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Versions: 00 01 02 03 04 05 draft-ietf-ccamp-wson-iv-info

CCAMP                                                 G. Martinelli, Ed.
Internet-Draft                                                     Cisco
Intended status: Informational                             X. Zhang, Ed.
Expires: August 16, 2014                             Huawei Technologies
                                                           G. Galimberti
                                                                   Cisco
                                                              A. Zanardi
                                                             D. Siracusa
                                                              CREATE-NET
                                                       February 12, 2014


Information Model for Wavelength Switched Optical Networks (WSONs) with
                         Impairments Validation
                 draft-martinelli-ccamp-wson-iv-info-03

Abstract

   This document defines an information model to support Impairment-
   Aware (IA) Routing and Wavelength Assignment (RWA) function.  This
   operation might be required in Wavelength Switched Optical Networks
   (WSON) that already support RWA and the information model defined
   here goes in addition and it is fully compatible with the already
   defined information model for impairment-free RWA process in WSON.

   This information model shall support all control plane architectural
   options defined for WSON with impairment validation.

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 August 16, 2014.







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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
   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
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   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.  Definitions, Applicability and Properties . . . . . . . . . .   3
     2.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Applicability . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Properties  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  ITU-T List of Optical Parameters  . . . . . . . . . . . . . .   6
   4.  Background from WSON-RWA Information Model  . . . . . . . . .   7
   5.  Optical Impairment Information Model  . . . . . . . . . . . .   8
     5.1.  The Optical Impairment Vector . . . . . . . . . . . . . .   9
     5.2.  Node Information  . . . . . . . . . . . . . . . . . . . .   9
       5.2.1.  Impairment Matrix . . . . . . . . . . . . . . . . . .  10
       5.2.2.  Impariment Resource Block Information . . . . . . . .  12
     5.3.  Link Information  . . . . . . . . . . . . . . . . . . . .  12
     5.4.  Path Information  . . . . . . . . . . . . . . . . . . . .  12
   6.  Encoding Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  Control Plane Architectures . . . . . . . . . . . . . . . . .  13
     7.1.  IV-Centralized  . . . . . . . . . . . . . . . . . . . . .  14
     7.2.  IV-Distributed  . . . . . . . . . . . . . . . . . . . . .  14
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   9.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  14
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     12.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  ITU-T Liason Tracking  . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17







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1.  Introduction

   In the context of Wavelength Switched Optical Network (WSON),
   [RFC6163] describes the basic framework for a GMPLS and PCE-based
   Routing and Wavelength Assignment (RWA) control plane.  The
   associated information model [I-D.ietf-ccamp-rwa-info] defines all
   information/parameters required by an RWA process.

   There are cases of WSON where optical impairments plays a significant
   role and are considered as important constraints.  The framework
   document [RFC6566] defines problem scope and related control plane
   architectural options for the Impairment Aware Routing and Wavelength
   Assignment (IA-RWA) operation.  Options include different
   combinations of Impairment Validation (IV) and RWA functions in term
   of different combination of control plane functions (i.e., PCE,
   Routing, Signaling).

   This document provides an information model for the impairment aware
   case to allow the impairment validation function implemented in the
   control plane or enabled by control plane available information.
   This model goes in addition to [I-D.ietf-ccamp-rwa-info] and it shall
   support any control plane architectural option described by the
   framework document (see sections 4.2 and 4.3 of [RFC6566]) where a
   set of control plane combinations of control plane functions vs. IV
   function is provided.

2.  Definitions, Applicability and Properties

   This section provides some concepts to help understand concepts used
   along the document and to make a clear sepration about what coming
   from data plane definitions (ITU-T G recomandations) and are taken as
   input for this Information Model.  The first sub-section provides raw
   definitions while the Applicability sections reuses the defined
   concepts to scope this document.

2.1.  Definitions

   o  Computational Model / Optical Computational Model.
      Defined by ITU standard documents.  In this context we looks for
      models that are able to compute optical impairments for a give
      lightpath.

   o  Information Model.
      It is defined by IETF (this draft) and provide the set of
      information required by the Computational Model to be applied.

   o  Level of Approximation.




