draft-ietf-ccamp-rwa-wson-framework-11.txt   draft-ietf-ccamp-rwa-wson-framework-12.txt 
Network Working Group Y. Lee (ed.) Network Working Group Y. Lee (ed.)
Internet Draft Huawei Internet Draft Huawei
Intended status: Informational G. Bernstein (ed.) Intended status: Informational G. Bernstein (ed.)
Expires: August 2011 Grotto Networking Expires: August 2011 Grotto Networking
Wataru Imajuku Wataru Imajuku
NTT NTT
February 7, 2011 February 8, 2011
Framework for GMPLS and PCE Control of Wavelength Switched Optical Framework for GMPLS and PCE Control of Wavelength Switched Optical
Networks (WSON) Networks (WSON)
draft-ietf-ccamp-rwa-wson-framework-11.txt draft-ietf-ccamp-rwa-wson-framework-12.txt
Abstract Abstract
This document provides a framework for applying Generalized Multi- This document provides a framework for applying Generalized Multi-
Protocol Label Switching (GMPLS) and the Path Computation Element Protocol Label Switching (GMPLS) and the Path Computation Element
(PCE) architecture to the control of wavelength switched optical (PCE) architecture to the control of wavelength switched optical
networks (WSON). In particular, it examines Routing and Wavelength networks (WSON). In particular, it examines Routing and Wavelength
Assignment (RWA) of optical paths. Assignment (RWA) of optical paths.
This document focuses on topological elements and path selection This document focuses on topological elements and path selection
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This Internet-Draft will expire on July 7, 2011. This Internet-Draft will expire on August 8, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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by the network elements on various optical signal parameters. The by the network elements on various optical signal parameters. The
subsequent sections review and model some of the major subsystems of subsequent sections review and model some of the major subsystems of
a WSON with an emphasis on those aspects that are of relevance to the a WSON with an emphasis on those aspects that are of relevance to the
control plane. In particular, WDM links, optical transmitters, control plane. In particular, WDM links, optical transmitters,
ROADMs, and wavelength converters are examined. ROADMs, and wavelength converters are examined.
3.1. WDM and CWDM Links 3.1. WDM and CWDM Links
WDM and CWDM links run over optical fibers, and optical fibers come WDM and CWDM links run over optical fibers, and optical fibers come
in a wide range of types that tend to be optimized for various in a wide range of types that tend to be optimized for various
applications examples include access networks, metro, long haul, and applications. Examples include access networks, metro, long haul, and
submarine links. International Telecommunication Union - submarine links. International Telecommunication Union -
Telecommunication Standardization Sector (ITU-T) standards exist for Telecommunication Standardization Sector (ITU-T) standards exist for
various types of fibers. Although fiber can be categorized into various types of fibers. Although fiber can be categorized into
Single mode fibers (SMF) and Multi-mode fibers (MMF), the latter are Single mode fibers (SMF) and Multi-mode fibers (MMF), the latter are
typically used for short-reach campus and premise applications. SMF typically used for short-reach campus and premise applications. SMF
are used for longer-reach applications and therefore are the primary are used for longer-reach applications and therefore are the primary
concern of this document. The following SMF fiber types are typically concern of this document. The following SMF fiber types are typically
encountered in optical networks: encountered in optical networks:
ITU-T Standard | Common Name ITU-T Standard | Common Name
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characteristics and stability, are used in the design of WDM characteristics and stability, are used in the design of WDM
subsystems consisting of transmitters, WDM links and receivers subsystems consisting of transmitters, WDM links and receivers
however they do not furnish additional information that will however they do not furnish additional information that will
influence the Label Switched Path (LSP) provisioning in a properly influence the Label Switched Path (LSP) provisioning in a properly
designed system. designed system.
Also note that optical components can degrade and fail over time. Also note that optical components can degrade and fail over time.
