draft-ietf-ccamp-rwa-wson-framework-12.txt   rfc6163.txt 
Network Working Group Y. Lee (ed.)
Internet Draft Huawei
Intended status: Informational G. Bernstein (ed.)
Expires: August 2011 Grotto Networking
Wataru Imajuku
NTT
February 8, 2011 Internet Engineering Task Force (IETF) Y. Lee, Ed.
Request for Comments: 6163 Huawei
Category: Informational G. Bernstein, Ed.
ISSN: 2070-1721 Grotto Networking
W. Imajuku
NTT
April 2011
Framework for GMPLS and PCE Control of Wavelength Switched Optical Framework for GMPLS and Path Computation Element (PCE) Control
Networks (WSON) of Wavelength Switched Optical Networks (WSONs)
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 (WSONs). 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
constraints that are common across different WSON environments as constraints that are common across different WSON environments; as
such it does not address optical impairments in any depth. such, it does not address optical impairments in any depth.
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Table of Contents Table of Contents
1. Introduction...................................................4 1. Introduction ....................................................4
2. Terminology....................................................5 2. Terminology .....................................................5
3. Wavelength Switched Optical Networks...........................6 3. Wavelength Switched Optical Networks ............................6
3.1. WDM and CWDM Links........................................6 3.1. WDM and CWDM Links .........................................6
3.2. Optical Transmitters and Receivers........................8 3.2. Optical Transmitters and Receivers .........................8
3.3. Optical Signals in WSONs..................................9 3.3. Optical Signals in WSONs ...................................9
3.3.1. Optical Tributary Signals...........................10 3.3.1. Optical Tributary Signals ..........................10
3.3.2. WSON Signal Characteristics.........................10 3.3.2. WSON Signal Characteristics ........................10
3.4. ROADMs, OXCs, Splitters, Combiners and FOADMs............11 3.4. ROADMs, OXCs, Splitters, Combiners, and FOADMs ............11
3.4.1. Reconfigurable Add/Drop Multiplexers and OXCs.......11 3.4.1. Reconfigurable Optical Add/Drop
3.4.2. Splitters...........................................14 Multiplexers and OXCs ..............................11
3.4.3. Combiners...........................................15 3.4.2. Splitters ..........................................14
3.4.4. Fixed Optical Add/Drop Multiplexers.................15 3.4.3. Combiners ..........................................15
3.5. Electro-Optical Systems..................................16 3.4.4. Fixed Optical Add/Drop Multiplexers ................15
3.5.1. Regenerators........................................16 3.5. Electro-Optical Systems ...................................16
3.5.2. OEO Switches........................................19 3.5.1. Regenerators .......................................16
3.6. Wavelength Converters....................................19 3.5.2. OEO Switches .......................................19
3.6.1. Wavelength Converter Pool Modeling..................21 3.6. Wavelength Converters .....................................19
3.7. Characterizing Electro-Optical Network Elements..........25 3.6.1. Wavelength Converter Pool Modeling .................21
3.7.1. Input Constraints...................................26 3.7. Characterizing Electro-Optical Network Elements ...........24
3.7.2. Output Constraints..................................26 3.7.1. Input Constraints ..................................25
3.7.3. Processing Capabilities.............................27 3.7.2. Output Constraints .................................25
4. Routing and Wavelength Assignment and the Control Plane.......28 3.7.3. Processing Capabilities ............................26
4.1. Architectural Approaches to RWA..........................28 4. Routing and Wavelength Assignment and the Control Plane ........26
4.1.1. Combined RWA (R&WA).................................29 4.1. Architectural Approaches to RWA ...........................27
4.1.2. Separated R and WA (R+WA)...........................29 4.1.1. Combined RWA (R&WA) ................................27
4.1.3. Routing and Distributed WA (R+DWA)..................30 4.1.2. Separated R and WA (R+WA) ..........................28
4.2. Conveying information needed by RWA......................30 4.1.3. Routing and Distributed WA (R+DWA) .................28
5. Modeling Examples and Control Plane Use Cases.................31 4.2. Conveying Information Needed by RWA .......................29
5.1. Network Modeling for GMPLS/PCE Control...................31
5.1.1. Describing the WSON nodes...........................32
5.1.2. Describing the links................................34
5.2. RWA Path Computation and Establishment...................35
5.3. Resource Optimization....................................36
5.4. Support for Rerouting....................................37
5.5. Electro-Optical Networking Scenarios.....................37
5.5.1. Fixed Regeneration Points...........................37
5.5.2. Shared Regeneration Pools...........................38
5.5.3. Reconfigurable Regenerators.........................38
5.5.4. Relation to Translucent Networks....................38
6. GMPLS and PCE Implications....................................39
6.1. Implications for GMPLS signaling.........................39
6.1.1. Identifying Wavelengths and Signals.................39
6.1.2. WSON Signals and Network Element Processing.........40
6.1.3. Combined RWA/Separate Routing WA support............40
6.1.4. Distributed Wavelength Assignment: Unidirectional, No
Converters.................................................41
6.1.5. Distributed Wavelength Assignment: Unidirectional,
Limited Converters.........................................41
6.1.6. Distributed Wavelength Assignment: Bidirectional, No
Converters.................................................41
6.2. Implications for GMPLS Routing...........................42
6.2.1. Electro-Optical Element Signal Compatibility........42
6.2.2. Wavelength-Specific Availability Information........43
6.2.3. WSON Routing Information Summary....................43
6.3. Optical Path Computation and Implications for PCE........45
6.3.1. Optical path Constraints and Characteristics........45
6.3.2. Electro-Optical Element Signal Compatibility........45
6.3.3. Discovery of RWA Capable PCEs.......................46
7. Security Considerations.......................................46
8. IANA Considerations...........................................47
9. Acknowledgments...............................................47
10. References...................................................48
10.1. Normative References....................................48
10.2. Informative References..................................49
11. Contributors.................................................51
Author's Addresses...............................................52
Intellectual Property Statement..................................52
Disclaimer of Validity...........................................53
1. Introduction 5. Modeling Examples and Control Plane Use Cases ..................30
5.1. Network Modeling for GMPLS/PCE Control ....................30
5.1.1. Describing the WSON Nodes ..........................31
5.1.2. Describing the Links ...............................34
5.2. RWA Path Computation and Establishment ....................34
5.3. Resource Optimization .....................................36
5.4. Support for Rerouting .....................................36
5.5. Electro-Optical Networking Scenarios ......................36
5.5.1. Fixed Regeneration Points ..........................37
5.5.2. Shared Regeneration Pools ..........................37
5.5.3. Reconfigurable Regenerators ........................37
5.5.4. Relation to Translucent Networks ...................38
6. GMPLS and PCE Implications .....................................38
6.1. Implications for GMPLS Signaling ..........................39
6.1.1. Identifying Wavelengths and Signals ................39
6.1.2. WSON Signals and Network Element Processing ........39
6.1.3. Combined RWA/Separate Routing WA support ...........40
6.1.4. Distributed Wavelength Assignment:
Unidirectional, No Converters ......................40
6.1.5. Distributed Wavelength Assignment:
Unidirectional, Limited Converters .................40
6.1.6. Distributed Wavelength Assignment:
Bidirectional, No Converters .......................40
6.2. Implications for GMPLS Routing ............................41
6.2.1. Electro-Optical Element Signal Compatibility .......41
6.2.2. Wavelength-Specific Availability Information .......42
6.2.3. WSON Routing Information Summary ...................43
6.3. Optical Path Computation and Implications for PCE .........44
6.3.1. Optical Path Constraints and Characteristics .......44
6.3.2. Electro-Optical Element Signal Compatibility .......45
6.3.3. Discovery of RWA-Capable PCEs ......................45
7. Security Considerations ........................................46
8. Acknowledgments ................................................46
9. References .....................................................46
9.1. Normative References ......................................46
9.2. Informative References ....................................47
1. Introduction
Wavelength Switched Optical Networks (WSONs) are constructed from Wavelength Switched Optical Networks (WSONs) are constructed from
subsystems that include Wavelength Division Multiplexed (WDM) links, subsystems that include Wavelength Division Multiplexing (WDM) links,
tunable transmitters and receivers, Reconfigurable Optical Add/Drop tunable transmitters and receivers, Reconfigurable Optical Add/Drop
Multiplexers (ROADM), wavelength converters, and electro-optical Multiplexers (ROADMs), wavelength converters, and electro-optical
network elements. A WSON is a WDM-based optical network in which network elements. A WSON is a WDM-based optical network in which
switching is performed selectively based on the center wavelength of switching is performed selectively based on the center wavelength of
an optical signal. an optical signal.
WSONs can differ from other types of GMPLS networks in that many WSONs can differ from other types of GMPLS networks in that many
types of WSON nodes are highly asymmetric with respect to their types of WSON nodes are highly asymmetric with respect to their
switching capabilities, compatibility of signal types and network switching capabilities, compatibility of signal types and network
elements may need to be considered, and label assignment can be non- elements may need to be considered, and label assignment can be non-
local. In order to provision an optical connection (an optical path) local. In order to provision an optical connection (an optical path)
through a WSON certain wavelength continuity and resource through a WSON certain wavelength continuity and resource
availability constraints must be met to determine viable and optimal availability constraints must be met to determine viable and optimal
paths through the WSON. The determination of paths is known as paths through the WSON. The determination of paths is known as
Routing and Wavelength Assignment (RWA). Routing and Wavelength Assignment (RWA).
Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] includes Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] includes
an architecture and a set of control plane protocols that can be used an architecture and a set of control plane protocols that can be used
to operate data networks ranging from packet switch capable networks, to operate data networks ranging from packet-switch-capable networks,
through those networks that use time division multiplexing, to WDM through those networks that use Time Division Multiplexing, to WDM
networks. The Path Computation Element (PCE) architecture [RFC4655] networks. The Path Computation Element (PCE) architecture [RFC4655]
defines functional components that can be used to compute and suggest defines functional components that can be used to compute and suggest
appropriate paths in connection-oriented traffic-engineered networks. appropriate paths in connection-oriented traffic-engineered networks.
This document provides a framework for applying the GMPLS This document provides a framework for applying the GMPLS
architecture and protocols [RFC3945], and the PCE architecture architecture and protocols [RFC3945] and the PCE architecture
[RFC4655] to the control and operation of WSONs. To aid in this [RFC4655] to the control and operation of WSONs. To aid in this
process this document also provides an overview of the subsystems and process, this document also provides an overview of the subsystems
processes that comprise WSONs, and describes RWA so that the and processes that comprise WSONs and describes RWA so that the
information requirements, both static and dynamic, can be identified information requirements, both static and dynamic, can be identified
to explain how the information can be modeled for use by GMPLS and to explain how the information can be modeled for use by GMPLS and
PCE systems. This work will facilitate the development of protocol PCE systems. This work will facilitate the development of protocol
solution models and protocol extensions within the GMPLS and PCE solution models and protocol extensions within the GMPLS and PCE
protocol families. protocol families.
Different WSONs such as access, metro, and long haul may apply Different WSONs such as access, metro, and long haul may apply
different techniques for dealing with optical impairments hence this different techniques for dealing with optical impairments; hence,
document does not address optical impairments in any depth. Note that this document does not address optical impairments in any depth.
this document focuses on the generic properties of links, switches Note that this document focuses on the generic properties of links,
and path selection constraints that occur in many types of WSONs. switches, and path selection constraints that occur in many types of
See [WSON-Imp] for more information on optical impairments and GMPLS. WSONs. See [WSON-Imp] for more information on optical impairments
and GMPLS.
2. Terminology 2. Terminology
Add/Drop Multiplexers (ADM): An optical device used in WDM networks Add/Drop Multiplexer (ADM): An optical device used in WDM networks
composed of one or more line side ports and typically many tributary and composed of one or more line side ports and typically many
ports. tributary ports.