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      This concept refer to the Computational Model as it may compute
      optical impairment with a certain level of uncertainty.  This
      level is generally not measured but [RFC6566] make a rough
      classification about it.

   o  Feasible Path.
      It is the output of the CSPF with RWA-IV capability.  It's a path
      that satisfies the constraints in particular the optical
      impairment contraints.  The path, instantiated through wavelength,
      may actually work or not work depending of the level of
      approximation.

   o  Existing Service Disruption.
      A known effect to optical network designers is the cross-
      interaction among adjacent (specrum) wavelengths, e,g,,a
      wavelength may exeperience some increased BER due to the setting
      up of an adjacent wavelength.  Solving this problem is a typical
      optical network design activity.  Just as an example a simple
      method is adding optical margings (e.g., additional OSNR), other
      complex and detailed methods exist.

2.2.  Applicability

   This document targets at Scenario C defined in [RFC6566] section
   4.1.1.  as approximate impairment estimation.  The Approximate
   concept refer to the fact that this Information Model cover
   information mainly provided by the [ITU.G680] Computational Model.

   Computational models having no approximation, referred as IV-Detailed
   in the [RFC6566], currently does not exist in term of ITU-T
   recomandation.  They generally refer to non-linear optical impairment
   and they are usually vendor specific.

   The current information model does not speculate about mathematical
   formula used to fill up information model parameters hence, it does
   not preclude changing the computational model.  At the same time
   authors does not belive this Information Model is exhaustive and if
   necessary further documents will cover additional models as long as
   they become available.

   The result of RWA-IV process implementing this Information Model will
   result in a path (a wavelength in the data plane) that have better
   chance to be feasible than if it was computed without any IV
   function.  The Existing Service Disruption, as per the definition
   above, would still be a problem left to network designers: this model
   does not replace by any means the optical network design phase.  The
   Information Model targets, the GMPLS context with the releated
   relationship between data plane(s) and control plane.



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2.3.  Properties

   An information model may have several attributes or properties that
   need to be defined for each optical parameter made available to the
   control plane.  The properties will help to determine how the control
   plane can deal with a specific impairment parameter, depending on
   architectural options chosen within the overall impairment framework
   [RFC6566].  In some case, properties value will help to identify the
   level of approximation supported by the IV process.

   o  Time Dependency
      This identifies how an impairment parameter may vary with time.
      There could be cases where there is no time dependency, while in
      other cases there may be need of re-evaluation after a certain
      time.  In this category, variations in impairments due to
      environmental factors such as those discussed in [G.sup47] are
      considered.  In some cases, an impairment parameter that has time
      dependency may be considered as a constant for approximation.  In
      this information model, we do neglect this property.

   o  Wavelength Dependency
      This property identifies if an impairment parameter can be
      considered as constant over all the wavelength spectrum of
      interest or not.  Also in this case a detailed impairment
      evaluation might lead to consider the exact value while an
      approximation IV might take a constant value for all wavelengths.
      In this information model, we consider both case: dependency / no
      dependency on a specific wavelength.  This property appears
      directly in the information model definitions and related
      encoding.

   o  Linearity
      As impairments are representation of physical effects, there are
      some that have a linear behavior while other are non-linear.
      Linear approximation is in scope of Scenario C of [RFC6566].
      During the impairment validation process, this property implies
      that the optical effect (or quantity) satisfies the superposition
      principle, thus a final result can be calculated by the sum of
      each component.  The linearity implies the additivity of optical
      quantities considered during an impairment validation process.
      The non-linear effects in general does not satisfy this property.
      The information model presented in this document however, easily
      allow introduction of non-linear optical effects with a linear
      approximated contribution to the linear ones.

   o  Multi-Channel
      There are cases where a channel's impairments take different
      values depending on the aside wavelengths already in place, this



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      is mostly due to non-linear impairments.  The result would be a
      dependency among different LSPs sharing the same path.  This
      information model do not cosider this kind of property.

   The following table summarize the above considerations where in the
   first column reports the list of properties to be considered for each
   optical parameter, while the second column states if this property is
   taken into account or not by this information model.

             +-----------------------+----------------------+
             |        Property       | Info Model Awareness |
             +-----------------------+----------------------+
             |    Time Dependency    |          no          |
             | Wavelength Dependency |         yes          |
             |       Linearity       |         yes          |
             |     Multi-channel     |          no          |
             +-----------------------+----------------------+

                  Table 1: Optical Impairment Properties

3.  ITU-T List of Optical Parameters

   [EDITOR NOTE: To better integrate material coming from ITU WD06-31
   October 2013 and future liasons]

   As stated by Section 2.2 this Information Model does not intend to be
   exaustive and targets an approximate computational model although not
   precluding future evolutions towards more detailed impairments
   estimation methods.