This presents the possibility of the failure of a LSP (optical path) This presents the possibility of the failure of a LSP (optical path)
without either a node or link failure. Hence, additional mechanisms without either a node or link failure. Hence, additional mechanisms
may be necessary to detect and differentiate this failure from the may be necessary to detect and differentiate this failure from the
others, e.g., one doesn't not want to initiate mesh restoration if others, e.g., one doesn't want to initiate mesh restoration if the
the source transmitter has failed, since the optical transmitter will source transmitter has failed, since the optical transmitter will
still be failed on the alternate optical path. still be failed on the alternate optical path.
3.3. Optical Signals in WSONs 3.3. Optical Signals in WSONs
In WSONs the fundamental unit of switching is intuitively that of a In WSONs the fundamental unit of switching is intuitively that of a
"wavelength". The transmitters and receivers in these networks will "wavelength". The transmitters and receivers in these networks will
deal with one wavelength at a time, while the switching systems deal with one wavelength at a time, while the switching systems
themselves can deal with multiple wavelengths at a time. Hence themselves can deal with multiple wavelengths at a time. Hence
multichannel DWDM networks with single channel interfaces are the multichannel DWDM networks with single channel interfaces are the
prime focus of this document general concern as opposed to multi- prime focus of this document as opposed to multi-channel interfaces.
channel interfaces. Interfaces of this type are defined in ITU-T Interfaces of this type are defined in ITU-T recommendations
recommendations [G.698.1] and [G.698.2]. Key non-impairment related [G.698.1] and [G.698.2]. Key non-impairment related parameters
parameters defined in [G.698.1] and [G.698.2] are: defined in [G.698.1] and [G.698.2] are:
(a) Minimum channel spacing (GHz) (a) Minimum channel spacing (GHz)
(b) Minimum and maximum central frequency (b) Minimum and maximum central frequency
(c) Bit-rate/Line coding (modulation) of optical tributary signals (c) Bit-rate/Line coding (modulation) of optical tributary signals
For the purposes of modeling the WSON in the control plane, (a) and For the purposes of modeling the WSON in the control plane, (a) and
(b) are considered as properties of the link and restrictions on the (b) are considered as properties of the link and restrictions on the
GMPLS labels while (c) is a property of the "signal". GMPLS labels while (c) is a property of the "signal".
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| | | |
| ROADM | | ROADM |
| | | |
| | | |
+---------------------+ +---------------------+
| | | | o o o o | | | | o o o o
| | | | | | | | | | | | | | | |
O O O O | | | | O O O O | | | |
Tributary Side: Drop (output) Add (input) Tributary Side: Drop (output) Add (input)
Figure 1. Degree-2 ROADM Figure 1. Degree-2 unidirectional ROADM
The key feature across all ROADM types is their highly asymmetric The key feature across all ROADM types is their highly asymmetric
switching capability. In the ROADM of Figure 1, signals introduced switching capability. In the ROADM of Figure 1, signals introduced
via the add ports can only be sent on the line side output port and via the add ports can only be sent on the line side output port and
not on any of the drop ports. The term "degree" is used to refer to not on any of the drop ports. The term "degree" is used to refer to
the number of line side ports (input and output) of a ROADM, and does the number of line side ports (input and output) of a ROADM, and does
not include the number of "add" or "drop" ports. The add and drop not include the number of "add" or "drop" ports. The add and drop
ports are sometimes also called tributary ports. As the degree of the ports are sometimes also called tributary ports. As the degree of the
ROADM increases beyond two it can have properties of both a switch ROADM increases beyond two it can have properties of both a switch
(OXC) and a multiplexer and hence it is necessary to know the (OXC) and a multiplexer and hence it is necessary to know the
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#1: 1 1 1 1 1 #1: 1 1 1 1 1
#2 1 0 0 0 0 #2 1 0 0 0 0
A = #3 1 0 0 0 0 A = #3 1 0 0 0 0
#4 1 0 0 0 0 #4 1 0 0 0 0
#5 1 0 0 0 0 #5 1 0 0 0 0
Where input ports 2-5 are add ports, output ports 2-5 are drop ports Where input ports 2-5 are add ports, output ports 2-5 are drop ports
and input port #1 and output port #1 are the line side (WDM) ports. and input port #1 and output port #1 are the line side (WDM) ports.
