CCAMP                                                 G. Martinelli, Ed.
Internet-Draft                                                     Cisco
Intended status: Informational                             X. Zhang, Ed.
Expires: January 14, 2014                            Huawei Technologies
                                                           G. Galimberti
                                                              A. Zanardi
                                                             D. Siracusa
                                                           July 13, 2013

Information Model for Wavelength Switched Optical Networks (WSONs) with
                         Impairments Validation


   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

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   This Internet-Draft will expire on January 14, 2014.

Copyright Notice

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   Copyright (c) 2013 IETF Trust and the persons identified as the
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   ( in effect on the date of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Applicability . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Properties of an Impairment Information Model . . . . . . . .   3
   3.  Background from WSON Information Model  . . . . . . . . . . .   5
   4.  Optical Impairment Information Model  . . . . . . . . . . . .   6
     4.1.  The Optical Impairment Vector . . . . . . . . . . . . . .   7
     4.2.  Node Information  . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Link Information  . . . . . . . . . . . . . . . . . . . .   9
     4.4.  Path Information  . . . . . . . . . . . . . . . . . . . .   9
   5.  Encoding Considerations . . . . . . . . . . . . . . . . . . .  10
   6.  Control Plane Architectures . . . . . . . . . . . . . . . . .  10
     6.1.  IV-Centralized  . . . . . . . . . . . . . . . . . . . . .  11
     6.2.  IV-Distributed  . . . . . . . . . . . . . . . . . . . . .  11
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  G.680 Essential information  . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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

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   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
   functions is provided.

1.1.  Applicability

   This document targets at Scenario C defined in [RFC6566] section
   4.1.1., i.e., approximate impairment estimation.  The usage of
   "Approximate" concept helps to clarify that a path resulting from a
   IV-RWA process are not guaranteed to work from an optical perspective
   however, has better chance to be feasible than other(s).  Setting up
   the ligth-path, there is still a possibility to fail but this is an
   acceptable in term of GMPLS control plane.

   The information model defined in this document strictly relates to a
   control plane information model hence it does not define any new
   Optical Computational Model.  Optical Computational Models are
   defined by ITU-T, [ITU.G680] defines transfer functions for some
   linear optical parameters while there's no general optical
   computational model for non-linear effects.  This information model
   uses the available optical computational model as a reference, and
   identify GMPLS WSON control plane extensions to allow IV functions to
   perform its task.

   Following here above considerations, scope of this information model
   is to provide a generic mechanism so will easily support additional
   impairment parameters and/or additional optical computational models.

2.  Properties of an Impairment Information Model

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   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

   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

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      There are cases where a channel's impairments take different
      values depending on the aside wavelengths already in place, this
      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.  Background from WSON 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:

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

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

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

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   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.

4.  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.

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

   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.

   In term of optical parameters, this document is not to rephrase
   content from [ITU.G680] but only provide necessary building blocks
   that allow the IA-RWA process to apply the specific Optical
   Computational Model (i.e. transfer functions).  Section 9 of
   [ITU.G680] defines the optical computational models and provides
   information to calculate the following optical parameters:

   o  OSNR.  Section 9.1

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

   o  Chromatic Dispersion (CD).  Section 9.2

   o  Polarization Mode Dispersion (PMD).  Section 9.3

   o  Polarization Dependent Loss (PDL).  Section 9.3

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   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.

4.1.  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

   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.

4.2.  Node Information

   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>) ...)

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      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

                         /        /       /       /       /       /|
                        /        /       /       /       /       / |
                       /________/_______/_______/_______/_______/  |
                      /        /       /       /       /       /| /|
                     /        /       /       /       /       / |  |
                    /________/_______/_______/_______/_______/  | /|
                   /        /       /       /       /       /| /|  |
                  /        /       /       /       /       / |  | /|
                 /________/_______/_______/_______/_______/  | /|  |
                /        /       /       /       /       /| /|  | /|
               /        /       /       /       /       / |  | /|  |
               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  | /|  | / 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>

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   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.]

4.3.  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

4.4.  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.

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   <PathInfo> ::=  <OIV>

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

5.  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.

   As an additional consideration, actual values for each optical
   parameter are provided by each optical node and it could provide by
   direct measurement or from some internal computation starting from
   indirect measurement.  In any case the encoding shall provide the
   possibility to associate a variance with the parameter.  This
   information will enable the function implementing 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.

6.  Control Plane Architectures

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

   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

   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:

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      a.  If the IV functions fail (path optically infeasible), the path
          computation function may use an available OEO point to find a
          feasible path.  In normally operated networks OEO are mainly
          uses to support optically unfeasible path than mere wavelength

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

6.1.  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]

6.2.  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]

7.  Acknowledgements


8.  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):

   Moustafa Kattan

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   DUBAI,   500321


   Tim Gibbon
   Department of Physics
   Nelson Mandela Metropolitan University


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

   Greg M. Bernstein
   Grotto Networking
   Fremont, CA

   Phone: +1 510 573 2237

   Phone: +1 972 509 5599 x2240
   Fax:   +1 469 229 5397

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

   Phone: +86-755-28972912

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9.  IANA Considerations

   This document does not contain any IANA requirement.

10.  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.

11.  References

11.1.  Normative References

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

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

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

11.2.  Informative References

              Bernstein, G., Lee, Y., Li, D., and W. Imajuku, "General
              Network Element Constraint Encoding for GMPLS Controlled
              Networks", draft-ietf-ccamp-general-constraint-encode-11
              (work in progress), May 2013.

              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-18
              (work in progress), May 2013.

              Martinelli, G., Kattan, M., Galimberti, G., and A.
              Zanardi, "Encoding for WSON Information Model with
              Impairments Validation.", draft-martinelli-ccamp-wson-iv-
              encode-01 (work in progress), February 2013.

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              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", draft-narten-iana-
              considerations-rfc2434bis-09 (work in progress), March

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July

   [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.  G.680 Essential information

   TBD if we need some info instead of reading [ITU.G680]

   [Xian's note]: I thought about listing paramters to show different
   categories. but it seems to contradict to the idea of providing a
   general enough information model.  Any suggestions?

Authors' Addresses

   Giovanni Martinelli (editor)
   via Philips 12
   Monza  20900

   Phone: +39 039 2092044

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

   Phone: +86 755 28972913

   Gabriele M. Galimberti
   Via Philips,12
   Monza  20900

   Phone: +39 039 2091462

   Andrea Zanardi
   via alla Cascata 56 C, Povo
   Trento  38100


   Domenico Siracusa
   via alla Cascata 56 C, Povo
   Trento  38100


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