draft-ietf-ccamp-wson-impairments-06.txt   draft-ietf-ccamp-wson-impairments-07.txt 
Network Working Group Y. Lee Network Working Group Y. Lee
Huawei Huawei
G. Bernstein G. Bernstein
Grotto Networking Grotto Networking
D. Li D. Li
Huawei Huawei
G. Martinelli G. Martinelli
Cisco Cisco
Internet Draft Internet Draft
Intended status: Informational April 12, 2011 Intended status: Informational April 29, 2011
Expires: October 2011 Expires: October 2011
A Framework for the Control of Wavelength Switched Optical Networks A Framework for the Control of Wavelength Switched Optical Networks
(WSON) with Impairments (WSON) with Impairments
draft-ietf-ccamp-wson-impairments-06.txt draft-ietf-ccamp-wson-impairments-07.txt
Status of this Memo Status of this Memo
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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
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the various physical processes in the optical fibers and devices it the various physical processes in the optical fibers and devices it
encounters. When such alterations result in signal degradation, these encounters. When such alterations result in signal degradation, these
processes are usually referred to as "impairments". These physical processes are usually referred to as "impairments". These physical
characteristics may be important constraints to consider when using a characteristics may be important constraints to consider when using a
GMPLS control plane to support path setup and maintenance in GMPLS control plane to support path setup and maintenance in
wavelength switched optical networks. wavelength switched optical networks.
This document provides a framework for applying GMPLS protocols and This document provides a framework for applying GMPLS protocols and
the PCE architecture to support Impairment Aware Routing and the PCE architecture to support Impairment Aware Routing and
Wavelength Assignment (IA-RWA) in wavelength switched optical Wavelength Assignment (IA-RWA) in wavelength switched optical
networks. networks. This document does not define optical data plane aspects;
impairment parameters, measurement of, or assessment and
qualification of a route, but rather it describes the architectural
and information components for protocol solutions.
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
2. Terminology....................................................4 2. Terminology....................................................3
3. Applicability..................................................5 3. Applicability..................................................5
4. Impairment Aware Optical Path Computation......................6 4. Impairment Aware Optical Path Computation......................6
4.1. Optical Network Requirements and Constraints..............7 4.1. Optical Network Requirements and Constraints..............7
4.1.1. Impairment Aware Computation Scenarios...............7 4.1.1. Impairment Aware Computation Scenarios...............8
4.1.2. Impairment Computation and Information Sharing 4.1.2. Impairment Computation and Information Sharing
Constraints.................................................8 Constraints.................................................9
4.1.3. Impairment Estimation Process.......................10 4.1.3. Impairment Estimation Process.......................10
4.2. IA-RWA Computation and Control Plane Architectures.......11 4.2. IA-RWA Computation and Control Plane Architectures.......12
4.2.1. Combined Routing, WA, and IV........................13 4.2.1. Combined Routing, WA, and IV........................14
4.2.2. Separate Routing, WA, or IV.........................13 4.2.2. Separate Routing, WA, or IV.........................14
4.2.3. Distributed WA and/or IV............................14 4.2.3. Distributed WA and/or IV............................14
4.3. Mapping Network Requirements to Architectures............15 4.3. Mapping Network Requirements to Architectures............15
5. Protocol Implications.........................................17 5. Protocol Implications.........................................18
5.1. Information Model for Impairments........................17 5.1. Information Model for Impairments........................18
5.2. Routing..................................................18 5.2. Routing..................................................19
5.3. Signaling................................................19 5.3. Signaling................................................20
5.4. PCE......................................................19 5.4. PCE......................................................20
5.4.1. Combined IV & RWA...................................19 5.4.1. Combined IV & RWA...................................20
5.4.2. IV-Candidates + RWA.................................20 5.4.2. IV-Candidates + RWA.................................21
5.4.3. Approximate IA-RWA + Separate Detailed IV...........21 5.4.3. Approximate IA-RWA + Separate Detailed IV...........23
6. Security Considerations.......................................23 6. Security Considerations.......................................24
7. IANA Considerations...........................................23 7. IANA Considerations...........................................25
8. References....................................................24 8. References....................................................25
8.1. Normative References.....................................24 8.1. Normative References.....................................25
8.2. Informative References...................................25 8.2. Informative References...................................25
9. Acknowledgments...............................................26 9. Acknowledgments...............................................25
1. Introduction 1. Introduction
Wavelength Switched Optical Networks (WSONs) are constructed from Wavelength Switched Optical Networks (WSONs) are constructed from
subsystems that may include Wavelength Division Multiplexed (WDM) subsystems that may include Wavelength Division Multiplexed (WDM)
links, tunable transmitters and receivers, Reconfigurable Optical links, tunable transmitters and receivers, Reconfigurable Optical
Add/Drop Multiplexers (ROADM), wavelength converters, and electro- Add/Drop Multiplexers (ROADM), wavelength converters, and electro-
optical network elements. A WSON is a wavelength division optical network elements. A WSON is a wavelength division
multiplexed (WDM)-based optical network in which switching is multiplexed (WDM)-based optical network in which switching is
performed selectively based on the center wavelength of an optical performed selectively based on the center wavelength of an optical
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processes are usually referred to as "impairments". Optical processes are usually referred to as "impairments". Optical
impairments accumulate along the path (without 3R regeneration) impairments accumulate along the path (without 3R regeneration)
traversed by the signal. They are influenced by the type of fiber traversed by the signal. They are influenced by the type of fiber
used, the types and placement of various optical devices and the used, the types and placement of various optical devices and the
presence of other optical signals that may share a fiber segment presence of other optical signals that may share a fiber segment
along the signal's path. The degradation of the optical signals due along the signal's path. The degradation of the optical signals due
to impairments can result in unacceptable bit error rates or even a to impairments can result in unacceptable bit error rates or even a
complete failure to demodulate and/or detect the received signal. complete failure to demodulate and/or detect the received signal.
In order to provision an optical connection (an optical path) through In order to provision an optical connection (an optical path) through
a WSON certain path continuity, resource availability and impairments a WSON, a combination of path continuity, resource availability and
constraints must be met to determine viable and optimal paths through impairments constraints must be met to determine viable and optimal
the network. The determination of paths is known as Impairment Aware paths through the network. The determination of appropriate paths is
Routing and Wavelength Assignment (IA-RWA). known as Impairment Aware Routing and Wavelength Assignment (IA-RWA).
Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] includes Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] provides
a set of control plane protocols that can be used to operate data a set of control plane protocols that can be used to operate networks
networks ranging from packet switch capable networks, through those ranging from packet switch capable networks, through those networks
networks that use time division multiplexing, and WDM. [RFC4054] that use time division multiplexing, and WDM. The Path Computation
gives an overview of some critical optical impairments and their Element (PCE) architecture [RFC4655] defines functional computation
routing (path selection) implications for GMPLS. The Path Computation components that can be used in cooperation with the GMPLS control
Element (PCE) architecture [RFC4655] defines functional components plane to compute and suggest appropriate paths. [RFC4054] provides an
that can be used to compute and suggest appropriate paths in overview of optical impairments and their routing (path selection)
connection-oriented traffic-engineered networks. implications for GMPLS. This document uses as reference [G.680] and
other ITU-T Recommendations for the optical data plane aspects.
This document provides a framework for applying GMPLS protocols and This document provides a framework for applying GMPLS protocols and
the PCE architecture to the control and operation of IA-RWA for the PCE architecture to the control and operation of IA-RWA for
WSONs. To aid in this process this document also provides an WSONs. To aid in this evaluation, this document provides an overview
overview of the subsystems and processes that comprise WSONs, and of the subsystems and processes that comprise WSONs and describes IA-
describes IA-RWA so that the information requirements can be RWA models based on the corresponding ITU-T Recommendations, so that
identified to explain how the information can be modeled for use by the information requirements for use by GMPLS and PCE systems can be
GMPLS and PCE systems. This work will facilitate the development of identified. This work will facilitate the development of protocol
protocol solution models and protocol extensions within the GMPLS and extensions in support of IA-RWA within the GMPLS and PCE protocol
PCE protocol families. families.
2. Terminology 2. Terminology
Add/Drop Multiplexers (ADM): An optical device used in WDM networks Add/Drop Multiplexers (ADM): An optical device used in WDM networks
composed of one or more line side ports and typically many tributary composed of one or more line side ports and typically many tributary
ports. ports.
CWDM: Coarse Wavelength Division Multiplexing. CWDM: Coarse Wavelength Division Multiplexing.
DWDM: Dense Wavelength Division Multiplexing. DWDM: Dense Wavelength Division Multiplexing.
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WDM: Wavelength Division Multiplexing. WDM: Wavelength Division Multiplexing.
Wavelength Switched Optical Networks (WSONs): WDM based optical Wavelength Switched Optical Networks (WSONs): WDM based optical
networks in which switching is performed selectively based on the networks in which switching is performed selectively based on the
center wavelength of an optical signal. center wavelength of an optical signal.
3. Applicability 3. Applicability
There are deployment scenarios for WSON networks where not all There are deployment scenarios for WSON networks where not all
possible paths will yield suitable signal quality. There are possible paths will yield suitable signal quality. There are
multiple reasons behind this choice; here below is a non-exhaustive multiple reasons; below is a non-exhaustive list of examples:
list of examples:
o WSON is evolving using multi-degree optical cross connects in a o WSON is evolving using multi-degree optical cross connects in a
way that network topologies are changing from rings (and way that network topologies are changing from rings (and
interconnected rings) to general mesh. Adding network equipment interconnected rings) to general mesh. Adding network equipment
such as amplifiers or regenerators, to make all paths feasible, such as amplifiers or regenerators, to ensure all paths are
leads to an over-provisioned network. Indeed, even with over feasible, leads to an over-provisioned network. Indeed, even with
provisioning, the network could still have some infeasible paths. over provisioning, the network could still have some infeasible
paths.
o Within a given network, the optical physical interface may change o Within a given network, the optical physical interface may change
over the network life, e.g., the optical interfaces might be over the network life, e.g., the optical interfaces might be
upgraded to higher bit-rates. Such changes could result in paths upgraded to higher bit-rates. Such changes could result in paths
being unsuitable for the optical signal. Moreover, the optical being unsuitable for the optical signal. Moreover, the optical
physical interfaces are typically provisioned at various stages of physical interfaces are typically provisioned at various stages of
the network's life span as needed by traffic demands. the network's life span as needed by traffic demands.
o There are cases where a network is upgraded by adding new optical o There are cases where a network is upgraded by adding new optical
cross connects to increase network flexibility. In such cases cross connects to increase network flexibility. In such cases
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paths will need to have their feasibility assessed. paths will need to have their feasibility assessed.
o With the recent bit rate increases from 10G to 40G and 100G over a o With the recent bit rate increases from 10G to 40G and 100G over a
single wavelength, WSON networks will likely be operated with a single wavelength, WSON networks will likely be operated with a
mix of wavelengths at different bit rates. This operational mix of wavelengths at different bit rates. This operational
scenario will impose impairment constraints due to different scenario will impose impairment constraints due to different
physical behavior of different bit rates and associated modulation physical behavior of different bit rates and associated modulation
formats. formats.
Not having an impairment aware control plane for such networks will Not having an impairment aware control plane for such networks will
require a more complex network design phase that takes into account require a more complex network design phase that needs to take into
evolving network status in term of equipments and traffic at the account the evolving network status in term of equipments and
beginning stage. This could result in over-engineering the DWDM traffic at the beginning stage. In addition, network operations such
network with additional regenerators and optical amplifiers. In as path establishment, will require significant pre-design via non-
addition, network operations such as path establishment, will control plane processes resulting in significantly slower network
require significant pre-design via non-control plane processes provisioning.
resulting in significantly slower network provisioning.
It should be highlighted that the impact of impairments and use in
determination of path viability is not sufficiently well established
for general applicability [G.680]; it will depend on network
implementations. The use of an impairment aware control plane and set
of information distributed will need to be evaluated on a case by
case scenario.
4. Impairment Aware Optical Path Computation 4. Impairment Aware Optical Path Computation
The basic criteria for path selection is whether one can successfully The basic criteria for path selection is whether one can successfully
transmit the signal from a transmitter to a receiver within a transmit the signal from a transmitter to a receiver within a
prescribed error tolerance, usually specified as a maximum prescribed error tolerance, usually specified as a maximum
permissible bit error ratio (BER). This generally depends on the permissible bit error ratio (BER). This generally depends on the
nature of the signal transmitted between the sender and receiver and nature of the signal transmitted between the sender and receiver and
the nature of the communications channel between the sender and the nature of the communications channel between the sender and
receiver. The optical path utilized (along with the wavelength) receiver. The optical path utilized (along with the wavelength)
determines the communications channel. determines the communications channel.
The optical impairments incurred by the signal along the fiber and at The optical impairments incurred by the signal along the fiber and at
each optical network element along the path determine whether the BER each optical network element along the path determine whether the BER
performance or any other measure of signal quality can be met for a performance or any other measure of signal quality can be met for a
signal on a particular end-to-end path. signal on a particular end-to-end path.
