Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Informational G. Bernstein
Expires: March 2012 Grotto Networking
D. Li
Huawei
W. Imajuku
NTT
September 9, 2011
Routing and Wavelength Assignment Information Model for Wavelength
Switched Optical Networks
draft-ietf-ccamp-rwa-info-12.txt
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Abstract
This document provides a model of information needed by the routing
and wavelength assignment (RWA) process in wavelength switched
optical networks (WSONs). The purpose of the information described
in this model is to facilitate constrained lightpath computation in
WSONs. This model takes into account compatibility constraints
between WSON signal attributes and network elements but does not
include constraints due to optical impairments. Aspects of this
information that may be of use to other technologies utilizing a
GMPLS control plane are discussed.
Table of Contents
1. Introduction...................................................3
1.1. Revision History..........................................4
1.1.1. Changes from 01......................................4
1.1.2. Changes from 02......................................4
1.1.3. Changes from 03......................................5
1.1.4. Changes from 04......................................5
1.1.5. Changes from 05......................................5
1.1.6. Changes from 06......................................5
1.1.7. Changes from 07......................................5
1.1.8. Changes from 08......................................5
1.1.9. Changes from 09......................................5
1.1.10. Changes from 10.....................................6
1.1.11. Changes from 11.....................................6
2. Terminology....................................................6
3. Routing and Wavelength Assignment Information Model............7
3.1. Dynamic and Relatively Static Information.................7
4. Node Information (General).....................................7
4.1. Connectivity Matrix.......................................8
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4.2. Shared Risk Node Group....................................9
5. Node Information (WSON specific)...............................9
5.1. Resource Accessibility/Availability......................10
5.2. Resource Signal Constraints and Processing Capabilities..14
5.3. Compatibility and Capability Details.....................15
5.3.1. Shared Input or Output Indication...................15
5.3.2. Modulation Type List................................15
5.3.3. FEC Type List.......................................15
5.3.4. Bit Rate Range List.................................15
5.3.5. Acceptable Client Signal List.......................16
5.3.6. Processing Capability List..........................16
6. Link Information (General)....................................16
6.1. Administrative Group.....................................17
6.2. Interface Switching Capability Descriptor................17
6.3. Link Protection Type (for this link).....................17
6.4. Shared Risk Link Group Information.......................17
6.5. Traffic Engineering Metric...............................17
6.6. Port Label (Wavelength) Restrictions.....................17
6.6.1. Port-Wavelength Exclusivity Example.................19
7. Dynamic Components of the Information Model...................20
7.1. Dynamic Link Information (General).......................21
7.2. Dynamic Node Information (WSON Specific).................21
8. Security Considerations.......................................21
9. IANA Considerations...........................................22
10. Acknowledgments..............................................22
11. References...................................................23
11.1. Normative References....................................23
11.2. Informative References..................................24
12. Contributors.................................................25
Author's Addresses...............................................25
Intellectual Property Statement..................................26
Disclaimer of Validity...........................................27
1. Introduction
The purpose of the following information model for WSONs is to
facilitate constrained lightpath computation and as such is not a
general purpose network management information model. 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 [RFC6163]. The model defined here includes
constraints between WSON signal attributes and network elements, but
does not include optical impairments.
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In addition to presenting an information model suitable for path
computation in WSON, this document also highlights model aspects that
may have general applicability to other technologies utilizing a
GMPLS control plane. The portion of the information model applicable
to other technologies beyond WSON is referred to as "general" to
distinguish it from the "WSON-specific" portion that is applicable
only to WSON technology.
1.1. Revision History
1.1.1. Changes from 01
Added text on multiple fixed and switched connectivity matrices.
Added text on the relationship between SRNG and SRLG and encoding
considerations.
Added clarifying text on the meaning and use of port/wavelength
restrictions.
Added clarifying text on wavelength availability information and how
to derive wavelengths currently in use.
1.1.2. Changes from 02
Integrated switched and fixed connectivity matrices into a single
"connectivity matrix" model. Added numbering of matrices to allow for
wavelength (time slot, label) dependence of the connectivity.
