Network Working Group                                             YF. Ji
Internet-Draft                                                  WW. Bian
Intended status: Informational                                  HX. Wang
Expires: April 21, 2011                                        SG. Huang
                                                                    BUPT
                                                               GY. Zhang
                                                                    CATR
                                                        October 18, 2010


      Performance Measurement Metrics of Label Switched Path (LSP)
         Establishment in Multi-Layer and Multi-Domain Networks
                        draft-jiyf-ccamp-lsp-00

Abstract

   As the increment of network scale and the variety of user request,
   traditional networks are to be partitioned into multi-layer and
   multi-domain networks for the purpose of better management.  In
   multi-layer and multi-domain networks, various user requests are
   mapped into different LSPs, and the performance of a LSP is of great
   importance for the users.  Therefore, the LSP is necessary to be
   evaluated as soon as it is established.  For the purpose of judging
   whether a LSP establishment meets a user requirement or not, typical
   performance measurement metrics need to be proposed.  In this
   document, LSP establishment delay and bit error ratio (BER) which are
   serving as the typical performance measurement metrics are
   illustrated, and the definition and methodologies are proposed.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 21, 2011.

Copyright Notice




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   Copyright (c) 2010 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
   (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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Overview of the Performance Measurement Metrics of LSP
       Establishment  . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Overview of LSP Establishment Delay  . . . . . . . . . . .  4
     2.2.  Overview of LSP Establishment BER  . . . . . . . . . . . .  5
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  LSP Establishment Delay in Multi-Layer and Multi-Domain
       Networks . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Measurement Metric Parameters  . . . . . . . . . . . . . .  6
     4.2.  Definition . . . . . . . . . . . . . . . . . . . . . . . .  7
       4.2.1.  A Definition in Single Layer and Multi-Domain
               Networks . . . . . . . . . . . . . . . . . . . . . . .  7
       4.2.2.  A Definition in Multi-Layer and Multi-Domain
               Networks . . . . . . . . . . . . . . . . . . . . . . .  8
       4.2.3.  A Definition in Other Networks . . . . . . . . . . . .  9
     4.3.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . 10
   5.  LSP Establishment BER in Multi-Domain Networks . . . . . . . . 10
     5.1.  General Assumptions  . . . . . . . . . . . . . . . . . . . 10
     5.2.  Definition . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Definition . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.2.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . 11
       6.2.1.  LSP Establishment Delay  . . . . . . . . . . . . . . . 11
       6.2.2.  LSP Establishment BER  . . . . . . . . . . . . . . . . 12
   7.  Protocol Extension Requirements  . . . . . . . . . . . . . . . 12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     10.2. Informative References . . . . . . . . . . . . . . . . . . 14



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   Appendix A.  Other Authors . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15

















































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1.  Introduction

   As the increment of network scale and the variety of user request,
   traditional networks are to be partitioned into multi-layer and
   multi-domain networks for the purpose of better management.  User
   requests are mapped into various LSPs in multi-layer and multi-domain
   networks.  Different users have different requirements, thus, LSP
   establishment is also different in order to satisfy different user
   requirements.  To measure whether a LSP establishment meets a user
   requirement or not, objective performance measurement metrics and
   methodologies should be proposed.  In this document, LSP
   establishment delay and BER are considered as the objective
   performance measurement metrics.

   This document defines the performance measurement metrics and
   methodologies that can be used to measure the LSP establishment
   quality in multi-layer and multi-domain networks.

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].

1.2.  Terminology

   BER: Bit Error Ratio.

   BRPC: Backward-Recursive PCE-Based Computation.

   GMPLS: Generalized Multiprotocol Label Switching.

   LID: Local Information Database.

   LSP: Label Switched Path.

   PCE: Path Computation Element.

   VSPT: Virtual Shortest Path Tree.


2.  Overview of the Performance Measurement Metrics of LSP Establishment

2.1.  Overview of LSP Establishment Delay

   In the process of LSP establishment, delay is considered as one of
   the main performance measurement metrics.  In the background of GMPLS
   networks, LSPs that have different granularities are established.



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   Two typical LSP establishment methods are explained here: LSP nesting
   and LSP stitching.  LSP nesting corresponds to the LSP establishment
   in the multi-layer networks, while LSP stitching corresponds to the
   LSP establishment in the same layer networks.  LSP establishment
   delay in above two methods is divided into two parts: path
   computation delay and LSP setup delay.

   In multi-layer and multi-domain networks, owing to the complexity of
   path computation, PCE-based path computation scheme is considered.
   Furthermore, optimal inter-domain LSP can not be got on a per-domain
   basis, so BRPC method is considered to complete inter-domain path
   computation in this document.  Path computation delay is
   approximately defined from the time that source node sends the path
   computation request to the time that source node receives the optimal
   path computation result.