For ROADMs, this matrix will be very sparse, and for OXCs the matrix For ROADMs, this matrix will be very sparse, and for OXCs the matrix
will be very dense, compact encodings and examples, including high will be very dense. Compact encodings and examples, including high
degree ROADMs/OXCs, are given in [Gen-Encode]. A degree-4 ROADM is degree ROADMs/OXCs, are given in [Gen-Encode]. A degree-4 ROADM is
shown in Figure 2. shown in Figure 2.
+-----------------------+ +-----------------------+
Line side-1 --->| |---> Line side-2 Line side-1 --->| |---> Line side-2
Input (I1) | | Output (E2) Input (I1) | | Output (E2)
Line side-1 <---| |<--- Line side-2 Line side-1 <---| |<--- Line side-2
Output (E1) | | Input (I2) Output (E1) | | Input (I2)
| ROADM | | ROADM |
Line side-3 --->| |---> Line side-4 Line side-3 --->| |---> Line side-4
Input (I3) | | Output (E4) Input (I3) | | Output (E4)
Line side-3 <---| |<--- Line side-4 Line side-3 <---| |<--- Line side-4
Output (E3) | | Input (I4) Output (E3) | | Input (I4)
| | | |
+-----------------------+ +-----------------------+
| O | O | O | O | O | O | O | O
| | | | | | | | | | | | | | | |
O | O | O | O | O | O | O | O |
Tributary Side: E5 I5 E6 I6 E7 I7 E8 I8 Tributary Side: E5 I5 E6 I6 E7 I7 E8 I8
Figure 2. Degree-4 ROADM Figure 2. Degree-4 bidirectional ROADM
Note that this example is 4-degree example with one (potentially Note that this example is 4-degree example with one (potentially
multi-channel) add/drop per line side port. multi-channel) add/drop per line side port.
Note also that the connectivity constraints for typical ROADM designs Note also that the connectivity constraints for typical ROADM designs
are "bidirectional", i.e. if input port X can be connected to output are "bidirectional", i.e. if input port X can be connected to output
port Y, typically input port Y can be connected to output port X, port Y, typically input port Y can be connected to output port X,
assuming the numbering is done in such a way that input X and output assuming the numbering is done in such a way that input X and output
X correspond to the same line side direction or the same add/drop X correspond to the same line side direction or the same add/drop
port. This makes the connectivity matrix symmetrical as shown below. port. This makes the connectivity matrix symmetrical as shown below.
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and emit an equivalent content optical signal at another wavelength and emit an equivalent content optical signal at another wavelength
on output. There are multiple approaches to building wavelength on output. There are multiple approaches to building wavelength
converters. One approach is based on OEO conversion with fixed or converters. One approach is based on OEO conversion with fixed or
tunable optics on output. This approach can be dependent upon the tunable optics on output. This approach can be dependent upon the
signal rate and format, i.e., this is basically an electrical signal rate and format, i.e., this is basically an electrical
regenerator combined with a laser/receiver. Hence, this type of regenerator combined with a laser/receiver. Hence, this type of
wavelength converter has signal processing restrictions that are wavelength converter has signal processing restrictions that are
essentially the same as those described for regenerators in Table 3 essentially the same as those described for regenerators in Table 3
of section 3.5.1. of section 3.5.1.