CWDM: Coarse Wavelength Division Multiplexing. CWDM: Coarse Wavelength Division Multiplexing.
DWDM: Dense Wavelength Division Multiplexing. DWDM: Dense Wavelength Division Multiplexing.
Degree: The degree of an optical device (e.g., ROADM) is given by a Degree: The degree of an optical device (e.g., ROADM) is given by a
count of its line side ports. count of its line side ports.
Drop and continue: A simple multi-cast feature of some ADM where a Drop and continue: A simple multicast feature of some ADMs where a
selected wavelength can be switched out of both a tributary (drop) selected wavelength can be switched out of both a tributary (drop)
port and a line side port. port and a line side port.
FOADM: Fixed Optical Add/Drop Multiplexer. FOADM: Fixed Optical Add/Drop Multiplexer.
GMPLS: Generalized Multi-Protocol Label Switching. GMPLS: Generalized Multi-Protocol Label Switching.
Line side: In WDM system line side ports and links typically can Line side: In a WDM system, line side ports and links can typically
carry the full multiplex of wavelength signals, as compared to carry the full multiplex of wavelength signals, as compared to
tributary (add or drop ports) that typically carry a few (typically tributary (add or drop) ports that typically carry a few (usually
one) wavelength signals. one) wavelength signals.
OXC: Optical cross connect. An optical switching element in which a OXC: Optical Cross-Connect. An optical switching element in which a
signal on any input port can reach any output port. signal on any input port can reach any output port.
PCC: Path Computation Client. Any client application requesting a PCC: Path Computation Client. Any client application requesting a
path computation to be performed by the Path Computation Element. path computation to be performed by the Path Computation Element.
PCE: Path Computation Element. An entity (component, application, or PCE: Path Computation Element. An entity (component, application, or
network node) that is capable of computing a network path or route network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints. based on a network graph and application of computational
constraints.
PCEP: PCE Communication Protocol. The communication protocol between PCEP: PCE Communication Protocol. The communication protocol between
a Path Computation Client and Path Computation Element. a Path Computation Client and Path Computation Element.
ROADM: Reconfigurable Optical Add/Drop Multiplexer. A wavelength ROADM: Reconfigurable Optical Add/Drop Multiplexer. A wavelength-
selective switching element featuring input and output line side selective switching element featuring input and output line side
ports as well as add/drop tributary ports. ports as well as add/drop tributary ports.
RWA: Routing and Wavelength Assignment. RWA: Routing and Wavelength Assignment.
Transparent Network: A wavelength switched optical network that does Transparent Network: A Wavelength Switched Optical Network that does
not contain regenerators or wavelength converters. not contain regenerators or wavelength converters.
Translucent Network: A wavelength switched optical network that is Translucent Network: A Wavelength Switched Optical Network that is
predominantly transparent but may also contain limited numbers of predominantly transparent but may also contain limited numbers of
regenerators and/or wavelength converters. regenerators and/or wavelength converters.
Tributary: A link or port on a WDM system that can carry Tributary: A link or port on a WDM system that can carry
significantly less than the full multiplex of wavelength signals significantly less than the full multiplex of wavelength signals
found on the line side links/ports. Typical tributary ports are the found on the line side links/ports. Typical tributary ports are the
add and drop ports on an ADM and these support only a single add and drop ports on an ADM, and these support only a single
wavelength channel. wavelength channel.
Wavelength Conversion/Converters: The process of converting an Wavelength Conversion/Converters: The process of converting an
information bearing optical signal centered at a given wavelength to information-bearing optical signal centered at a given wavelength to
one with "equivalent" content centered at a different wavelength. one with "equivalent" content centered at a different wavelength.
Wavelength conversion can be implemented via an optical-electronic- Wavelength conversion can be implemented via an optical-electronic-
optical (OEO) process or via a strictly optical process. optical (OEO) process or via a strictly optical process.
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. Wavelength Switched Optical Networks 3. Wavelength Switched Optical Networks
WSONs range in size from continent spanning long haul networks, to WSONs range in size from continent-spanning long-haul networks, to
metropolitan networks, to residential access networks. In all these metropolitan networks, to residential access networks. In all these
cases, the main concern is those properties that constrain the choice cases, the main concern is those properties that constrain the choice
of wavelengths that can be used, i.e., restrict the wavelength label of wavelengths that can be used, i.e., restrict the wavelength Label
set, impact the path selection process, and limit the topological Set, impact the path selection process, and limit the topological
connectivity. In addition, if electro-optical network elements are connectivity. In addition, if electro-optical network elements are
used in the WSON, additional compatibility constraints may be imposed used in the WSON, additional compatibility constraints may be imposed
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,
submarine links. International Telecommunication Union - and 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 (SMFs) and Multi-Mode Fibers (MMFs), the latter
typically used for short-reach campus and premise applications. SMF are typically used for short-reach campus and premise applications.
are used for longer-reach applications and therefore are the primary SMFs are used for longer-reach applications and are therefore the
concern of this document. The following SMF fiber types are typically primary concern of this document. The following SMF types are
encountered in optical networks: typically encountered in optical networks:
ITU-T Standard | Common Name ITU-T Standard | Common Name
------------------------------------------------------------ ------------------------------------------------------------
G.652 [G.652] | Standard SMF | G.652 [G.652] | Standard SMF |
G.653 [G.653] | Dispersion shifted SMF | G.653 [G.653] | Dispersion shifted SMF |
G.654 [G.654] | Cut-off shifted SMF | G.654 [G.654] | Cut-off shifted SMF |
G.655 [G.655] | Non-zero dispersion shifted SMF | G.655 [G.655] | Non-zero dispersion shifted SMF |
G.656 [G.656] | Wideband non-zero dispersion shifted SMF | G.656 [G.656] | Wideband non-zero dispersion shifted SMF |
------------------------------------------------------------ ------------------------------------------------------------
Typically WDM links operate in one or more of the approximately Typically, WDM links operate in one or more of the approximately
defined optical bands [G.Sup39]: defined optical bands [G.Sup39]:
Band Range (nm) Common Name Raw Bandwidth (THz) Band Range (nm) Common Name Raw Bandwidth (THz)
O-band 1260-1360 Original 17.5 O-band 1260-1360 Original 17.5
E-band 1360-1460 Extended 15.1 E-band 1360-1460 Extended 15.1
S-band 1460-1530 Short 9.4 S-band 1460-1530 Short 9.4
C-band 1530-1565 Conventional 4.4 C-band 1530-1565 Conventional 4.4
L-band 1565-1625 Long 7.1 L-band 1565-1625 Long 7.1
U-band 1625-1675 Ultra-long 5.5 U-band 1625-1675 Ultra-long 5.5
Not all of a band may be usable, for example in many fibers that Not all of a band may be usable; for example, in many fibers that
support E-band there is significant attenuation due to a water support E-band, there is significant attenuation due to a water
absorption peak at 1383nm. Hence a discontinuous acceptable absorption peak at 1383 nm. Hence, a discontinuous acceptable
wavelength range for a particular link may be needed and is modeled. wavelength range for a particular link may be needed and is modeled.
Also some systems will utilize more than one band. This is Also, some systems will utilize more than one band. This is
particularly true for CWDM systems. particularly true for CWDM systems.
Current technology subdivides the bandwidth capacity of fibers into Current technology subdivides the bandwidth capacity of fibers into
distinct channels based on either wavelength or frequency. There are distinct channels based on either wavelength or frequency. There are
two standards covering wavelengths and channel spacing. ITU-T two standards covering wavelengths and channel spacing. ITU-T
Recommendation G.694.1, Spectral grids for WDM applications: DWDM Recommendation G.694.1, "Spectral grids for WDM applications: DWDM
frequency grid [G.694.1] describes a DWDM grid defined in terms of frequency grid" [G.694.1], describes a DWDM grid defined in terms of
frequency grids of 12.5GHz, 25GHz, 50GHz, 100GHz, and other multiples frequency grids of 12.5 GHz, 25 GHz, 50 GHz, 100 GHz, and other
of 100GHz around a 193.1THz center frequency. At the narrowest multiples of 100 GHz around a 193.1 THz center frequency. At the
channel spacing this provides less than 4800 channels across the O narrowest channel spacing, this provides less than 4800 channels
through U bands. ITU-T Recommendation G.694.2, Spectral grids for WDM across the O through U bands. ITU-T Recommendation G.694.2,
applications: CWDM wavelength grid [G.694.2] describes a CWDM grid "Spectral grids for WDM applications: CWDM wavelength grid"
defined in terms of wavelength increments of 20nm running from 1271nm [G.694.2], describes a CWDM grid defined in terms of wavelength
to 1611nm for 18 or so channels. The number of channels is increments of 20 nm running from 1271 nm to 1611 nm for 18 or so
significantly smaller than the 32 bit GMPLS label space defined for channels. The number of channels is significantly smaller than the
GMPLS, see [RFC3471]. A label representation for these ITU-T grids 32-bit GMPLS Label space defined for GMPLS (see [RFC3471]). A label
is given in [Otani] and provides a common label format to be used in representation for these ITU-T grids is given in [RFC6205] and
signaling optical paths. Further, these ITU-T grid based labels can provides a common label format to be used in signaling optical paths.
also be used to describe WDM links, ROADM ports, and wavelength
converters for the purposes of path selection. Further, these ITU-T grid-based labels can also be used to describe
WDM links, ROADM ports, and wavelength converters for the purposes of
path selection.
Many WDM links are designed to take advantage of particular fiber Many WDM links are designed to take advantage of particular fiber
characteristics or to try to avoid undesirable properties. For characteristics or to try to avoid undesirable properties. For
example dispersion shifted SMF [G.653] was originally designed for example, dispersion-shifted SMF [G.653] was originally designed for
good long distance performance in single channel systems, however good long-distance performance in single-channel systems; however,
putting WDM over this type of fiber requires significant system putting WDM over this type of fiber requires significant system
engineering and a fairly limited range of wavelengths. Hence the engineering and a fairly limited range of wavelengths. Hence, the
following information is needed as parameters to perform basic, following information is needed as parameters to perform basic,
impairment unaware, modeling of a WDM link: impairment-unaware modeling of a WDM link:
o Wavelength range(s): Given a mapping between labels and the ITU-T o Wavelength range(s): Given a mapping between labels and the ITU-T
grids each range could be expressed in terms of a tuple (lambda1, grids, each range could be expressed in terms of a tuple,
lambda2) or (freq1, freq1) where the lambdas or frequencies can be (lambda1, lambda2) or (freq1, freq2), where the lambdas or
represented by 32 bit integers. frequencies can be represented by 32-bit integers.
o Channel spacing: Currently there are five channel spacings used in o Channel spacing: Currently, there are five channel spacings used
DWDM systems and a single channel spacing defined for CWDM in DWDM systems and a single channel spacing defined for CWDM
systems. systems.
For a particular link this information is relatively static, as For a particular link, this information is relatively static, as
changes to these properties generally require hardware upgrades. Such changes to these properties generally require hardware upgrades.
information may be used locally during wavelength assignment via Such information may be used locally during wavelength assignment via
signaling, similar to label restrictions in MPLS or used by a PCE in signaling, similar to label restrictions in MPLS, or used by a PCE in
providing combined RWA. providing combined RWA.