   In multi-layer and multi-domain networks, end-to-end LSP setup is
   mainly considered in this document.  LSP setup delay is approximately
   defined from the time that source node sends the LSP setup message to
   the time that source node receives the confirm message of successful
   reservation.

2.2.  Overview of LSP Establishment BER

   To measure the performance of LSP establishment, physical impairment
   parameter is one of the main performance measurement metrics, and BER
   is the main embodiment among all of physical impairment parameters,
   so BER is considered as one of the performance measurement metrics in
   the process of LSP establishment.

   In the measurement process of LSP establishment BER, BRPC method is
   used for the path computation and end-to-end way is used for the LSP
   setup, and BER is evaluated in the LSP setup process.  The
   approximate procedure is as follows: the signaling collects some
   physical parameter information from source node to destination node,
   and destination node evaluates the LSP performance combining
   corresponding physical parameter information, then destination node
   returns Resv message to establish LSP if the LSP performance meets
   the user request, otherwise, LSP establishment fails.


3.  Motivation

   LSP establishment delay in multi-layer and multi-domain networks is
   useful for several reasons:

   o  Average LSP establishment delay is an important performance
      measurement metric that MAY reflect the scalability ability of a



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      multi-layer and multi-domain network.  Longer LSP establishment
      delay with the increasing numbers of domains and nodes or traffic
      volumes will most likely show that the network scalability is not
      good, especially when the LSP establishment delay surpasses
      linearity curve.

   o  LSP establishment delay is an important performance measurement
      metric that MAY reflect the quality of LSP establishment in multi-
      layer and multi-domain networks.  Longer LSP establishment delay
      will most likely show that the quality of LSP establishment is not
      good.

   o  The values in the samples of LSP establishment delay MAY serve as
      an early indicator to provide references on whether to accept a
      service request that has stringent establishment delay requirement
      or not.

   LSP establishment BER in multi-domain networks is useful for several
   reasons:

   o  LSP establishment BER is an important performance measurement
      metric that MAY reflect the quality of LSP establishment in multi-
      domain networks.  Higher LSP establishment BER will most likely
      show that the quality of LSP establishment is not good.

   o  The values in the samples of LSP establishment BER MAY serve as an
      early indicator to provide references on whether to accept a
      service request that has stringent establishment BER requirement
      or not.


4.  LSP Establishment Delay in Multi-Layer and Multi-Domain Networks

   This section integrally defines a performance measurement metric
   named LSP establishment delay in multi-layer and multi-domain
   networks.

4.1.  Measurement Metric Parameters

   o  ID0, the source node ID.

   o  ID1, the destination node ID.

   o  T0, a time when the path computation is attempted.

   o  T1, a time when the LSP setup is attempted.





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4.2.  Definition

4.2.1.  A Definition in Single Layer and Multi-Domain Networks

   In single layer and multi-domain networks, LSP can be established
   using LSP stitching method.  In this method, the LSP establishment
   delay is collected from two parts: path computation delay and LSP
   setup delay.

   The path computation from source node ID0 to destination node ID1
   mainly includes following process: source node ID0 sends a path
   computation Req message to the PCE responsible for the source domain.
   This request is forwarded between PCEs, domain-by-domain, to the PCE
   responsible for the destination domain.  The PCE in the destination
   domain creates a set of optimal paths from all of the domain ingress
   nodes to the destination node.  This set is represented as a tree of
   potential paths called a VSPT, and the PCE passes it back to the
   previous PCE in a Rep message.  Each PCE in turn adds to the VSPT and
   passes it back until the PCE in the source domain uses the VSPT to
   select an optimal end-to-end path from the tree, and returns the path
   to the source node.  The BRPC procedure above makes an assumption
   that the sequence of domains is known in advance.  The path
   computation delay from source node ID0 to destination node ID1 at T0
   is dT means that source node ID0 sends the path computation Req
   message to the PCE responsible for the source domain at time T0, and
   that source node receives the path computation results from the PCE
   responsible for the source domain at time T0+dT.

