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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: September 6, 2014                                Telefonica I+D
                                                                F. Zhang
                                                                X. Zhang
                                                     Huawei Technologies
                                                                  Z. Ali
                                                     Cisco Systems, Inc.
                                                                  R. Rao
                                                    Infinera Corporation
                                                              S. Belotti
                                                          Alcatel-Lucent
                                                           March 5, 2014


     Use cases for operating networks in the overlay model context
              draft-ceccadedios-ccamp-overlay-use-cases-05

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 September 6, 2014.

Copyright Notice

   Copyright (c) 2014 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



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   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Client domain to server domain connectivity  . . . . . . . . .  6
     3.1.  Single homing  . . . . . . . . . . . . . . . . . . . . . .  6
     3.2.  Dual homing  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Services between different pairs of nodes  . . . . . . . .  8
   4.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  UC 1 - Provisioning  . . . . . . . . . . . . . . . . . . .  9
     4.2.  UC 2 - Provisioning with optimization  . . . . . . . . . .  9
     4.3.  UC 3 - Provisioning with constraints . . . . . . . . . . . 10
     4.4.  UC 4 - Diversity . . . . . . . . . . . . . . . . . . . . . 11
     4.5.  UC 4A - Service Affinity . . . . . . . . . . . . . . . . . 13
     4.6.  UC 5 - Concurrent provisioning . . . . . . . . . . . . . . 13
     4.7.  UC 6 - Reoptimization  . . . . . . . . . . . . . . . . . . 14
     4.8.  UC 7 - Query . . . . . . . . . . . . . . . . . . . . . . . 14
     4.9.  UC 8 - Availability check  . . . . . . . . . . . . . . . . 15
     4.10. UC 9 - P2MP services . . . . . . . . . . . . . . . . . . . 15
     4.11. UC 10 - Privacy  . . . . . . . . . . . . . . . . . . . . . 15
     4.12. UC 12 - Stacking of overlay interfaces . . . . . . . . . . 15
     4.13. UC 13 - Server layer resiliency parameters . . . . . . . . 16
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Appendix I - Colored overlay  . . . . . . . . . . . . 18
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21











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1.  Introduction

   The GMPLS overlay model [RFC 4208] specifies a control plane client-
   server relationship between networks where client and server domains
   are managed as separate domains because of trustiness, control plane
   scalability and operational issues.  By means of procedures from the
   GMPLS protocol suite it is possible to build a topology in the client
   (overlay) domain from Traffic Engineering paths in the server domain.
   In this context, the UNI (User to Network Interface) is the service
   demarcation point between domains.  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.

   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
      in its same administrative domain.

      - Local trigger: LSP setup request issued to an edge node.  It
      triggers the setup of a client domain LSP 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 domain LSP which, upon reaching an
      edge node, will use connectivity in the server domain.



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

      * Local or remote trigger

      * Administrative boundary or administrative plus technological
      boundary

      * Layer transition on edge node or on core node (applicable to
      administrative plus technological boundary case)

   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
   overlay interface (R3-A).  Once the LSP in the server domain is setup
   and an adjacency in the packet domain 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 domain LSPs.

   On the other hand, the remote signaling consists on the utilization
   of a connection oriented signaling protocol in the overlay domain
   that allows issuing the end to end service setup trigger directly on
   the end nodes of the client domain.  The signaling message, upon



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   reaching the edge node (R3), will trigger the setup of the service in
   the server domain 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 domain (R3 and R5).  The
   network operator is supposed to know that the edge nodes to be used
   are R3 and R5.

   The second bullet above speaks about administrative boundaries and
   administrative plus technological boundaries.  Since the overlay is
   an administrative boundary between an overlay network and a core
   network it may happen that overlay and core network can be configured
   based on the same switching capabilities (e.g., IP over IP) or with
   different switching capabilities (e.g.  ODU over OCh).  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.

   In the case of boundary which is both administrative and
   technological a further distinction is needed and regards the node
   where the technological transition occurs, i.e., on the edge or on
   the core node.




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   One of the most common cases of administrative and technological
   boundary is the IP over WDM, where we speak about grey and colored
   overlay interfaces.  In other words, in the case of grey interface
   the transponder and the domain transition are on the core node, while
   in the case of colored interface (i.e.  OTN multi-vendor IsDI based
   upon G.698.2) they are on the edge node.  The physical impairments to
   be considered are different in the two cases (for further details
   please see Appendix A) but the behavior of the interface does not
   change and all use cases depicted below can be applied both to the
   grey and colored interfaces.

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


3.  Client domain to server domain connectivity

   A further distinction criterion, which is applicable to most of the
   use cases below, is the degree of connectivity between the client
   domain and the server domain.  Three scenarios are identified:

      * Single homing

      * Dual homing

      * Services between different pairs of nodes

3.1.  Single homing

   In the case of single homing we consider an end to end tunnel with a
   single LSP in the client domain and one or more LSPs in the server
   domain but a single overlay interface connecting them.  The scenario
   is shown in figure below, where an end to end circuit between R1 and
   R7 is built over a tunnel between R3 and R5 composed by a single LSP
   restorable between A and C or more (possibly restorable) LSPs between
   A and C.