3.2. Optical Transmitters and Receivers 3.2. Optical Transmitters and Receivers
WDM optical systems make use of optical transmitters and receivers WDM optical systems make use of optical transmitters and receivers
utilizing different wavelengths (frequencies). Some transmitters are utilizing different wavelengths (frequencies). Some transmitters are
manufactured for a specific wavelength of operation, that is, the manufactured for a specific wavelength of operation; that is, the
manufactured frequency cannot be changed. First introduced to reduce manufactured frequency cannot be changed. First introduced to reduce
inventory costs, tunable optical transmitters and receivers are inventory costs, tunable optical transmitters and receivers are
deployed in some systems, and allow flexibility in the wavelength deployed in some systems and allow flexibility in the wavelength used
used for optical transmission/reception. Such tunable optics aid in for optical transmission/reception. Such tunable optics aid in path
path selection. selection.
Fundamental modeling parameters from the control plane perspective Fundamental modeling parameters for optical transmitters and
optical transmitters and receivers are: receivers from the control plane perspective are:
o Tunable: Do the transmitter and receivers operate at variable or o Tunable: Do the transmitters and receivers operate at variable or
fixed wavelength. fixed wavelength?
o Tuning range: This is the frequency or wavelength range over which o Tuning range: This is the frequency or wavelength range over which
the optics can be tuned. With the fixed mapping of labels to the optics can be tuned. With the fixed mapping of labels to
lambdas as proposed in [Otani] this can be expressed as a tuple lambdas as proposed in [RFC6205], this can be expressed as a
(lambda1, lambda2) or (freq1, freq2) where lambda1 and lambda2 or tuple, (lambda1, lambda2) or (freq1, freq2), where lambda1 and
freq1 and freq2 are the labels representing the lower and upper lambda2 or freq1 and freq2 are the labels representing the lower
bounds in wavelength. and upper bounds in wavelength.
o Tuning time: Tuning times highly depend on the technology used. o Tuning time: Tuning times highly depend on the technology used.
Thermal drift based tuning may take seconds to stabilize, whilst Thermal-drift-based tuning may take seconds to stabilize, whilst
electronic tuning might provide sub-ms tuning times. Depending on electronic tuning might provide sub-ms tuning times. Depending on
the application this might be critical. For example, thermal drift the application, this might be critical. For example, thermal
might not be usable for fast protection applications. drift might not be usable for fast protection applications.
o Spectral characteristics and stability: The spectral shape of a o Spectral characteristics and stability: The spectral shape of a
laser's emissions and its frequency stability put limits on laser's emissions and its frequency stability put limits on
various properties of the overall WDM system. One relatively easy various properties of the overall WDM system. One constraint that
to characterize constraint is the closest channel spacing with is relatively easy to characterize is the closest channel spacing
which the transmitter can be used. with which the transmitter can be used.
Note that ITU-T recommendations specify many aspects of an optical Note that ITU-T recommendations specify many aspects of an optical
transmitter. Many of these parameters, such as spectral transmitter. Many of these parameters, such as spectral
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 an 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 want to initiate mesh restoration if the others; for example, one does not want to initiate mesh restoration
source transmitter has failed, since the optical transmitter will if the source transmitter has failed since the optical transmitter
still be failed on the alternate optical path. will 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 The fundamental unit of switching in WSONs 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 multi-channel DWDM networks with single-channel interfaces are the
prime focus of this document as opposed to multi-channel interfaces. prime focus of this document as opposed to multi-channel interfaces.
Interfaces of this type are defined in ITU-T recommendations Interfaces of this type are defined in ITU-T Recommendations
[G.698.1] and [G.698.2]. Key non-impairment related parameters [G.698.1] and [G.698.2]. Key non-impairment-related 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
(c) Bit-rate/Line coding (modulation) of optical tributary signals (b) Minimum and maximum central frequency
(c) Bitrate/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 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".
3.3.1. Optical Tributary Signals 3.3.1. Optical Tributary Signals
The optical interface specifications [G.698.1], [G.698.2], and The optical interface specifications [G.698.1], [G.698.2], and
[G.959.1] all use the concept of an optical tributary signal which is [G.959.1] all use the concept of an optical tributary signal, which
defined as "a single channel signal that is placed within an optical is defined as "a single channel signal that is placed within an
channel for transport across the optical network". Note the use of optical channel for transport across the optical network". Note the
the qualifier "tributary" to indicate that this is a single channel use of the qualifier "tributary" to indicate that this is a single-
entity and not a multichannel optical signal. channel entity and not a multi-channel optical signal.
There are currently a number of different types of optical tributary There are currently a number of different types of optical tributary
signals, which are known as "optical tributary signal classes". These signals, which are known as "optical tributary signal classes".
are currently characterized by a modulation format and bit rate range These are currently characterized by a modulation format and bitrate
[G.959.1]: range [G.959.1]:
(a) Optical tributary signal class NRZ 1.25G (a) Optical tributary signal class Non-Return-to-Zero (NRZ) 1.25G
(b) Optical tributary signal class NRZ 2.5G (b) Optical tributary signal class NRZ 2.5G
(c) Optical tributary signal class NRZ 10G (c) Optical tributary signal class NRZ 10G
(d) Optical tributary signal class NRZ 40G (d) Optical tributary signal class NRZ 40G
(e) Optical tributary signal class RZ 40G (e) Optical tributary signal class Return-to-Zero (RZ) 40G
Note that with advances in technology more optical tributary signal Note that, with advances in technology, more optical tributary signal
classes may be added and that this is currently an active area for classes may be added and that this is currently an active area for
development and standardization. In particular at the 40G rate there development and standardization. In particular, at the 40G rate,
are a number of non-standardized advanced modulation formats that there are a number of non-standardized advanced modulation formats
have seen significant deployment including Differential Phase Shift that have seen significant deployment, including Differential Phase
Keying (DPSK) and Phase Shaped Binary Transmission (PSBT). Shift Keying (DPSK) and Phase Shaped Binary Transmission (PSBT).
According to [G.698.2] it is important to fully specify the bit rate According to [G.698.2], it is important to fully specify the bitrate
of the optical tributary signal. Hence it is seen that modulation of the optical tributary signal. Hence, modulation format (optical
format (optical tributary signal class) and bit rate are key tributary signal class) and bitrate are key parameters in
parameters in characterizing the optical tributary signal. characterizing the optical tributary signal.
3.3.2. WSON Signal Characteristics 3.3.2. WSON Signal Characteristics
An optical tributary signal referenced in ITU-T [G.698.1] and The optical tributary signal referenced in ITU-T Recommendations
[G.698.2] is referred to as the "signal" in this document. This [G.698.1] and [G.698.2] is referred to as the "signal" in this
corresponds to the "lambda" LSP in GMPLS. For signal compatibility document. This corresponds to the "lambda" LSP in GMPLS. For signal
purposes with electro-optical network elements, the following signal compatibility purposes with electro-optical network elements, the
characteristics are considered: following signal characteristics are considered:
1. Optical tributary signal class (modulation format). 1. Optical tributary signal class (modulation format)
2. FEC: whether forward error correction is used in the digital stream
and what type of error correcting code is used. 2. Forward Error Correction (FEC): whether forward error correction
3. Center frequency (wavelength). is used in the digital stream and what type of error correcting
4. Bit rate. code is used
5. G-PID: general protocol identifier for the information format.
3. Center frequency (wavelength)
4. Bitrate
5. General Protocol Identifier (G-PID) for the information format
The first three items on this list can change as a WSON signal The first three items on this list can change as a WSON signal
traverses the optical network with elements that include traverses the optical network with elements that include
regenerators, Optical-to-Electrical (OEO) switches, or wavelength regenerators, OEO switches, or wavelength converters.
converters.
Bit rate and G-PID would not change since they describe the encoded Bitrate and G-PID would not change since they describe the encoded
bit stream. A set of G-PID values is already defined for lambda bitstream. A set of G-PID values is already defined for lambda
switching in [RFC3471] and [RFC4328]. switching in [RFC3471] and [RFC4328].
Note that a number of non-standard or proprietary modulation formats Note that a number of non-standard or proprietary modulation formats
and FEC codes are commonly used in WSONs. For some digital bit and FEC codes are commonly used in WSONs. For some digital
streams the presence of Forward Error Correction (FEC) can be bitstreams, the presence of FEC can be detected; for example, in
detected, e.g., in [G.707] this is indicated in the signal itself via [G.707], this is indicated in the signal itself via the FEC Status
the FEC Status Indication (FSI) byte, while in [G.709] this can be Indication (FSI) byte while in [G.709], this can be inferred from
inferred from whether the FEC field of the Optical Channel Transport whether or not the FEC field of the Optical Channel Transport Unit-k
Unit-k (OTUk) is all zeros or not. (OTUk) is all zeros.
3.4. ROADMs, OXCs, Splitters, Combiners and FOADMs 3.4. ROADMs, OXCs, Splitters, Combiners, and FOADMs
Definitions of various optical devices such as ROADMs, Optical Cross- Definitions of various optical devices such as ROADMs, Optical Cross-
connects (OXCs), splitters, combiners and Fixed Optical Add-Drop Connects (OXCs), splitters, combiners, and Fixed Optical Add/Drop
Multiplexers (FOADMs) and their parameters can be found in [G.671]. Multiplexers (FOADMs) and their parameters can be found in [G.671].
Only a subset of these relevant to the control plane and their non- Only a subset of these relevant to the control plane and their non-
impairment related properties are considered in the following impairment-related properties are considered in the following
sections. sections.
3.4.1. Reconfigurable Add/Drop Multiplexers and OXCs 3.4.1. Reconfigurable Optical Add/Drop Multiplexers and OXCs
ROADMs are available in different forms and technologies. This is a ROADMs are available in different forms and technologies. This is a
key technology that allows wavelength based optical switching. A key technology that allows wavelength-based optical switching. A
classic degree-2 ROADM is shown in Figure 1. classic degree-2 ROADM is shown in Figure 1.
Line side input +---------------------+ Line side output Line side input +---------------------+ Line side output
--->| |---> --->| |--->
| | | |
| 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 unidirectional 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
ROADM increases beyond two it can have properties of both a switch the ROADM increases beyond two, it can have properties of both a
(OXC) and a multiplexer and hence it is necessary to know the switch (OXC) and a multiplexer; hence, it is necessary to know the
switched connectivity offered by such a network element to switched connectivity offered by such a network element to
effectively utilize it. A straightforward way to represent this is effectively utilize it. A straightforward way to represent this is
via a "switched connectivity" matrix A where Amn = 0 or 1, depending via a "switched connectivity" matrix A where Amn = 0 or 1, depending
upon whether a wavelength on input port m can be connected to output upon whether a wavelength on input port m can be connected to output
port n [Imajuku]. For the ROADM shown in Figure 1 the switched port n [Imajuku]. For the ROADM shown in Figure 1, the switched
connectivity matrix can be expressed as: connectivity matrix can be expressed as:
Input Output Port Input Output Port
Port #1 #2 #3 #4 #5 Port #1 #2 #3 #4 #5
-------------- --------------
#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 bidirectional ROADM Figure 2. Degree-4 Bidirectional ROADM
Note that this example is 4-degree example with one (potentially Note that this is a 4-degree example with one (potentially multi-
multi-channel) add/drop per line side port. 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"; that is, if input port X can be connected to
port Y, typically input port Y can be connected to output port X, output port Y, typically input port Y can be connected to output port
assuming the numbering is done in such a way that input X and output X, assuming the numbering is done in such a way that input X and
X correspond to the same line side direction or the same add/drop output X correspond to the same line side direction or the same
port. This makes the connectivity matrix symmetrical as shown below. add/drop port. This makes the connectivity matrix symmetrical as
shown below.