Another approach performs the wavelength conversion, optically via Another approach performs the wavelength conversion optically via
non-linear optical effects, similar in spirit to the familiar non-linear optical effects, similar in spirit to the familiar
frequency mixing used in radio frequency systems, but significantly frequency mixing used in radio frequency systems, but significantly
harder to implement. Such processes/effects may place limits on the harder to implement. Such processes/effects may place limits on the
range of achievable conversion. These may depend on the wavelength of range of achievable conversion. These may depend on the wavelength of
the input signal and the properties of the converter as opposed to the input signal and the properties of the converter as opposed to
only the properties of the converter in the OEO case. Different WSON only the properties of the converter in the OEO case. Different WSON
system designs may choose to utilize this component to varying system designs may choose to utilize this component to varying
degrees or not at all. degrees or not at all.
Current or envisioned contexts for wavelength converters are: Current or envisioned contexts for wavelength converters are:
1. Wavelength conversion associated with OEO switches and fixed or 1. Wavelength conversion associated with OEO switches and fixed or
tunable optics. In this case there are typically multiple tunable optics. In this case there are typically multiple
converters available since each on the use of an OEO switch can be converters available since each use of an OEO switch can be thought
thought of as a potential wavelength converter. of as a potential wavelength converter.
2. Wavelength conversion associated with ROADMs/OXCs. In this case 2. Wavelength conversion associated with ROADMs/OXCs. In this case
there may be a limited pool of wavelength converters available. there may be a limited pool of wavelength converters available.
Conversion could be either all optical or via an OEO method. Conversion could be either all optical or via an OEO method.
3. Wavelength conversion associated with fixed devices such as FOADMs. 3. Wavelength conversion associated with fixed devices such as FOADMs.
In this case there may be a limited amount of conversion. Also in In this case there may be a limited amount of conversion. Also in
this case the conversion may be used as part of optical path this case the conversion may be used as part of optical path
routing. routing.
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reach the converters. Hence regardless of where the converters reach the converters. Hence regardless of where the converters
actually are they can be associated with input ports. actually are they can be associated with input ports.
3. Wavelength converters have range restrictions that are either 3. Wavelength converters have range restrictions that are either
independent or dependent upon the input wavelength. independent or dependent upon the input wavelength.
In WSONs where wavelength converters are sparse an optical path may In WSONs where wavelength converters are sparse an optical path may
appear to loop or "backtrack" upon itself in order to reach a appear to loop or "backtrack" upon itself in order to reach a
wavelength converter prior to continuing on to its destination. The wavelength converter prior to continuing on to its destination. The
lambda used on input to the wavelength converter would be different lambda used on input to the wavelength converter would be different
the lambda coming back from the wavelength converter. from the lambda coming back from the wavelength converter.
A model for an individual O-E-O wavelength converter would consist A model for an individual O-E-O wavelength converter would consist
of: of:
o Input lambda or frequency range. o Input lambda or frequency range.
o Output lambda or frequency range. o Output lambda or frequency range.
3.6.1. Wavelength Converter Pool Modeling 3.6.1. Wavelength Converter Pool Modeling
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1. The nodes that support wavelength conversion. 1. The nodes that support wavelength conversion.
2. The accessibility and availability of a wavelength converter to 2. The accessibility and availability of a wavelength converter to
convert from a given input wavelength on a particular input port convert from a given input wavelength on a particular input port
to a desired output wavelength on a particular output port. to a desired output wavelength on a particular output port.
3. Limitations on the types of signals that can be converted and the 3. Limitations on the types of signals that can be converted and the
conversions that can be performed. conversions that can be performed.
To model point 2 above, a similar technique can be used to model To model point 2 above, a technique similar to that used to model
ROADMs and optical switches, i.e., matrices to indicate possible ROADMs and optical switches can be used, i.e., matrices to indicate
connectivity along with wavelength constraints for links/ports. Since possible connectivity along with wavelength constraints for
wavelength converters are considered a scarce resource it will be links/ports. Since wavelength converters are considered a scarce
desirable to include as a minimum the usage state of individual resource it will be desirable to include as a minimum the usage state
wavelength converters in the pool. of individual wavelength converters in the pool.
A three stage model is used as shown schematically in Figure 3. A three stage model is used as shown schematically in Figure 3.