Impairment-aware path calculation also needs to take into account Impairment-aware path calculation also needs to take into account
when regeneration is used along the path. [WSON-Frame] provides when regeneration is used along the path. [RFC6163] provides
background on the concept of optical translucent networks which background on the concept of optical translucent networks which
contains transparent elements and electro-optical elements such as contains transparent elements and electro-optical elements such as
OEO regenerations. In such networks a generic light path can go OEO regenerations. In such networks a generic light path can go
through a number of regeneration points. through a number of regeneration points.
Regeneration points could happen for two reasons: Regeneration points could happen for two reasons:
(i) wavelength conversion to assist RWA to avoid wavelength blocking. (i) wavelength conversion to assist RWA to avoid wavelength blocking.
This is the impairment free case covered by [WSON-Frame]. This is the impairment free case covered by [RFC6163].
(ii) the optical signal without regeneration would be too degraded (ii) the optical signal without regeneration would be too degraded
to meet end to end BER requirements. This is the case when RWA to meet end to end BER requirements. This is the case when RWA
takes into consideration impairment estimation covered by this takes into consideration impairment estimation covered by this
document. document.
In the latter case an optical path can be seen as a set of transparent In the latter case an optical path can be seen as a set of transparent
segments. The optical impairments calculation needs to be reset at each segments. The optical impairments calculation needs to be reset at each
regeneration point so each transparent segment will have its own regeneration point so each transparent segment will have its own
impairment evaluation. impairment evaluation.
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This situation is covered by existing GMPLS with local wavelength This situation is covered by existing GMPLS with local wavelength
(label) assignment. (label) assignment.
B. No concern for impairments but Wavelength Continuity Constraints B. No concern for impairments but Wavelength Continuity Constraints
This situation is applicable to networks designed such that every This situation is applicable to networks designed such that every
possible path is valid for the signal types permitted on the network. possible path is valid for the signal types permitted on the network.
In this case impairments are only taken into account during network In this case impairments are only taken into account during network
design and after that, for example during optical path computation, design and after that, for example during optical path computation,
they can be ignored. This is the case discussed in [WSON-Frame] where they can be ignored. This is the case discussed in [RFC6163] where
impairments may be ignored by the control plane and only optical impairments may be ignored by the control plane and only optical
parameters related to signal compatibility are considered. parameters related to signal compatibility are considered.
C. Approximated Impairment Estimation C. Approximated Impairment Estimation
This situation is applicable to networks in which impairment effects This situation is applicable to networks in which impairment effects
need to be considered but there is sufficient margin such that they need to be considered but there is sufficient margin such that they
can be estimated via approximation techniques such as link budgets can be estimated via approximation techniques such as link budgets
and dispersion [G.680],[G.sup39]. The viability of optical paths for and dispersion [G.680],[G.sup39]. The viability of optical paths for
a particular class of signals can be estimated using well defined a particular class of signals can be estimated using well defined
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1. The authority in control of the "black links" can furnish a list 1. The authority in control of the "black links" can furnish a list
of all viable paths between all viable node pairs to a of all viable paths between all viable node pairs to a
computational entity. This information would be particularly computational entity. This information would be particularly
useful as an input to RWA optimization to be performed by another useful as an input to RWA optimization to be performed by another
computation entity. The difficulty here is for larger networks computation entity. The difficulty here is for larger networks
such a list of paths along with any wavelength constraints could such a list of paths along with any wavelength constraints could
get unmanageably large. get unmanageably large.
2. The authority in control of the "black links" could provide a PCE 2. The authority in control of the "black links" could provide a PCE
like entity that would furnish a list of viable paths/wavelengths like entity a list of viable paths/wavelengths between two
between two requested nodes. This is useful as an input to RWA requested nodes. This is useful as an input to RWA optimizations
optimizations and can reduce the scaling issue previously and can reduce the scaling issue previously mentioned. Such a PCE
mentioned. Such a PCE like entity would not need to perform a full like entity would not need to perform a full RWA computation,
RWA computation, i.e., it would not need to take into account i.e., it would not need to take into account current wavelength
current wavelength availability on links. Such an approach may availability on links. Such an approach may require PCEP
require PCEP extensions for both the request and response extensions for both the request and response information.
information.
3. The authority in control of the "black links" can provide a PCE 3. The authority in control of the "black links" provides a PCE that
that performs full IA-RWA services. The difficulty is this performs full IA-RWA services. The difficulty is this requires the
requires the one authority to also become the sole source of all one authority to also become the sole source of all RWA
RWA optimization algorithms and such. optimization algorithms.
In all the above cases it would be the responsibility of the In all the above cases it would be the responsibility of the
authority in control of the "black links" to import the shared authority in control of the "black links" to import the shared
impairment information from the other NEs via the control plane or impairment information from the other NEs via the control plane or
other means as necessary. other means as necessary.
4.1.3. Impairment Estimation Process 4.1.3. Impairment Estimation Process
The Impairment Estimation Process can be modeled through the The Impairment Estimation Process can be modeled through the
following functional blocks. These blocks are independent of any following functional blocks. These blocks are independent of any
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| || | | || |
| \/ | | \/ |
| +------------+ | | +------------+ |
| | BER / | | | | BER / | |
| | Q Factor | | | | Q Factor | |
| +------------+ | | +------------+ |
+-----------------+ +-----------------+
Starting from functional block on the left the Optical Interface Starting from functional block on the left the Optical Interface
represents where the optical signal is transmitted or received and represents where the optical signal is transmitted or received and
defines the properties at the end points path. Even the no-impairment defines the properties at the path end points. Even the no-impairment
case like scenario B in section 4.1.1 needs to consider a minimum set case like scenario B in section 4.1.1 needs to consider a minimum set
of interface characteristics. In such case only a few parameters used of interface characteristics. In such case only a few parameters used
to assess the signal compatibility will be taken into account (see to assess the signal compatibility will be taken into account (see
[WSON-Frame]). For the impairment-aware case these parameters may be [RFC6163]). For the impairment-aware case these parameters may be
sufficient or not depending on the accepted level of approximation sufficient or not depending on the accepted level of approximation
(scenarios C and D). This functional block highlights the need to (scenarios C and D). This functional block highlights the need to
consider a set of interface parameters during an Impairment consider a set of interface parameters during an Impairment
Validation Process. Validation Process.