Input Output Port Input Output Port
Port E1 E2 E3 E4 E5 E6 E7 E8 Port E1 E2 E3 E4 E5 E6 E7 E8
----------------------- -----------------------
I1 0 1 1 1 0 1 0 0 I1 0 1 1 1 0 1 0 0
I2 1 0 1 1 0 0 1 0 I2 1 0 1 1 0 0 1 0
A = I3 1 1 0 1 1 0 0 0 A = I3 1 1 0 1 1 0 0 0
I4 1 1 1 0 0 0 0 1 I4 1 1 1 0 0 0 0 1
I5 0 0 1 0 0 0 0 0 I5 0 0 1 0 0 0 0 0
I6 1 0 0 0 0 0 0 0 I6 1 0 0 0 0 0 0 0
I7 0 1 0 0 0 0 0 0 I7 0 1 0 0 0 0 0 0
I8 0 0 0 1 0 0 0 0 I8 0 0 0 1 0 0 0 0
Where I5/E5 are add/drop ports to/from line side-3, I6/E6 are where I5/E5 are add/drop ports to/from line side-3, I6/E6 are
add/drop ports to/from line side-1, I7/E7 are add/drop ports to/from add/drop ports to/from line side-1, I7/E7 are add/drop ports to/from
line side-2 and I8/E8 are add/drop ports to/from line side-4. Note line side-2, and I8/E8 are add/drop ports to/from line side-4. Note
that diagonal elements are zero since loopback is not supported in that diagonal elements are zero since loopback is not supported in
the example. If ports support loopback, diagonal elements would be the example. If ports support loopback, diagonal elements would be
set to one. set to one.
Additional constraints may also apply to the various ports in a Additional constraints may also apply to the various ports in a
ROADM/OXC. The following restrictions and terms may be used: ROADM/OXC. The following restrictions and terms may be used:
Colored port: an input or more typically an output (drop) port o Colored port: an input or, more typically, an output (drop) port
restricted to a single channel of fixed wavelength. restricted to a single channel of fixed wavelength
Colorless port: an input or more typically an output (drop) port o Colorless port: an input or, more typically, an output (drop) port
restricted to a single channel of arbitrary wavelength. restricted to a single channel of arbitrary wavelength
In general a port on a ROADM could have any of the following In general, a port on a ROADM could have any of the following
wavelength restrictions: wavelength restrictions:
o Multiple wavelengths, full range port. o Multiple wavelengths, full range port
o Single wavelength, full range port. o Single wavelength, full range port
o Single wavelength, fixed lambda port. o Single wavelength, fixed lambda port
o Multiple wavelengths, reduced range port (for example wave band o Multiple wavelengths, reduced range port (for example wave band
switching). switching)
To model these restrictions it is necessary to have two pieces of To model these restrictions, it is necessary to have two pieces of
information for each port: (a) number of wavelengths, (b) wavelength information for each port: (a) the number of wavelengths and (b) the
range and spacing. Note that this information is relatively static. wavelength range and spacing. Note that this information is
More complicated wavelength constraints are modeled in [WSON-Info]. relatively static. More complicated wavelength constraints are
modeled in [WSON-Info].
3.4.2. Splitters 3.4.2. Splitters
An optical splitter consists of a single input port and two or more An optical splitter consists of a single input port and two or more
output ports. The input optical signaled is essentially copied (with output ports. The input optical signaled is essentially copied (with
power loss) to all output ports. power loss) to all output ports.
Using the modeling notions of Section 3.4.1. (Reconfigurable Add/Drop Using the modeling notions of Section 3.4.1, the input and output
Multiplexers and OXCs) the input and output ports of a splitter would ports of a splitter would have the same wavelength restrictions. In
have the same wavelength restrictions. In addition a splitter is addition, a splitter is modeled by a connectivity matrix Amn as
modeled by a connectivity matrix Amn as follows: follows:
Input Output Port Input Output Port
Port #1 #2 #3 ... #N Port #1 #2 #3 ... #N
----------------- -----------------
A = #1 1 1 1 ... 1 A = #1 1 1 1 ... 1
The difference from a simple ROADM is that this is not a switched The difference from a simple ROADM is that this is not a switched
connectivity matrix but the fixed connectivity matrix of the device. connectivity matrix but the fixed connectivity matrix of the device.
3.4.3. Combiners 3.4.3. Combiners
An optical combiner is a device that combines the optical wavelengths An optical combiner is a device that combines the optical wavelengths
carried by multiple input ports into a single multi-wavelength output carried by multiple input ports into a single multi-wavelength output
port. The various ports may have different wavelength restrictions. port. The various ports may have different wavelength restrictions.
It is generally the responsibility of those using the combiner to It is generally the responsibility of those using the combiner to
assure that wavelength collision does not occur on the output port. ensure that wavelength collision does not occur on the output port.
The fixed connectivity matrix Amn for a combiner would look like: The fixed connectivity matrix Amn for a combiner would look like:
Input Output Port Input Output Port
Port #1 Port #1
--- ---
#1: 1 #1: 1
#2 1 #2 1
A = #3 1 A = #3 1
... 1 ... 1
#N 1 #N 1
3.4.4. Fixed Optical Add/Drop Multiplexers 3.4.4. Fixed Optical Add/Drop Multiplexers
A fixed optical add/drop multiplexer can alter the course of an input A Fixed Optical Add/Drop Multiplexer can alter the course of an input
wavelength in a preset way. In particular a given wavelength (or wavelength in a preset way. In particular, a given wavelength (or
waveband) from a line side input port would be dropped to a fixed waveband) from a line side input port would be dropped to a fixed
"tributary" output port. Depending on the device's construction that "tributary" output port. Depending on the device's construction,
same wavelength may or may not also be sent out the line side output that same wavelength may or may not also be sent out the line side
port. This is commonly referred to as "drop and continue" operation. output port. This is commonly referred to as a "drop and continue"
There also may exist tributary input ports ("add" ports) whose operation. Tributary input ports ("add" ports) whose signals are
signals are combined with each other and other line side signals. combined with each other and other line side signals may also exist.
In general, to represent the routing properties of an FOADM it is In general, to represent the routing properties of an FOADM, it is
necessary to have both a fixed connectivity matrix Amn as previously necessary to have both a fixed connectivity matrix Amn, as previously
discussed and the precise wavelength restrictions for all input and discussed, and the precise wavelength restrictions for all input and
output ports. From the wavelength restrictions on the tributary output ports. From the wavelength restrictions on the tributary
output ports, what wavelengths have been selected can be derived. output ports, the wavelengths that have been selected can be derived.
From the wavelength restrictions on the tributary input ports, it can From the wavelength restrictions on the tributary input ports, it can
be seen which wavelengths have been added to the line side output be seen which wavelengths have been added to the line side output
port. Finally from the added wavelength information and the line side port. Finally, from the added wavelength information and the line
output wavelength restrictions it can be inferred which wavelengths side output wavelength restrictions, it can be inferred which
have been continued. wavelengths have been continued.
To summarize, the modeling methodology introduced in Section 3.4.1. To summarize, the modeling methodology introduced in Section 3.4.1,
(Reconfigurable Add/Drop Multiplexers and OXCs) consisting of a which consists of a connectivity matrix and port wavelength
connectivity matrix and port wavelength restrictions can be used to restrictions, can be used to describe a large set of fixed optical
describe a large set of fixed optical devices such as combiners, devices such as combiners, splitters, and FOADMs. Hybrid devices
splitters and FOADMs. Hybrid devices consisting of both switched and consisting of both switched and fixed parts are modeled in
fixed parts are modeled in [WSON-Info]. [WSON-Info].
3.5. Electro-Optical Systems 3.5. Electro-Optical Systems
This section describes how Electro-Optical Systems (e.g., OEO This section describes how Electro-Optical Systems (e.g., OEO
switches, wavelength converters, and regenerators) interact with the switches, wavelength converters, and regenerators) interact with the
WSON signal characteristics listed in Section 3.3.2. (WSON Signal WSON signal characteristics listed in Section 3.3.2. OEO switches,
Characteristics) OEO switches, wavelength converters and regenerators wavelength converters, and regenerators all share a similar property:
all share a similar property: they can be more or less "transparent" they can be more or less "transparent" to an "optical signal"
to an "optical signal" depending on their functionality and/or depending on their functionality and/or implementation. Regenerators
implementation. Regenerators have been fairly well characterized in have been fairly well characterized in this regard and hence their
this regard and hence their properties can be described first. properties can be described first.
3.5.1. Regenerators 3.5.1. Regenerators
The various approaches to regeneration are discussed in ITU-T G.872 The various approaches to regeneration are discussed in ITU-T
Annex A [G.872]. They map a number of functions into the so-called [G.872], Annex A. They map a number of functions into the so-called
1R, 2R and 3R categories of regenerators as summarized in Table 1 1R, 2R, and 3R categories of regenerators as summarized in Table 1
below: below:
Table 1. Regenerator functionality mapped to general regenerator Table 1. Regenerator Functionality Mapped to General Regenerator
classes from [G.872]. Classes from [G.872]
--------------------------------------------------------------------- --------------------------------------------------------------------
1R | Equal amplification of all frequencies within the amplification 1R | Equal amplification of all frequencies within the amplification
| bandwidth. There is no restriction upon information formats. | bandwidth. There is no restriction upon information formats.
+----------------------------------------------------------------- +----------------------------------------------------------------
| Amplification with different gain for frequencies within the | Amplification with different gain for frequencies within the
| amplification bandwidth. This could be applied to both single- | amplification bandwidth. This could be applied to both single-
| channel and multi-channel systems. | channel and multi-channel systems.
+----------------------------------------------------------------- +----------------------------------------------------------------
| Dispersion compensation (phase distortion). This analogue | Dispersion compensation (phase distortion). This analogue
| process can be applied in either single-channel or multi- | process can be applied in either single-channel or multi-
| channel systems. | channel systems.
--------------------------------------------------------------------- --------------------------------------------------------------------
2R | Any or all 1R functions. Noise suppression. 2R | Any or all 1R functions. Noise suppression.
+----------------------------------------------------------------- +----------------------------------------------------------------
| Digital reshaping (Schmitt Trigger function) with no clock | Digital reshaping (Schmitt Trigger function) with no clock
| recovery. This is applicable to individual channels and can be | recovery. This is applicable to individual channels and can be
| used for different bit rates but is not transparent to line | used for different bitrates but is not transparent to line
| coding (modulation). | coding (modulation).
-------------------------------------------------------------------- --------------------------------------------------------------------
3R | Any or all 1R and 2R functions. Complete regeneration of the 3R | Any or all 1R and 2R functions. Complete regeneration of the
| pulse shape including clock recovery and retiming within | pulse shape including clock recovery and retiming within
| required jitter limits. | required jitter limits.
-------------------------------------------------------------------- --------------------------------------------------------------------
From this table it is seen that 1R regenerators are generally This table shows that 1R regenerators are generally independent of
independent of signal modulation format (also known as line coding), signal modulation format (also known as line coding) but may work
but may work over a limited range of wavelength/frequencies. 2R over a limited range of wavelengths/frequencies. 2R regenerators are
regenerators are generally applicable to a single digital stream and generally applicable to a single digital stream and are dependent
are dependent upon modulation format (line coding) and to a lesser upon modulation format (line coding) and, to a lesser extent, are
extent are limited to a range of bit rates (but not a specific bit limited to a range of bitrates (but not a specific bitrate).
rate). Finally, 3R regenerators apply to a single channel, are Finally, 3R regenerators apply to a single channel, are dependent
dependent upon the modulation format and generally sensitive to the upon the modulation format, and are generally sensitive to the
bit rate of digital signal, i.e., either are designed to only handle bitrate of digital signal, i.e., either are designed to only handle a
a specific bit rate or need to be programmed to accept and regenerate specific bitrate or need to be programmed to accept and regenerate a
a specific bit rate. In all these types of regenerators the digital specific bitrate. In all these types of regenerators, the digital
bit stream contained within the optical or electrical signal is not bitstream contained within the optical or electrical signal is not
modified. modified.