Discussed general use of this node parameter beyond WSON.
Integrated switched and fixed port wavelength restrictions into a
single port wavelength restriction of which there can be more than
one and added a reference to the corresponding connectivity matrix if
there is one. Also took into account port wavelength restrictions in
the case of symmetric switches, developed a uniform model and
specified how general label restrictions could be taken into account
with this model.
Removed the Shared Risk Node Group parameter from the node info, but
left explanation of how the same functionality can be achieved with
existing GMPLS SRLG constructs.
Removed Maximum bandwidth per channel parameter from link
information.
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1.1.3. Changes from 03
Removed signal related text from section 3.2.4 as signal related
information is deferred to a new signal compatibility draft.
Removed encoding specific text from Section 3.3.1 of version 03.
1.1.4. Changes from 04
Removed encoding specific text from Section 4.1.
Removed encoding specific text from Section 3.4.
1.1.5. Changes from 05
Renumbered sections for clarity.
Updated abstract and introduction to encompass signal
compatibility/generalization.
Generalized Section on wavelength converter pools to include electro
optical subsystems in general. This is where signal compatibility
modeling was added.
1.1.6. Changes from 06
Simplified information model for WSON specifics, by combining similar
fields and introducing simpler aggregate information elements.
1.1.7. Changes from 07
Added shared fiber connectivity to resource pool modeling. This
includes information for determining wavelength collision on an
internal fiber providing access to resource blocks.
1.1.8. Changes from 08
Added PORT_WAVELENGTH_EXCLUSIVITY in the RestrictionType parameter.
Added section 6.6.1 that has an example of the port wavelength
exclusivity constraint.
1.1.9. Changes from 09
Section 5: clarified the way that the resource pool is modeled from
blocks of identical resources.
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Section 5.1: grammar fixes. Removed reference to "academic" modeling
pre-print. Clarified RBNF resource pool model details.
Section 5.2: Formatting fixes.
1.1.10. Changes from 10
Enhanced the explanation of shared fiber access to resources and
updated Figure 2 to show a more general situation to be modeled.
Removed all 1st person idioms.
1.1.11. Changes from 11
Replace all instances of "ingress" with "input" and all instances of
"egress" with "output". Added clarifying text on relationship between
resource block model and physical entities such as line cards.
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 input and
output 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
The following WSON RWA information model is grouped 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, where applicable, the reduced Backus-Naur form
(RBNF) syntax of [RBNF] is used to aid in defining the RWA
information model.
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 potential port connectivity of
a WDM ROADM, and the channel spacing on a WDM link.
This document separates, 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.
4. Node Information (General)
The node information described here contains the relatively static
information related to a WSON node. This includes connectivity
constraints amongst ports and wavelengths since WSON switches can
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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. These connectivity
matrices are included with the node information while the switched
and fixed port wavelength constraints are included with the link
information.
Formally,
<Node_Information> ::= <Node_ID> [<ConnectivityMatrix>...]
Where the Node_ID would be an appropriate identifier for the node
within the WSON RWA context.
Note that multiple connectivity matrices are allowed and hence can
fully support the most general cases enumerated in [Switch].
4.1. Connectivity Matrix
The connectivity matrix (ConnectivityMatrix) represents either the
potential connectivity matrix for asymmetric switches (e.g. ROADMs
and such) or fixed connectivity for an asymmetric device such as a
multiplexer. Note that this matrix does not represent any particular
internal blocking behavior but indicates which inputinput ports and
wavelengths could possibly be connected to a particular output port.
Representing internal state dependent blocking for a switch or ROADM
is beyond the scope of this document and due to its highly
implementation dependent nature would most likely not be subject to
standardization in the future. The connectivity matrix is a
conceptual M by N matrix representing the potential switched or fixed
connectivity, where M represents the number of inputinput ports and N
the number of outputoutput ports. This is a "conceptual" matrix since
the matrix tends to exhibit structure that allows for very compact
representations that are useful for both transmission and path
computation [Encode].
Note that the connectivity matrix information element can be useful
in any technology context where asymmetric switches are utilized.
