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Versions: 00 01 02 03 04 05                                             
CCAMP Working Group                                        D. Ceccarelli
Internet-Draft                                                  Ericsson
Intended status: Informational                       O. Gonzalez de Dios
Expires: April 24, 2014                                   Telefonica I+D
                                                                F. Zhang
                                                                X. Zhang
                                                     Huawei Technologies
                                                        October 21, 2013


     Use cases for operating networks in the overlay model context
              draft-ceccadedios-ccamp-overlay-use-cases-03

Abstract

   This document defines a set of use cases for operating networks in
   the overlay model context through the Generalized Multiprotocol Label
   Switching (GMPLS) overlay interfaces.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   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 April 24, 2014.

Copyright Notice

   Copyright (c) 2013 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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Background and Assumptions . . . . . . . . . . . . . . . . . .  4
   4.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  UC 1 - Provisioning  . . . . . . . . . . . . . . . . . . .  6
     4.2.  UC 2 - Provisioning with optimization  . . . . . . . . . .  7
     4.3.  UC 3 - Provisioning with constraints . . . . . . . . . . .  7
     4.4.  UC 4 - Provisioning with diversity . . . . . . . . . . . .  8
     4.5.  UC 5 - Concurrent provisioning . . . . . . . . . . . . . .  9
     4.6.  UC 6 - Reoptimization  . . . . . . . . . . . . . . . . . . 10
     4.7.  UC 7 - Query . . . . . . . . . . . . . . . . . . . . . . . 10
     4.8.  UC 8 - Availability check  . . . . . . . . . . . . . . . . 11
     4.9.  UC 9 - P2MP services . . . . . . . . . . . . . . . . . . . 11
     4.10. UC 10 - Privacy  . . . . . . . . . . . . . . . . . . . . . 11
     4.11. UC 11 - Colored overlay  . . . . . . . . . . . . . . . . . 11
     4.12. UC 12 - Stacking of overlay interfaces . . . . . . . . . . 13
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15






















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1.  Introduction

   The GMPLS overlay model [RFC 4208] specifies a client-server
   relationship between networks where client and server layers are
   managed as separate domains because of trustiness, scalability and
   operational issue.  By means of procedures from the GMPLS protocol
   suite it is possible to build a topology in the client (overlay)
   network from Traffic Engineering paths in the server network.  In
   this context, the UNI (User to Network Interface) is the demarcation
   point between networks.  It is a boundary where policies,
   administrative and confidentiality issues apply that limit the
   exchange of information.

   This GMPLS overlay model supports a wide variety of network
   scenarios.  The packet over optical scenario is probably the most
   popular example where the overlay model applies.

   In order to exploit the full potential of client/server network
   interworking in the overlay model, it may be desirable to know in
   advance whether is it feasible or not to connect two client network
   nodes [INTERCON-TE].  This requires to have a certain amount of TE
   information of the server network in the client network.  This need
   not be the full set of TE information available within each network,
   but does need to express the potential of providing TE connectivity.
   This subset of TE information is called TE reachability information.

   The goal of this document is to define a set of solution independent
   use cases applicable to the overlay model.  In particular it focuses
   on the network scenarios where the overlay model applies and analyzes
   the most interesting aspects of provisioning, recovery and path
   computation.


2.  Terminology

   The following terms are used within the document:

      - Edge node [RFC4208]: node of the client domain belonging to the
      overlay network, i.e. nodes with at least one interface connected
      to the server domain.

      - Core node [RFC4208]: node of the server domain.

      - Access link: link between core node and edge node.  It is the
      link where the UNI is usually implemented.

      - Remote node: node in the client domain which has no direct
      access to the server domain but can reach it through an edge node



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      in its same administrative domain.

      - Local trigger: LSP setup request issued to an edge node.  It
      triggers the setup of a client layer FA through the server domain
      via a UNI interface.

      - Remote trigger: LSP setup request issued to a remote node.  It
      triggers the setup of a client layer LSP which, upon reaching an
      edge node, will use connectivity in the server domain dynamically
      provided via an UNI interface.


3.  Background and Assumptions

   All the use cases listed in the sections below can be applied to any
   combination of, unless otherwise specified:

      * Local trigger or remote signaling

      * Grey interface or colored interface

   With local trigger we mean the case in which a trigger for the
   provisioning of a service over the overlay interface is issued to one
   of the edge nodes belonging to the overlay network, i.e. directly
   connected to the UNI.