It is common for regenerators to modify the digital bit stream for It is common for regenerators to modify the digital bitstream for
performance monitoring and fault management purposes. Synchronous performance monitoring and fault management purposes. Synchronous
Optical Networking (SONET), Synchronous Digital Hierarchy (SDH) and Optical Networking (SONET), Synchronous Digital Hierarchy (SDH), and
Interfaces for the Optical Transport Network (G.709) all have digital Interfaces for the Optical Transport Network [G.709] all have digital
signal "envelopes" designed to be used between "regenerators" (in signal "envelopes" designed to be used between "regenerators" (in
this case 3R regenerators). In SONET this is known as the "section" this case, 3R regenerators). In SONET, this is known as the
signal, in SDH this is known as the "regenerator section" signal, in "section" signal; in SDH, this is known as the "regenerator section"
G.709 this is known as an OTUk. These signals reserve a portion of signal; and, in G.709, this is known as an OTUk. These signals
their frame structure (known as overhead) for use by regenerators. reserve a portion of their frame structure (known as overhead) for
The nature of this overhead is summarized in Table 2 below. use by regenerators. The nature of this overhead is summarized in
Table 2 below.
Table 2. SONET, SDH, and G.709 regenerator related overhead. Table 2. SONET, SDH, and G.709 Regenerator-Related Overhead
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
|Function | SONET/SDH | G.709 OTUk | |Function | SONET/SDH | G.709 OTUk |
| | Regenerator | | | | Regenerator | |
| | Section | | | | Section | |
|------------------+----------------------+-----------------------| |------------------+----------------------+-----------------------|
|Signal | J0 (section | Trail Trace | |Signal | J0 (section | Trail Trace |
|Identifier | trace) | Identifier (TTI) | |Identifier | trace) | Identifier (TTI) |
|------------------+----------------------+-----------------------| |------------------+----------------------+-----------------------|
|Performance | BIP-8 (B1) | BIP-8 (within SM) | |Performance | BIP-8 (B1) | BIP-8 (within SM) |
|Monitoring | | | |Monitoring | | |
|------------------+----------------------+-----------------------| |------------------+----------------------+-----------------------|
|Management | D1-D3 bytes | GCC0 (general | |Management | D1-D3 bytes | GCC0 (general |
|Communications | | communications | |Communications | | communications |
| | | channel) | | | | channel) |
|------------------+----------------------+-----------------------| |------------------+----------------------+-----------------------|
|Fault Management | A1, A2 framing | FAS (frame alignment | |Fault Management | A1, A2 framing | FAS (frame alignment |
| | bytes | signal), BDI(backward| | | bytes | signal), BDI (backward|
| | | defect indication)BEI| | | | defect indication), |
| | | (backward error | | | | BEI (backward error |
| | | indication) | | | | indication) |
+------------------+----------------------+-----------------------| +------------------+----------------------+-----------------------|
|Forward Error | P1,Q1 bytes | OTUk FEC | |Forward Error | P1,Q1 bytes | OTUk FEC |
|Correction (FEC) | | | |Correction (FEC) | | |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
In the previous table it is seen that frame alignment, signal Table 2 shows that frame alignment, signal identification, and FEC
identification, and FEC are supported. What table 2 also shows by its are supported. By omission, Table 2 also shows that no switching or
omission is that no switching or multiplexing occurs at this layer. multiplexing occurs at this layer. This is a significant
This is a significant simplification for the control plane since simplification for the control plane since control plane standards
control plane standards require a multi-layer approach when there are require a multi-layer approach when there are multiple switching
multiple switching layers, but not for "layering" to provide the layers but do not require the "layering" to provide the management
management functions of Table 2. That is, many existing technologies functions shown in Table 2. That is, many existing technologies
covered by GMPLS contain extra management related layers that are covered by GMPLS contain extra management-related layers that are
essentially ignored by the control plane (though not by the essentially ignored by the control plane (though not by the
management plane!). Hence, the approach here is to include management plane). Hence, the approach here is to include
regenerators and other devices at the WSON layer unless they provide regenerators and other devices at the WSON layer unless they provide
higher layer switching and then a multi-layer or multi-region higher layer switching; then, a multi-layer or multi-region approach
approach [RFC5212] is called for. However, this can result in [RFC5212] is called for. However, this can result in regenerators
regenerators having a dependence on the client signal type. having a dependence on the client signal type.
Hence depending upon the regenerator technology the following Hence, depending upon the regenerator technology, the constraints
constraints may be imposed by a regenerator device: listed in Table 3 may be imposed by a regenerator device:
Table 3. Regenerator Compatibility Constraints. Table 3. Regenerator Compatibility Constraints
+--------------------------------------------------------+ +--------------------------------------------------------+
| Constraints | 1R | 2R | 3R | | Constraints | 1R | 2R | 3R |
+--------------------------------------------------------+ +--------------------------------------------------------+
| Limited Wavelength Range | x | x | x | | Limited Wavelength Range | x | x | x |
+--------------------------------------------------------+ +--------------------------------------------------------+
| Modulation Type Restriction | | x | x | | Modulation Type Restriction | | x | x |
+--------------------------------------------------------+ +--------------------------------------------------------+
| Bit Rate Range Restriction | | x | x | | Bitrate Range Restriction | | x | x |
+--------------------------------------------------------+ +--------------------------------------------------------+
| Exact Bit Rate Restriction | | | x | | Exact Bitrate Restriction | | | x |
+--------------------------------------------------------+ +--------------------------------------------------------+
| Client Signal Dependence | | | x | | Client Signal Dependence | | | x |
+--------------------------------------------------------+ +--------------------------------------------------------+
Note that the limited wavelength range constraint can be modeled for Note that the limited wavelength range constraint can be modeled for
GMPLS signaling with the label set defined in [RFC3471] and that the GMPLS signaling with the Label Set defined in [RFC3471] and that the
modulation type restriction constraint includes FEC. modulation type restriction constraint includes FEC.
3.5.2. OEO Switches 3.5.2. OEO Switches
A common place where OEO processing may take place is within WSON A common place where OEO processing may take place is within WSON
switches that utilize (or contain) regenerators. This may be to switches that utilize (or contain) regenerators. This may be to
convert the signal to an electronic form for switching then convert the signal to an electronic form for switching then reconvert
reconverting to an optical signal prior to output from the switch. to an optical signal prior to output from the switch. Another common
Another common technique is to add regenerators to restore signal technique is to add regenerators to restore signal quality either
quality either before or after optical processing (switching). In before or after optical processing (switching). In the former case,
the former case the regeneration is applied to adapt the signal to the regeneration is applied to adapt the signal to the switch fabric
the switch fabric regardless of whether or not it is needed from a regardless of whether or not it is needed from a signal-quality
signal quality perspective. perspective.
In either case these optical switches have essentially the same In either case, these optical switches have essentially the same
compatibility constraints as those which are described for compatibility constraints as those described for regenerators in
regenerators in Table 3. Table 3.
3.6. Wavelength Converters 3.6. Wavelength Converters
Wavelength converters take an input optical signal at one wavelength Wavelength converters take an input optical signal at one wavelength
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; that is, 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
the input signal and the properties of the converter as opposed to of 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 use of an OEO switch can be thought converters available since each use of an OEO switch can be
of as a potential wavelength converter. thought 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
In this case there may be a limited amount of conversion. Also in FOADMs. In this case, there may be a limited amount of
this case the conversion may be used as part of optical path conversion. Also, the conversion may be used as part of optical
routing. path routing.
Based on the above considerations, wavelength converters are modeled Based on the above considerations, wavelength converters are modeled
as follows: as follows:
1. Wavelength converters can always be modeled as associated with 1. Wavelength converters can always be modeled as associated with
network elements. This includes fixed wavelength routing elements. network elements. This includes fixed wavelength routing
elements.
2. A network element may have full wavelength conversion capability, 2. A network element may have full wavelength conversion capability
i.e., any input port and wavelength, or a limited number of (i.e., any input port and wavelength) or a limited number of
wavelengths and ports. On a box with a limited number of wavelengths and ports. On a box with a limited number of
converters there also may exist restrictions on which ports can converters, there also may exist restrictions on which ports can
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
from 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 OEO 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
A WSON node may include multiple wavelength converters. These are A WSON node may include multiple wavelength converters. These are
usually arranged into some type of pool to promote resource sharing. usually arranged into some type of pool to promote resource sharing.
There are a number of different approaches used in the design of There are a number of different approaches used in the design of
switches with converter pools. However, from the point of view of switches with converter pools. However, from the point of view of
path computation it is necessary to know the following: path computation, it is necessary to know the following:
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 technique similar to that used to model To model point 2 above, a technique similar to that used to model
ROADMs and optical switches can be used, i.e., matrices to indicate ROADMs and optical switches can be used, i.e., matrices to indicate
possible connectivity along with wavelength constraints for possible connectivity along with wavelength constraints for
links/ports. Since wavelength converters are considered a scarce links/ports. Since wavelength converters are considered a scarce
resource it will be desirable to include as a minimum the usage state resource, it is desirable to include, at a minimum, the usage state
of individual 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. This
(Schematic diagram of wavelength converter pool model). This model model represents N input ports (fibers), P wavelength converters, and
represents N input ports (fibers), P wavelength converters, and M 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 potentially reach input matrix WI(i,p) = {0,1}, where input port i can potentially
wavelength converter p. reach 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 a limited input wavelength range, there is a
of input port constraints for each wavelength converter. Currently it set of input port constraints for each wavelength converter.
is assumed that a wavelength converter can only take a single Currently, it is assumed that a wavelength converter can only take a
wavelength on input. Each wavelength converter input port constraint single wavelength on input. Each wavelength converter input port
can be modeled via a wavelength set mechanism. constraint can be modeled via a wavelength set mechanism.
Next a state vector WC(j) = {0,1} dependent upon whether wavelength Next, there is a state vector WC(j) = {0,1} dependent upon whether
converter j in the pool is in use. This is the only state kept in the wavelength converter j in the pool is in use. This is the only state
converter pool model. This state is not necessary for modeling kept in the converter pool model. This state is not necessary for
"fixed" transponder system, i.e., systems where there is no sharing. modeling "fixed" transponder system, i.e., systems where there is no
In addition, this state information may be encoded in a much more sharing. In addition, this state information may be encoded in a
compact form depending on the overall connectivity structure [Gen- much more compact form depending on the overall connectivity
Encode]. structure [Gen-Encode].
After that, a set of wavelength converter output wavelength After that, a set of wavelength converter output wavelength
constraints is used. These constraints indicate what wavelengths a constraints is used. These constraints indicate what wavelengths a
particular wavelength converter can generate or are restricted to particular wavelength converter can generate or are restricted to
generating due to internal switch structure. generating due to internal switch structure.
Finally, a wavelength pool output matrix WE(p,k) = {0,1} indicating Finally, a wavelength pool output matrix WE(p,k) = {0,1} indicates
whether the output from wavelength converter p can reach output port whether the output from wavelength converter p can reach output port
k. Examples of this method being used to model wavelength converter k. Examples of this method being used to model wavelength converter
pools for several switch architectures are given in reference [Gen- pools for several switch architectures are given in [Gen-Encode].
Encode].