ConnectivityMatrix ::= <MatrixID> <ConnType> <Matrix>
Where
<MatrixID> is a unique identifier for the matrix.
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<ConnType> can be either 0 or 1 depending upon whether the
connectivity is either fixed or potentially switched.
<Matrix> represents the fixed or switched connectivity in that
Matrix(i, j) = 0 or 1 depending on whether inputinput port i can
connect to outputoutput port j for one or more wavelengths.
4.2. 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.
Since the failure of a node implies the failure of all links
associated with that node a sufficiently general shared risk link
group (SRLG) encoding, such as that used in GMPLS routing extensions
can explicitly incorporate SRNG information.
5. Node Information (WSON specific)
As discussed in [RFC6163] a WSON node may contain electro-optical
subsystems such as regenerators, wavelength converters or entire
switching subsystems. The model present here can be used in
characterizing the accessibility and availability of limited
resources such as regenerators or wavelength converters as well as
WSON signal attribute constraints of electro-optical subsystems. As
such this information element is fairly specific to WSON
technologies.
A WSON node may include regenerators or wavelength converters
arranged in a shared pool. As discussed in [RFC6163] this can include
OEO based WDM switches as well. There are a number of different
approaches used in the design of WDM switches containing regenerator
or converter pools. However, from the point of view of path
computation the following need to be known:
1. The nodes that support regeneration or wavelength conversion.
2. The accessibility and availability of a wavelength converter to
convert from a given inputinput wavelength on a particular
inputinput port to a desired outputoutput wavelength on a
particular outputoutput port.
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3. Limitations on the types of signals that can be converted and the
conversions that can be performed.
Since resources tend to be packaged together in blocks of similar
devices, e.g., on line cards or other types of modules, the
fundamental unit of identifiable resource in this document is the
"resource block". A resource block may contain one or more resources.
As resource blocks are the smallest identifiable unit of processing
resource, one can group together resources into blocks if they have
similar characteristics relevant to the optical system being modeled,
e.g., processing properties, accessibility, etc.
This leads to the following formal high level model:
<Node_Information> ::= <Node_ID> [<ConnectivityMatrix>...]
[<ResourcePool>]
Where
<ResourcePool> ::= <ResourceBlockInfo>...
[<ResourceAccessibility>...] [<ResourceWaveConstraints>...]
[<RBPoolState>]
First the accessibility of resource blocks is addressed then their
properties are discussed.
5.1. Resource Accessibility/Availability
A similar technique as used to model ROADMs and optical switches can
be used to model regenerator/converter accessibility. This technique
was generally discussed in [RFC6163] and consisted of a matrix to
indicate possible connectivity along with wavelength constraints for
links/ports. Since regenerators or wavelength converters may be
considered a scarce resource it is desirable that the model include,
if desired, the usage state (availability) of individual regenerators
or converters in the pool. Models that incorporate more state to
further reveal blocking conditions on input or output to particular
converters are for further study and not included here.
The three stage model is shown schematically in Figure 1 and Figure
2. The difference between the two figures is that Figure 1 assumes
that each signal that can get to a resource block may do so, while in
Figure 2 the access to sets of resource blocks is via a shared fiber
which imposes its own wavelength collision constraint. The
representation of Figure 1 can have more than one input to each
resource block since each input represents a single wavelength
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signal, while in Figure 2 shows a single multiplexed WDM inputinput
or output, e.g., a fiber, to/from each set of block.
This model assumes N input ports (fibers), P resource blocks
containing one or more identical resources (e.g. wavelength
converters), and M output ports (fibers). Since not all input ports
can necessarily reach each resource block, the model starts with a
resource pool input matrix RI(i,p) = {0,1} whether input port i can
reach potentially reach resource block p.
Since not all wavelengths can necessarily reach all the resources or
the resources may have limited input wavelength range the model has a
set of relatively static input port constraints for each resource. In
addition, if the access to a set of resource blocks is via a shared
fiber (Figure 2) this would impose a dynamic wavelength availability
constraint on that shared fiber. The resource block input port
constraint is modeled via a static wavelength set mechanism and the
case of shared access to a set of blocks is modeled via a dynamic
wavelength set mechanism.
