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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: March 29, 2014                                   Telefonica I+D
                                                                F. Zhang
                                                                X. Zhang
                                                     Huawei Technologies
                                                      September 25, 2013


     Use cases for operating networks in the overlay model context
              draft-ceccadedios-ccamp-overlay-use-cases-02

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
   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 March 29, 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  . . . . . . . . . .  6
     4.3.  UC 3 - Provisioing with constraints  . . . . . . . . . . .  7
     4.4.  UC 4 - Provisioing with diversity  . . . . . . . . . . . .  8
     4.5.  UC 5 - Concurrent provisioing  . . . . . . . . . . . . . .  9
     4.6.  UC 6 - Reoptimization  . . . . . . . . . . . . . . . . . .  9
     4.7.  UC 7 - Query . . . . . . . . . . . . . . . . . . . . . . . 10
     4.8.  UC 8 - Availability check  . . . . . . . . . . . . . . . . 10
     4.9.  UC 9 - P2MP services . . . . . . . . . . . . . . . . . . . 10
     4.10. UC 10 - Privacy  . . . . . . . . . . . . . . . . . . . . . 10
     4.11. UC 11 - Colored overlay  . . . . . . . . . . . . . . . . . 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13























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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
   provisioing 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.


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.

   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



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   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 - Provisioing 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.

   This use cases is extremely similar to the Provisioing 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.




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4.4.  UC 4 - Provisioing 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
   the client layer which are supposed to be in a protection
   relationship between each other (e.g. 1+1 protection).


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


                   Figure 5: Provisioing with diversity

   In a scenario like the one depicted above, it is possible to use
   Service A and Service B 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 A (or a set of identifiers indicating its
   resources) is needed so that the request for the setup of Service B
   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



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   computation constraint in the service setup request.

4.5.  UC 5 - Concurrent provisioing

   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
   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





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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).

   Editor note: collection of other TE metrics (e.g. latency, jitter) to
   be considered?

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: 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



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   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.

   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).












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        -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
   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)


5.  Security Considerations

   TBD


6.  IANA Considerations

   TBD




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7.  Contributors

   TBD


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


   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









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   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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