   On the same line, ITU SG15/Q6 provides a list of optitical parameters
   with following observations:

   (a)  the problem of calculating the non-linear impairments in a
        multi-vendor environment is not solved.  The transfer functions
        works only for the so called [ITU.G680] "Situation 1".

   (b)  The generated list of parameters is not definitive or exaustive.

   In particular, [ITU.G680] contains many parameters that would be
   required to estimate linear impairments and [ITU.G697] contains
   information on which parameters can be monitored in an optical
   network.

   [ITU.G671] contains some additional parameters defintions required by
   here above recomandation.





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   The list of optical parameters starts from [ITU.G680] Section 9 which
   provides the optical computational models for the following:

   P1  OSNR.  Section 9.1

   P2  Optical Power.  As per Section 9.1, required by Optical
       Computation Model for OSNR calculation.

   P3  Chromatic Dispersion (CD).  Section 9.2

   P4  Polarization Mode Dispersion (PMD).  Section 9.3

   P5  Polarization Dependent Loss (PDL).  Section 9.3

   In addition to the above, the following list of parameters has been
   mentioned by ITU SG15/Q6.

   P6  Channel Frequency Range [ITU.G671].

   P7  Ripple

   P8  Channel Signal-Spontaneous noise figure.  This is considered
       within OSNR computational model above.

   P9  Differential Group Delay [ITU.G671].  Required for PMD above.

   P10 Reflectance.

   P11 Isolation.

   P12 Channel extintion.

   P13 Non-Linear Coefficient (for a fibre segment).  Needed for non-
       linear impairment

4.  Background from WSON-RWA Information Model

   In this section we report terms already defined for the WSON-RWA
   (impairment free) as in [I-D.ietf-ccamp-rwa-info] and
   [I-D.ietf-ccamp-general-constraint-encode].  The purpose is to
   provide essential information that will be reused or extended for the
   impairment case.

   In particular [I-D.ietf-ccamp-rwa-info] defines the connectivity
   matrix as the following:






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   ConnectivityMatrix ::= <MatrixID> <ConnType> <Matrix>


   According to [I-D.ietf-ccamp-general-constraint-encode], this
   definition is further detailed as:


   ConnectivityMatrix ::=
         <MatrixID> <ConnType> ((<LinkSet> <LinkSet>) ...)


   This second formula highlights how the connectivity matrix is built
   by pairs of LinkSet objects identifying the internal connectivity
   capability due to internal optical node constraint(s).  It's
   essentially binary information and tell if a wavelength or a set of
   wavelengths can go from an input port to an output port.

   As an additional note, connectivity matrix belongs to node
   information and is purely static.  Dynamic information related to the
   actual usage of the connections is available through specific
   extension to link information.

   Furthermore [I-D.ietf-ccamp-rwa-info] define the resource block as
   follow:


    ResourceBlockInfo ::= <ResourceBlockSet> [<InputConstraints>]
      [<ProcessingCapabilities>] [<OutputConstraints>]


   Which is an efficient way to model constrains of a WSON node.

5.  Optical Impairment Information Model

   The idea behind this information model is to categorize the
   impairment parameters into three types and extend the information
   model already defined for impairment-free WSONs.  The three
   categories are:

   o  Node Information.  The concept of connectivity matrix is reused
      and extended to introduce an impairment matrix, which represents
      the impairments suffered on the internal path between two ports.
      In addition, the concept of Resource Block is also reused and
      extended to provide an efficient modelization of per-port
      impairment.

   o  Link Information representing impairment information related to a
      specific link or hop.



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   o  Path Information representing the impairment information related
      to the whole path.

   All the above three categories will make use of a generic container,
   the Impairment Vector, to transport optical impairment information.

   This information model however will allow however to add additional
   parameters beyond the one defined by [ITU.G680] in order to support
   additional computational models.  This mechanism could eventually
   applicable to both linear and non-linear parameters.