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   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7|
   +--+   +--+   +--+     \-/       \-/\    \-/      +--+   +--+   +--+
     \            /        | \     / |  \    |         \           /
      \          /         |  \   /  |   \   |          \         /
       \        /          |   \ /   |    \  |           \       /
        \ +--+ /           |    \    |     \ |            \ +--+/
          |R4|             |   / \   |      \|              |R8|
          +--+            /-\ /    \/-\     /-\             +--+
                         ( D )-----( E )---( F )
                          \-/       \-/     \-/
        *** = overlay interfaces


                          Figure 3: Single homing

   Typical examples of single restorable LSP between A and C is the case
   of IP over WDM with single transponder on A and single transponder of
   C with restoration capability in the WDM domain.  A common case of
   multiple LSPs between A and C, on the other side, it the splitting of
   the electrical signal between a couple of transponders on A creating
   a 1+1 protection terminated on a couple of transponders of C.

3.2.  Dual homing

   The dual homing is used to indicate a case in which two (or more)
   access links between the edge node and one or more core nodes exist.
   In this case we have an end to end tunnel with one or more LSPs in
   the server domain with two or more overlay interface connecting them.
   The scenario is shown in figure below, where an end to end circuit
   between R1 and R7 is built over a tunnel between R3 and R5 composed
   by two LSPs between different pairs of ingress/egress nodes (A-C and
   D-F).


















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


                           Figure 4: Dual homing

   This network setup typically allows for fast client domain protection
   mechanisms, e.g., Fast ReRoute (FRR).

3.3.  Services between different pairs of nodes

   This scenario is based on an end to end tunnel with two (or more)
   LSPs in the client domain each of which relies on one (or more) LSPs
   in the server domain.  It is based on multiple independent single
   homing scenarios and is typically used to provide end to end
   diversity between two or more services.  In figure below it is
   possible to see an end to end circuit between R1 and R8 composed by
   two services (A and B) which are built over two independent tunnels
   between R3 and R6 and between R5 and R9 respectively.


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

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


            Figure 5: Services between different pairs of nodes




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   Typical usage of this network scenario consists on the combination of
   fast client domain protection mechaninsms (e.g.,1+1 protection) and
   server domain restoration mechanisms.


4.  Use Cases

4.1.  UC 1 - Provisioning

   Requirement: It must be possible to setup an unprotected end to end
   service between two client domain nodes with no constraint in the
   server domain.

   This use case simply consists on providing an operator with the
   capability of setting up a service in the client domain either by
   means or local trigger or remote signaling.  The operator does not
   put any constraint over the path computation in the server domain
   (e.g. unprotected, no TE metric bounds).

4.2.  UC 2 - Provisioning with optimization

   Requirement: It must be possible to setup a client service expressing
   server layer parameter(s) to be optimized when computing server
   domain path.

   This use case applies both to the local trigger and the remote
   signaling scenarios.  In both cases the path computation function in
   the server domain (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).





















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               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 6: 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 minimized 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: It must be possible to setup a service imposing TE-
   metrics upper bounds for a set of parameters during the path
   computation.

   This use cases is extremely similar to the provisioning with
   Optimization one.  This time, instead of/in addition 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.













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               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 7: 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 - Diversity

   Requirement: It must be possible to setup a service in the server
   domain in diversity with respect to server domain resources or not
   sharing the same fate with other server domain services.  The network
   operator must also be able to decide whether such diversity degree
   must be automatically kept by the network upon failures and
   optimization procedures.

   This scenario is extremely common in those cases where different
   services in the server domain are used to provision protected
   services in the client domain.  The services in the server domain 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 domain does not impact two or more services in
   the client domain which are supposed to be in a protection
   relationship between each other (e.g. 1+1 protection).







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   +--+   +--+   +--+     /-\       /-\     /-\      +--+   +--+   +--+
   |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 8: 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, an
   identifier 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.  Please note that while Figure 8 depicts that the
   service X and the service Y have different ingress core nodes (node A
   and node D) but both service X and the service Y may share same
   ingress core node.

   Another case of provisioning with diversity is the one where the
   operator in the client domains wants the server domain to exclude
   some resources from the path computation.  In such a case, it must be
   possible to indicate them as path computation constraint in the
   service setup request.  Requesting an LSP with SRLG exclusion is an
   example of such service request.

   In addition to the provisioning of services with given diversity (and
   inclusion/exclusion) constraints, it must be possible to ask the
   server domain to at least keep such constraints also upon restoration
   or optimization procedures.  It would be desirable to ask the server
   domain to relax constraints to be kept.  The relaxation can be needed
   depending on resources availability, e.g., restoration of service X
   with partial diversity with service Y when total diversity is not
   possible).







