One document matched: draft-bernstein-ccamp-wson-info-03.txt
Differences from draft-bernstein-ccamp-wson-info-02.txt
Network Working Group G. Bernstein
Internet Draft Grotto Networking
Intended status: Informational Y. Lee
Expires: January 2009 D. Li
Huawei
W. Imajuku
NTT
July 7, 2008
Routing and Wavelength Assignment Information Model for Wavelength
Switched Optical Networks
draft-bernstein-ccamp-wson-info-03.txt
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Abstract
This document provides an information model of information needed by
the routing and wavelength assignment (RWA) process in wavelength
switched optical networks (WSONs). The purpose of information
described in this model is to facilitate constrained lightpath
computation in WSONs. In particular in cases where there are no or a
limited number of wavelength converters available in the WSON. This
model currently does not include optical impairments.
Table of Contents
1. Introduction...................................................3
2. Terminology....................................................3
3. Routing and Wavelength Assignment Information Model............4
3.1. Dynamic and Relatively Static Information.................4
3.2. Node Information..........................................4
3.2.1. Switched Connectivity Matrix.........................5
3.2.2. Fixed Connectivity Matrix............................5
3.2.3. Shared Risk Node Group...............................6
3.2.4. Wavelength Converter Pool............................6
3.2.4.1. OEO Wavelength Converter Info...................6
3.3. Link Information..........................................7
3.3.1. Link ID..............................................7
3.3.2. Administrative Group.................................8
3.3.3. Interface Switching Capability Descriptor............8
3.3.4. Link Protection Type (for this link).................8
3.3.5. Shared Risk Link Group Information...................8
3.3.6. Traffic Engineering Metric...........................8
3.3.7. Maximum Bandwidth Per Channel........................8
3.3.8. Switched and Fixed Port Wavelength Restrictions......9
3.4. Dynamic Link Information.................................10
3.5. Dynamic Node Information.................................10
4. Security Considerations.......................................10
5. IANA Considerations...........................................11
6. Acknowledgments...............................................11
7. References....................................................12
7.1. Normative References.....................................12
7.2. Informative References...................................12
8. Contributors..................................................13
Author's Addresses...............................................13
Intellectual Property Statement..................................14
Disclaimer of Validity...........................................15
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1. Introduction
The purpose of the following information model for WSONs is to
facilitate constrained lightpath computation and as such this is not
a general purpose network management information model. In particular
this model has particular value in the cases where there are no or a
limited number of wavelength converters available in the WSON. This
constraint is frequently referred to as the "wavelength continuity"
constraint, and the corresponding constrained lightpath computation
is known as the routing and wavelength assignment (RWA) problem.
Hence the information model must provide sufficient topology and
wavelength restriction and availability information to support this
computation. More details on the RWA process and WSON subsystems and
their properties can be found in [WSON-Frame]. The model defined here
does not currently include impairments however optical impairments
can be accommodated by the general framework presented here.
2. Terminology
CWDM: Coarse Wavelength Division Multiplexing.
DWDM: Dense Wavelength Division Multiplexing.
FOADM: Fixed Optical Add/Drop Multiplexer.
ROADM: Reconfigurable Optical Add/Drop Multiplexer. A reduced port
count wavelength selective switching element featuring ingress and
egress line side ports as well as add/drop side ports.
RWA: Routing and Wavelength Assignment.
Wavelength Conversion. The process of converting an information
bearing optical signal centered at a given wavelength to one with
"equivalent" content centered at a different wavelength. Wavelength
conversion can be implemented via an optical-electronic-optical (OEO)
process or via a strictly optical process.
WDM: Wavelength Division Multiplexing.
Wavelength Switched Optical Network (WSON): A WDM based optical
network in which switching is performed selectively based on the
center wavelength of an optical signal.
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3. Routing and Wavelength Assignment Information Model
We group the following WSON RWA information model into four
categories regardless of whether they stem from a switching subsystem
or from a line subsystem:
o Node Information
o Link Information
o Dynamic Node Information
o Dynamic Link Information
Note that this is roughly the categorization used in [G.7715] section
7.
In the following we use a BNF/Regular expression like syntax where
the symbol "|" indicates a choice between two or more elements; the
symbol "*" indicates zero or more occurrences of an element; the
symbol "?" indicates zero or one occurrences; and the symbol "+"
indicates one or more occurrences.