               1.Trigger
                  |            2. Setup
                  V   -------------------->
   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
     \            /        | \     / |  \    |         \           /
      \          /         |  \   /  |   \   |          \         /
       \        /          |   \ /   |    \  |           \       /
        \ +--+ /           |    \    |     \ |            \ +--+/
          |R4|             |   / \   |      \|              |R8|
          +--+            /-\ /    \/-\     /-\             +--+
     3.Advertisement     ( D )-----( E )---( F )      3.Advertisement
                          \-/       \-/     \-/
        *** = overlay interfaces


                          Figure 1: Local trigger

   As it is possible to see in the figure above, a trigger is issued on
   R3 (edge node) for starting the setup request procedure over the



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   overlay interface (R3-A).  Once the LSP in the server domain is setup
   and an adjacency in the packet layer between R3 and R5 is created, it
   can be advertised in the rest of the client domain and used by the
   signaling protocol (e.g.  LDP) for setting up end-to-end (e.g. from
   R1 to R7) client layer LSPs.

   On the other hand, the remote signaling consists on the utilization
   of a connection oriented signaling protocol in the client domain that
   allows issuing the end to end service setup trigger directly on the
   end nodes of the client domain.  The signaling message, upon reaching
   the edge node (R3), will trigger the setup of the service in the
   server layer via the overlay interface.


    1.Trigger
    | 2. Signaling  3. Trigger
    V ------------->                                  |------------>|
                    |------>----------------->------->|
                    |<-----<-----------------<--------|
   <----------------|---------------------------------|-------------|
   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
     \            /        | \     / |  \    |         \           /
      \          /         |  \   /  |   \   |          \         /
       \        /          |   \ /   |    \  |           \       /
        \ +--+ /           |    \    |     \ |            \ +--+/
          |R4|             |   / \   |      \|              |R8|
          +--+            /-\ /    \/-\     /-\             +--+
                         ( D )-----( E )---( F )
                          \-/       \-/     \-/


                        Figure 2: Remote Signaling

   The utilization of the remote trigger allows for a strict control of
   the resources that will be used for the setup of the end to end
   service.  In order to have a correct setup of the end to end service
   the trigger issued to R1 must include the overlay nodes to be used
   for the setup of the service in the server layer (R3 and R5).  The
   network operator is supposed to know that the edge nodes to be used
   are R3 and R5.

   When operating an IP over WDM network in the overlay context, a
   further distinction between grey and colored interfaces needs to be
   taken into account.  In other words in the former case the
   transponder is hosted on the core border nodes, while in the latter
   in the edge node.  The physical impairments to be considered are



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   different in the two cases (for further details please see
   Section 4.11) but the behaviour of the interface does not change and
   all use cases depicted below can be applied both to the grey and
   colored interfaces.

   The particular case of grey and colored interfaces can be generalized
   introducing two further differentiation criteria for the
   characterization of overlay interfaces:

      * Administrative boundary or administrative plus technological
      boundary

   Since the overlay is an administrative boundary between a client and
   a server layer, it is possible to configure it between a client and a
   server domain with the same switching capabilities (e.g., IP over IP)
   or between domains with different switching capabilities (e.g., OTN
   over WDM).  In the former case the boundary is referred to as
   administrative domain, while in the latter, it is referred to as both
   administrative and technological boundary.

   The second differentation mentioned above refers to technological
   boundaries and in particular to:

      * Layer transition on edge node or on core node

   When layer transition occurs on the edge node, the edge node is
   equipped with at least one interface with the switching capability of
   the client domain and one interface with the switching capability of
   the server domain.  Referring to the IP over WDM this is the case of
   colored overlay interface with transponder hosted in the edge node.
   Viceversa, when layer transition occurs on the core node, it is the
   core node the one with at least two different interfaces with
   different switching capabilities and we speak about grey interfaces
   in the IP over WDM context.

   Editor note: Actually path computation is assumed to be performed
   tipically at the server layer.  The client layer can request the
   server layer for computing a path or select among a set of paths
   computed by the server layer and exported to the client layer as
   virtual/abstract topology.


4.  Use Cases

4.1.  UC 1 - Provisioning

   Requirement: The network operator must be allowed to setup an
   unprotected end to end service between two client layer nodes.



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   This use case simply consists on providing an operator with the
   capability of setting up a service in the client layer either by
   means or local trigger or remote signaling.  The operator does not
   put any constraint over the path computation in the server layer.