(Schematic diagram of wavelength converter pool model). This model (Schematic diagram of wavelength converter pool model). This model
represents N input ports (fibers), P wavelength converters, and M represents N input ports (fibers), P wavelength converters, and M
output ports (fibers). Since not all input ports can necessarily output ports (fibers). Since not all input ports can necessarily
reach the converter pool, the model starts with a wavelength pool reach the converter pool, the model starts with a wavelength pool
input matrix WI(i,p) = {0,1} where input port i can reach potentially input matrix WI(i,p) = {0,1} where input port i can potentially reach
reach wavelength converter p. wavelength converter p.
Since not all wavelengths can necessarily reach all the converters or Since not all wavelengths can necessarily reach all the converters or
the converters may have limited input wavelength range there is a set the converters may have limited input wavelength range there is a set
of input port constraints for each wavelength converter. Currently it of input port constraints for each wavelength converter. Currently it
is assumed that a wavelength converter can only take a single is assumed that a wavelength converter can only take a single
wavelength on input. Each wavelength converter input port constraint wavelength on input. Each wavelength converter input port constraint
can be modeled via a wavelength set mechanism. can be modeled via a wavelength set mechanism.
Next a state vector WC(j) = {0,1} dependent upon whether wavelength Next a state vector WC(j) = {0,1} dependent upon whether wavelength
converter j in the pool is in use. This is the only state kept in the converter j in the pool is in use. This is the only state kept in the
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at a minimum: at a minimum:
1. Regeneration capability: (a)fixed, (b) selective, (c) none. 1. Regeneration capability: (a)fixed, (b) selective, (c) none.
2. Regeneration type: 1R, 2R, 3R. 2. Regeneration type: 1R, 2R, 3R.
3. Regeneration pool properties for the case of selective 3. Regeneration pool properties for the case of selective
regeneration (input and output restrictions, availability). regeneration (input and output restrictions, availability).
Note that the properties of shared regenerator pools would be Note that the properties of shared regenerator pools would be
essentially the same at that of wavelength converter pools modeled in essentially the same as that of wavelength converter pools modeled in
section 3.6.1. (Wavelength Pool Convertor Modeling). section 3.6.1. (Wavelength Pool Convertor Modeling).
Item (B), fault and performance monitoring, is typically outside the Item (B), fault and performance monitoring, is typically outside the
scope of the control plane. However, when the operations are to be scope of the control plane. However, when the operations are to be
performed on an LSP basis or on part of an LSP then the control plane performed on an LSP basis or on part of an LSP then the control plane
can be of assistance in their configuration. Per LSP, per node, fault can be of assistance in their configuration. Per LSP, per node, fault
and performance monitoring examples include setting up a "section and performance monitoring examples include setting up a "section
trace" (a regenerator overhead identifier) between two nodes, or trace" (a regenerator overhead identifier) between two nodes, or
intermediate optical performance monitoring at selected nodes along a intermediate optical performance monitoring at selected nodes along a
path. path.
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of these architectural approaches over another generally impacts the of these architectural approaches over another generally impacts the
demands placed on the various control plane protocols. The approaches demands placed on the various control plane protocols. The approaches
are provided for reference purposes only, and other approaches are are provided for reference purposes only, and other approaches are
possible. possible.
4.1.1. Combined RWA (R&WA) 4.1.1. Combined RWA (R&WA)
In this case, a unique entity is in charge of performing routing and In this case, a unique entity is in charge of performing routing and
wavelength assignment. This approach relies on a sufficient knowledge wavelength assignment. This approach relies on a sufficient knowledge
of network topology, of available network resources and of network of network topology, of available network resources and of network
nodes capabilities. This solution is compatible with most known RWA nodes' capabilities. This solution is compatible with most known RWA
algorithms, and in particular those concerned with network algorithms, and in particular those concerned with network
optimization. On the other hand, this solution requires up-to-date optimization. On the other hand, this solution requires up-to-date
and detailed network information. and detailed network information.