   This information model makes the assumption that the each optical
   node in the network is able to provide the control plane protocols
   with its own parameter values however, no assumption is made on how
   the optical node gets those value information (e.g. internally
   computed, provisioned by a network management system, etc.).  To this
   extent, the information model intentionally ignores all internal
   detailed parameters that are used by the formulas of the Optical
   Computational Model (i.e., "transfer function") and simply provides
   the object containers to carry results of the formulas.

5.1.  The Optical Impairment Vector

   Optical Impairment Vector (OIV) is defined as a list of optical
   parameters to be associated to a WSON node or a WSON link.  It is
   defined as:


   <OIV> ::= ([<LabelSet>] <OPTICAL_PARAM>) ...


   The optional LabelSet object enables wavelength dependency property
   as per Table 1.  LabelSet has its definition in
   [I-D.ietf-ccamp-general-constraint-encode].

   OPTICAL_PARAM.  This object represents an optical parameter.  The
   Impairment vector can contain a set of parameters as identified by
   [ITU.G697] since those parameters match the terms of the linear
   impairments computational models provided by [ITU.G680].  This
   information model does not speculate about the set of parameters
   (since defined elsewhere, e.g. ITU-T), however it does not preclude
   extentions by adding new parameters.

5.2.  Node Information







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5.2.1.  Impairment Matrix

   Impairment matrix describes a list of the optical parameters that
   applies to a network element as a whole or ingress/egress port pairs
   of a network element.  Wavelength dependency property of optical
   paramters is also considered.


   ImpairmentMatrix ::=  <MatrixID> <ConnType>
         ((<LinkSet> <LinkSet> <OIV>) ...)


   Where:

      MatrixID.  This ID is a unique identifier for the matrix.  It
      shall be unique in scope among connectivity matrices defined in
      [I-D.ietf-ccamp-rwa-info] and impairment matrices defined here.

      ConnType.  This number identifies the type of matrix and it shall
      be unique in scope with other values defined by impairment-free
      WSON documents.

      LinkSet.  Same object definition and usage as
      [I-D.ietf-ccamp-general-constraint-encode].  The pairs of LinkSet
      identify one or more internal node constrain.

      OIV.  The Optical Impairment Vector defined above.

   The model can be represented as a multidimensional matrix shown in
   the following picture





















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                          _________________________________________
                         /        /       /       /       /       /|
                        /        /       /       /       /       / |
                       /________/_______/_______/_______/_______/  |
                      /        /       /       /       /       /| /|
                     /        /       /       /       /       / |  |
                    /________/_______/_______/_______/_______/  | /|
                   /        /       /       /       /       /| /|  |
                  /        /       /       /       /       / |  | /|
                 /________/_______/_______/_______/_______/  | /|  |
                /        /       /       /       /       /| /|  | /|
               /        /       /       /       /       / |  | /|  |
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  | /|  | / PDL
   <LinkSet#1> |   -   |       |       |       |       | /|  | /|/
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  | /|  /
   <linkSet#2> |       |   -   |       |       |       | /|  | / PND
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  | /|/
   <linkSet#3> |       |       |   -   |       |       | /|  /
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  | / Chr.Disp.
   <linkSet#4> |       |       |       |   -   |       | /|/
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  /
   <linkSet#5> |       |       |       |       |   -   | / OSNR
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                <LS#1>  <LS#2>  <LS#3>  <LS#4>  <LS#5>


   The connectivity matrix from
   [I-D.ietf-ccamp-general-constraint-encode] is only a two dimensional
   matrix, containing only binary information, through the LinkSet
   pairs.  In this model, a third dimension is added by generalizing the
   binary information through the Optical Impairment Vector associated
   with each LinkSet pair.  Optical parameters in the picture are
   reported just as examples while details go into specific encoding
   draft [I-D.martinelli-ccamp-wson-iv-encode].

   This representation shows the most general case however, the total
   amount of information transported by control plane protocols can be
   greatly reduced by proper encoding when the same set of values apply
   to all LinkSet pairs.

   [EDITOR NODE: first run of the information model does looks for
   generality not for optimizing the quantity of information.  We'll
   deal with optimization in a further step.]








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5.2.2.  Impariment Resource Block Information

   This information model reuse the definition of Resource Block
   Information adding the associated impairment vector.