The block "Optical Impairment Path" represents all kinds of The block "Optical Impairment Path" represents the types of
impairments affecting a wavelength as it traverses the networks impairments affecting a wavelength as it traverses the networks
through links and nodes. In the case where the control plane has no through links and nodes. In the case of a network where there are no
IV this block will not be present. Otherwise, this function must be impairments (Scenario A), this block will not be present. Otherwise,
implemented in some way via the control plane. Options for this will this function must be implemented in some way via the control plane.
be given in the next section on architectural alternatives. This Options for this will be given in the next section on architectural
block implementation (e.g. through routing, signaling or PCE) may alternatives. This block implementation (e.g. through routing,
influence the way the control plane distributes impairment signaling or PCE) may influence the way the control plane distributes
information within the network. impairment information within the network.
The last block implements the decision function for path feasibility. The last block implements the decision function for path feasibility.
Depending on the IA level of approximation this function can be more Depending on the IA level of approximation this function can be more
or less complex. For example in case of no IA only the signal class or less complex. For example in case of no IA only the signal class
compatibility will be verified. In addition to feasible/not-feasible compatibility will be verified. In addition to feasible/not-feasible
result, it may be worthwhile for decision functions to consider the result, it may be worthwhile for decision functions to consider the
case in which paths can be likely-to-be-feasible within some degree case in which paths can be likely-to-be-feasible within some degree
of confidence. The optical impairments are usually not fixed values of confidence. The optical impairments are usually not fixed values
as they may vary within ranges of values according to the approach as they may vary within ranges of values according to the approach
taken in the physical modeling (worst-case, statistical or based on taken in the physical modeling (worst-case, statistical or based on
typical values). For example, the utilization of the worst-case value typical values). For example, the utilization of the worst-case value
for each parameter within impairment validation process may lead to for each parameter within impairment validation process may lead to
marking some paths as not-feasible while they are very likely to be marking some paths as not-feasible while they are very likely to be
feasible in reality. feasible in reality.
4.2. IA-RWA Computation and Control Plane Architectures 4.2. IA-RWA Computation and Control Plane Architectures
From a control plane point of view optical impairments are additional From a control plane point of view optical impairments are additional
constraints to the impairment-free RWA process described in [WSON- constraints to the impairment-free RWA process described in
Frame]. In impairment aware routing and wavelength assignment (IA- [RFC6163]. In impairment aware routing and wavelength assignment (IA-
RWA), there are conceptually three general classes of processes to be RWA), there are conceptually three general classes of processes to be
considered: Routing (R), Wavelength Assignment (WA), and Impairment considered: Routing (R), Wavelength Assignment (WA), and Impairment
Validation (estimation) (IV). Validation (estimation) (IV).
Impairment validation may come in many forms, and maybe invoked at Impairment validation may come in many forms, and may be invoked at
different levels of detail in the IA-RWA process. From a process different levels of detail in the IA-RWA process. From a process
point of view the following three forms of impairment validation will point of view the following three forms of impairment validation will
be considered: be considered:
o IV-Candidates o IV-Candidates
In this case an Impairment Validation (IV) process furnishes a set of In this case an Impairment Validation (IV) process furnishes a set of
paths between two nodes along with any wavelength restrictions such paths between two nodes along with any wavelength restrictions such
that the paths are valid with respect to optical impairments. These that the paths are valid with respect to optical impairments. These
paths and wavelengths may not be actually available in the network paths and wavelengths may not be actually available in the network
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In this case impairments to a path are computed at a single entity. In this case impairments to a path are computed at a single entity.
The information concerning impairments, however, may still be The information concerning impairments, however, may still be
gathered from network elements. Depending how information is gathered gathered from network elements. Depending how information is gathered
this may put additional requirements on routing protocols. This will this may put additional requirements on routing protocols. This will
be detailed in later sections. be detailed in later sections.
o IV-Distributed o IV-Distributed
In the distributed IV process, approximate degradation measures such In the distributed IV process, approximate degradation measures such
as OSNR, dispersion, DGD, etc. are accumulated along the path via a as OSNR, dispersion, DGD, etc. may be accumulated along the path via
signaling like protocol. Each node on the path may already perform signaling. Each node on the path may already perform some part of the
some part of the impairment computation (i.e. distributed). When the impairment computation (i.e. distributed). When the accumulated
accumulated measures reach the destination node a decision on the measures reach the destination node a decision on the impairment
impairment validity of the path can be made. Note that such a process validity of the path can be made. Note that such a process would
would entail revealing an individual network element's impairment entail revealing an individual network element's impairment
information but it does not generally require distributing optical information but it does not generally require distributing optical
parameters to the entire network. parameters to the entire network.
The Control Plane must not preclude the possibility to operate one or The Control Plane must not preclude the possibility to operate one or
all the above cases concurrently in the same network. For example all the above cases concurrently in the same network. For example
there could be cases where a certain number of paths are already pre- there could be cases where a certain number of paths are already pre-
validated (IV-Candidates) so the control plane may setup one of those validated (IV-Candidates) so the control plane may setup one of those
path without requesting any impairment validation procedure. On the paths without requesting any impairment validation procedure. On the
same network however the control plane may compute a path outside the same network however the control plane may compute a path outside the
set of IV-Candidates for which an impairment evaluation can be set of IV-Candidates for which an impairment evaluation can be
necessary. necessary.
The following subsections present three major classes of IA-RWA path The following subsections present three major classes of IA-RWA path
computation architectures and reviews some of their respective computation architectures and reviews some of their respective
advantages and disadvantages. advantages and disadvantages.
4.2.1. Combined Routing, WA, and IV 4.2.1. Combined Routing, WA, and IV
From the point of view of optimality, reasonably good IA-RWA From the point of view of optimality, reasonably good IA-RWA
solutions can be achieved if the path computation entity (PCE) can solutions can be achieved if the path computation entity (PCE) can
conceptually/algorithmically combine the processes of routing, conceptually/algorithmically combine the processes of routing,
wavelength assignment and impairment validation. wavelength assignment and impairment validation.
Such a combination can take place if the PCE is given: (a) the Such a combination can take place if the PCE is given: (a) the
impairment-free WSON network information as discussed in [WSON-Frame] impairment-free WSON network information as discussed in [RFC6163]
and (b) impairment information to validate potential paths. and (b) impairment information to validate potential paths.
4.2.2. Separate Routing, WA, or IV 4.2.2. Separate Routing, WA, or IV
Separating the processes of routing, WA and/or IV can reduce the need Separating the processes of routing, WA and/or IV can reduce the need
for sharing of different types of information used in path for sharing of different types of information used in path
computation. This was discussed for routing separate from WA in computation. This was discussed for routing separate from WA in
[WSON-Frame]. In addition, as was discussed some impairment [RFC6163]. In addition, as was discussed some impairment information
information may not be shared and this may lead to the need to may not be shared and this may lead to the need to separate IV from
separate IV from RWA. In addition, if IV needs to be done at a high RWA. In addition, if IV needs to be done at a high level of
level of precision it may be advantageous to offload this computation precision it may be advantageous to offload this computation to a
to a specialized server. specialized server.