Such a computational entity could reside in two different places: Such a computational entity could reside in two different places:
o In a PCE which maintains a complete and updated view of network o In a PCE which maintains a complete and updated view of network
state and provides path computation services to nodes (PCCs). state and provides path computation services to nodes (PCCs).
o In an ingress node, in which case all nodes have the R&WA o In an ingress node, in which case all nodes have the R&WA
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reasonable optimization can be performed. reasonable optimization can be performed.
The entity performing the routing assignment needs the topology The entity performing the routing assignment needs the topology
information of the network, whereas the entity performing the information of the network, whereas the entity performing the
wavelength assignment needs information on the network's available wavelength assignment needs information on the network's available
resources and specific network node capabilities. resources and specific network node capabilities.
4.1.3. Routing and Distributed WA (R+DWA) 4.1.3. Routing and Distributed WA (R+DWA)
In this case, one entity performs routing, while wavelength In this case, one entity performs routing, while wavelength
assignment is performed on a hop-by-hop, distributed, manner along assignment is performed on a hop-by-hop, distributed manner along the
the previously computed path. This mechanism relies on updating of a previously computed path. This mechanism relies on updating of a list
list of potential wavelengths used to ensure conformance with the of potential wavelengths used to ensure conformance with the
wavelength continuity constraint. wavelength continuity constraint.
As currently specified, the GMPLS protocol suite signaling protocol As currently specified, the GMPLS protocol suite signaling protocol
can accommodate such an approach. GMPLS, per [RFC3471], includes can accommodate such an approach. GMPLS, per [RFC3471], includes
support for the communication of the set of labels (wavelengths) that support for the communication of the set of labels (wavelengths) that
may be used between nodes via a Label Set. When conversion is not may be used between nodes via a Label Set. When conversion is not
performed at an intermediate node, a hop generates the Label Set it performed at an intermediate node, a hop generates the Label Set it
sends to the next hop based on the intersection of the Label Set sends to the next hop based on the intersection of the Label Set
received from the previous hop and the wavelengths available on the received from the previous hop and the wavelengths available on the
node's switch and ongoing interface. The generation of the outgoing node's switch and ongoing interface. The generation of the outgoing
Label Set is up to the node local policy (even if one expects a Label Set is up to the node local policy (even if one expects a
consistent policy configuration throughout a given transparency consistent policy configuration throughout a given transparency
domain). When wavelength conversion is performed at an intermediate domain). When wavelength conversion is performed at an intermediate
node, a new Label Set is generated. The egress node selects one label node, a new Label Set is generated. The egress node selects one label
in the Label Set which it received; additionally the node can apply in the Label Set which it received; additionally the node can apply
local policy during label selection. GMPLS also provides support for local policy during label selection. GMPLS also provides support for
the signaling of bidirectional optical paths. the signaling of bidirectional optical paths.
Depending on these policies a wavelength assignment may not be found Depending on these policies a wavelength assignment may not be found
or one consuming too many conversion resources relative to what a or one may be found that consumes too many conversion resources
dedicated wavelength assignment policy would have achieved. Hence, relative to what a dedicated wavelength assignment policy would have
this approach may generate higher blocking probabilities in a heavily achieved. Hence, this approach may generate higher blocking
loaded network. probabilities in a heavily loaded network.
This solution may be facilitated via signaling extensions which ease This solution may be facilitated via signaling extensions which ease
its functioning and possibly enhance its performance relatively to its functioning and possibly enhance its performance with respect to
blocking. Note that this approach requires less information blocking probability. Note that this approach requires less
dissemination than the other techniques described. information dissemination than the other techniques described.
The first entity may be a PCE or the ingress node of the LSP. The first entity may be a PCE or the ingress node of the LSP.