   The LSP setup from source node ID0 to destination node ID1 mainly
   includes following process: source node ID0 firstly sends the LSP
   setup message, which includes two procedures: determining if service
   layer exist and sending Path message.  The detailed procedures are as
   follows: source node ID0 firstly determine if service layers exist.
   If service layer exists, source node needs to finishes the switch
   reversing function, then sends Path message to the next node to
   reserve resource, and the next node carries out the same function
   like source node until Path message arrives at destination node ID1.
   Subsequently, destination node returns Resv message to the previous
   node until source node receives the Resv message.  If service layer
   does not exist, source node firstly establishes a service layer using
   signaling, then source node sends Path message to determine an
   available wavelength set until Path message arrives at destination
   node.  If the available wavelength set exists, then destination node
   sends Resv message to source node to reserve available resources, and
   the switch reversing function of corresponding nodes are also
   finished simultaneously, otherwise, PathErr message is returned to
   the source node.  In the circumstance of service layer exists, any
   node which Path message traverses detects the unavailable service



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   layer, then PathErr message is also returned to the source node.  The
   LSP setup delay from source node ID0 to destination node ID1 at T1 is
   dT means that source node ID0 sends the LSP setup message at time T1,
   and that source node receives the corresponding Resv message from
   destination node ID1 at time T1+dT.

   The value of LSP establishment delay in single layer and multi-domain
   networks is a real number of milliseconds.

   There is another case in which source node does not receive the
   optimal path computation result or the LSP confirm message of
   successful reservation within a reasonable period of time, and the
   value of LSP establishment delay in this case is marked undefined.

4.2.2.  A Definition in Multi-Layer and Multi-Domain Networks

   In multi-layer and multi-domain networks, LSP can be established
   using LSP nesting method.  In this method, the LSP establishment
   delay is collected from two parts: path computation delay and LSP
   setup delay.

   The path computation from source node ID0 to destination node ID1
   mainly includes following process: source node ID0 sends a path
   computation Req message to the PCE responsible for the source domain.
   This request is forwarded between PCEs, domain-by-domain, to the PCE
   responsible for the destination domain.  The PCE in the destination
   domain creates a set of optimal paths from all of the domain ingress
   nodes to the destination node.  This set is represented as a tree of
   potential paths called a VSPT, and the PCE passes it back to the
   previous PCE in a Rep message.  Each PCE in turn adds to the VSPT and
   passes it back until the PCE in the source domain uses the VSPT to
   select an optimal end-to-end path from the tree, and returns the path
   to the source node.  The BRPC procedure above makes an assumption
   that the sequence of domains is known in advance.  The path
   computation delay from source node ID0 to destination node ID1 at T0
   is dT means that source node ID0 sends the path computation Req
   message to the PCE responsible for the source domain at time T0, and
   that source node receives the path computation results from the PCE
   responsible for the source domain at time T0+dT.

   The LSP setup from source node ID0 to destination node ID1 mainly
   includes following process: source node ID0 firstly sends the LSP
   setup message, which includes two procedures: determining if service
   layer exist and sending Path message.  The detailed procedures are as
   follows: source node ID0 firstly determine if service layers exist.
   If service layer exists, source node needs to finishes the switch
   reversing function, then sends Path message to the next node to
   reserve resource, and the next node carries out the same function



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   like source node until Path message arrives at destination node ID1.
   Subsequently, destination node returns Resv message to the previous
   node until source node receives the Resv message.  If the capacity of
   existing service layer is not fully occupied, then fine granularity
   service that capacity is no more than remaining capacity of existing
   service layer can still be accepted in this service layer.  If
   service layer does not exist, source node firstly establishes a
   service layer using signaling, then source node sends Path message to
   determine an available wavelength set until Path message arrives at
   destination node.  If the available wavelength set exists, then
   destination node sends Resv message to source node to reserve
   available resources, and the switch reversing function of
   corresponding nodes are also finished simultaneously, otherwise,
   PathErr message is returned to the source node.  In the circumstance
   of service layer exists, any node which Path message traverses
   detects the unavailable service layer, then PathErr message is also
   returned to the source node.  If the capacity of new established
   service layer is not fully occupied, then fine granularity service
   that capacity is no more than remaining capacity of new established
   service layer can still be accepted in this service layer.  The LSP
   setup delay from source node ID0 to destination node ID1 at T1 is dT
   means that source node ID0 sends the LSP setup message at time T1,
   and that source node receives the corresponding Resv message from
   destination node ID1 at time T1+dT.

   The value of LSP establishment delay in multi-layer and multi-domain
   networks is a real number of milliseconds.

   There is another case in which source node does not receive the
   optimal path computation result or the LSP confirm message of
   successful reservation within a reasonable period of time, and the
   value of LSP establishment delay in this case is marked undefined.