4.2.  UC 2 - Provisioning with optimization

   Requirement: The network operator must be allowed to setup a service
   expressing which parameter must be optimized when computing the path.

   This use case applies both to the local trigger and the remote
   signaling scenarios.  In both cases the path computation element in
   the server layer (being it centralized or distributed) is demanded to
   provide a path between R3 and R5 which minimizes a given parameter
   (e.g. delay, jitter, TE metric).


               1.Trigger(param min)
                  |  2. Setup(param min)   3.Path computation(param min)
                  V  ------>
   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
     \            /        | \     / |  \    |         \           /
      \          /         |  \   /  |   \   |          \         /
       \        /          |   \ /   |    \  |           \       /
        \ +--+ /           |    \    |     \ |            \ +--+/
          |R4|             |   / \   |      \|              |R8|
          +--+            /-\ /    \/-\     /-\             +--+
                         ( D )-----( E )---( F )
                          \-/       \-/     \-/
        *** = overlay interfaces


                 Figure 3: Provisioning with optimization

   In the figure above the case of local trigger with specified
   parameter to be minimized is depicted, but same considerations apply
   to the remoe signaling (trigger on R1).  In that case the parameter
   to be minized needs to be conveyed from R1 to R3 so that the setup
   request over the overlay interface can be issued taking into account
   the OF.

4.3.  UC 3 - Provisioning with constraints

   Requirement: The network operator must be allowed to setup a service
   imposing upper bounds for a set of parameters during the path
   computation.



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   This use cases is extremely similar to the provisioning with
   Optimization one.  This time, instead of/in addittion to giving the
   possibility of specifying which parameter needs to be optimized
   during the path computation, the network operator is also able to
   indicate and upper bound for a set of parameters which is not being
   minimized in the path computation.


               1.Trigger(constraint)
                  |  2.Setup(const) 3.Path computation(const)
                  V  ------>
   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
     \            /        | \     / |  \    |         \           /
      \          /         |  \   /  |   \   |          \         /
       \        /          |   \ /   |    \  |           \       /
        \ +--+ /           |    \    |     \ |            \ +--+/
          |R4|             |   / \   |      \|              |R8|
          +--+            /-\ /    \/-\     /-\             +--+
                         ( D )-----( E )---( F )
                          \-/       \-/     \-/
        *** = overlay interfaces


                  Figure 4: Provisioning with constraints

   It is possible for example to ask for a path between R3 and R5 which,
   in addition to minimizing a given OF, does not introduce a delay
   higher than 10ms or where the jitter is not more than 3ms.

   As per the optimization use case, when remote signaling is used
   (trigger on R1) a mean to convey the path computation constraints
   till the edge node (R3) is needed.

4.4.  UC 4 - Provisioning with diversity

   Requirement: The network operator must be allowed to setup a services
   in the server layer in diversity with respect to server layer
   resources or not sharing the same fate with other server layer
   services.

   This scenario is extremely common in those cases where different
   services in the server domain are used to provision protected
   services in the client layer.  The services in the server layer can
   be computed/provisioned sequentially or in parallel but in both cases
   the requirement is to have them totally disjoint, so that a single
   failure in the server layer does not impact two or more services in



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   the client layer which are supposed to be in a protection
   relationship between each other (e.g. 1+1 protection).


   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|*X**( A )--X--( B )-X-( C )**X**|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
                   *       | \     / |  \    |      *
                    *      |  \   /  |   \   |     *
                     Y     |   \ /   |    \  |    Y
                      *    |    \    |     \ |   *
                       *   |   / \   |      \|  *     *X*=Service X
                        * /-\ /    \/-\     /-\*      *Y*=Service Y
                         ( D )--Y--( E )-Y-( F )
                          \-/       \-/     \-/


                   Figure 5: provisioning with diversity

   In a scenario like the one depicted above, it is possible to use
   Service X and Service Y for the setup of a protected service in the
   client domain as a fault in the server domain would not impact both
   of them.  In the case of parallel request, R3 asks the path
   computation in the server domain to provide two totally disjoint
   paths.  On the other side, when sequential requests are issued, and
   identifiers for Service X (or a set of identifiers indicating its
   resources) is needed so that the request for the setup of Service Y
   can be issued with the constraint of avoiding the resources related
   to such identifier.