4.2. Conveying information needed by RWA 4.2. Conveying information needed by RWA
The previous sections have characterized WSONs and optical path The previous sections have characterized WSONs and optical path
requests. In particular, high level models of the information used by requests. In particular, high level models of the information used by
RWA process were presented. This information can be viewed as either RWA process were presented. This information can be viewed as either
relatively static, i.e., changing with hardware changes (including relatively static, i.e., changing with hardware changes (including
possibly failures), or relatively dynamic, i.e., those that can possibly failures), or relatively dynamic, i.e., those that can
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o Management protocols such as NetConf, SNMPv3, CLI, and CORBA. o Management protocols such as NetConf, SNMPv3, CLI, and CORBA.
o Directory services and accompanying protocols. These are typically o Directory services and accompanying protocols. These are typically
used for the dissemination of relatively static information. used for the dissemination of relatively static information.
Directory services are not suited to manage information in dynamic Directory services are not suited to manage information in dynamic
and fluid environments. and fluid environments.
o Other techniques for dynamic information, e.g., sending o Other techniques for dynamic information, e.g., sending
information directly from NEs to PCE to avoid flooding. This would information directly from NEs to PCE to avoid flooding. This would
be useful if the number of PCEs is significantly less than number be useful if the number of PCEs is significantly less than number
of WSON NEs. Or other ways to limit flooding to "interested" NEs. of WSON NEs. There may be other ways to limit flooding to
"interested" NEs.
Possible mechanisms to improve scaling of dynamic information Possible mechanisms to improve scaling of dynamic information
include: include:
o Tailor message content to WSON. For example the use of wavelength o Tailor message content to WSON. For example the use of wavelength
ranges, or wavelength occupation bit maps. ranges, or wavelength occupation bit maps.
o Utilize incremental updates if feasible. o Utilize incremental updates if feasible.
5. Modeling Examples and Control Plane Use Cases 5. Modeling Examples and Control Plane Use Cases
This section provides examples of the fixed and switched optical node This section provides examples of the fixed and switched optical node
and wavelength constraint models of Section 3. and WSON control and wavelength constraint models of Section 3. and use cases for WSON
plane use cases related to path computation, establishment, control plane path computation, establishment, rerouting, and
rerouting, and optimization. optimization.
5.1. Network Modeling for GMPLS/PCE Control 5.1. Network Modeling for GMPLS/PCE Control
Consider a network containing three routers (R1 through R3), eight Consider a network containing three routers (R1 through R3), eight
WSON nodes (N1 through N8) and 18 links (L1 through L18) and one OEO WSON nodes (N1 through N8) and 18 links (L1 through L18) and one OEO
converter (O1) in a topology shown below. converter (O1) in a topology shown below.
+--+ +--+ +--+ +--------+ +--+ +--+ +--+ +--------+
+-L3-+N2+-L5-+ +--------L12--+N6+--L15--+ N8 + +-L3-+N2+-L5-+ +--------L12--+N6+--L15--+ N8 +
| +--+ |N4+-L8---+ +--+ ++--+---++ | +--+ |N4+-L8---+ +--+ ++--+---++
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1. Permitted optical tributary signal classes: A list of optical 1. Permitted optical tributary signal classes: A list of optical
tributary signal classes that can be processed by this network tributary signal classes that can be processed by this network
element or carried over this link. (configuration type) element or carried over this link. (configuration type)
2. Acceptable FEC codes. (configuration type) 2. Acceptable FEC codes. (configuration type)
3. Acceptable Bit Rate Set: a list of specific bit rates or bit rate 3. Acceptable Bit Rate Set: a list of specific bit rates or bit rate
ranges that the device can accommodate. Coarse bit rate info is ranges that the device can accommodate. Coarse bit rate info is
included with the optical tributary signal class restrictions. included with the optical tributary signal class restrictions.
4. Acceptable G-PID list: a list of G-PIDs corresponding to the 4. Acceptable G-PID list: a list of G-PIDs corresponding to the
"client" digital streams that is compatible with this device. "client" digital streams that is compatible with this device.