The following conceptual architectures belong in this general The following conceptual architectures belong in this general
category: category:
o R+WA+IV -- separate routing, wavelength assignment, and impairment o R+WA+IV -- separate routing, wavelength assignment, and impairment
validation. validation.
o R + (WA & IV) -- routing separate from a combined wavelength o R + (WA & IV) -- routing separate from a combined wavelength
assignment and impairment validation process. Note that impairment assignment and impairment validation process. Note that impairment
validation is typically wavelength dependent hence combining WA validation is typically wavelength dependent hence combining WA
skipping to change at page 14, line 21 skipping to change at page 14, line 49
separate impairment validation process. separate impairment validation process.
Note that the IV process may come before or after the RWA processes. Note that the IV process may come before or after the RWA processes.
If RWA comes first then IV is just rendering a yes/no decision on the If RWA comes first then IV is just rendering a yes/no decision on the
selected path and wavelength. If IV comes first it would need to selected path and wavelength. If IV comes first it would need to
furnish a list of possible (valid with respect to impairments) routes furnish a list of possible (valid with respect to impairments) routes
and wavelengths to the RWA processes. and wavelengths to the RWA processes.
4.2.3. Distributed WA and/or IV 4.2.3. Distributed WA and/or IV
In the non-impairment RWA situation [WSON-Frame] it was shown that a In the non-impairment RWA situation [RFC6163] it was shown that a
distributed wavelength assignment (WA) process carried out via distributed wavelength assignment (WA) process carried out via
signaling can eliminate the need to distribute wavelength signaling can eliminate the need to distribute wavelength
availability information via an interior gateway protocol (IGP). A availability information via an interior gateway protocol (IGP). A
similar approach can allow for the distributed computation of similar approach can allow for the distributed computation of
impairment effects and avoid the need to distribute impairment impairment effects and avoid the need to distribute impairment
characteristics of network elements and links via routing protocols characteristics of network elements and links via routing protocols
or by other means. An example of such an approach is given in or by other means. So the following conceptual options belong to this
[Martinelli] and utilizes enhancements to RSVP signaling to carry category:
accumulated impairment related information. So the following
conceptual options belong to this category:
o RWA + D(IV) - Combined routing and wavelength assignment and o RWA + D(IV) - Combined routing and wavelength assignment and
distributed impairment validation. distributed impairment validation.
o R + D(WA & IV) -- routing separate from a distributed wavelength o R + D(WA & IV) -- routing separate from a distributed wavelength
assignment and impairment validation process. assignment and impairment validation process.
Distributed impairment validation for a prescribed network path Distributed impairment validation for a prescribed network path
requires that the effects of impairments be calculated by approximate requires that the effects of impairments be calculated by approximate
models with cumulative quality measures such as those given in models with cumulative quality measures such as those given in
[G.680]. For such a system to be interoperable the exact encoding of [G.680]. The protocol encoding of the impairment related information
the techniques from [G.680] would need to be agreed upon. from [G.680] would need to be agreed upon.
If distributed WA is being done at the same time as distributed IV If distributed WA is being done at the same time as distributed IV
then it is necessary to accumulate impairment related information for then it is necessary to accumulate impairment related information for
all wavelengths that could be used. This is somewhat winnowed down as all wavelengths that could be used. This is somewhat windowed down as
potential wavelengths are discovered to be in use, but could be a potential wavelengths are discovered to be in use, but could be a
significant burden for lightly loaded high channel count networks. significant burden for lightly loaded high channel count networks.
4.3. Mapping Network Requirements to Architectures 4.3. Mapping Network Requirements to Architectures
Figure 2 shows process flows for three main architectural Figure 2 shows process flows for three main architectural
alternatives to IA-RWA when approximate impairment validation alternatives to IA-RWA when approximate impairment validation is
suffices. Figure 3 shows process flows for two main architectural sufficient. Figure 3 shows process flows for two main architectural
alternatives when detailed impairment verification is required. alternatives when detailed impairment verification is required.
+-----------------------------------+ +-----------------------------------+
| +--+ +-------+ +--+ | | +--+ +-------+ +--+ |
| |IV| |Routing| |WA| | | |IV| |Routing| |WA| |
| +--+ +-------+ +--+ | | +--+ +-------+ +--+ |
| | | |
| Combined Processes | | Combined Processes |
+-----------------------------------+ +-----------------------------------+
(a) (a)
skipping to change at page 16, line 17 skipping to change at page 17, line 11
process needs to know impairment information from all optical network process needs to know impairment information from all optical network
elements, while the RWA process needs to know non-impairment RWA elements, while the RWA process needs to know non-impairment RWA
information from the network elements. This alternative can be used information from the network elements. This alternative can be used
with "black links", but the authority in control of the "black links" with "black links", but the authority in control of the "black links"
would need to provide the functionality of the IV-candidates process. would need to provide the functionality of the IV-candidates process.
Note that this is still very useful since the algorithmic areas of IV Note that this is still very useful since the algorithmic areas of IV
and RWA are very different and prone to specialization. and RWA are very different and prone to specialization.
o Routing + Distributed WA and IV o Routing + Distributed WA and IV
In this alternative a signaling protocol is extended and leveraged in In this alternative a signaling protocol may be extended and
the wavelength assignment and impairment validation processes. leveraged in the wavelength assignment and impairment validation
Although this doesn't enable as high a potential degree of optimality processes. Although this doesn't enable as high a potential degree of
of optimality as (a) or (b), it does not require distribution of optimality of optimality as (a) or (b), it does not require
either link wavelength usage or link/node impairment information. distribution of either link wavelength usage or link/node impairment
Note that this is most likely not suitable for "black links". information. Note that this is most likely not suitable for "black
links".
+-----------------------------------+ +------------+ +-----------------------------------+ +------------+
| +-----------+ +-------+ +--+ | | +--------+ | | +-----------+ +-------+ +--+ | | +--------+ |
| | IV | |Routing| |WA| | | | IV | | | | IV | |Routing| |WA| | | | IV | |
| |approximate| +-------+ +--+ |---->| |Detailed| | | |approximate| +-------+ +--+ |---->| |Detailed| |
| +-----------+ | | +--------+ | | +-----------+ | | +--------+ |
| Combined Processes | | | | Combined Processes | | |
+-----------------------------------+ +------------+ +-----------------------------------+ +------------+
(a) (a)
skipping to change at page 17, line 23 skipping to change at page 18, line 19
high degree of potential optimality and efficiency in IA-RWA; then a high degree of potential optimality and efficiency in IA-RWA; then a
separate computation entity performs detailed impairment validation. separate computation entity performs detailed impairment validation.