   Another case of provisioning with diversity is the one where the
   operator in the client domains wants the server domain PCE to exclude
   some resources from the path computation because of e.g. trustness
   reasons.  In such a case, supposing that such resources are known to
   the operator, it must be possible to indicate them as path
   computation constraint in the service setup request.

4.5.  UC 5 - Concurrent provisioning

   Requirement: The network operator must be allowed to setup a
   plurality of services not necessarily between the same pair of edge
   nodes.

   Here is another case particularly interesting from a protection point
   of view.  In the case above the same edge node was asking for
   different services in the server layer, but in order to have end to
   end diversity (i.e. from R1 to R8 in figure below), there is the need
   to be able to provide disjoint services between different pairs of



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   edge nodes.


   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )*****( B )***( C )*****|R6|---|R7|---|R8|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
       \                   | \     / |  \    |                     /
        \                  |  \   /  |   \   |                    /
         \                 |   \ /   |    \  |                   /
          \                |    \    |     \ |                  /
           \               |   / \   |      \|                 /
          +--+   +--+     /-\ /    \/-\     /-\      +--+   +---+
          |R4|---|R5|####( D )#####( E )###( F )#####|R9|---|R10|
          +--+   +--+     \-/       \-/     \-/      +--+   +---+

      ***=Service A
      ###=Service B


                     Figure 6: Concurrent provisioning

   In this example Service A is provided between R3 and R6 and Service B
   between R5 and R9.  Some sort of coordination is needed between R3
   and R5 (directly between them or via R1) so that the requests to the
   server layer can be conveniently issued.

4.6.  UC 6 - Reoptimization

   Requirement: The network operator must be allowed to setup a
   plurality of services so that the overall cost of the network is
   minimized and not the cost of a single service.

   TBD

4.7.  UC 7 - Query

   Requirement: The server network must be able to tell the network
   operator the actual parameters characterizing an existing service.

   The capability of retrieving from the server domain some parameters
   qualifying a service can be estremely useful in different cases.  One
   of them is the case o sequential provisioning with diversity
   requirements.  In the case the operator wants to set-up a service in
   diversity from an existing one, hence it must be possible for the
   server domain to export some parameters univocally identifying the
   resources (e.g.  SRLGs).





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4.8.  UC 8 - Availability check

   Requirement: The network operator must be allowed to check if in the
   server layer there are enough resources to setup a service with given
   parameters.

   TBD

4.9.  UC 9 - P2MP services

   Requirement: If allowed by the technology, the network operator must
   be allowed to setup a P2MP service with given parameters.

   TBD

4.10.  UC 10 - Privacy

   Requirement: The network operator must be allowed to provision
   different groups of users with independent addressing spaces.

   This is a particularly useful functionality for those cases where the
   resources of the service provider are leased and shared among several
   other service providers or customers.

4.11.  UC 11 - Colored overlay

   Requirement: The network operator must be allowed to provision a
   service in the server layer through a colored overlay interface.

   This use case applies to networks where the server domain is a WDM
   network.  In those cases it is possible to either have a grey
   interface between client and server domains (i.e. transponder on the
   border core node) or a colored interface between them (i.e.
   transponder on the edge node).

   All the previous use cases assume the case of grey interface, but
   there are particular network scenarios in which it is possible to
   move the transponders from the core to the edge nodes and hence save
   on expensive pieces of hardware.

   The issue with this solution is that the PCE in the server layer,
   being either centralized or distributed, has only visibility of what
   is inside the server domain and hence has not all the info needed to
   perform the validation of a path.  The edge node must provide the PCE
   in the server domain with a set of info needed for a correct path
   computation and path validation from transponder to transponder (i.e.
   between edge nodes) all along the server domain.




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   The type of information needed for this scenario can be classified
   into three categories:

      - Feasibility: Parameters like the output power of the transponder
      are needed in order to state e.g. the amount of km that can be
      reached without regeneration.

      - Compatibility: The egress transponder must be compatible with
      the ingress one.  Parameters that influence the level of
      compatibility can be for example the type of FEC (Forward Error
      Correction) used or the modulation format (which also impacts the
      feasibility together with the bit rate).

      - Availability: Transponders can be tunable within a range of
      lambdas or even locked to a single lambda.  This impacts the path
      computation as not every path in the network might have such
      lambda(s) supported or available at the time the path computation
      is performed.

   In figure below it is possible to see that the PCE is aware of all
   the info between A and C (i.e. within the server domain scope) but
   what is missing is info related to the transponders on R1 and on R2
   and of the access links. (i.e.  R1-A and C-R2).