    ResourceBlockInfo ::= <ResourceBlockSet> [<InputConstraints>]
      [<ProcessingCapabilities>] [<OutputConstraints>] [<OIV>]


   The object ResourceBlockInfo is than used as specified within
   [I-D.ietf-ccamp-rwa-info].

5.3.  Link Information

   For the list of optical parameters associated to the link, the same
   approach used for the node-specific impairment information can be
   applied.  The link-specific impairment information is extended from
   [I-D.ietf-ccamp-rwa-info] as the following:


   <DynamicLinkInfo> ::=  <LinkID> <AvailableLabels>
           [<SharedBackupLabels>] [<OIV>]


   DynamicLinkInfo is already defined in [I-D.ietf-ccamp-rwa-info] while
   OIV is the Optical Impairment Vector is defined in the previous
   section.

5.4.  Path Information

   There are cases where the optical impariments can only be described
   as a contrains on the overall end to end path.  In such case, the
   optical impariment and/or parameter, cannot be derived (using a
   simple function) from the set of node / link contributions.

   An equivalent case is the option reported by [RFC6566] on IV-
   Candidate paths where, the control plane knows a list of optically
   feasible paths so a new path setup can be selected among that list.
   Independent from the protocols and functions combination (i.e. RWA
   vs. Routing vs. PCE), the IV-Candidates imply a path property stating
   that a path is optically feasible.


   <PathInfo> ::=  <OIV>






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   [EDITOR NOTE: section to be completed, especially to evaluate
   protocol implications.  Likely resemble to RSVP ADSPEC].

6.  Encoding Considerations

   Details about encoding will be defined in a separate document
   [I-D.martinelli-ccamp-wson-iv-encode] however worth remembering that,
   within [ITU.G697] Appending V, ITU already provides a guideline for
   encoding some optical parameters.

   In particular [ITU.G697] indicates that each parameter shall be
   represented by a 32 bit floating point number.

   Values for optical parameters are provided by optical node and it
   could provide by direct measurement or from some internal computation
   starting from indirect measurement.  In such cases could be useful to
   un understand the variance associated with the value of the optical
   parmater hence, the encoding shall provide the possibility to include
   a variance as well.

   This kind of information will enable IA-RWA process to make some
   additional considerations on wavelength feasibility.  [RFC6566]
   Section 4.1.3 reports some considerations regarding this degree of
   confidence during the impairment validation process.

7.  Control Plane Architectures

   This section briefly describes how the defintions contained in this
   information model will match the architectural options described by
   [RFC6566].

   The first assumption is that the WSON GMPLS extentions are available
   and operational.  To such extent, the WSON-RWA will provide the
   following information through its path computation (and RWA process):

   o  The wavelengths connectivity, considering also the connectivity
      constraints limited by reconfigurable optics, and wavelengths
      availability.

   o  The interface compatibility at the physical level.

   o  The Optical-Elettro-Optical (OEO) availability within the network
      (and related physical interface compatibility).  As already stated
      by the framework this information it's very important for
      impairment validation:

      A.  If the IV functions fail (path optically infeasible), the path
          computation function may use an available OEO point to find a



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          feasible path.  In normally operated networks OEO are mainly
          uses to support optically unfeasible path than mere wavelength
          conversion.

      B.  The OEO points reset the optical impairment information since
          a new light is generated.

7.1.  IV-Centralized

   Centralized IV process is performed by a single entity (e.g., a PCE).
   Given sufficient impairment information, it can either be used to
   provide a list of paths between two nodes, which are valid in terms
   of optical impairments.  Alternatively, it can help validate whether
   a particular selected path and wavelength is feasiable or not.  This
   requires distribution of impairment information to the entity
   performing the IV process.

   [EDITOR NOTE: to be completed]

7.2.  IV-Distributed

   For the distributed IV process, common computational models are
   needed together with the information model defined in this document.
   Computational models for the optical impairments are defined by ITU
   standard body.  The currently available computation models are
   reported in [ITU.G680] and only cover the linear impairment case.
   This does not require the distribution of impairment information
   since they can be collected hop-by-hop using a control plane
   signaling protocol.

   [EDITOR NOTE: to be completed]

8.  Acknowledgements

   Authors would like to thank ITU SG15/Q6 and in particular Pete Anslow
   for providing text and information to CCAMP through join meetings and
   liasons.