Note that detailed impairment estimation is not standardized. Note that detailed impairment estimation is not standardized.
5. Protocol Implications 5. Protocol Implications
The previous IA-RWA architectural alternatives and process flows make The previous IA-RWA architectural alternatives and process flows make
differing demands on a GMPLS/PCE based control plane. This section differing demands on a GMPLS/PCE based control plane. This section
discusses the use of (a) an impairment information model, (b) PCE as discusses the use of (a) an impairment information model, (b) PCE as
computational entity assuming the various process roles and computational entity assuming the various process roles and
consequences for PCEP, (c) any needed extensions to signaling, and consequences for PCEP, (c) possible extensions to signaling, and (d)
(d) extensions to routing. The impacts to the control plane for IA- possible extensions to routing. This document is providing this
RWA are summarized in Figure 4. evaluation to aid protocol solutions work. The protocol
specifications may deviate from this assessment. The assessment of
the impacts to the control plane for IA-RWA is summarized in Figure
4.
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| IA-RWA Option |PCE |Sig |Info Model| Routing| | IA-RWA Option |PCE |Sig |Info Model| Routing|
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| Combined |Yes | No | Yes | Yes | | Combined |Yes | No | Yes | Yes |
| IV & RWA | | | | | | IV & RWA | | | | |
+-------------------+----+----+----------+--------+- +-------------------+----+----+----------+--------+-
| IV-Candidates |Yes | No | Yes | Yes | | IV-Candidates |Yes | No | Yes | Yes |
| + RWA | | | | | | + RWA | | | | |
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| Routing + |No | Yes| Yes | No | | Routing + |No | Yes| Yes | No |
|Distributed IV, RWA| | | | | |Distributed IV, RWA| | | | |
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
Figure 4 IA-RWA architectural options and control plane impacts. Figure 4 IA-RWA architectural options and control plane impacts.
5.1. Information Model for Impairments 5.1. Information Model for Impairments
As previously discussed all IA-RWA scenarios to a greater or lesser As previously discussed most IA-RWA scenarios to a greater or lesser
extent rely on a common impairment information model. A number of extent rely on a common impairment information model. A number of
ITU-T recommendations cover detailed as well as approximate ITU-T recommendations cover detailed as well as approximate
impairment characteristics of fibers and a variety of devices and impairment characteristics of fibers and a variety of devices and
subsystems. A well integrated impairment model for optical network subsystems. An impairment model which can be used as a guideline for
elements is given in [G.680] and is used to form the basis for an optical network elements and assessment of path viability is given in
optical impairment model in a companion document [Imp-Info]. [G.680].
It should be noted that the current version of [G.680] is limited to It should be noted that the current version of [G.680] is limited to
the networks composed of a single WDM line system vendor combined the networks composed of a single WDM line system vendor combined
with OADMs and/or PXCs from potentially multiple other vendors, this with OADMs and/or PXCs from potentially multiple other vendors, this
is known as situation 1 and is shown in Figure 1-1 of [G.680]. It is is known as situation 1 and is shown in Figure 1-1 of [G.680]. It is
planed in the future that [G.680] will include networks incorporating planed in the future that [G.680] will include networks incorporating
line systems from multiple vendors as well as OADMs and/or PXCs from line systems from multiple vendors as well as OADMs and/or PXCs from
potentially multiple other vendors, this is known as situation 2 and potentially multiple other vendors, this is known as situation 2 and
is shown in Figure 1-2 of [G.680]. is shown in Figure 1-2 of [G.680].
The case of distributed impairment validation actually requires a bit For the case of distributed impairment validation (distributed IV),
more than an impairment information model. In particular, it needs a this would require more than an impairment information model. It
common impairment "computation" model. In the distributed IV case one would need a common impairment "computation" model. In the
needs to standardize the accumulated impairment measures that will be distributed IV case one needs to standardize the accumulated
conveyed and updated at each node. Section 9 of [G.680] provides impairment measures that will be conveyed and updated at each node.
guidance in this area with specific formulas given for OSNR, residual Section 9 of [G.680] provides guidance in this area with specific
dispersion, polarization mode dispersion/polarization dependent loss, formulas given for OSNR, residual dispersion, polarization mode
effects of channel uniformity, etc... However, specifics of what dispersion/polarization dependent loss, and effects of channel
intermediate results are kept and in what form would need to be uniformity. However, specifics of what intermediate results are kept
standardized. and in what form for the protocol would need to be standardized for
interoperability. As noted in [G.680], this information may possibly
not be sufficient, and in such case the applicability would be
network dependent.
5.2. Routing 5.2. Routing
Different approaches to path/wavelength impairment validation gives Different approaches to path/wavelength impairment validation gives
rise to different demands placed on GMPLS routing protocols. In the rise to different demands placed on GMPLS routing protocols. In the
case where approximate impairment information is used to validate case where approximate impairment information is used to validate
paths GMPLS routing may be used to distribute the impairment paths GMPLS routing may be used to distribute the impairment
characteristics of the network elements and links based on the characteristics of the network elements and links based on the
impairment information model previously discussed. impairment information model previously discussed.
Depending on the computational alternative the routing protocol may Depending on the computational alternative the routing protocol may
need to advertise information necessary to impairment validation need to advertise information necessary to impairment validation
process. This can potentially cause scalability issues due to the process. This can potentially cause scalability issues due to the
high amount of data that need to be advertised. Such issue can be high amount of data that need to be advertised. Such issue can be
addressed separating data that need to be advertised rarely and data addressed separating data that need to be advertised rarely and data
that need to be advertised more frequently or adopting other form of that need to be advertised more frequently or adopting other form of
awareness solutions described in previous sections (e.g. centralized awareness solutions described in previous sections (e.g. centralized
and/or external IV entity). and/or external IV entity).
In term of approximated scenario (see Section 4.1.1. ) the model In term of approximated scenario (see Section 4.1.1.) the model
defined by [G.680] will apply and routing protocol will need to defined by [G.680] will apply and routing protocol will need to
gather information required for such computation. gather information required for such computation.
In the case of distributed-IV no new demands would be placed on the In the case of distributed-IV no new demands would be placed on the
routing protocol. routing protocol.