3.1. Dynamic and Relatively Static Information
All the RWA information of concern in a WSON network is subject to
change over time. Equipment can be upgraded; links may be placed in
or out of service and the like. However, from the point of view of
RWA computations there is a difference between information that can
change with each successive connection establishment in the network
and that information that is relatively static on the time scales of
connection establishment. A key example of the former is link
wavelength usage since this can change with connection setup/teardown
and this information is a key input to the RWA process. Examples of
relatively static information are the internal connectivity of a WDM
ROADM, and the channel spacing on a WDM link.
In this document we will separate, where possible, dynamic and static
information so that these can be kept separate in possible encodings
and hence allowing for separate updates of these two types of
information thereby reducing processing and traffic load caused by
the timely distribution of the more dynamic RWA WSON information.
3.2. Node Information
The node information described here contains the relatively static
information related to a WSON node. This includes connectivity
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constraints amongst ports and wavelengths since WSON switches can
exhibit asymmetric switching properties. Additional information could
include properties of wavelength converters in the node if any are
present. In [Switch] it was shown that the wavelength connectivity
constraints for a large class of practical WSON devices can be
modeled via switched and fixed connectivity matrices along with
corresponding switched and fixed port constraints. We include these
connectivity matrices with our node information the switched and
fixed port wavelength constraints with the link information.
Formally,
Node Information := Node_ID, SwitchedConnectivityMatrix?,
FixedConnectivityMatrix?, SRNG?, WavelengthConverterPool?
Where the Node_ID would be an appropriate identifier for the node
within the WSON RWA context.
3.2.1. Switched Connectivity Matrix
The switched connectivity matrix (SwitchConnectivityMatrix)
represents the potential connectivity matrix for asymmetric switches
(e.g. ROADMs and such). This is a conceptual M by N matrix
representing the switched connectivity, where M represents the number
of ingress ports and N the number of egress ports. We say this is a
"conceptual" since this matrix tends to exhibit structure that allows
for very compact representations that are useful for both
transmission and path computation [Encode]
SwitchedConnectivityMatrix(i, j) = 0 or 1 depending on whether
ingress port i can connect to egress port j for one or more
wavelengths.
3.2.2. Fixed Connectivity Matrix
The fixed connectivity matrix (FixedConnectivityMatrix) represents
the connectivity for asymmetric fixed devices or the fixed part of a
"hybrid" device [Switch]. This is a conceptual M by N matrix, where M
represents the number of ingress ports and N the number of egress
ports. We say this is a "conceptual" since this matrix tends to
exhibit structure that allows for very compact representations.
FixedConnectivityMatrix(i, j) = 0 or 1 depending on whether ingress
port i is connected to egress port j for one or more wavelengths.
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3.2.3. Shared Risk Node Group
SRNG: Shared risk group for nodes. The concept of a shared risk link
group was defined in [RFC4202]. This can be used to achieve a desired
"amount" of link diversity. It is also desirable to have a similar
capability to achieve various degrees of node diversity. This is
explained in [G.7715]. Typical risk groupings for nodes can include
those nodes in the same building, within the same city, or geographic
region.
3.2.4. Wavelength Converter Pool
A WSON node may include wavelength converters. These are usually
arranged into some type of pool to promote resource sharing. There
are a number of different approaches used in the design of switches
with converter pools. However, from the point of view of path
computation we need to know the following:
1. The nodes that support wavelength conversion.
2. The accessibility of the wavelength converter pool from a
particular port and wavelength.
3. Limitations on the types of signals that can be converted and the
conversions that can be performed.
A general representation of the converter pool with respect to
resource availability from a particular port and wavelength is TBD
and will be furnished in a subsequent revision of this draft.
Particular types of individual wavelength converters, such as those
based on an OEO approach can be characterized fairly completely as
specified below.
3.2.4.1. OEO Wavelength Converter Info
An OEO based wavelength converter can be characterized by an input
wavelength set and an output wavelength set. In addition any
constraints on the signal formats and rates accommodated by the
converter must be described. Such a wavelength converter can be
modeled by:
OEOWavelengthConverterInfo := RegeneratorType,
IngressWavelengthRange, EgressWavelengthRange, BitRateRange?,
AcceptableSignals?
Where the RegeneratorType is used to model an OEO regenerator.
Regenerators are usually classified into three types. Level 1
provides signal amplification, level 2 amplification and pulse
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shaping, and level 3 amplification, pulse shaping and timing
regeneration. Level 2 regenerators can have a restricted bit rate
range, while level 3 regenerators can also be specialized to a
particular signal type.
