Information Model for Wavelength Switched Optical Networks (WSON) with Optical Impairments Validation.
draft-martinelli-ccamp-wson-iv-info-01
CCAMP G. Martinelli, Ed.
Internet-Draft M. Kattan
Intended status: Informational G. Galimberti
Expires: August 27, 2013 Cisco
A. Zanardi, Ed.
CREATE-NET
February 23, 2013
Information Model for Wavelength Switched Optical Networks (WSON) with
Optical Impairments Validation.
draft-martinelli-ccamp-wson-iv-info-01
Abstract
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
Task Force (IETF). Note that other groups may also distribute
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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 27, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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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 . . . . . . . . . . . . . 6
4.1. Node Information . . . . . . . . . . . . . . . . . . . . . 7
4.2. Link Information . . . . . . . . . . . . . . . . . . . . . 8
4.3. Path Information . . . . . . . . . . . . . . . . . . . . . 9
5. Encoding Considerations . . . . . . . . . . . . . . . . . . . 9
6. Information model versus Control Plane Architectures . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Security Considerations . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
11.1. Normative References . . . . . . . . . . . . . . . . . . . 11
11.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. G.680 Essential information . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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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
case.
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 provides the 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 is
independent from any architectural option described by the framework
[RFC6566]: it shall support all of them.
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 only the linear impairment
case. This perfectly fit with scenario C defined in [RFC6566]
section 4.1.1 and is considered in scope with WSON activity. The
non-linear case is left for further study since currently no ITU
computational models are available for an accurate optical impairment
estimation.
The information model defined here provides a generic enough
mechanism that could be easily extended to additional impairments
models.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
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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.
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].
During the impairment validation process, this property implies
that the optical effect (or quantity) satisfy 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. 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
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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.
+-----------------------+----------------------+
| 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 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 node
connectivity capability due to internal optical node constrain. It's
essentially a binary information and tell us if a wavelengths or a
set of wavelengths can go from an input port to an output port.
As a additional note, Connectivity Matrix belong to Node Information
and is purely static. Dynamic information related to the actual
usage of the connections are available through specific extension to
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link 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 and Links (i.e. fibers).
The goal of this document 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. [ITU.G680] computational models defined in section 9
provide information to calculate the following optical 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
The recommendation [ITU.G680] call its computational model "transfer
function" and details formulas for a set of different optical
equipments. For the purpose of this information model, only the set
of parameter is important.
This Information Model makes the assumption that the each Optical
Node in the network is able to provide it's own contribution to above
parameters. To this extent the Information Model intentionally
ignore all internal detailed parameters that are used to by the
formulas (i.e. "transfer function") but simply provide the object to
carry results of the formulas. However no assumption is made on how
the Optical node get the result of parameter contribution (e.g.
computed, provisioned, known by design, etc.).
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 provides an
abstract view for an optical node and link to enable WSON protocol
extension with optical impairments validation.
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4.1. Node Information
This model defines the Impairment Matrix as the following:
ImpairmentMatrix ::= <MatrixID> <ConnType>
((<LinkSet> <LinkSet> <ImpairmemtVector>) ...)
Where:
MatrixID. Is a unique identifier for the Matrix. This ID 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 WSON documents.
LinkSet. Same object definition and usage as
[I-D.ietf-ccamp-general-constraint-encode].
ImpairmentVector is defined as list of optical parameters associated
to the internal node connection.
<ImpairmentVector> ::= [<LinkSet>] <OPTICAL_PARAM> ...
The optional LinkSet object enable wavelength dependency property as
per Table 1.
OPTICAL_PARAM is an object representing an optical parameter. The
Impairment vector 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 set of parameters (since
defined elsewhere, e.g. ITU-T), however it does not preclude
extentions by adding new parameters.
The model can be represented as the 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] only defines the two
dimensional matrix, containining only binary information, through the
LinkSet pairsa binary information. In this model a third dimension
is added by generalizing the bnary information through the
ImpairmentVector associated with each LinkSet pair. Optical
parameter names in the picture are reported just as an example while
detailed definitions will go into specific encoding drafts
[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 same set of values apply to
all LinkSet pairs.
4.2. Link Information
The same approach used for the Node information can be used at Link
Level. The Link information for WSON is extended in
[I-D.ietf-ccamp-rwa-info]. This information model provide the
following additional extension:
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<DynamicLinkInfo> ::= <LinkID> <AvailableLabels>
[<SharedBackupLabels>] [<ImpairmentVector>]
DynamicLinkInfo is exactly the only already defined in
[I-D.ietf-ccamp-rwa-info] while ImpairmentVector is defined in the
previous section. Is considered as optional since apply as an
extention to existing Link information.
In this case the list of contained optical parameters are associated
to the link.
4.3. Path Information
In case of a control plane with impairment validation awareness
there's might be cases where informations apply to the whole path and
cannot be composed by individual contributions of links and nodes.
The cases where this kind of information might be required are
reported within [RFC6566] (Section 4.2.2 IV-Canditates or Sharing
Constraints).
<PathInfo> ::= <ImpairmentVector>
[EDITOR NOTE: section to be completed].
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 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
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
feasibility. [RFC6566] Section 4.1.3 reports some considerations
regarding this degree of confidence during the impairment validation
process.
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6. Information model versus Control Plane Architectures
This section will briefly describe how the wholes set of informations
defined by this info model will match the architectural options
defined in [RFC6566]
The first assumption is that the RWA-WSON extentions are available
and operationals. To such extent, the RWA-WSON will provide the
following information through it's path computation (and RWA
process):
o The wavelenght connectivity (considering also the connectivity
constrains by limited reconfigurable optics).
o The interface compatibility at the physical level.
o The Optical-Elettro-Optical (OEO) availability within the network
(and releater physical interface compatibility as here above).
[EDITOR NOTE: to be completed]
7. Acknowledgements
TBD
8. Contributors
Tim Gibbon
Department of Physics
Nelson Mandela Metropolitan University
SOUTH AFRICA
Email: Tim.Gibbon@nmmu.ac.za
9. IANA Considerations
This document does not contain any IANA requirement
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10. Security Considerations
All drafts are required to have a security considerations section.
See RFC 3552 [RFC3552] for a guide.
11. References
11.1. Normative References
[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.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. 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-08
(work in progress), July 2012.
[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-14
(work in progress), March 2012.
[I-D.martinelli-ccamp-wson-iv-encode]
Martinelli, G., Kattan, M., Galimberti, G., and A.
Zanardi, "Encoding for WSON Information Model with
Impairments Validation.",
draft-martinelli-ccamp-wson-iv-encode-00 (work in
progress), July 2012.
[I-D.narten-iana-considerations-rfc2434bis]
Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs",
draft-narten-iana-considerations-rfc2434bis-09 (work in
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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 (editor)
Cisco
via Philips 12
Monza, 20900
Italy
Phone: +39 039 2092044
Email: giomarti@cisco.com
Moustafa Kattan
Cisco
DUBAI, 500321
UNITED ARAB EMIRATES
Phone:
Email: mkattan@cisco.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 (editor)
CREATE-NET
via alla Cascata 56 C, Povo
Trento 38100
Italy
Email: andrea.zanardi@create-net.org
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