4.2.3.  A Definition in Other Networks

   There are two types of other networks: single layer and single domain
   networks and multi-layer and single domain networks.  The definition
   in single layer and single domain networks is similar to the
   definition in single layer and multi-domain networks, and the
   difference is that inter-domain LSP establishment process in single
   layer and single domain networks is not considered.  Accordingly, the
   definition in multi-layer and single domain networks is similar to
   the definition in multi-layer and multi-domain networks, and the
   difference is that inter-domain LSP establishment process in multi-
   layer and single domain networks is not considered.

   The value of LSP establishment delay in single layer and single
   domain networks and multi-layer and single domain networks is a real



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   number of milliseconds.

   There is another case in which source node does not receive the
   optimal path computation result or the LSP confirm message of
   successful reservation within a reasonable period of time, and the
   value of LSP establishment delay in this case is marked undefined.

4.3.  Discussion

   The reason that LSP establishment delay is set to undefined not only
   lies in source node never receives the corresponding reply message
   within a reasonable period of time , but also consists in that source
   node receives the PathErr message.  There are many possible reasons
   for receiving the PathErr message: for example, network does not have
   enough resources to establish the service layer for the user requests
   or network element failure occurs.


5.  LSP Establishment BER in Multi-Domain Networks

   This section integrally defines a performance measurement metric
   named LSP establishment BER in multi-domain networks.

5.1.  General Assumptions

   o  Every node has a LID which stores the node physical information.

   o  Destination node has a performance evaluation module which can
      evaluate the established LSP performance combining corresponding
      physical parameter information.

5.2.  Definition

   In the measurement process of LSP establishment BER, no matter that
   the network is single domain or multi-domain, the evaluation method
   is the same, and only the wavelength lightpath has physical
   parameters, so single layer network is considered.

   In multi-domain networks, as physical parameters are collected and
   measured in the process of LSP setup, so only the LSP setup process
   is considered.

   The LSP setup from source node to destination node mainly includes
   following process: source node firstly determine if service layers
   exist.  If service layer exists, source node sends Path message to
   the next node to reserve resource and collects physical information
   of nodes and links, and the next node carries out the same function
   like source node until Path message arrives at destination node, then



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   destination node evaluates the LSP performance combining
   corresponding physical parameter information.  If computed BER is
   within the tolerable range, then destination node returns Resv
   message to the previous node until source node receives the Resv
   message, otherwise, destination node returns PathErr message to the
   previous node until source node receives the PathErr message, and LSP
   setup fails.  If service layer does not exist, source node firstly
   establishes a service layer using signaling, then source node sends
   Path message to determine an available wavelength set until Path
   message arrives at destination node.  Meanwhile, signaling collects
   physical information of nodes and links.  If the available wavelength
   set exists and BER that is computed by destination node is within the
   tolerable range, then destination node sends Resv message to source
   node to reserve available resources, otherwise, PathErr message is
   returned to the source node and LSP setup fails.  In the circumstance
   of service layer exists, any node which Path message traverses
   detects the unavailable service layer, then PathErr message is also
   returned to the source node and LSP setup fails.


6.  Methodologies

6.1.  Definition

   o  T0, a time when the path computation is attempted.

   o  T1, a time when the LSP setup is attempted.

   o  T2, a time when the optimal path computation result is returned.

   o  T3, a time when the LSP confirm message of successful reservation
      is returned.

6.2.  Methodologies

6.2.1.  LSP Establishment Delay

   o  Make sure that the PCE has enough computation ability to compute
      the path that conforms to user request.

   o  Make sure that the network has enough resources to establish the
      requested path.

   o  At the source node, form the path computation Req message.  A
      timestamp (T0) may be stored locally on the source node when the
      path computation Req message is sent towards the PCE responsible
      for the source domain, and a timestamp (T1) may be stored locally
      on the source node when source node ID0 sends the LSP setup



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      message.

   o  If the corresponding end-to-end path computation results and Resv
      message arrive at source node within a reasonable period of time,
      take the timestamp (T2) and timestamp (T3) upon receipt of the
      messages.  By subtracting the two timestamps, an estimate of path
      computation delay (T2-T0) and LSP setup delay (T3-T1) can be
      computed.

   o  If the corresponding end-to-end path computation results and Resv
      message fails to arrive at source node within a reasonable period
      of time, the path computation delay and LSP setup delay are
      considered to be undefined.

   o  If the corresponding response is a PathErr message, then the path
      computation delay and LSP setup delay are considered to be
      undefined.

6.2.2.  LSP Establishment BER

   o  Make sure that the PCE has enough computation ability to compute
      the path that conforms to user request.

   o  Make sure that the network has enough resources to establish the
      requested path.

   o  In the process of path computation, BRPC is used as the
      computation method.

   o  In the process of LSP setup, when Path message arrives at
      destination node, then the destination node computes the BER
      combining the corresponding physical parameter information which
      is collected from the traversing nodes and links.  If the computed
      BER is within the tolerable range, then Resv message is returned
      to source node.

   o  If the computed BER is outside the tolerable range, then PathErr
      message is returned to source node and LSP establishment fails.


