Internet DRAFT - draft-pce-traffic-prediction

draft-pce-traffic-prediction







PCE Working Group                                            B. Yan, Ed.
Internet-Draft                                              Y. Zhao, Ed.
Intended status: Standards Track                            W. Wang, Ed.
Expires: July 7, 2018                                         X. Yu, Ed.
                                                           J. Zhang, Ed.
                                                                    bupt
                                                         January 3, 2018


                 PCEP Extension for Traffic Prediction
                    draft-pce-traffic-prediction-01

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.
   It is helpful for PCEs to calculate more reasonable path if PCCs can
   provide information of traffic prediction.  This memo specifies
   extensions to PCEP that allow PCE to request prediction-related
   information.

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 July 7, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Overview of Protocol Extensions . . . . . . . . . . . . . . .   4
     5.1.  Capability Advertisement  . . . . . . . . . . . . . . . .   4
     5.2.  New Messages  . . . . . . . . . . . . . . . . . . . . . .   4
     5.3.  Normal Communication Procedure  . . . . . . . . . . . . .   5
       5.3.1.  Initialization Phase  . . . . . . . . . . . . . . . .   5
       5.3.2.  Traffic Prediction Request Sent by a PCE to a PCC . .   6
       5.3.3.  Traffic Prediction Reply Sent by a PCC to a PCE . . .   6
     5.4.  Error Reporting . . . . . . . . . . . . . . . . . . . . .   7
   6.  PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  The TPReq Message . . . . . . . . . . . . . . . . . . . .   8
     6.2.  The TPRep Message . . . . . . . . . . . . . . . . . . . .   8
     6.3.  The PAUpd Message . . . . . . . . . . . . . . . . . . . .   8
     6.4.  The PCErr Message . . . . . . . . . . . . . . . . . . . .   8
   7.  Object Formats  . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  OPEN Object . . . . . . . . . . . . . . . . . . . . . . .   8
       7.1.1.  Traffic Prediction Capability TLV . . . . . . . . . .   8
     7.2.  No Prediction Object  . . . . . . . . . . . . . . . . . .   9
     7.3.  Prediction Tracker Object . . . . . . . . . . . . . . . .   9
       7.3.1.  Traffic Prediction Identifier TLV . . . . . . . . . .   9
       7.3.2.  Traffic Prediction State TLV  . . . . . . . . . . . .   9
       7.3.3.  Prediction Attribute TLV  . . . . . . . . . . . . . .  10
     7.4.  Prediction Requirement Object . . . . . . . . . . . . . .  10
       7.4.1.  Prediction Sequence TLV . . . . . . . . . . . . . . .  10
       7.4.2.  Prediction Expired Time TLV . . . . . . . . . . . . .  10
     7.5.  Prediction Information Object . . . . . . . . . . . . . .  10
       7.5.1.  Link Prediction TLV . . . . . . . . . . . . . . . . .  10
     7.6.  Prediction Area Object  . . . . . . . . . . . . . . . . .  11
       7.6.1.  Link TLV  . . . . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  12
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12





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1.  Introduction

   [RFC5440] provides the Path Computation Element Communication
   Protocol (PCEP).  PCEP defines the communication between a Path
   Computation Client (PCC) and a Path Control Element (PCE), or between
   PCE and PCE, enabling computation of Multiprotocol Label Switching
   (MPLS) for Traffic Engineering Label Switched Path (TE LSP)
   characteristics.

   For calculating proper path according to the tendency of traffic
   distribution in specific network area, this memo introduce a
   mechanism to make PCE able to get predicted information from PCC for
   specific path computation request.

2.  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].

3.  Terminology

   This memo uses the following terms defined in [RFC5440]: PCC, PCE,
   PCEP Speaker.