5.3. Signaling 5.3. Signaling
The largest impacts on signaling occur in the cases where distributed The largest impacts on signaling occur in the cases where distributed
impairment validation is performed. In this case, it ie necessary to impairment validation is performed. In this case, it ie necessary to
skipping to change at page 19, line 30 skipping to change at page 20, line 34
additional information to a connection request such as desired egress additional information to a connection request such as desired egress
signal quality (defined in some appropriate sense) in non-distributed signal quality (defined in some appropriate sense) in non-distributed
IV scenarios. IV scenarios.
5.4. PCE 5.4. PCE
In section 4.3. a number of computation architectural alternatives In section 4.3. a number of computation architectural alternatives
were given that could be used to meet the various requirements and were given that could be used to meet the various requirements and
constraints of section 4.1. Here the focus is how these alternatives constraints of section 4.1. Here the focus is how these alternatives
could be implemented via either a single PCE or a set of two or more could be implemented via either a single PCE or a set of two or more
cooperating PCEs, and the impacts on the PCEP protocol. cooperating PCEs, and the impacts on the PCEP protocol. This document
is providing this evaluation to aid solutions work. The protocol
specifications may deviate from this assessment.
5.4.1. Combined IV & RWA 5.4.1. Combined IV & RWA
In this situation, shown in Figure 2(a), a single PCE performs all In this situation, shown in Figure 2(a), a single PCE performs all
the computations needed for IA-RWA. the computations needed for IA-RWA.
o TE Database Requirements: WSON Topology and switching o TE Database Requirements: WSON Topology and switching
capabilities, WSON WDM link wavelength utilization, and WSON capabilities, WSON WDM link wavelength utilization, and WSON
impairment information impairment information
o PCC to PCE Request Information: Signal characteristics/type, o PCC to PCE Request Information: Signal characteristics/type,
required quality, source node, destination node required quality, source node, destination node
o PCE to PCC Reply Information: If the computations completed o PCE to PCC Reply Information: If the computations completed
successfully then the PCE returns the path and its assigned successfully then the PCE returns the path and its assigned
wavelength. If the computations could not complete successfully it wavelength. If the computations could not complete successfully it
would be potentially useful to know the reason why. At a very would be potentially useful to know the reason why. At a minimum,
crude level it is of interest to know if this was due to lack of it is of interest to know if this was due to lack of wavelength
wavelength availability or impairment considerations or a bit of availability or impairment considerations or both. The information
both. The information to be conveyed is for further study. to be conveyed is for further study.
5.4.2. IV-Candidates + RWA 5.4.2. IV-Candidates + RWA
In this situation, as shown in Figure 2(b), two separate processes In this situation, as shown in Figure 2(b), two separate processes
are involved in the IA-RWA computation. This requires two cooperating are involved in the IA-RWA computation. This requires two cooperating
path computation entities: one for the Candidates-IV process and path computation entities: one for the Candidates-IV process and
another for the RWA process. In addition, the overall process needs another for the RWA process. In addition, the overall process needs
to be coordinated. This could be done with yet another PCE or this to be coordinated. This could be done with yet another PCE or this
functionality can be added to one of previously defined entities. functionality can be added to one of previously defined entities.
This later option requires the RWA entity to also act as the overall This later option requires the RWA entity to also act as the overall
skipping to change at page 21, line 5 skipping to change at page 22, line 13
computation. It needs not take into account current link wavelength computation. It needs not take into account current link wavelength
utilization, but this is not prohibited. The Candidates-PCE is only utilization, but this is not prohibited. The Candidates-PCE is only
required to interact with the RWA-PCE as indicated above and not the required to interact with the RWA-PCE as indicated above and not the
initiating PCC. (Note: RWA-Coord PCE is also a PCC with respect to initiating PCC. (Note: RWA-Coord PCE is also a PCC with respect to
the IV-Candidate) the IV-Candidate)
o TE Database Requirements: WSON Topology and switching capabilities o TE Database Requirements: WSON Topology and switching capabilities
and WSON impairment information (no information link wavelength and WSON impairment information (no information link wavelength
utilization required). utilization required).
Figure 5 shows a sequence diagram for the interactions between the Figure 5 shows a sequence diagram for the possible interactions
PCC, RWA-Coord PCE and IV-Candidates PCE. between the PCC, RWA-Coord PCE and IV-Candidates PCE.
+---+ +-------------+ +-----------------+ +---+ +-------------+ +-----------------+
|PCC| |RWA-Coord PCE| |IV-Candidates PCE| |PCC| |RWA-Coord PCE| |IV-Candidates PCE|
+-+-+ +------+------+ +---------+-------+ +-+-+ +------+------+ +---------+-------+
...___ (a) | | ...___ (a) | |
| ````---...____ | | | ````---...____ | |
| ```-->| | | ```-->| |
| | | | | |
| |--..___ (b) | | |--..___ (b) |
| | ```---...___ | | | ```---...___ |
skipping to change at page 22, line 18 skipping to change at page 23, line 27
o TE Database Requirements: The IV-Detailed-PCE will need optical o TE Database Requirements: The IV-Detailed-PCE will need optical
impairment information, WSON topology, and possibly WDM link impairment information, WSON topology, and possibly WDM link
wavelength usage information. This document puts no restrictions wavelength usage information. This document puts no restrictions
on the type of information that may be used in these computations. on the type of information that may be used in these computations.
o Coordinating-PCE to IV-Detailed-PCE request: The coordinating-PCE o Coordinating-PCE to IV-Detailed-PCE request: The coordinating-PCE
will furnish signal characteristics, quality requirements, path will furnish signal characteristics, quality requirements, path
and wavelength to the IV-Detailed-PCE. and wavelength to the IV-Detailed-PCE.
o IV-Detailed-PCE to Coordinating-PCE reply: The reply is essential o IV-Detailed-PCE to Coordinating-PCE reply: The reply is
an yes/no decision as to whether the requirements could actually essentially a yes/no decision as to whether the requirements could
be met. In the case where the impairment validation fails it would actually be met. In the case where the impairment validation fails
be helpful to convey information related to cause or quantify the it would be helpful to convey information related to cause or
failure, e.g., so a judgment can be made whether to try a quantify the failure, e.g., so a judgment can be made whether to
different signal or adjust signal parameters. try a different signal or adjust signal parameters.
Figure 6 shows a sequence diagram for the interactions for the Figure 6 shows a sequence diagram for the interactions for the
process shown in Figure 3(b). This involves interactions between the process shown in Figure 3(b). This involves interactions between the
PCC, RWA-PCE (acting as coordinator), IV-Candidates-PCE and the IV- PCC, RWA-PCE (acting as coordinator), IV-Candidates-PCE and the IV-
Detailed-PCE. Detailed-PCE.