7.  Protocol Extension Requirements

   o  In the measurement process of LSP establishment delay, the start
      time of LSP establishment and the stop time of LSP establishment
      need to be determined using corresponding protocol.  In the
      process of path computation, a new object that includes timestamp
      needs to be added in routing protocol in order to record the start
      time of path computation and the stop time of path computation; In



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      the process of LSP setup, a new object that includes timestamp
      needs to be added in signaling protocol in order to record the
      start time of LSP setup and the stop time of LSP setup.

   o  In the measurement process of LSP establishment BER, the physical
      information of nodes and links needs to be collected using
      signaling protocol, and BER is evaluated in the destination node
      combining corresponding physical parameter information, so a new
      object that includes network physical parameters needs to be added
      in signaling protocol in order to collect the physical information
      of nodes and links.


8.  Security Considerations

   This document involves some information collection about network
   physical parameters.  Such information would need to be protected
   from intentional or unintentional disclosure.


9.  Acknowledgments

   We wish to thank Yongli Zhao, Linna Xia, Haoyuan Lin, Hongrui Han for
   their comments and help.

   The RFC text was produced using Marshall Rose's xml2rfc tool.


10.  References

10.1.  Normative References

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

   [RFC3473]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.

   [RFC3945]  Eric, M., "Generalized Multi-Protocol Label Switching
              (GMPLS) Architecture", RFC 3945, October 2004.

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

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



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   [RFC5441]  Vasseur, J., 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.

   [RFC5814]  Sun, W. and G. Zhang, "Label Switched Path (LSP) Dynamic
              Provisioning Performance Metrics in Generalized MPLS
              Networks", RFC 5814, March 2010.

10.2.  Informative References

   [I-D.ietf-ccamp-wson-impairments]
              Lee, Y., Bernstein, G., Li, D., and G. Martinelli, "The
              Application of the Path Computation Element Architecture
              to the Determination of a Sequence of Domains in MPLS &
              GMPLS", July 2010.

   [Interdomain-LSP]
              Aslam, F., Uzmi, ZA., and A. Farrel, "Interdomain Path
              Computation: Challenges and Solutions for Label Switched
              Networks", IEEE Communications Magazine, October 2007.

   [RFC5212]  Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureu,
              M., and D. Brungard, "Requirements for GMPLS-Based Multi-
              Region and Multi-Layer Networks (MRN/MLN)", RFC 5212,
              July 2008.


Appendix A.  Other Authors

   1.  Min Zhang

   BUPT

   No.10,Xitucheng Road,Haidian District

   Beijing 100876

   P.R.China

   Phone: +8613910621756

   Email: mzhang@bupt.edu.cn

   URI: http://www.bupt.edu.cn/

   2.  Yunbin Xu




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   CATR

   No.52 Hua Yuan Bei Lu,Haidian District

   Beijing 100083

   P.R.China

   Phone: ++8613681485428

   Email: xuyunbin@mail.ritt.com.cn

   URI: http://www.bupt.edu.cn/


Authors' Addresses

   Yuefeng Ji
   BUPT
   No.10,Xitucheng Road,Haidian District
   Beijing  100876
   P.R.China

   Phone: +8613701131345
   Email: jyf@bupt.edu.cn
   URI:   http://www.bupt.edu.cn


   Weiwei Bian
   BUPT
   No.10,Xitucheng Road,Haidian District
   Beijing  100876
   P.R.China

   Phone: +8615210837998
   Email: bianweiwei2008@163.com
   URI:   http://www.bupt.edu.cn/














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   Hongxiang Wang
   BUPT
   No.10,Xitucheng Road,Haidian District
   Beijing  100876
   P.R.China

   Phone: +8613683683550
   Email: wanghx@bupt.edu.cn
   URI:   http://www.bupt.edu.cn/


   Shanguo Huang
   BUPT
   No.10,Xitucheng Road,Haidian District
   Beijing  100876
   P.R.China

   Phone: +86 1062282048
   Email: shghuang@bupt.edu.cn
   URI:   http://www.bupt.edu.cn/


   Guoying Zhang
   CATR
   No.52 Hua Yuan Bei Lu,Haidian District
   Beijing  100083
   P.R.China

   Phone: +86 1062300103
   Email: zhangguoying@mail.ritt.com.cn
   URI:   http://www.catr.cn/




















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