Next a state vector RA(j) = {0,...,k} is used to track the number of
resources in resource block j in use. This is the only state kept in
the resource pool model. This state is not necessary for modeling
"fixed" transponder system or full OEO switches with WDM interfaces,
i.e., systems where there is no sharing.
After that, a set of static resource output wavelength constraints
and possibly dynamic shared output fiber constraints maybe used. The
static constraints indicate what wavelengths a particular resource
block can generate or are restricted to generating e.g., a fixed
regenerator would be limited to a single lambda. The dynamic
constraints would be used in the case where a single shared fiber is
used to output the resource block (Figure 2).
Finally, to complete the model, a resource pool output matrix RE(p,k)
= {0,1} depending on whether the output from resource block p can
reach output port k, may be used.
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I1 +-------------+ +-------------+ E1
----->| | +--------+ | |----->
I2 | +------+ Rb #1 +-------+ | E2
----->| | +--------+ | |----->
| | | |
| Resource | +--------+ | Resource |
| Pool +------+ +-------+ Pool |
| | + Rb #2 + | |
| Input +------+ +-------| Output |
| Connection | +--------+ | Connection |
| Matrix | . | Matrix |
| | . | |
| | . | |
IN | | +--------+ | | EM
----->| +------+ Rb #P +-------+ |----->
| | +--------+ | |
+-------------+ ^ ^ +-------------+
| |
| |
| |
| |
Input wavelength Output wavelength
constraints for constraints for
each resource each resource
Figure 1 Schematic diagram of resource pool model.
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I1 +-------------+ +-------------+ E1
----->| | +--------+ | |----->
I2 | +======+ Rb #1 +-+ + | E2
----->| | +--------+ | | |----->
| | |=====| |
| Resource | +--------+ | | Resource |
| Pool | +-+ Rb #2 +-+ | Pool |
| | | +--------+ + |
| Input |====| | Output |
| Connection | | +--------+ | Connection |
| Matrix | +-| Rb #3 |=======| Matrix |
| | +--------+ | |
| | . | |
| | . | |
| | . | |
IN | | +--------+ | | EM
----->| +======+ Rb #P +=======+ |----->
| | +--------+ | |
+-------------+ ^ ^ +-------------+
| |
| |
| |
Single (shared) fibers for block input and output
Input wavelength Output wavelength
availability for availability for
each block input fiber each block output fiber
Figure 2 Schematic diagram of resource pool model with shared block
accessibility.
Formally the model can be specified as:
<ResourceAccessibility ::= <PoolInputMatrix> <PoolOutputMatrix>
[<ResourceWaveConstraints> ::= <InputWaveConstraints>
<OutputOutputWaveConstraints>
<RBPoolState>
::=(<ResourceBlockID><NumResourcesInUse><InAvailableWavelengths><OutA
vailableWavelengths>)...
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Note that except for <ResourcePoolState> all the other components of
<ResourcePool> are relatively static. Also the
<InAvailableWavelengths> and <OutAvailableWavelengths> are only used
in the cases of shared input or output access to the particular
block. See the resource block information in the next section to see
how this is specified.
5.2. Resource Signal Constraints and Processing Capabilities
The wavelength conversion abilities of a resource (e.g. regenerator,
wavelength converter) were modeled in the <OutputWaveConstraints>
previously discussed. As discussed in [RFC6163] the constraints on an
electro-optical resource can be modeled in terms of input
constraints, processing capabilities, and output constraints:
<ResourceBlockInfo> ::= ([<ResourceSet>] <InputConstraints>
<ProcessingCapabilities> <OutputConstraints>)*
Where <ResourceSet> is a list of resource block identifiers with the
same characteristics. If this set is missing the constraints are
applied to the entire network element.
The <InputConstraints> are signal compatibility based constraints
and/or shared access constraint indication. The details of these
constraints are defined in section 5.3.
<InputConstraints> ::= <SharedInput> <ModulationTypeList>
<FECTypeList> <BitRateRange> <ClientSignalList>
The <ProcessingCapabilities> are important operations that the
resource (or network element) can perform on the signal. The details
of these capabilities are defined in section 5.3.