IngressWavelengthRange and EgressWavelengthRange are sets of
wavelengths that characterize the input wavelengths acceptable to the
wavelength converter and the outputs that can be generated by the
wavelength converter.
BitRateRange: indicates the range of bit rates that can be
accommodated by the wavelength converter.
AcceptableSignals: is a list of signals that the wavelength converter
can handle. This could be fairly general for Level 1 and Level 2
regenerators, e.g., characterized by general signal properties such
as modulation type and related parameters, or fairly specific signal
types for Level 3 based regenerators.
3.3. Link Information
MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630,
RFC3784] along with GMPLS routing protocol extensions for OSPF and
IS-IS [RFC4203, RFC4205] provide the bulk of the relatively static
link information needed by the RWA process. WSON networks bring in
additional link related constraints. These stem from WDM line system
characterization, laser transmitter tuning restrictions, and
switching subsystem port wavelength constraints, e.g., colored ROADM
drop ports.
In the following summarize both information from existing route
protocols and new information that maybe needed by the RWA process.
LinkInfo := LinkID, AdministrativeGroup?, InterfaceCapDesc?,
Protection?, SRLG*, TrafficEngineeringMetric?,
MaximumBandwidthPerChannel?, SwitchedPortWavelengthRestriction?,
FixedPortWavelengthRestriction?
3.3.1. Link ID
LinkID: LocalLinkID, LocalNodeID, RemoteLinkID, RemoteNodeID
Here we can generally identify a link via a combination of local and
remote node identifiers along with the corresponding local and remote
link identifiers per [RFC4202, RFC4203, RFC4205]. Note that reference
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[RFC3630] provides other ways to identify local and remote link ends
in the case of numbered links.
3.3.2. Administrative Group
AdministrativeGroup: Defined in [RFC3630]. Each set bit corresponds
to one administrative group assigned to the interface. A link may
belong to multiple groups. This is a configured quantity and can be
used to influence routing decisions.
3.3.3. Interface Switching Capability Descriptor
InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different
switching capabilities on this GMPLS interface. In both [RFC4203] and
[RFC4205] this information gets combined with the maximum LSP
bandwidth that can be used on this link at eight different priority
levels.
3.3.4. Link Protection Type (for this link)
Protection: Defined in [RFC4202] and implemented in [RFC4203,
RFC4205]. Used to indicate what protection, if any, is guarding this
link.
3.3.5. Shared Risk Link Group Information
SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC4205].
This allows for the grouping of links into shared risk groups, i.e.,
those links that are likely, for some reason, to fail at the same
time.
3.3.6. Traffic Engineering Metric
TrafficEngineeringMetric: Defined in [RFC3630]. This allows for the
definition of one additional link metric value for traffic
engineering separate from the IP link state routing protocols link
metric. Note that multiple "link metric values" could find use in
optical networks, however it would be more useful to the RWA process
to assign these specific meanings such as link mile metric, or
probability of failure metric, etc...
3.3.7. Maximum Bandwidth Per Channel
TBD: Need to check if we still want this.
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3.3.8. Switched and Fixed Port Wavelength Restrictions
Switch and fixed port wavelength
restrictions(SwitchedPortWavelengthRestriction,
FixedPortWavelengthRestriction) model the wavelength restrictions
that various optical devices such as OXCs, ROADMs, and waveband
mulitplexers may impose on a port. This plays an important role in
fully characterizing a WSON switching device[Switch]. The
SwitchedPortWavelengthRestriction is used with ports specified in the
SwitchedConnectivityMatrix while the FixedPortWavelengthRestriction
is used with ports specified in the FixedConnectivityMatrix.
Reference [Switch] gives an example where both switch and fixed
connectivity matrices are used and both types of constraints are
occur on the same port.
SwitchedPortWavelengthRestriction := PortWavelengthRestriction
FixedPortWavelengthRestriction := PortWavelengthRestriction
PortWavelengthRestriction := RestrictionKind, RestrictionParameters,
WavelengthSet
RestrictionParameters := MaxNumChannels, OthersTBD?
Where WavelengthSet is a conceptual set of wavelengths,
MaxNumChannels is the number of channels permitted on the port, and
RestrictionKind can take the following values and meanings:
SIMPLE: Simple wavelength selective restriction. Max number of
channels indicates the number of wavelengths permitted on the port
and the accompanying wavelength set indicates the permitted values.
