CCAMP                                                      G. Martinelli
Internet-Draft                                                 M. Kattan
Intended status: Informational                             G. Galimberti
Expires: January 31, 2013                                          Cisco
                                                              A. Zanardi
                                                           July 30, 2012

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


   This document defines the Information Model to support Impairment-
   Aware (IA) Routing an 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 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
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   This Internet-Draft will expire on January 31, 2013.

Copyright Notice

   Copyright (c) 2012 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
   ( 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Properties of an Impairment Information Model . . . . . . . . . 3
   3.  Background from WSON Information Model  . . . . . . . . . . . . 5
   4.  Optical Impairment Information Model  . . . . . . . . . . . . . 5
     4.1.  Node Information  . . . . . . . . . . . . . . . . . . . . . 6
     4.2.  Link Information  . . . . . . . . . . . . . . . . . . . . . 7
   5.  Encoding Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Appendix A.  G.680 Essential information  . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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1.  Introduction

   In the context of Wavelength Switched Optical Network (WSON),
   [RFC6163] defines the basic framework for a GMPLS control plane.  The
   associated info model [I-D.ietf-ccamp-rwa-info] defines all
   parameters required for the related RWA process.  These references
   are the foundation but they do not consider the Optical Impairment

   In case of WSON where optical impairments plays a significant role,
   the framework document [RFC6566] defines related control plane
   architectural options for an Impairment Aware routing and wavelength
   assignment (IA-RWA).  Options include different combinations of
   Impairment Validation (IV) and RWA functions through control plane
   elements and operations (PCE, Routing, Signaling).

   This document intent to provide the information model for the
   impairment aware case to allow the impairment validation function.
   It goes in addition with [I-D.ietf-ccamp-rwa-info] and the model
   itself is independ of any architectural option described by the
   framework and shall support all of them.

   Models for the optical impairments are defined by ITU and the only
   available models are reported in [ITU.G680] to cover only the linear
   impairment case while non-linear case is left for further study.  The
   information model defined here however provide a generic enough
   mechanism that could be easily extended to additional impairments

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Properties of an Impairment Information Model

   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 it 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.

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   o  Time Dependency.
      This will identify how the impairment may vary with time.  There
      could be cases where there is no time dependency, while in other
      cases there may be need of impairment 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 a level of approximation will consider
      an impairment that has time dependency as constant.  In this
      Information Model we do neglect this property.

   o  Wavelength Dependency.
      This property will identify if an impairment value can be
      considered as constant over all the wavelength spectrum of
      interest or if it has different values.  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 / not dependency from a specific wavelengths.  This
      property may appear directly in the Information model definitions
      or in the 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].  The
      linearity implies the additivity optical quantities considered
      during an Impairment Validation process.  As an additional
      approximation level, non-linear impairments as contribution into
      linear ones.  This Information Model deals with the linear
      properties of optical impairments.

   o  Multi-Channel.
      There are cases where a channel's impairments take different
      values depending on the aside wavelengths already in place.  In
      this case a dependency among different LSP is introduced and is
      typically a result of linear effects.  This Information Model
      neglect this effects on neighbor LSPs.

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

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             |        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 (not
   impairment aware) 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 follow:

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

   However according to [I-D.ietf-ccamp-general-constraint-encode] this
   definitions can be further detailed as:

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

   This second definition highlights how the connectivity matrix is
   built by pairs of LinkSet objects identifying the internal node
   connectivity capability.

   As a additional note, Connectivity Matrix belong to Node Information.

4.  Optical Impairment Information Model

   The idea behind this Information Model is to reuse the concept of the
   Connectivity Matrix and defines an Impairment Matrix that summarize
   optical impairments provided by the Node.

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   The goal of the information model is not to rephrase content from
   [ITU.G680] but only provide necessary building blocks that allow the
   IW-RWA process to apply the computational model defined by such
   recommendation.  Then the [ITU.G680] model defined in section 9
   provide information to calculate the following parameters:

   o  OSNR.  Section 9.1

   o  Chromatic Dispersion (CD).  Section 9.2

   o  Polarization Mode Dispersion (PMD).  Section 9.3

   o  Polarization Dependent Loss (PDL).  Section 9.3

   It should be noted that [ITU.G697] already defines an encoding for
   all these parameters and in Section 5 we report some encoding
   consideration.  The [ITU.G697] is mainly oriented for monitoring so
   the purpose is only reuse parameter definitions for those parameters
   required by Impairment Validation process.

   The information model defined here make the assumption that the
   Optical Node is able to provide it's own contribution to such
   parameters.  To this extend the information model intentionally
   ignore all internal detailed parameters that are used to by the
   formulas.  As an additional note, as reported in in [ITU.G680]
   Section 10, each parameter can be reported as an OSNR contribution,
   in such way the Optical Node not necessarily embed optical
   computational capability but can provide an approximated contribution
   to optical impairments.

   With the above considerations this Information Model is able provide
   an abstract view for an optical node to enable WSON protocol
   extension with optical impairments validation.

4.1.  Node Information

   This model defines the Impairment Matrix as the following:

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


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

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      ConnType.  The type of matrix.  Since values 0 and 1 are already
      defined.  This document defines the value 2.

      LinkSet.  Same object definition and usage as

   ImpairmentVector is defined as list of optical parmeters associated
   to the internal node connection.

   ImpairmentVector ::= <OPTICAL_PARAM> ...

   The set of OPTICAL_PARAM is identified by [ITU.G697] since they match
   with parameters required by the linear impairments evaluation
   provided by [ITU.G680].  This info model does not preclude any of
   such parameters and eventually new parameters can be added to the

4.2.  Link Information

   Currently not evaluated yet any information is required at Link Level
   however the same approach can be used as in case of Node Information
   section.  The Link information defined in [I-D.ietf-ccamp-rwa-info]
   is extend in the following way:

   <DynamicLinkInfo> ::=  <LinkID> <AvailableLabels>

   With ImpairmentVector defined as previous section.

5.  Encoding Considerations

   Details about encoding will be defined in a separate document 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 parameters shall be
   represented by a 32 bit floating point number.

   As an additional consideration, actual values for parameters defined
   in the information models are provided by the Optical Node and it
   could provide by direct measurement or from some internal computation
   starting from indirect measurement.  In any case the encoding shall

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   provide an the possibility to associate a variance with the
   parameter.  This information will enable the function implementing
   IV-RWA process to make some additional considerations on wavelength

6.  Acknowledgements


7.  IANA Considerations

   This document does not have ant IANA requirement.

8.  Security Considerations

   All drafts are required to have a security considerations section.
   See RFC 3552 [RFC3552] for a guide.

9.  References

9.1.  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.

9.2.  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-08
              (work in progress), July 2012.


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              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-14
              (work in progress), March 2012.

              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs",
              draft-narten-iana-considerations-rfc2434bis-09 (work in
              progress), March 2008.

   [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 2003.

   [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]

Authors' Addresses

   Giovanni Martinelli
   via Philips 12
   Monza,   20900

   Phone: +39 039 2092044

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   Moustafa Kattan
   DUBAI,   500321


   Gabriele M. Galimberti
   Via Philips,12
   Monza  20900

   Phone: +39 039 2091462

   Andrea Zanardi
   via alla Cascata 56 C, Povo
   Trento  38100


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