<ProcessingCapabilities> ::= <NumResources>
<RegenerationCapabilities> <FaultPerfMon> <VendorSpecific>
The <OutputConstraints> are either restrictions on the properties of
the signal leaving the block, options concerning the signal
properties when leaving the resource or shared fiber output
constraint indication.
<OutputConstraints> := <SharedOutput> <ModulationTypeList>
<FECTypeList>
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5.3. Compatibility and Capability Details
5.3.1. Shared Input or Output Indication
As discussed in the previous section and shown in Figure 2 the input
or output access to a resource block may be via a shared fiber. The
<SharedInput> and <SharedOutput> elements are indicators for this
condition with respect to the block being described.
5.3.2. Modulation Type List
Modulation type, also known as optical tributary signal class,
comes in two distinct flavors: (i) ITU-T standardized types; (ii)
vendor specific types. The permitted modulation type list can
include any mixture of standardized and vendor specific types.
<modulation-list>::=
[<STANDARD_MODULATION>|<VENDOR_MODULATION>]...
Where the STANDARD_MODULATION object just represents one of the
ITU-T standardized optical tributary signal class and the
VENDOR_MODULATION object identifies one vendor specific modulation
type.
5.3.3. FEC Type List
Some devices can handle more than one FEC type and hence a list is
needed.
<fec-list>::= [<FEC>]
Where the FEC object represents one of the ITU-T standardized FECs
defined in [G.709], [G.707], [G.975.1] or a vendor-specific FEC.
5.3.4. Bit Rate Range List
Some devices can handle more than one particular bit rate range
and hence a list is needed.
<rate-range-list>::= [<rate-range>]...
<rate-range>::=<START_RATE><END_RATE>
Where the START_RATE object represents the lower end of the range
and the END_RATE object represents the higher end of the range.
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5.3.5. Acceptable Client Signal List
The list is simply:
<client-signal-list>::=[<GPID>]...
Where the Generalized Protocol Identifiers (GPID) object
represents one of the IETF standardized GPID values as defined in
[RFC3471] and [RFC4328].
5.3.6. Processing Capability List
The ProcessingCapabilities were defined in Section 5.2 as follows:
<ProcessingCapabilities> ::= <NumResources>
<RegenerationCapabilities> <FaultPerfMon> <VendorSpecific>
The processing capability list sub-TLV is a list of processing
functions that the WSON network element (NE) can perform on the
signal including:
1. Number of Resources within the block
2. Regeneration capability
3. Fault and performance monitoring
4. Vendor Specific capability
Note that the code points for Fault and performance monitoring and
vendor specific capability are subject to further study.
6. Link Information (General)
MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630],
[RFC5305] along with GMPLS routing protocol extensions for OSPF and
IS-IS [RFC4203, RFC5307] provide the bulk of the relatively static
link information needed by the RWA process. However, 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 GMPLS route
protocols and new information that maybe needed by the RWA process.
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<LinkInfo> ::= <LinkID> [<AdministrativeGroup>] [<InterfaceCapDesc>]
[<Protection>] [<SRLG>]... [<TrafficEngineeringMetric>]
[<PortLabelRestriction>]
6.1. 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.
6.2. Interface Switching Capability Descriptor
InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different
switching capabilities on this GMPLS interface. In both [RFC4203] and
[RFC5307] this information gets combined with the maximum LSP
bandwidth that can be used on this link at eight different priority
levels.
6.3. Link Protection Type (for this link)
Protection: Defined in [RFC4202] and implemented in [RFC4203,
RFC5307]. Used to indicate what protection, if any, is guarding this
link.
6.4. Shared Risk Link Group Information
SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC5307].
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.
6.5. 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...