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4.5.  UC 4A - Service Affinity

   There are scenarios that require two or more Label Switched Paths
   (LSPs) to follow same route in the network.  E.g., many deployments
   require member LSPs of a bundle/ aggregated link (or Forwarding
   Adjacency (FA)) follow the same route.  Possible reasons for two or
   more LSPs to follow the same end-to-end or partial route include, but
   are not limited to:

      o Fate sharing: an application may require that two or more LSPs
      fail together.  In the example of bundle link this would mean that
      if one component goes down, the entire bundle goes down.

      o Homogeneous Attributes: it is often required that two or more
      LSPs have the same TE metrics like latency, latency variation,
      etc.  In the example of a bundle/ aggregated link this would meet
      the requirement that all component links (FAs) of a bundle should
      have same latency and latency variation.  As noted in [OSPF-TE-
      METRIC] and [ISIS-TE-METRIC], in certain networks, such as
      financial information networks, network performance (e.g. latency
      and latency variation) is becoming critical and hence having
      bundles with component links (FAs) with homogeneous latency and
      latency variation is important.

4.6.  UC 5 - Concurrent provisioning

   Requirement: The client network must be able to setup plurality of
   services which are diverse and not between same pair of egde 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 domain, 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.
















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

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


                     Figure 9: 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 domain can be conveniently issued.

4.7.  UC 6 - Reoptimization

   Requirement: It must be possible 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

4.8.  UC 7 - Query

   Requirement: It must be possible to request information from the
   provider regarding the actual parameters characterizing an existing
   service (if supported by the SLA).

   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).  Another case where capability of retrieving
   from the server domain some parameters of service is useful is for
   flooding these parameters for the forwarding or routing adjacencies
   in the client network.  Examples of recording of such parameters are
   SRLGs, latency, latency variation and cost.



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4.9.  UC 8 - Availability check

   Requirement: It must be possible to check if in the server domain
   there are enough resources to setup a service with given parameters
   or to check attributes of a better path for an existing service to
   enable client to make reoptimization decision.

   Client node may like to check feasibility and attributes of a better
   path for an existing service.  SRLG, Latency, latency variation,
   Cost, etc. values are examples of attributes that client node may
   like to inquire about (e.g., before making a reoptimization
   decision).

4.10.  UC 9 - P2MP services

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

   TBD

4.11.  UC 10 - Privacy

   Requirement: It must be possible 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.

4.12.  UC 12 - Stacking of overlay interfaces

   Requirement: It must be possible to 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:












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

      *** = overlay interfaces


                     Figure 10: 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
   domain to the "Ax" nodes domain but client to the "Cx" nodes domain.

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

4.13.  UC 13 - Server layer resiliency parameters

   Requirement: It must be possible to request an LSP in the server
   domain with resilience parameters.  The minimum set of such
   parameters includes 1+1 protection and restoration.  Moreover, it
   must be possible for the operator to change the resilience level
   after the path is established in the network (e.g. dynamic SLA
   negotiation).

   This functionality is interesting in a scenario like the one in
   Figure 9 with two concurrent paths.  Let us assume service A and B
   are requested without any resilience requirements.  If there is a
   failure in service A, the operator can request for protection in
   service B once this situation is detected.



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   These parameters can be used both in the case of single homing (UC1)
   and concurrent paths (UC6).  The aim of this section is to highlight
   two sub-cases for every resilience case:

      (1) during the provisioning the client domain can request to the
      server domain for resilience parameters.

      (2) Once a failure occurs, the client domain has to be notified
      via the overlay interface thus carrying information about the
      situation in the server domain, so the client domain can take its
      own decisions.

   For the different sub-use cases, the provisioning use case already
   highlights which is the workflow and the requirements for each
   scenario.  This section does not include an example for each of them.


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





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      140 Caspian CT., Sunnyvale - CA - USA

      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



      Victor Lopez, Telefonica I+D

      Email: vlopez@tid.es


Appendix A.  Appendix I - Colored overlay

   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 hardware cost.

   The issue with this solution is that the path computation in the
   server domain, 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 pach computation functions in the server domain with
   a set of info needed for a correct path computation and path



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   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 and must be in the context of G.698.2:

      - 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.

   Feasibility and compatibility are all governed by the application
   codes.  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 11: 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)


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.






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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


   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


   Zafar Ali
   Cisco Systems, Inc.

   Email: zali@cisco.com






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   Rajan Rao
   Infinera Corporation
   140, Caspian CT.
   Sunnyvale, CA-94089
   USA

   Email: rrao@infinera.com


   Sergio Belotti
   Alcatel-Lucent
   Via Trento, 30
   Vimercate
   Italy

   Email: sergio.belotti@alcatel-lucent.com



































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