4.  Motivation

   Along the network scale expansion and incremental diversity of
   network equipments, the network complexity increases exponentially,
   then the path computation in network becomes harder.  Considering
   both traffic distribution at present and its trend in future in time
   dimension, PCE could make better decision to reduce network
   congestion, and optimize network performance.  There are many
   effective methods which can complete traffic prediction accurately,
   however, the key point is where the past data set for prediction to
   be saved.  In some scenarios, as a requester, PCC holds much more
   information than the responser PCE which can be used to do
   prediction, and not limited within single informations such as
   occupied bandwidth on specific network links.

   Another reason for this memo is the tradeoff between PCCs and PCEs on
   storage resource and computing resource.  If vendor choose
   computational resource intensive methods to predict, such as machine
   learning, there should be much more computing resource request.







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5.  Overview of Protocol Extensions

5.1.  Capability Advertisement

   During PCEP Initialization Phase, PCEP Speakers (PCC or PCE)
   advertise their support of extensions for traffic prediction.  A PCEP
   Speaker includes the "Traffic Prediction Capability" TLV, described
   in Section 7.1.1, in the OPEN Object to advertise its support for
   traffic prediction extensions.  The Traffic Prediction Capability TLV
   includes the 'Prediction Capability' Flag that indicates whether the
   PCEP Speaker supports prediction operations, and other Flags
   indicates further capabilities.

   The PCEP extensions for traffic prediction MUST NOT be used if one or
   both PCEP Speakers have not included the Traffic Prediction
   Capability TLV in their respective OPEN message.  If the PCEP Speaker
   on the PCC supports the extensions of this memo but does not set this
   flag as 1, then if the PCC receive TPReq message from the PCE, it
   MUST generate a PCErr with error-type ..., error-value... and it
   SHOULD terminate the PCEP session.

   this block should describe the error condition!!!

5.2.  New Messages

   This memo define the following new PCEP messages:

   Traffic Prediction Request Message for Path Computation (TPReq): A
   PCEP message sent by a PCE to a PCC to request prediction for subset
   of whole network which contains specific network elements and network
   links.  Each TPReq message MUST contain the predicted time sequence
   and expired time, MAY contain the sub-network description to be
   predicted and requirement for prediction accuracy, A PCE MAY send
   traffic prediction request message to a PCC at any time as long as it
   consideres this operation necessary.  The details of TPReq message is
   described in Section 6.1.

   Traffic Prediction Reply Message for Path Computation (TPRep): A PCEP
   message sent by a PCC to a PCE to reply specific TPReq message, which
   contains prediction results for specific sub-network.  Each TPRep
   message MUST contain predicted sub-network description, and related
   prediction information sequence.  A PCC sends traffic prediction
   reply message if and only if it received related TPReq message.  The
   details of TPRep message is described in Section 6.2.

   Precdiction Attribute Update Message for Path Computation (PAUpd): A
   PCEP message sent by a PCC to a PCE to indicate the scope changes of
   prediction attributes.  Each PAUpd MAY contain sub-network



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   description, prediction time scope, and prediction accuracy scope.  A
   PCC MUST send prediction attribute update message to a PCE immediatly
   after OPEN message defined in [RFC5440], or some attributes has been
   changed.  The details of PAUpd message is described in Section 6.3.

5.3.  Normal Communication Procedure

5.3.1.  Initialization Phase

   In initialization phase of a PCEP session, the Traffic Prediction
   Capability TLV in OPEN message sent by PCC indicates the capability
   about traffic prediction that PCC can do, while the TLV sent by PCE
   indicates the requests about traffic prediction that PCE MAY make.
   If any flag in Traffic Prediction Capability TLV was set to 1 by both
   sides, then they reached an agreement about the function advertised
   by this flag.  However, if P flag was not set to 1 by both sides,
   then all other flags SHOULD NOT be parsed; and if not, PCC MUST send
   a PAUpd message to PCE to initialize the scope of variable prediction
   attributes with TPS-ID (see Section 7.3.2) set to 1.  After received
   the first PAUpd message from PCC, PCE MUST send a TPReq message to
   confirm it with TPS-ID set to 1, too.  The Initialization Phase is
   shown in Figure 1.