I1 +-------------+ +-------------+ E1 I1 +-------------+ +-------------+ E1
----->| | +--------+ | |-----> ----->| | +--------+ | |----->
I2 | +------+ WC #1 +-------+ | E2 I2 | +------+ WC #1 +-------+ | E2
----->| | +--------+ | |-----> ----->| | +--------+ | |----->
| Wavelength | | Wavelength | | Wavelength | | Wavelength |
| Converter | +--------+ | Converter | | Converter | +--------+ | Converter |
| Pool +------+ WC #2 +-------+ Pool | | Pool +------+ WC #2 +-------+ Pool |
| | +--------+ | | | | +--------+ | |
| Input | | Output | | Input | | Output |
skipping to change at page 23, line 28 skipping to change at page 22, line 41
IN | | +--------+ | | EM IN | | +--------+ | | EM
----->| +------+ WC #P +-------+ |-----> ----->| +------+ WC #P +-------+ |----->
| | +--------+ | | | | +--------+ | |
+-------------+ ^ ^ +-------------+ +-------------+ ^ ^ +-------------+
| | | |
| | | |
| | | |
| | | |
Input wavelength Output wavelength Input wavelength Output wavelength
constraints for constraints for constraints for constraints for
each converter each converter each converter each converter
Figure 3. Schematic diagram of wavelength converter pool model. Figure 3. Schematic Diagram of Wavelength Converter Pool Model
Figure 4 below shows a simple optical switch in a four wavelength Figure 4 shows a simple optical switch in a four-wavelength DWDM
DWDM system sharing wavelength converters in a general shared "per system sharing wavelength converters in a general shared "per-node"
node" fashion. fashion.
+-----------+ ___________ +------+ +-----------+ ___________ +------+
| |--------------------------->| | | |--------------------------->| |
| |--------------------------->| C | | |--------------------------->| C |
/| | |--------------------------->| o | E1 /| | |--------------------------->| o | E1
I1 /D+--->| |--------------------------->| m | I1 /D+--->| |--------------------------->| m |
+ e+--->| | | b |====> + e+--->| | | b |====>
====>| M| | Optical | +-----------+ +----+ | i | ====>| M| | Optical | +-----------+ +----+ | i |
+ u+--->| Switch | | WC Pool | |O S|-->| n | + u+--->| Switch | | WC Pool | |O S|-->| n |
\x+--->| | | +-----+ | |p w|-->| e | \x+--->| | | +-----+ | |p w|-->| e |
\| | +----+->|WC #1|--+->|t i| | r | \| | +----+->|WC #1|--+->|t i| | r |
| | | +-----+ | |i t| +------+ | | | +-----+ | |i t| +------+
| | | | |c c| +------+ | | | | |c c| +------+
/| | | | +-----+ | |a h|-->| | /| | | | +-----+ | |a h|-->| |
I2 /D+--->| +----+->|WC #2|--+->|l |-->| C | E2 I2 /D+--->| +----+->|WC #2|--+->|l |-->| C | E2
+ e+--->| | | +-----+ | | | | o | + e+--->| | | +-----+ | | | | o |
====>| M| | | +-----------+ +----+ | m |====> ====>| M| | | +-----------+ +----+ | m |====>
+ u+--->| | | b | + u+--->| | | b |
\x+--->| |--------------------------->| i | \x+--->| |--------------------------->| i |
\| | |--------------------------->| n | \| | |--------------------------->| n |
| |--------------------------->| e | | |--------------------------->| e |
|___________|--------------------------->| r | |___________|--------------------------->| r |
+-----------+ +------+ +-----------+ +------+
Figure 4. An optical switch featuring a shared per node wavelength Figure 4. An Optical Switch Featuring a Shared Per-Node Wavelength
converter pool architecture. Converter Pool Architecture
In this case the input and output pool matrices are simply: In this case, the input and output pool matrices are simply:
+-----+ +-----+ +-----+ +-----+
| 1 1 | | 1 1 | | 1 1 | | 1 1 |
WI =| |, WE =| | WI =| |, WE =| |
| 1 1 | | 1 1 | | 1 1 | | 1 1 |
+-----+ +-----+ +-----+ +-----+
Figure 5 shows a different wavelength pool architecture known as Figure 5 shows a different wavelength pool architecture known as
"shared per fiber". In this case the input and output pool matrices "shared per fiber". In this case, the input and output pool matrices
are simply: are simply:
+-----+ +-----+ +-----+ +-----+
| 1 1 | | 1 0 | | 1 1 | | 1 0 |
WI =| |, WE =| | WI =| |, WE =| |
| 1 1 | | 0 1 | | 1 1 | | 0 1 |
+-----+ +-----+ +-----+ +-----+
+-----------+ +------+ +-----------+ +------+
| |--------------------------->| | | |--------------------------->| |
| |--------------------------->| C | | |--------------------------->| C |
/| | |--------------------------->| o | E1 /| | |--------------------------->| o | E1
I1 /D+--->| |--------------------------->| m | I1 /D+--->| |--------------------------->| m |
+ e+--->| | | b |====> + e+--->| | | b |====>
====>| M| | Optical | +-----------+ | i | ====>| M| | Optical | +-----------+ | i |
+ u+--->| Switch | | WC Pool | | n | + u+--->| Switch | | WC Pool | | n |
\x+--->| | | +-----+ | | e | \x+--->| | | +-----+ | | e |
\| | +----+->|WC #1|--+---------->| r | \| | +----+->|WC #1|--+---------->| r |
| | | +-----+ | +------+ | | | +-----+ | +------+
| | | | +------+ | | | | +------+
/| | | | +-----+ | | | /| | | | +-----+ | | |
I2 /D+--->| +----+->|WC #2|--+---------->| C | E2 I2 /D+--->| +----+->|WC #2|--+---------->| C | E2
+ e+--->| | | +-----+ | | o | + e+--->| | | +-----+ | | o |
====>| M| | | +-----------+ | m |====> ====>| M| | | +-----------+ | m |====>
+ u+--->| | | b | + u+--->| | | b |
\x+--->| |--------------------------->| i | \x+--->| |--------------------------->| i |
\| | |--------------------------->| n | \| | |--------------------------->| n |
| |--------------------------->| e | | |--------------------------->| e |
|___________|--------------------------->| r | |___________|--------------------------->| r |
+-----------+ +------+ +-----------+ +------+
Figure 5. An optical switch featuring a shared per fiber wavelength
converter pool architecture.
3.7. Characterizing Electro-Optical Network Elements Figure 5. An Optical Switch Featuring a Shared Per-Fiber Wavelength
Converter Pool Architecture
In this section electro-optical WSON network elements are 3.7. Characterizing Electro-Optical Network Elements
In this section, electro-optical WSON network elements are
characterized by the three key functional components: input characterized by the three key functional components: input
constraints, output constraints and processing capabilities. constraints, output constraints, and processing capabilities.
WSON Network Element WSON Network Element
+-----------------------+ +-----------------------+
WSON Signal | | | | WSON Signal WSON Signal | | | | WSON Signal
| | | | | | | |
---------------> | | | | -----------------> ---------------> | | | | ----------------->
| | | | | | | |
+-----------------------+ +-----------------------+
<-----> <-------> <-----> <-----> <-------> <----->
Input Processing Output Input Processing Output
Figure 6. WSON Network Element Figure 6. WSON Network Element
3.7.1. Input Constraints
Section 3. (Wavelength Switched Optical Networks) discussed the basic 3.7.1. Input Constraints
properties regenerators, OEO switches and wavelength converters. From
these the following possible types of input constraints and
properties are derived:
1. Acceptable Modulation formats. Sections 3.5 and 3.6 discuss the basic properties of regenerators,
OEO switches, and wavelength converters. From these, the following
possible types of input constraints and properties are derived:
2. Client Signal (G-PID) restrictions. 1. Acceptable modulation formats
3. Bit Rate restrictions. 2. Client signal (G-PID) restrictions
4. FEC coding restrictions. 3. Bitrate restrictions
5. Configurability: (a) none, (b) self-configuring, (c) required. 4. FEC coding restrictions
These constraints are represented via simple lists. Note that the 5. Configurability: (a) none, (b) self-configuring, (c) required
These constraints are represented via simple lists. Note that the
device may need to be "provisioned" via signaling or some other means device may need to be "provisioned" via signaling or some other means
to accept signals with some attributes versus others. In other cases to accept signals with some attributes versus others. In other
the devices maybe relatively transparent to some attributes, e.g., cases, the devices may be relatively transparent to some attributes,
such as a 2R regenerator to bit rate. Finally, some devices may be e.g., a 2R regenerator to bitrate. Finally, some devices may be able
able to auto-detect some attributes and configure themselves, e.g., a to auto-detect some attributes and configure themselves, e.g., a 3R
3R regenerator with bit rate detection mechanisms and flexible phase regenerator with bitrate detection mechanisms and flexible phase
locking circuitry. To account for these different cases item 5 has locking circuitry. To account for these different cases, item 5 has
been added, which describes the devices configurability. been added, which describes the device's configurability.
Note that such input constraints also apply to the termination of the Note that such input constraints also apply to the termination of the
WSON signal. WSON signal.
3.7.2. Output Constraints 3.7.2. Output Constraints
None of the network elements considered here modifies either the bit None of the network elements considered here modifies either the
rate or the basic type of the client signal. However, they may modify bitrate or the basic type of the client signal. However, they may
the modulation format or the FEC code. Typically the following types modify the modulation format or the FEC code. Typically, the
of output constraints are seen: following types of output constraints are seen:
1. Output modulation is the same as input modulation (default). 1. Output modulation is the same as input modulation (default)
2. A limited set of output modulations is available. 2. A limited set of output modulations is available
3. Output FEC is the same as input FEC code (default). 3. Output FEC is the same as input FEC code (default)
4. A limited set of output FEC codes is available. 4. A limited set of output FEC codes is available
Note that in cases (2) and (4) above, where there is more than one Note that in cases 2 and 4 above, where there is more than one choice
choice in the output modulation or FEC code then the network element in the output modulation or FEC code, the network element will need
will need to be configured on a per LSP basis as to which choice to to be configured on a per-LSP basis as to which choice to use.
use.
3.7.3. Processing Capabilities 3.7.3. Processing Capabilities
A general WSON network element (NE) can perform a number of signal A general WSON network element (NE) can perform a number of signal
processing functions including: processing functions including:
(A) Regeneration (possibly different types). (A) Regeneration (possibly different types)
(B) Fault and Performance Monitoring. (B) Fault and performance monitoring
(C) Wavelength Conversion. (C) Wavelength conversion
(D) Switching. (D) Switching
An NE may or may not have the ability to perform regeneration (of the An NE may or may not have the ability to perform regeneration (of one
one of the types previously discussed). In addition some nodes may of the types previously discussed). In addition, some nodes may have
have limited regeneration capability, i.e., a shared pool, which may limited regeneration capability, i.e., a shared pool, which may be
be applied to selected signals traversing the NE. Hence to describe applied to selected signals traversing the NE. Hence, to describe
the regeneration capability of a link or node it is necessary to have the regeneration capability of a link or node, it is necessary to
at a minimum: have, 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 as 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.
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, the control plane can
can be of assistance in their configuration. Per LSP, per node, fault be of assistance in their configuration. Per-LSP, per-node, and
and performance monitoring examples include setting up a "section fault and performance monitoring examples include setting up a
trace" (a regenerator overhead identifier) between two nodes, or "section trace" (a regenerator overhead identifier) between two nodes
intermediate optical performance monitoring at selected nodes along a or intermediate optical performance monitoring at selected nodes
path. along a path.
4. Routing and Wavelength Assignment and the Control Plane 4. Routing and Wavelength Assignment and the Control Plane
From a control plane perspective, a wavelength-convertible network From a control plane perspective, a wavelength-convertible network
with full wavelength-conversion capability at each node can be with full wavelength-conversion capability at each node can be
controlled much like a packet MPLS-labeled network or a circuit- controlled much like a packet MPLS-labeled network or a circuit-
switched Time-division multiplexing (TDM) network with full time slot switched Time Division Multiplexing (TDM) network with full-time slot
interchange capability is controlled. In this case, the path interchange capability is controlled. In this case, the path
selection process needs to identify the Traffic Engineered (TE) links selection process needs to identify the Traffic Engineered (TE) links
to be used by an optical path, and wavelength assignment can be made to be used by an optical path, and wavelength assignment can be made
on a hop-by-hop basis. on a hop-by-hop basis.