In step (a) the PCC requests a path meeting specified quality In step (a) the PCC requests a path meeting specified quality
constraints between two nodes (A and Z) for a given signal constraints between two nodes (A and Z) for a given signal
represented either by a specific type or a general class with represented either by a specific type or a general class with
associated parameters. In step (b) the RWA-Coordinating-PCE requests associated parameters. In step (b) the RWA-Coordinating-PCE requests
skipping to change at page 23, line 42 skipping to change at page 24, line 44
Figure 6 Sequence diagram for the interactions between PCC, RWA- Figure 6 Sequence diagram for the interactions between PCC, RWA-
Coordinating-PCE, IV-Candidates-PCE and IV-Detailed-PCE. Coordinating-PCE, IV-Candidates-PCE and IV-Detailed-PCE.
6. Security Considerations 6. Security Considerations
This document discusses a number of control plane architectures that This document discusses a number of control plane architectures that
incorporate knowledge of impairments in optical networks. If such incorporate knowledge of impairments in optical networks. If such
architecture is put into use within a network it will by its nature architecture is put into use within a network it will by its nature
contain details of the physical characteristics of an optical contain details of the physical characteristics of an optical
network. Such information would need to be protected from intentional network. Such information would need to be protected from intentional
or unintentional disclosure. or unintentional disclosure similar to other network information used
within intra-domain protocols. It is expected that protocol solutions
work will address any issues on the use of impairment information.
7. IANA Considerations 7. IANA Considerations
This draft does not currently require any consideration from IANA. This draft does not currently require any consideration from IANA.
8. References 8. References
8.1. Normative References 8.1. Normative References
[G.650.1] ITU-T Recommendation G.650.1, Definitions and test methods
for linear, deterministic attributes of single-mode fibre
and cable, June 2004.
[G.650.2] ITU-T Recommendation G.650.2, Definitions and test methods
for statistical and non-linear related attributes of
single-mode fibre and cable, July 2007.
[G.650.3] ITU-T Recommendation G.650.3
[G.652] ITU-T Recommendation G.652, Characteristics of a single-mode
optical fibre and cable, June 2005.
[G.653] ITU-T Recommendation G.653, Characteristics of a dispersion-
shifted single-mode optical fibre and cable, December 2006.
[G.654] ITU-T Recommendation G.654, Characteristics of a cut-off
shifted single-mode optical fibre and cable, December 2006.
[G.655] ITU-T Recommendation G.655, Characteristics of a non-zero
dispersion-shifted single-mode optical fibre and cable,
March 2006.
[G.656] ITU-T Recommendation G.656, Characteristics of a fibre and
cable with non-zero dispersion for wideband optical
transport, December 2006.
[G.661] ITU-T Recommendation G.661, Definition and test methods for
the relevant generic parameters of optical amplifier
devices and subsystems, March 2006.
[G.662] ITU-T Recommendation G.662, Generic characteristics of
optical amplifier devices and subsystems, July 2005.
[G.671] ITU-T Recommendation G.671, Transmission characteristics of
optical components and subsystems, January 2005.
[G.680] ITU-T Recommendation G.680, Physical transfer functions of [G.680] ITU-T Recommendation G.680, Physical transfer functions of
optical network elements, July 2007. optical network elements, July 2007.
[G.691] ITU-T Recommendation G.691, Optical interfaces for [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
multichannel systems with optical amplifiers, November Switching (GMPLS) Architecture", RFC 3945, October 2004.
1998.
[G.692] ITU-T Recommendation G.692, Optical interfaces for single
channel STM-64 and other SDH systems with optical
amplifiers, March 2006.
[G.872] ITU-T Recommendation G.872, Architecture of optical
transport networks, November 2001.
[G.957] ITU-T Recommendation G.957, Optical interfaces for
equipments and systems relating to the synchronous digital
hierarchy, March 2006.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation
Physical Layer Interfaces, March 2006. Element (PCE)-Based Architecture", RFC 4655, August 2006.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM 8.2. Informative References
applications: DWDM frequency grid, June 2002.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM [G.Sup39] ITU-T Series G Supplement 39, Optical system design and
applications: CWDM wavelength grid, December 2003. engineering considerations, February 2006.
[G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM [G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM
applications with Single-Channel optical interface, applications with Single-Channel optical interface,
December 2006. December 2006.
[G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM [G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM
applications with Single-Channel optical interface, July applications with Single-Channel optical interface, July
2007. 2007.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and
engineering considerations, February 2006.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other
Constraints on Optical Layer Routing", RFC 4054, May 2005. Constraints on Optical Layer Routing", RFC 4054, May 2005.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation [RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and
Element (PCE)-Based Architecture", RFC 4655, August 2006. PCE Control of Wavelength Switched Optical Networks", RFC
6163, April 2011.
8.2. Informative References
[WSON-Frame] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS
and PCE Control of Wavelength Switched Optical Networks",
work in progress: draft-ietf-ccamp-wavelength-switched-
framework.
[Imp-Info] G. Bernstein, Y. Lee, D. Li, "A Framework for the Control
and Measurement of Wavelength Switched Optical Networks
(WSON) with Impairments", work in progress: draft-
bernstein-wson-impairment-info.
[Martinelli] G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS
Signaling Extensions for Optical Impairment Aware Lightpath
Setup", Work in Progress: draft-martinelli-ccamp-optical-
imp-signaling.
9. Acknowledgments 9. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
Copyright (c) 2011 IETF Trust and the persons identified as authors Copyright (c) 2011 IETF Trust and the persons identified as authors
of the code. All rights reserved. of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions modification, are permitted provided that the following conditions
skipping to change at page 27, line 40 skipping to change at page 27, line 40
Email: danli@huawei.com Email: danli@huawei.com
Giovanni Martinelli Giovanni Martinelli
Cisco Cisco
Via Philips 12 Via Philips 12
20052 Monza, Italy 20052 Monza, Italy
Phone: +39 039 2092044 Phone: +39 039 2092044
Email: giomarti@cisco.com Email: giomarti@cisco.com
Contributor's Addresses Contributor's Addresses
Ming Chen Ming Chen
Huawei Technologies Co., Ltd. Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base, F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District Bantian, Longgang District
Shenzhen 518129 P.R.China Shenzhen 518129 P.R.China
Phone: +86-755-28973237 Phone: +86-755-28973237
Email: mchen@huawei.com Email: mchen@huawei.com
Rebecca Han Rebecca Han
Huawei Technologies Co., Ltd. Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base, F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District Bantian, Longgang District
Shenzhen 518129 P.R.China Shenzhen 518129 P.R.China
Phone: +86-755-28973237 Phone: +86-755-28973237
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