                  +-+-+                 +-+-+
                  |PCC|                 |PCE|
                  +-+-+                 +-+-+
                    |                     |
                    | Open msg            |
                    |--------             |
   (Exchange Traffic|        \   Open msg |
    Prediction      |         \  ---------|
    Capability)     |          \/         |
                    |          /\         |
                    |         /  -------->|
                    |        /            |
                    |<------              |
                    |                     |
                    | PAUpd msg           |
   (Initialize      |-------------------->|
    Scop of         |                     |
    Attributes)     |           TPReq msg |
                    |<--------------------|
                    |                     |

                      Figure 1: Initialization Phase






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5.3.2.  Traffic Prediction Request Sent by a PCE to a PCC

   Once a PCE has sucessfully established a PCEP session with one or
   more PCEs, if a traffic prediction event is triggered that requires
   the traffic prediction results of a subset of network, the PCE first
   selects one or more PCCs which have advertised they can predict
   traffic for the subset.

   Once the PCE has selected a PCC, it sends a TPReq message to the PCE.
   For example, "Predict the traffic in 5 minutes with link=link_id...".
   Each request is uniquely identified by a tp-id (See Section 7.3.1)
   number and PCC-PCE address pair.  The process is shown in Figure 2.

   Details about the TPReq message can be found in Section 6.1.

                 +-+-+                  +-+-+
                 |PCC|                  |PCE|
                 +-+-+                  +-+-+
                   |                      | 1)Traffic Prediction Event
                   |                      | 2)PCC Selection
                   |                      | 3)Traffic Prediction Request
                   |<--- TPReq message----|   Sent to the Selected PCC
                   |                      |
                   |                      |

                   Figure 2: Traffic Prediction Request

5.3.3.  Traffic Prediction Reply Sent by a PCC to a PCE

   After receiving a traffic prediction request form a PCE, the PCC
   triggers a prediction computation, If the PCC manages to predict
   traffic in time that satisfies the set of required constraints, the
   PCC returns the result to the requesting PCE.  The process is shown
   in Figure 3.

















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                          +-+-+                  +-+-+
                          |PCC|                  |PCE|
                          +-+-+                  +-+-+
                            |                      |
                            |                      |
                            |                      |
                            |<--- TPReq message----|
      1) Traffic Prediction |                      |
         Request Received   |                      |
      2) Predict Succefully |                      |
      3) Predicted Result   |                      |
         Sent to the PCE    |                      |
                            |---- TPRep message--->|

               Figure 3: Traffic Prediction Reply (Success)

   However, if the PCC can not predict traffic in time, it SHOULD
   provide the reason let to failure by sending a TPRep message with No-
   Prediction object (See Section 7.2).  Upon receiving a reply like
   this, a PCE MAY decide to resend a modified request or take any other
   appropriate action.

                           +-+-+                  +-+-+
                           |PCC|                  |PCE|
                           +-+-+                  +-+-+
                             |                      |
                             |                      |
                             |                      |
                             |<--- TPReq message----|
      1) Traffic Prediction  |                      |
         Request Received    |                      |
      2) Predict Unsuccefully|                      |
      3) Cause of Failure    |                      |
         Sent to the PCE     |                      |
                             |---- TPRep message--->|

               Figure 4: Traffic Prediction Reply (Failure)

   Details about the TPRep message can be found in Section 6.2.

5.4.  Error Reporting

6.  PCEP Messages








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6.1.  The TPReq Message

      <TPReq Message> ::= <Common Header>
                               <PCE-prediction-request>
   Where:

      <PCE-prediction-request> ::= <prediction-tracker>
                                   [<prediction-area>]
                                   <prediction-requirement>

6.2.  The TPRep Message

   <TPRep Message> ::= <Common Header>
                            <PCC-prediction-reply>
Where:

   <PCC-prediction-reply> ::= <prediction-tracker>
                              ([<prediction-info-list>] | no-prediction)

   <prediction-info-list> ::= <prediction-info>
                              [<prediction-info-list>]

6.3.  The PAUpd Message

              <PAUpd Message> ::= <Common Header>
                               <prediction-tracker>

6.4.  The PCErr Message



7.  Object Formats

7.1.  OPEN Object

7.1.1.  Traffic Prediction Capability TLV

    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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Flags                       |A|S|P|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 5: The Traffic Prediction Capability TLV format





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   The type (16 bits) of the TLV is to be assigned by IANA.  The length
   field is 16 bit-long and has a fixed value of 4.