WAVEBAND1: Waveband device with a tunable center frequency and
passband. In this case the maximum number of channels indicates the
maximum width of the waveband in terms of the channels spacing given
in the wavelength set. The corresponding wavelength set is used to
indicate the overall tuning range. Specific center frequency tuning
information can be obtained from dynamic channel in use information.
It is assumed that both center frequency and bandwidth (Q) tuning can
be done without causing faults in existing signals.
For example, if the port is a "colored" drop port of a ROADM then the
value of RestrictionKind = SIMPLE for a simple wavelength selective
restriction, the MaxNumberOfChannels = 1, and the wavelength
restriction is just a wavelength set consisting of a single member
corresponding to the frequency of the permitted wavelength. See
[Switch] for a complete waveband example.
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3.4. Dynamic Link Information
By dynamic information we mean information that is subject to change
on a link with subsequent connection establishment or teardown.
Currently for WSON the only information we currently envision is
wavelength availability and wavelength in use for shared backup
purposes.
DynamicLinkInfo := LinkID, AvailableWavelengths,
SharedBackupWavelengths?
Where
LinkID: LocalLinkID, LocalNodeID, RemoteLinkID, RemoteNodeID
AvailableWavelengths is a set of wavelengths available on the link.
SharedBackupWavelengths is a set of wavelengths currently used for
shared backup protection on the link. An example usage of this
information in a WSON setting is given in [Shared].
3.5. Dynamic Node Information
Dynamic node information is used to hold information for a node that
can change frequently. Currently only wavelength converter pool
information is included as a possible (but not required) information
sub-element.
DynamicNodeInfo := NodeID, WavelengthConverterPoolStatus?
Where NodeID is a node identifier and the exact form of the
wavelength converter pool status information is TBD.
4. Security Considerations
This document discussed an information model for RWA computation in
WSONs. Such a model is very similar from a security standpoint of the
information that can be currently conveyed via GMPLS routing
protocols. Such information includes network topology, link state
and current utilization, and well as the capabilities of switches and
routers within the network. As such this information should be
protected from disclosure to unintended recipients. In addition, the
intentional modification of this information can significantly affect
network operations, particularly due to the large capacity of the
optical infrastructure to be controlled.
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5. IANA Considerations
This informational document does not make any requests for IANA
action.
6. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
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7. References
7.1. Normative References
[Encode] Reference the encoding draft here.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
[RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005
[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC4205] Kompella, K., Ed., and Y. Rekhter, Ed., "Intermediate
System to Intermediate System (IS-IS) Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)", RFC
4205, October 2005.
[WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for GMPLS
and PCE Control of Wavelength Switched Optical Networks",
work in progress: draft-bernstein-ccamp-wavelength-
switched-02.txt, February 2008.
7.2. Informative References
[Shared] G. Bernstein, Y. Lee, "Shared Backup Mesh Protection in PCE-
based WSON Networks", iPOP 2008, http://www.grotto-
networking.com/wson/iPOP2008_WSON-shared-mesh-poster.pdf .
[Switch] G. Bernstein, Y. Lee, A. Gavler, J. Martensson, " Modeling
WDM Wavelength Switching Systems for use in Automated Path
Computation", http://www.grotto-
networking.com/wson/ModelingWSONswitchesV2a.pdf , June, 2008
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8. Contributors
Diego Caviglia
Ericsson
Via A. Negrone 1/A 16153
Genoa Italy
Phone: +39 010 600 3736
Email: diego.caviglia@(marconi.com, ericsson.com)
Anders Gavler
Acreo AB
Electrum 236
SE - 164 40 Kista Sweden
Email: Anders.Gavler@acreo.se
Jonas Martensson
Acreo AB
Electrum 236
SE - 164 40 Kista, Sweden
Email: Jonas.Martensson@acreo.se
Itaru Nishioka
NEC Corp.
1753 Simonumabe, Nakahara-ku, Kawasaki, Kanagawa 211-8666
Japan
Phone: +81 44 396 3287
Email: i-nishioka@cb.jp.nec.com
Lyndon Ong
Ciena
Email: lyong@ciena.com
Author's Addresses
Greg Bernstein (ed.)
Grotto Networking
Fremont, CA, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
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Young Lee (ed.)
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075
USA
Phone: (972) 509-5599 (x2240)
Email: ylee@huawei.com
Dan Li
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237
Email: danli@huawei.com
Wataru Imajuku
NTT Network Innovation Labs
1-1 Hikari-no-oka, Yokosuka, Kanagawa
Japan
Phone: +81-(46) 859-4315
Email: imajuku.wataru@lab.ntt.co.jp
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