6.6. Port Label (Wavelength) Restrictions
Port label (wavelength) restrictions (PortLabelRestriction) model the
label (wavelength) restrictions that the link and various optical
devices such as OXCs, ROADMs, and waveband multiplexers may impose on
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a port. These restrictions tell us what wavelength may or may not be
used on a link and are relatively static. This plays an important
role in fully characterizing a WSON switching device [Switch]. Port
wavelength restrictions are specified relative to the port in general
or to a specific connectivity matrix (section 4.1. Reference
[Switch] gives an example where both switch and fixed connectivity
matrices are used and both types of constraints occur on the same
port. Such restrictions could be applied generally to other label
types in GMPLS by adding new kinds of restrictions.
<PortLabelRestriction> ::= [<GeneralPortRestrictions>...]
[<MatrixSpecificRestrictions>...]
<GeneralPortRestrictions> ::= <RestrictionType>
[<RestrictionParameters>]
<MatrixSpecificRestriction> ::= <MatrixID> <RestrictionType>
[<RestrictionParameters>]
<RestrictionParameters> ::= [<LabelSet>...] [<MaxNumChannels>]
[<MaxWaveBandWidth>]
Where
MatrixID is the ID of the corresponding connectivity matrix (section
4.1.
The RestrictionType parameter is used to specify general port
restrictions and matrix specific restrictions. It can take the
following values and meanings:
SIMPLE_WAVELENGTH: Simple wavelength set restriction; The
wavelength set parameter is required.
CHANNEL_COUNT: The number of channels is restricted to be less than
or equal to the Max number of channels parameter (which is required).
PORT_WAVELENGTH_EXCLUSIVITY: A wavelength can be used at most once
among a given set of ports. The set of ports is specified as a
parameter to this constraint.
WAVEBAND1: Waveband device with a tunable center frequency and
passband. This constraint is characterized by the MaxWaveBandWidth
parameters which indicates the maximum width of the waveband in terms
of channels. Note that an additional wavelength set can be used to
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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.
Restriction specific parameters are used with one or more of the
previously listed restriction types. The currently defined parameters
are:
LabelSet is a conceptual set of labels (wavelengths).
MaxNumChannels is the maximum number of channels that can be
simultaneously used (relative to either a port or a matrix).
MaxWaveBandWidth is the maximum width of a tunable waveband
switching device.
PortSet is a conceptual set of ports.
For example, if the port is a "colored" drop port of a ROADM then
there are two restrictions: (a) CHANNEL_COUNT, with MaxNumChannels =
1, and (b) SIMPLE_WAVELENGTH, with the wavelength set consisting of a
single member corresponding to the frequency of the permitted
wavelength. See [Switch] for a complete waveband example.
This information model for port wavelength (label) restrictions is
fairly general in that it can be applied to ports that have label
restrictions only or to ports that are part of an asymmetric switch
and have label restrictions. In addition, the types of label
restrictions that can be supported are extensible.
6.6.1. Port-Wavelength Exclusivity Example
Although there can be many different ROADM or switch architectures
that can lead to the constraint where a lambda (label) maybe used at
most once on a set of ports Figure 3 shows a ROADM architecture based
on components known as a Wavelength Selective Switch (WSS)[OFC08].
This ROADM is composed of splitters, combiners, and WSSes. This ROADM
has 11 output ports, which are numbered in the diagram. Output ports
1-8 are known as drop ports and are intended to support a single
wavelength. Drop ports 1-4 output from WSS #2, which is fed from WSS
#1 via a single fiber. Due to this internal structure a constraint is
placed on the output ports 1-4 that a lambda can be only used once
over the group of ports (assuming uni-cast and not multi-cast
operation). Similarly the output ports 5-8 have a similar constraint
due to the internal structure.