        -Feasibility
        -Compatibility |=====|
        -Availability  | PCE |
           /---------->|=====|
          /
         /
   +--+ /      /-\       /-\     /-\         +--+
   |R1|*******( A )-----( B )---( C )********|R2|
   +--+        \-/       \-/\    \-/         +--+
                | \     / |  \    |
                |  \   /  |   \   |
                |   \ /   |    \  |
                |    \    |     \ |
                |   / \   |      \|
               /-\ /    \/-\     /-\
              ( D )-----( E )---( F )
               \-/       \-/     \-/
        *** = colored overlay interfaces


                   Figure 7: PCE feeding for colored UNI

   There is not yet a standard set of parameters that is needed for path



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   computation in WDM networks but an example of some of them is
   provided in the following list:

      o Modulation format

      o FEC (type or gain)

      o Minimum transponder output power

      o Bitrate

      o Dispersion tolerance

      o OSNR (minimum required)

4.12.  UC 12 - Stacking of overlay interfaces

   Requirement: The network operator must be allowed manage a network
   with an arbitrarily high number of administrative boundaries
   (i.e.,>2).

   Operators might want to split their overlay networks in a number of
   administrative domains for several reasons, among which simplifying
   network operations and improving scalability.  In order to do so it
   must be possible to create a stack of overlay interfaces between the
   different domains as shown in figure below:


 +--+  +--+                                                   +--+  +--+
 |A1|--|A2|*                                                 *|A4|--|A5|
 +--+  +--+ *  /-\    /-\                      /-\     /-\  * +--+  +--+
  \ +--+ /   *( B1)--( B2)                    ( B3)---( B4)*   \ +--+ /
   \|A3|/      \-/    \-/                      \-/     \-/      \|A6|/
    +--+                *                      *                 +--+
                         * ====   ====   ==== *
                          *|C1|---|C2|---|C3|*
                           ====   ====   ====

      *** = overlay interfaces


                     Figure 8: Stacking of interfaces

   Nodes "Ax" belong to a domain which is client to the domain composed
   by nodes "Bx".  The domain composed by nodes Bx is hence server layer
   to the "Ax" nodes domain but client to the "Cx" nodes domain.

   A pretty common deployment of this scenario consists of IP over OTN



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   over WDM layers, where the OTN digital layer is used for the grooming
   of IP traffic over high bit rate lambdas.  In figure 8, Node Bx can
   be assumed to be digital layer, which is interfacing with packet
   layer nodes (Ax) across overlay interface.  Digital layer nodes Bx
   are interfacing with DWDM layer nodes Cx.  If OTN (Bx) and DWDM (Cx)
   node belong to same IGP, then this becomes multi-layer path
   computation and signaling case, and it is out of scope of this
   document.

   However, as already shown in the intro of this memo, the three
   different domains of the example could have the same switching
   capability (e.g., IP) and be kept separate just for administrative
   reasons.


5.  Security Considerations

   TBD


6.  IANA Considerations

   TBD


7.  Contributors

      Diego Caviglia, Ericsson

      Via E.Melen, 77 - Genova - Italy

      Email: diego.caviglia@ericsson.com



      Jeff Tantsura, Ericsson

      300 Holger Way, San Jose, CA 95134 - USA

      Email: jeff.tantsura@ericsson.com



      Khuzema Pithewan, Infinera Corporation

      140 Caspian CT., Sunnyvale - CA - USA





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      Email: kpithewan@infinera.com



      Cyril Margaria, Wandl

      Email: cyril.margaria@googlemail.com



      John Drake, Juniper

      Email: jdrake@juniper.net



      Sergio Belotti, Alcatel-Lucent

      Email: sergio.belotti@alcatel-lucent.com


8.  References

8.1.  Normative References

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

8.2.  Informative References


Authors' Addresses

   Daniele Ceccarelli
   Ericsson
   Via E. Melen 77
   Genova - Erzelli
   Italy

   Email: daniele.ceccarelli@ericsson.com











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

   Email: ogondio@tid.es


   Fatai Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Shenzhen 518129 P.R.China  Bantian, Longgang District
   Phone: +86-755-28972912

   Email: zhangfatai@huawei.com


   Xian Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Shenzhen 518129 P.R.China  Bantian, Longgang District
   Phone: +86-755-28972913

   Email: zhang.xian@huawei.com


























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