However, in the case of an optical network without wavelength However, in the case of an optical network without wavelength
converters, an optical path needs to be routed from source to converters, an optical path needs to be routed from source to
destination and must use a single wavelength that is available along destination and must use a single wavelength that is available along
that path without "colliding" with a wavelength used by any other that path without "colliding" with a wavelength used by any other
optical path that may share an optical fiber. This is sometimes optical path that may share an optical fiber. This is sometimes
referred to as a "wavelength continuity constraint". referred to as a "wavelength continuity constraint".
In the general case of limited or no wavelength converters the In the general case of limited or no wavelength converters, the
computation of both the links and wavelengths is known as RWA. computation of both the links and wavelengths is known as RWA.
The inputs to basic RWA are the requested optical path's source and The inputs to basic RWA are the requested optical path's source and
destination, the network topology, the locations and capabilities of destination, the network topology, the locations and capabilities of
any wavelength converters, and the wavelengths available on each any wavelength converters, and the wavelengths available on each
optical link. The output from an algorithm providing RWA is an optical link. The output from an algorithm providing RWA is an
explicit route through ROADMs, a wavelength for optical transmitter, explicit route through ROADMs, a wavelength for optical transmitter,
and a set of locations (generally associated with ROADMs or switches) and a set of locations (generally associated with ROADMs or switches)
where wavelength conversion is to occur and the new wavelength to be where wavelength conversion is to occur and the new wavelength to be
used on each component link after that point in the route. used on each component link after that point in the route.
It is to be noted that the choice of specific RWA algorithm is out of It is to be noted that the choice of a specific RWA algorithm is out
the scope for this document. However there are a number of different of the scope of this document. However, there are a number of
approaches to dealing with RWA algorithm that can affect the division different approaches to dealing with RWA algorithms that can affect
of effort between path computation/routing and signaling. the division of effort between path computation/routing and
signaling.
4.1. Architectural Approaches to RWA 4.1. Architectural Approaches to RWA
Two general computational approaches are taken to performing RWA. Two general computational approaches are taken to performing RWA.
Some algorithms utilize a two-step procedure of path selection Some algorithms utilize a two-step procedure of path selection
followed by wavelength assignment, and others perform RWA in a followed by wavelength assignment, and others perform RWA in a
combined fashion. combined fashion.
In the following, three different ways of performing RWA in In the following sections, three different ways of performing RWA in
conjunction with the control plane are considered. The choice of one conjunction with the control plane are considered. The choice of one
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
are provided for reference purposes only, and other approaches are approaches are provided for reference purposes only, and other
possible. approaches are 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
of network topology, of available network resources and of network knowledge of network topology, of available network resources, and of
nodes' capabilities. This solution is compatible with most known RWA network nodes' capabilities. This solution is compatible with most
algorithms, and in particular those concerned with network known RWA algorithms, particularly 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 that 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
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
functionality and network state is obtained by a periodic flooding functionality and network state is obtained by a periodic flooding
of information provided by the other nodes. of information provided by the other nodes
4.1.2. Separated R and WA (R+WA) 4.1.2. Separated R and WA (R+WA)
In this case, one entity performs routing, while a second performs In this case, one entity performs routing while a second performs
wavelength assignment. The first entity furnishes one or more paths wavelength assignment. The first entity furnishes one or more paths
to the second entity which will perform wavelength assignment and to the second entity, which will perform wavelength assignment and
final path selection. final path selection.
As the entities computing the path and the wavelength assignment are The separation of the entities computing the path and the wavelength
separated, this constrains the class of RWA algorithms that may be assignment constrains the class of RWA algorithms that may be
implemented. Although it may seem that algorithms optimizing a joint implemented. Although it may seem that algorithms optimizing a joint
usage of the physical and wavelength paths are excluded from this usage of the physical and wavelength paths are excluded from this
solution, many practical optimization algorithms only consider a solution, many practical optimization algorithms only consider a
limited set of possible paths, e.g., as computed via a k-shortest limited set of possible paths, e.g., as computed via a k-shortest
path algorithm. Hence, while there is no guarantee that the selected path algorithm. Hence, while there is no guarantee that the selected
final route and wavelength offers the optimal solution, by allowing final route and wavelength offer the optimal solution, reasonable
multiple routes to pass to the wavelength selection process optimization can be performed by allowing multiple routes to pass to
reasonable optimization can be performed. the wavelength selection process.
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 the assignment is performed on a hop-by-hop, distributed manner along the
previously computed path. This mechanism relies on updating of a list previously computed path. This mechanism relies on updating of a
of potential wavelengths used to ensure conformance with the list 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
in the Label Set which it received; additionally the node can apply label in the Label Set that it received; additionally, the node can
local policy during label selection. GMPLS also provides support for apply local policy during label selection. GMPLS also provides
the signaling of bidirectional optical paths. support for 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
or one may be found that consumes too many conversion resources found, or one may be found that consumes too many conversion
relative to what a dedicated wavelength assignment policy would have resources relative to what a dedicated wavelength assignment policy
achieved. Hence, this approach may generate higher blocking would have achieved. Hence, this approach may generate higher
probabilities in a heavily loaded network. blocking probabilities in a heavily loaded network.
This solution may be facilitated via signaling extensions which ease This solution may be facilitated via signaling extensions that ease
its functioning and possibly enhance its performance with respect to its functioning and possibly enhance its performance with respect to
blocking probability. Note that this approach requires less blocking probability. Note that this approach requires less
information 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
RWA process were presented. This information can be viewed as either by RWA process were presented. This information can be viewed as
relatively static, i.e., changing with hardware changes (including either relatively static, i.e., changing with hardware changes
possibly failures), or relatively dynamic, i.e., those that can (including possibly failures), or relatively dynamic, i.e., those
change with optical path provisioning. The time requirement in which that can change with optical path provisioning. The time requirement
an entity involved in RWA process needs to be notified of such in which an entity involved in RWA process needs to be notified of
changes is fairly situational. For example, for network restoration such changes is fairly situational. For example, for network
purposes, learning of a hardware failure or of new hardware coming restoration purposes, learning of a hardware failure or of new
online to provide restoration capability can be critical. hardware coming online to provide restoration capability can be
critical.
Currently there are various methods for communicating RWA relevant Currently, there are various methods for communicating RWA relevant
information, these include, but are not limited to: information. These include, but are not limited to, the following:
o Existing control plane protocols, i.e., GMPLS routing and o Existing control plane protocols, i.e., GMPLS routing and
signaling. Note that routing protocols can be used to convey both signaling. Note that routing protocols can be used to convey both
static and dynamic information. static and dynamic information.
o Management protocols such as NetConf, SNMPv3, CLI, and CORBA. o Management protocols such as NetConf, SNMPv3, and CORBA.
o Directory services and accompanying protocols. These are typically o Methods to access configuration and status information such as a
used for the dissemination of relatively static information. command line interface (CLI).
Directory services are not suited to manage information in dynamic
and fluid environments. o Directory services and accompanying protocols. These are
typically used for the dissemination of relatively static
information. Directory services are not suited to manage
information in dynamic 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 PCEs to avoid flooding. This
be useful if the number of PCEs is significantly less than number would be useful if the number of PCEs is significantly less than
of WSON NEs. There may be other ways to limit flooding to the number of WSON NEs. There may be other ways to limit flooding
"interested" NEs. 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 Tailoring message content to WSON, e.g., the use of wavelength
ranges, or wavelength occupation bit maps. ranges or wavelength occupation bit maps
o Utilize incremental updates if feasible. o Utilizing 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 use cases for WSON and wavelength constraint models of Section 3 and use cases for WSON
control plane path computation, establishment, rerouting, and control plane path computation, establishment, 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), 18 links (L1 through L18), and one OEO
converter (O1) in a topology shown below. converter (O1) in a topology shown in Figure 7.
+--+ +--+ +--+ +--------+ +--+ +--+ +--+ +--------+
+-L3-+N2+-L5-+ +--------L12--+N6+--L15--+ N8 + +-L3-+N2+-L5-+ +--------L12--+N6+--L15--+ N8 +
| +--+ |N4+-L8---+ +--+ ++--+---++ | +--+ |N4+-L8---+ +--+ ++--+---++
| | +-L9--+| | | | | | +-L9--+| | | |
+--+ +-+-+ ++-+ || | L17 L18 +--+ +-+-+ ++-+ || | L17 L18
| ++-L1--+ | | ++++ +----L16---+ | | | ++-L1--+ | | ++++ +----L16---+ | |
|R1| | N1| L7 |R2| | | | |R1| | N1| L7 |R2| | | |
| ++-L2--+ | | ++-+ | ++---++ | ++-L2--+ | | ++-+ | ++---++
+--+ +-+-+ | | | + R3 | +--+ +-+-+ | | | + R3 |
| +--+ ++-+ | | +-----+ | +--+ ++-+ | | +-----+
+-L4-+N3+-L6-+N5+-L10-+ ++----+ +-L4-+N3+-L6-+N5+-L10-+ ++----+
+--+ | +--------L11--+ N7 + +--+ | +--------L11--+ N7 +
+--+ ++---++ +--+ ++---++
| | | |
L13 L14 L13 L14
| | | |
++-+ | ++-+ |
|O1+-+ |O1+-+
+--+ +--+
Figure 7. Routers and WSON nodes in a GMPLS and PCE Environment. Figure 7. Routers and WSON Nodes in a GMPLS and PCE Environment
5.1.1. Describing the WSON nodes 5.1.1. Describing the WSON Nodes
The eight WSON nodes described in Figure 7 have the following The eight WSON nodes described in Figure 7 have the following
properties: properties:
o Nodes N1, N2, N3 have FOADMs installed and can therefore only o Nodes N1, N2, and N3 have FOADMs installed and can therefore only
access a static and pre-defined set of wavelengths. access a static and pre-defined set of wavelengths.
o All other nodes contain ROADMs and can therefore access all o All other nodes contain ROADMs and can therefore access all
wavelengths. wavelengths.
o Nodes N4, N5, N7 and N8 are multi-degree nodes, allowing any o Nodes N4, N5, N7, and N8 are multi-degree nodes, allowing any
wavelength to be optically switched between any of the links. Note wavelength to be optically switched between any of the links.
however, that this does not automatically apply to wavelengths Note, however, that this does not automatically apply to
that are being added or dropped at the particular node. wavelengths that are being added or dropped at the particular
node.
o Node N4 is an exception to that: This node can switch any o Node N4 is an exception to that: this node can switch any
wavelength from its add/drop ports to any of its output links (L5, wavelength from its add/drop ports to any of its output links (L5,
L7 and L12 in this case). L7, and L12 in this case).
o The links from the routers are only able to carry one wavelength o The links from the routers are only able to carry one wavelength,
with the exception of links L8 and L9 which are capable to with the exception of links L8 and L9, which are capable to
add/drop any wavelength. add/drop any wavelength.
o Node N7 contains an OEO transponder (O1) connected to the node via o Node N7 contains an OEO transponder (O1) connected to the node via
links L13 and L14. That transponder operates in 3R mode and does links L13 and L14. That transponder operates in 3R mode and does
not change the wavelength of the signal. Assume that it can not change the wavelength of the signal. Assume that it can
regenerate any of the client signals, however only for a specific regenerate any of the client signals but only for a specific
wavelength. wavelength.