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| A
v 10 |
+-------+ +-------+
| Split | |WSS 6 |
+-------+ +-------+
+----+ | | | | | | | |
| W | | | | | | | | +-------+ +----+
| S |--------------+ | | | +-----+ | +----+ | | S |
9 | S |----------------|---|----|-------|------|----|---| p |
<--| |----------------|---|----|-------|----+ | +---| l |<--
| 5 |--------------+ | | | +-----+ | | +--| i |
+----+ | | | | | +------|-|-----|--| t |
+--------|-+ +----|-|---|------|----+ | +----+
+----+ | | | | | | | | |
| S |-----|--------|----------+ | | | | | | +----+
| p |-----|--------|------------|---|------|----|--|--| W |
-->| l |-----|-----+ | +----------+ | | | +--|--| S |11
| i |---+ | | | | +------------|------|-------|--| S |-->
| t | | | | | | | | | | +---|--| |
+----+ | | +---|--|-|-|------------|------|-|-|---+ | 7 |
| | | +--|-|-|--------+ | | | | | +----+
| | | | | | | | | | | |
+------+ +------+ +------+ +------+
| WSS 1| | Split| | WSS 3| | Split|
+--+---+ +--+---+ +--+---+ +--+---+
| A | A
v | v |
+-------+ +--+----+ +-------+ +--+----+
| WSS 2 | | Comb. | | WSS 4 | | Comb. |
+-------+ +-------+ +-------+ +-------+
1|2|3|4| A A A A 5|6|7|8| A A A A
v v v v | | | | v v v v | | | |
Figure 3 A ROADM composed from splitter, combiners, and WSSs.
7. Dynamic Components of the Information Model
In the previously presented information model there are a limited
number of information elements that are dynamic, i.e., subject to
change with subsequent establishment and teardown of connections.
Depending on the protocol used to convey this overall information
model it may be possible to send this dynamic information separate
from the relatively larger amount of static information needed to
characterize WSON's and their network elements.
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7.1. Dynamic Link Information (General)
For WSON links wavelength availability and wavelengths in use for
shared backup purposes can be considered dynamic information and
hence are grouped with the dynamic information in the following set:
<DynamicLinkInfo> ::= <LinkID> <AvailableLabels>
[<SharedBackupLabels>]
AvailableLabels is a set of labels (wavelengths) currently available
on the link. Given this information and the port wavelength
restrictions one can also determine which wavelengths are currently
in use. This parameter could potential be used with other
technologies that GMPLS currently covers or may cover in the future.
SharedBackupLabels is a set of labels (wavelengths) currently used
for shared backup protection on the link. An example usage of this
information in a WSON setting is given in [Shared]. This parameter
could potential be used with other technologies that GMPLS currently
covers or may cover in the future.
7.2. Dynamic Node Information (WSON Specific)
Currently the only node information that can be considered dynamic is
the resource pool state and can be isolated into a dynamic node
information element as follows:
<DynamicNodeInfo> ::= <NodeID> [<ResourcePoolState>]
8. 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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9. IANA Considerations
This informational document does not make any requests for IANA
action.
10. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
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11. References
11.1. Normative References
[Encode] G. Bernstein, Y. Lee, D. Li, W. Imajuku, "Routing and
Wavelength Assignment Information Encoding for Wavelength
Switched Optical Networks", work in progress: draft-ietf-
ccamp-rwa-wson-encode.
[G.707] ITU-T Recommendation G.707, Network node interface for the
synchronous digital hierarchy (SDH), January 2007.
[G.709] ITU-T Recommendation G.709, Interfaces for the Optical
Transport Network(OTN), March 2003.
[G.975.1] ITU-T Recommendation G.975.1, Forward error correction for
high bit-rate DWDM submarine systems, February 2004.
[RBNF] A. Farrel, "Reduced Backus-Naur Form (RBNF) A Syntax Used in
Various Protocol Specifications", RFC 5511, April 2009.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[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.
[RFC4328] Papadimitriou, D., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
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[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, October 2008.
11.2. Informative References
[OFC08] P. Roorda and B. Collings, "Evolution to Colorless and
Directionless ROADM Architectures," Optical Fiber
communication/National Fiber Optic Engineers Conference,
2008. OFC/NFOEC 2008. Conference on, 2008, pp. 1-3.
[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 GMPLS and
Automated Path Computation", Journal of Optical
Communications and Networking, vol. 1, June, 2009, pp. 187-
195.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and
engineering considerations, February 2006.
[RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and
PCE Control of Wavelength Switched Optical Networks", RFC
6163, April 2011.
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12. 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 M. Bernstein (ed.)
Grotto Networking
Fremont California, 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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