CCAMP G. Martinelli
Internet-Draft M. Kattan
Intended status: Informational G. Galimberti
Expires: January 31, 2013 Cisco
A. Zanardi
CREATE-NET
July 30, 2012
Information Model for Wavelength Switched Optical Networks (WSON) with
Optical Impairments Validation.
draft-martinelli-ccamp-wson-iv-info-00
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
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material or to cite them other than as "work in progress."
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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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
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 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
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
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>) ...)
Where:
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
[I-D.ietf-ccamp-general-constraint-encode].
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
list.
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>
[<SharedBackupLabels>]
<ImpairmentVector>
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
feasibility.
6. Acknowledgements
TBD
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
[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.
9.2. 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]
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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.
[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
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
Cisco
via Philips 12
Monza, 20900
Italy
Phone: +39 039 2092044
Email: giomarti@cisco.com
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Moustafa Kattan
Cisco
DUBAI, 500321
UNITED ARAB EMIRATES
Phone:
Email: mkattan@cisco.com
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 C, Povo
Trento 38100
Italy
Email: andrea.zanardi@create-net.org
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