (to be assigned by IANA, recommended bit
      0): if set, it would signal that the child PCE wishes to use the
      peer PCE as a parent PCE.

   o  Parent PCE Indication bit (to be assigned by IANA, recommended bit
      1): if set, it would signal that the PCE can be used as a parent
      PCE by the peer PCE.

3.1.3.  Domain-ID TLV

   The Domain-ID TLV for this H-PCE experiment is defined below:





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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Domain Type         |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Domain ID                               |
      //                                                             //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 1: Domain-ID TLV

   Domain Type (8 bits): Indicates the domain type.  Two types of domain
   are currently defined:

   o  Type=1: the Domain ID field carries an IGP Area ID.

   o  Type=2: the Domain ID field carries an AS number.

   Domain ID (variable): Indicates an IGP Area ID or AS number.  It can
   be 2 bytes, 4 bytes or 8 bytes long depending on the domain
   identifier used.

   [Editor's note: draft-dhody-pce-pcep-domain-sequence, section 3.2
   deals with the encoding of domain sequences, using ERO-subobjects.
   Work is ongoing to define domain identifiers for OSPF-TE areas, IS-IS
   area (which are variable sized), 2-byte and 4-byte AS number, and any
   other domain that may be defined in the future.  It uses RSVP-TE
   subobject discriminators, rather than new type 1/ type 2.  A domain
   sequence may be encoded as a route object.  The "VALUE" part of the
   TLV could follow common RSVP-TE subobject format:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0|    Type     |     Length    |         Reserved              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          AS Id (4 bytes)                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0|    Type     |     Length    |  AS Id (2 bytes)              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: Alternative Domain-ID TLV


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3.1.4.  PCE-ID TLV

   The type of PCE-ID TLV for this H-PCE experiment is defined below:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Address Type        |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                     PCE IP Address                          //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 3: PCE-ID TLV

   Address Type (16 bits): Indicates the address type of PCE IP Address.
   1 means IPv4 address type, 2 means IPv6 address type.

   PCE IP Address: Indicates the reachable address of a PCE.

   [Editor's note: [RFC5886] already defines the PCE-ID object.  If a
   semantically equivalent PCE-ID TLV is needed (to avoid modifying
   message grammars to include the object), it can align with the PCEP
   object: in any case, the length (4 / 16 bytes) can be used to know
   whether it is an IPv4 or an IPv6 PCE, the address type is not
   needed.]

3.2.  RP object

3.2.1.  RP Object Flags

   The following RP object flags are defined for this H-PCE experiment:

   o  Domain Path Request bit: if set, it means the child PCE wishes to
      get the domain sequence.

   o  Destination Domain Query bit: if set, it means the parent PCE
      wishes to get the destination domain ID.

3.2.2.  Domain-ID TLV

   The format of this TLV is defined in Section 3.1.3.  This TLV can be
   carried in an OPEN object to indicate a (list of) managed domains, or
   carried in a RP object to indicate the destination domain ID when a
   child PCE responds to the parent PCE's destination domain query by a
   PCRep message.



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   [Editors note.  In some cases, the Parent PCE may need to allocate a
   node which is not necessarily the destination node.]

3.3.  Metric Object

   There are two new metrics defined in this document for H-PCE:

   o  Domain count (number of domains crossed).

   o  Border Node Count (number of border nodes crossed).

3.4.  PCEP-ERROR object

3.4.1.  Hierarchy PCE Error-Type

   A new PCEP Error-Type is used for this H-PCE experiment and is
   defined below:

   +------------+------------------------------------------------------+
   | Error-Type | Meaning                                              |
   +------------+------------------------------------------------------+
   | 19         | H-PCE error Error-value=1: parent PCE capability     |
   |            | cannot be provided                                   |
   +------------+------------------------------------------------------+

                             H-PCE error table

3.5.  NO-PATH Object

   To communicate the reason(s) for not being able to find a multi-
   domain path or domain sequence, the NO-PATH object can be used in the
   PCRep message.  [RFC5440] defines the format of the NO-PATH object.
   The object may contain a NO-PATH-VECTOR TLV to provide additional
   information about why a (domain) path computation has failed.

   Three new bit flags are defined to be carried in the Flags field in
   the NO-PATH-VECTOR TLV carried in the NO-PATH Object.

   o  Bit 23: When set, the parent PCE indicates that destination domain
      unknown;

   o  Bit 22: When set, the parent PCE indicates unresponsive child
   PCE(s);

   o  Bit 21: When set, the parent PCE indicates no available resource
      available in one or more domain(s).


4.  H-PCE Procedures

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4.1.  OPEN Procedure between Child PCE and Parent PCE

   If a child PCE wants to use the peer PCE as a parent, it can set the
   parent PCE request bit in the OPEN object carried in the Open message
   during the PCEP session creation procedure.  If the peer PCE does not
   want to provide the parent function to the child PCE, it must send a
   PCErr message to the child PCE and clear the parent PCE indication
   bit in the OPEN object.