   The value comprises several field - Flags (32 bits) :

   A (PREDICTION-ACCURACY-CAPABILITY - 1 bit): if set to 1 by a PCC, the
   A Flag indicates that the PCC can measure the accuracy of prediction
   results; if set to 1 by a PCE, the A Flag indicates that the PCE is
   capable of requesting prediction results satisfying the lowest
   accuracy.

   S (PREDICTION-TIME-SEQUENCE-CAPABILITY - 1 bit): if set to 1 by a
   PCC, the S Flag indicates that the PCC can provide a sequence of
   prediction in time dimension; if set to 1 by a PCE, the S Flag
   indicates that the PCE is capable of requesting a sequence prediction
   results.

   P (PREDICTION-CAPABILITY - 1 bit): if set to 1 by a PCC, the P Flag
   indicates that the PCC can provide traffic prediction ability to PCE;
   if set to 1 by a PCE, the P Flag indicates that the PCE is capable of
   requesting traffic prediction.  The PREDICTION-CAPABILITY Flag must
   be advertised by both a PCC and a PCE to allow TPReq, TPRep, and
   PAUpd messages on a PCEP session.  If P Flag is set to 0, other Flags
   in this TLV don't make sense.

7.2.  No Prediction Object

7.3.  Prediction Tracker Object

7.3.1.  Traffic Prediction Identifier TLV

    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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             TP-ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.3.2.  Traffic Prediction State TLV

    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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             TPS-ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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7.3.3.  Prediction Attribute TLV

7.4.  Prediction Requirement Object

7.4.1.  Prediction Sequence TLV

    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=[TBD]      |            Length=8N          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Datetime                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Datetime                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                             ......                          //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Datetime                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.4.2.  Prediction Expired Time TLV

    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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Datetime                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.5.  Prediction Information Object

7.5.1.  Link Prediction TLV













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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Type=[TBD]      |            Length=16          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             LS-ID                             |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Datetime                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Predicted Speed (kb/s)                  |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.6.  Prediction Area Object

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Object-Class  |   OT  |Res|P|I|   Object Length (bytes)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Flag                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                          Link TLvs                          //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 6: Prediction Area Object Format

7.6.1.  Link TLV

    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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             LS-ID                             |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 7: Link TLV Format








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8.  IANA Considerations

9.  Security Considerations

10.  Acknowledgments

11.  Contributors

12.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

Authors' Addresses

   Boyuan Yan (editor)
   Beijing University of Posts and Telecommunications
   Xitucheng Road
   Beijing, Haidian Dist  100876
   China

   Phone: +86-18810528290
   Email: yanboyuan@bupt.edu.cn


   Yongli Zhao (editor)
   Beijing University of Posts and Telecommunications
   Xitucheng Road
   Beijing, Haidian Dist  100876
   China

   Phone: +86-13811761857
   Email: yonglizhao@bupt.edu.cn











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   Wei Wang (editor)
   Beijing University of Posts and Telecommunications
   Xitucheng Road
   Beijing, Haidian Dist  100876
   China

   Phone: +86-15210830183
   Email: weiw@bupt.edu.cn


   Xiaosong Yu (editor)
   Beijing University of Posts and Telecommunications
   Xitucheng Road
   Beijing, Haidian Dist  100876
   China

   Phone: +86-13811731723
   Email: xiaosongyu@bupt.edu.cn


   Jie Zhang (editor)
   Beijing University of Posts and Telecommunications
   Xitucheng Road
   Beijing, Haidian Dist  100876
   China

   Phone: +86-13911060930
   Email: lgr24@bupt.edu.cn























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