Note that since the bit rate of the signal does not change over the Note that the bit rate of the signal does not change over the LSP.
LSP. This can be communicated as an LSP parameter and hence this This can be communicated as an LSP parameter and hence this
information would be available for any NE that needs to use it for information would be available for any NE that needs to use it for
configuration. Hence it is not necessary to have "configuration type" configuration. Hence it is not necessary to have "configuration type"
for the NE with respect to bit rate. for the NE with respect to bit rate.
Output constraints: Output constraints:
1. Output modulation: (a)same as input, (b) list of available types 1. Output modulation: (a)same as input, (b) list of available types
2. FEC options: (a) same as input, (b) list of available codes 2. FEC options: (a) same as input, (b) list of available codes
Processing capabilities: Processing capabilities:
1. Regeneration: (a) 1R, (b) 2R, (c) 3R, (d)list of selectable 1. Regeneration: (a) 1R, (b) 2R, (c) 3R, (d)list of selectable
regeneration types regeneration types
2. Fault and performance monitoring: (a) G-PID particular 2. Fault and performance monitoring: (a) G-PID particular
capabilities, (b) optical performance monitoring capabilities. capabilities, (b) optical performance monitoring capabilities.
Note that such parameters could be specified on an (a) Network Note that such parameters could be specified on an (a) Network
element wide basis, (b) a per port basis, (c) on a per regenerator element wide basis, (b) a per port basis, (c) on a per regenerator
basis. Typically such information has been on a per port basis, see, basis. Typically such information has been on a per port basis; see
the GMPLS interface switching capability descriptor [RFC4202]. the GMPLS interface switching capability descriptor [RFC4202].
6.2.2. Wavelength-Specific Availability Information 6.2.2. Wavelength-Specific Availability Information
For wavelength assignment it is necessary to know which specific For wavelength assignment it is necessary to know which specific
wavelengths are available and which are occupied if a combined RWA wavelengths are available and which are occupied if a combined RWA
process or separate WA process is run as discussed in sections 4.1.1. process or separate WA process is run as discussed in sections 4.1.1.
4.1.2. This is currently not possible with GMPLS routing. 4.1.2. This is currently not possible with GMPLS routing.
In the routing extensions for GMPLS [RFC4202], requirements for In the routing extensions for GMPLS [RFC4202], requirements for
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provided in [WSON-Info], [Gen-Encode] and [WSON-Encode]. provided in [WSON-Info], [Gen-Encode] and [WSON-Encode].
6.3. Optical Path Computation and Implications for PCE 6.3. Optical Path Computation and Implications for PCE
As previously noted RWA can be computationally intensive. Such As previously noted RWA can be computationally intensive. Such
computationally intensive path computations and optimizations were computationally intensive path computations and optimizations were
part of the impetus for the PCE architecture [RFC4655]. part of the impetus for the PCE architecture [RFC4655].
The Path Computation Element Protocol (PCEP) defines the procedures The Path Computation Element Protocol (PCEP) defines the procedures
necessary to support both sequential [RFC5440] and global concurrent necessary to support both sequential [RFC5440] and global concurrent
path computations (PCE-GCO) [RFC5557], PCE is well positioned to path computations (PCE-GCO) [RFC5557]. The PCEP is well positioned to
support WSON-enabled RWA computation with some protocol enhancement. support WSON-enabled RWA computation with some protocol enhancement.
Implications for PCE generally fall into two main categories: (a) Implications for PCE generally fall into two main categories: (a)
optical path constraints and characteristics, (b) computation optical path constraints and characteristics, (b) computation
architectures. architectures.
6.3.1. Optical path Constraints and Characteristics 6.3.1. Optical path Constraints and Characteristics
For the varying degrees of optimization that may be encountered in a For the varying degrees of optimization that may be encountered in a
network the following models of bulk and sequential optical path network the following models of bulk and sequential optical path
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