   If the parent PCE can provide the parent function to the peer PCE, it
   may set the parent PCE indication bit in the OPEN object carried in
   the Open message during the PCEP session creation procedure.

   The PCE may also report its PCE ID and list of domain ID to the peer
   PCE by specifying them in the PCE-ID TLV and List of Domain-ID TLVs
   in the OPEN object carried in the Open message during the PCEP
   session creation procedure.

   The OF codes defined in this document can be carried in the OF-list
   TLV of the OPEN object.  If the OF-list TLV carries the OF codes, it
   means that the PCE is capable of implementing the corresponding
   objective functions.  This information can be used for selecting a
   proper parent PCE when a child PCE wants to get a path that satisfies
   a certain objective function.

   When a specific child PCE sends a PCReq to a peer PCE that requires
   parental activity and the peer PCE does not want to act as the parent
   for it, the peer PCE should send a PCErr message to the child PCE and
   specify the error-type (IANA) and error-value (1) in the PCEP-ERROR
   object.

4.2.  Procedure to obtain Domain Sequence

   If a child PCE only wants to get the domain sequence for a multi-
   domain path computation from a parent PCE, it can set the Domain Path
   Request bit in the RP object carried in a PCReq message.  The parent
   PCE which receives the PCReq message tries to compute a domain
   sequence for it.  If the domain path computation succeeds the parent
   PCE sends a PCRep message which carries the domain sequence in the
   ERO to the child PCE.  The domain sequence is specified as AS or AREA
   ERO sub-objects (type 32 for AS [RFC3209] or a to-be-defined IGP area
   type).  Otherwise it sends a PCReq message which carries the NO-PATH
   object to the child PCE.


5.  Error Handling

   A PCE that is capable of acting as a parent PCE might not be
   configured or willing to act as the parent for a specific child PCE.

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   This fact could be determined when the child sends a PCReq that
   requires parental activity (such as querying other child PCEs), and
   could result in a negative response in a PCEP Error (PCErr) message
   and indicate the hierarchy PCE error types.

   Additionally, the parent PCE may fail to find the multi-domain path
   or domain sequence due to one or more of the following reasons:

   o  A child PCE cannot find a suitable path to the egress;

   o  The parent PCE do not hear from a child PCE for a specified time;

   o  The objective functions specified in the path request cannot be
      met.

   In this case, the parent PCE MAY need to send a negative path
   computation reply specifying the reason.  This can be achieved by
   including NO-PATH object in the PCRep message.  Extension to NO-PATH
   object is needed to include the aforementioned reasons.


6.  Manageability Considerations

   TBD.


7.  IANA Considerations

   Due to the experimental nature of this draft no IANA requests are
   made.


8.  Security Considerations

   To be added.


9.  Contributing Authors

      Xian Zhang
      Huawei
      zhang.xian@huawei.com


10.  Acknowledgments

   To be added.



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11.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

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

   [RFC5152]  Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain
              Path Computation Method for Establishing Inter-Domain
              Traffic Engineering (TE) Label Switched Paths (LSPs)",
              RFC 5152, February 2008.

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

   [RFC5441]  Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A
              Backward-Recursive PCE-Based Computation (BRPC) Procedure
              to Compute Shortest Constrained Inter-Domain Traffic
              Engineering Label Switched Paths", RFC 5441, April 2009.

   [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.

   [RFC6805]  King, D. and A. Farrel, "The Application of the Path
              Computation Element Architecture to the Determination of a
              Sequence of Domains in MPLS and GMPLS", RFC 6805,
              November 2012.


Authors' Addresses

   Fatai Zhang (editor)
   Huawei
   Huawei Base, Bantian, Longgang District
   Shenzhen,   518129
   China

   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com




Zhang, et al.              February 18, 2014               [Page 13]


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   Quintin Zhao
   Huawei
   125 Nagog Technology Park
   Acton, MA  01719
   US

   Phone:
   Email: qzhao@huawei.com


   Oscar Gonzalez de Dios (editor)
   Telefonica I+D
   Don Ramon de la Cruz 82-84
   Madrid,   28045
   Spain

   Phone: +34913128832
   Email: ogondio@tid.es


   Ramon Casellas
   CTTC
   Av. Carl Friedrich Gauss n.7
   Castelldefels,   Barcelona
   Spain

   Phone: +34 93 645 29 00
   Email: ramon.casellas@cttc.es


   Daniel King
   Old Dog Consulting
   UK

   Phone:
   Email: daniel@olddog.co.uk














Zhang, et al.              February 18, 2014               [Page 14]

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