9.  Contributing Authors

   This document was the collective work of several authors.  The text
   and content of this document was contributed by the editors and the
   co-authors listed below (the contact information for the editors
   appears in appropriate section and is not repeated below):







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   Moustafa Kattan
   Cisco
   DUBAI,   500321
   UNITED ARAB EMIRATES

   Email: mkattan@cisco.com


   Young Lee
   Huawei
   1700 Alma Drive, Suite 100
   Plano, TX  75075
   USA

   Phone: +1 972 509 5599 x2240
   Fax:   +1 469 229 5397
   Email: ylee@huawei.com


   Greg M. Bernstein
   Grotto Networking
   Fremont, CA
   USA

   Phone: +1 510 573 2237
   Email: gregb@grotto-networking.com


   Fatai Zhang
   Huawei
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   P.R. China

   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com


   Federico Pederzolli
   CREATE-NET
   via alla Cascata 56/D, Povo
   Trento  38123
   Italy

   Email: federico.pederzolli@create-net.org






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10.  IANA Considerations

   This document does not contain any IANA requirement.

11.  Security Considerations

   This document defines an information model for impairments in optical
   networks.  If such a model is put into use within a network it will
   by its nature contain details of the physical characteristics of an
   optical network.  Such information would need to be protected from
   intentional or unintentional disclosure.

12.  References

12.1.  Normative References

   [ITU.G671]
              International Telecommunications Union, "Transmission
              characteristics of optical components and subsystems",
              ITU-T Recommendation G.671, February 2012.

   [ITU.G680]
              International Telecommunications Union, "Physical transfer
              functions of optical network elements", ITU-T
              Recommendation G.680, July 2007.

   [ITU.G697]
              International Telecommunications Union, "Optical
              monitoring for dense wavelength division multiplexing
              systems", ITU-T Recommendation G.697, February 2012.

12.2.  Informative References

   [I-D.ietf-ccamp-general-constraint-encode]
              Bernstein, G., Lee, Y., Li, D., and W. Imajuku, "General
              Network Element Constraint Encoding for GMPLS Controlled
              Networks", draft-ietf-ccamp-general-constraint-encode-13
              (work in progress), November 2013.

   [I-D.ietf-ccamp-rwa-info]
              Lee, Y., Bernstein, G., Li, D., and W. Imajuku, "Routing
              and Wavelength Assignment Information Model for Wavelength
              Switched Optical Networks", draft-ietf-ccamp-rwa-info-19
              (work in progress), November 2013.







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   [I-D.martinelli-ccamp-wson-iv-encode]
              Martinelli, G., Zanardi, A., Zhang, X., Galimberti, G.,
              and D. Siracusa, "Information Encoding for WSON with
              Impairments Validation", draft-martinelli-ccamp-wson-iv-
              encode-02 (work in progress), July 2013.

   [RFC6163]  Lee, Y., Bernstein, G., and W. Imajuku, "Framework for
              GMPLS and Path Computation Element (PCE) Control of
              Wavelength Switched Optical Networks (WSONs)", RFC 6163,
              April 2011.

   [RFC6566]  Lee, Y., Bernstein, G., Li, D., and G. Martinelli, "A
              Framework for the Control of Wavelength Switched Optical
              Networks (WSONs) with Impairments", RFC 6566, March 2012.

Appendix A.  ITU-T Liason Tracking

   [EDITOR NOTE: appendix reserved to track liason to/from ITU related
   to this draft]

Authors' Addresses

   Giovanni Martinelli (editor)
   Cisco
   via Philips 12
   Monza  20900
   Italy

   Phone: +39 039 2092044
   Email: giomarti@cisco.com


   Xian Zhang (editor)
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzen  518129
   P.R. China

   Phone: +86 755 28972465
   Email: zhang.xian@huawei.com










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   Gabriele M. Galimberti
   Cisco
   Via Philips,12
   Monza  20900
   Italy

   Phone: +39 039 2091462
   Email: ggalimbe@cisco.com


   Andrea Zanardi
   CREATE-NET
   via alla Cascata 56/D, Povo
   Trento  38123
   Italy

   Email: andrea.zanardi@create-net.org


   Domenico Siracusa
   CREATE-NET
   via alla Cascata 56/D, Povo
   Trento  38123
   Italy

   Email: domenico.siracusa@create-net.org

























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