Given the above restrictions, the node information for the eight Given the above restrictions, the node information for the eight
nodes can be expressed as follows: (where ID == identifier, SCM == nodes can be expressed as follows (where ID = identifier, SCM =
switched connectivity matrix, and FCM == fixed connectivity matrix). switched connectivity matrix, and FCM = fixed connectivity matrix):
+ID+SCM +FCM + +ID+SCM +FCM +
| | |L1 |L2 |L3 |L4 | | |L1 |L2 |L3 |L4 | | | | |L1 |L2 |L3 |L4 | | |L1 |L2 |L3 |L4 | |
| |L1 |0 |0 |0 |0 | |L1 |0 |0 |1 |0 | | | |L1 |0 |0 |0 |0 | |L1 |0 |0 |1 |0 | |
|N1|L2 |0 |0 |0 |0 | |L2 |0 |0 |0 |1 | | |N1|L2 |0 |0 |0 |0 | |L2 |0 |0 |0 |1 | |
| |L3 |0 |0 |0 |0 | |L3 |1 |0 |0 |1 | | | |L3 |0 |0 |0 |0 | |L3 |1 |0 |0 |1 | |
| |L4 |0 |0 |0 |0 | |L4 |0 |1 |1 |0 | | | |L4 |0 |0 |0 |0 | |L4 |0 |1 |1 |0 | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L3 |L5 | | | | |L3 |L5 | | | | | | |L3 |L5 | | | | |L3 |L5 | | | |
|N2|L3 |0 |0 | | | |L3 |0 |1 | | | | |N2|L3 |0 |0 | | | |L3 |0 |1 | | | |
| |L5 |0 |0 | | | |L5 |1 |0 | | | | | |L5 |0 |0 | | | |L5 |1 |0 | | | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L4 |L6 | | | | |L4 |L6 | | | | | | |L4 |L6 | | | | |L4 |L6 | | | |
|N3|L4 |0 |0 | | | |L4 |0 |1 | | | | |N3|L4 |0 |0 | | | |L4 |0 |1 | | | |
| |L6 |0 |0 | | | |L6 |1 |0 | | | | | |L6 |0 |0 | | | |L6 |1 |0 | | | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L5 |L7 |L8 |L9 |L12| |L5 |L7 |L8 |L9 |L12| | | |L5 |L7 |L8 |L9 |L12| |L5 |L7 |L8 |L9 |L12|
| |L5 |0 |1 |1 |1 |1 |L5 |0 |0 |0 |0 |0 | | |L5 |0 |1 |1 |1 |1 |L5 |0 |0 |0 |0 |0 |
|N4|L7 |1 |0 |1 |1 |1 |L7 |0 |0 |0 |0 |0 | |N4|L7 |1 |0 |1 |1 |1 |L7 |0 |0 |0 |0 |0 |
| |L8 |1 |1 |0 |1 |1 |L8 |0 |0 |0 |0 |0 | | |L8 |1 |1 |0 |1 |1 |L8 |0 |0 |0 |0 |0 |
| |L9 |1 |1 |1 |0 |1 |L9 |0 |0 |0 |0 |0 | | |L9 |1 |1 |1 |0 |1 |L9 |0 |0 |0 |0 |0 |
| |L12|1 |1 |1 |1 |0 |L12|0 |0 |0 |0 |0 | | |L12|1 |1 |1 |1 |0 |L12|0 |0 |0 |0 |0 |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L6 |L7 |L10|L11| | |L6 |L7 |L10|L11| | | | |L6 |L7 |L10|L11| | |L6 |L7 |L10|L11| |
| |L6 |0 |1 |0 |1 | |L6 |0 |0 |1 |0 | | | |L6 |0 |1 |0 |1 | |L6 |0 |0 |1 |0 | |
|N5|L7 |1 |0 |0 |1 | |L7 |0 |0 |0 |0 | | |N5|L7 |1 |0 |0 |1 | |L7 |0 |0 |0 |0 | |
| |L10|0 |0 |0 |0 | |L10|1 |0 |0 |0 | | | |L10|0 |0 |0 |0 | |L10|1 |0 |0 |0 | |
| |L11|1 |1 |0 |0 | |L11|0 |0 |0 |0 | | | |L11|1 |1 |0 |0 | |L11|0 |0 |0 |0 | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L12|L15| | | | |L12|L15| | | | | | |L12|L15| | | | |L12|L15| | | |
|N6|L12|0 |1 | | | |L12|0 |0 | | | | |N6|L12|0 |1 | | | |L12|0 |0 | | | |
| |L15|1 |0 | | | |L15|0 |0 | | | | | |L15|1 |0 | | | |L15|0 |0 | | | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L11|L13|L14|L16| | |L11|L13|L14|L16| | | | |L11|L13|L14|L16| | |L11|L13|L14|L16| |
| |L11|0 |1 |0 |1 | |L11|0 |0 |0 |0 | | | |L11|0 |1 |0 |1 | |L11|0 |0 |0 |0 | |
|N7|L13|1 |0 |0 |0 | |L13|0 |0 |1 |0 | | |N7|L13|1 |0 |0 |0 | |L13|0 |0 |1 |0 | |
| |L14|0 |0 |0 |1 | |L14|0 |1 |0 |0 | | | |L14|0 |0 |0 |1 | |L14|0 |1 |0 |0 | |
| |L16|1 |0 |1 |0 | |L16|0 |0 |1 |0 | | | |L16|1 |0 |1 |0 | |L16|0 |0 |1 |0 | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
| | |L15|L16|L17|L18| | |L15|L16|L17|L18| | | | |L15|L16|L17|L18| | |L15|L16|L17|L18| |
| |L15|0 |1 |0 |0 | |L15|0 |0 |0 |1 | | | |L15|0 |1 |0 |0 | |L15|0 |0 |0 |1 | |
|N8|L16|1 |0 |0 |0 | |L16|0 |0 |1 |0 | | |N8|L16|1 |0 |0 |0 | |L16|0 |0 |1 |0 | |
| |L17|0 |0 |0 |0 | |L17|0 |1 |0 |0 | | | |L17|0 |0 |0 |0 | |L17|0 |1 |0 |0 | |
| |L18|0 |0 |0 |0 | |L18|1 |0 |1 |0 | | | |L18|0 |0 |0 |0 | |L18|1 |0 |1 |0 | |
+--+---+---+---+---+---+---+---+---+---+---+---+---+ +--+---+---+---+---+---+---+---+---+---+---+---+---+
5.1.2. Describing the links 5.1.2. Describing the Links
For the following discussion some simplifying assumptions are made: For the following discussion, some simplifying assumptions are made:
o It is assumed that the WSON node support a total of four o It is assumed that the WSON node supports a total of four
wavelengths designated WL1 through WL4. wavelengths, designated WL1 through WL4.
o It is assumed that the impairment feasibility of a path or path o It is assumed that the impairment feasibility of a path or path
segment is independent from the wavelength chosen. segment is independent from the wavelength chosen.
For the discussion of RWA operation to build LSPs between two For the discussion of RWA operation, to build LSPs between two
routers, the wavelength constraints on the links between the routers routers, the wavelength constraints on the links between the routers
and the WSON nodes as well as the connectivity matrix of these links and the WSON nodes as well as the connectivity matrix of these links
needs to be specified: need to be specified:
+Link+WLs supported +Possible output links+ +Link+WLs supported +Possible output links+
| L1 | WL1 | L3 | | L1 | WL1 | L3 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L2 | WL2 | L4 | | L2 | WL2 | L4 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L8 | WL1 WL2 WL3 WL4 | L5 L7 L12 | | L8 | WL1 WL2 WL3 WL4 | L5 L7 L12 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L9 | WL1 WL2 WL3 WL4 | L5 L7 L12 | | L9 | WL1 WL2 WL3 WL4 | L5 L7 L12 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
skipping to change at page 35, line 38 skipping to change at page 34, line 42
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L14| WL1 WL2 WL3 WL4 | L13 L16 | | L14| WL1 WL2 WL3 WL4 | L13 L16 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L17| WL2 | L16 | | L17| WL2 | L16 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
| L18| WL1 | L15 | | L18| WL1 | L15 |
+----+-----------------+---------------------+ +----+-----------------+---------------------+
Note that the possible output links for the links connecting to the Note that the possible output links for the links connecting to the
routers is inferred from the switched connectivity matrix and the routers is inferred from the switched connectivity matrix and the
fixed connectivity matrix of the Nodes N1 through N8 and is show here fixed connectivity matrix of the Nodes N1 through N8 and is shown
for convenience, i.e., this information does not need to be repeated. here for convenience; that is, this information does not need to be
repeated.
5.2. RWA Path Computation and Establishment 5.2. RWA Path Computation and Establishment
The calculation of optical impairment feasible routes is outside the The calculation of optical impairment feasible routes is outside the
scope of this document. In general optical impairment feasible routes scope of this document. In general, optical impairment feasible
serve as an input to RWA algorithm. routes serve as an input to an RWA algorithm.
For the example use case shown here, assume the following feasible For the example use case shown here, assume the following feasible
routes: routes:
+Endpoint 1+Endpoint 2+Feasible Route + +Endpoint 1+Endpoint 2+Feasible Route +
| R1 | R2 | L1 L3 L5 L8 | | R1 | R2 | L1 L3 L5 L8 |
| R1 | R2 | L1 L3 L5 L9 | | R1 | R2 | L1 L3 L5 L9 |
| R1 | R2 | L2 L4 L6 L7 L8 | | R1 | R2 | L2 L4 L6 L7 L8 |
| R1 | R2 | L2 L4 L6 L7 L9 | | R1 | R2 | L2 L4 L6 L7 L9 |
| R1 | R2 | L2 L4 L6 L10 | | R1 | R2 | L2 L4 L6 L10 |
| R1 | R3 | L1 L3 L5 L12 L15 L18 | | R1 | R3 | L1 L3 L5 L12 L15 L18 |
| R1 | N7 | L2 L4 L6 L11 | | R1 | N7 | L2 L4 L6 L11 |
| N7 | R3 | L16 L17 | | N7 | R3 | L16 L17 |
| N7 | R2 | L16 L15 L12 L9 | | N7 | R2 | L16 L15 L12 L9 |
| R2 | R3 | L8 L12 L15 L18 | | R2 | R3 | L8 L12 L15 L18 |
| R2 | R3 | L8 L7 L11 L16 L17 | | R2 | R3 | L8 L7 L11 L16 L17 |
| R2 | R3 | L9 L12 L15 L18 | | R2 | R3 | L9 L12 L15 L18 |
| R2 | R3 | L9 L7 L11 L16 L17 | | R2 | R3 | L9 L7 L11 L16 L17 |
Given a request to establish a LSP between R1 and R2 RWA algorithm Given a request to establish an LSP between R1 and R2, an RWA
finds the following possible solutions: algorithm finds the following possible solutions:
+WL + Path + +WL + Path +
| WL1| L1 L3 L5 L8 | | WL1| L1 L3 L5 L8 |
| WL1| L1 L3 L5 L9 | | WL1| L1 L3 L5 L9 |
| WL2| L2 L4 L6 L7 L8| | WL2| L2 L4 L6 L7 L8|
| WL2| L2 L4 L6 L7 L9| | WL2| L2 L4 L6 L7 L9|
| WL2| L2 L4 L6 L10 | | WL2| L2 L4 L6 L10 |
Assume now that RWA algorithm yields WL1 and the Path L1 L3 L5 L8 for Assume now that an RWA algorithm yields WL1 and the path L1 L3 L5 L8
the requested LSP. for the requested LSP.
Next, another LSP is signaled from R1 to R2. Given the established Next, another LSP is signaled from R1 to R2. Given the established
LSP using WL1, the following table shows the available paths: LSP using WL1, the following table shows the available paths:
+WL + Path + +WL + Path +
| WL2| L2 L4 L6 L7 L9| | WL2| L2 L4 L6 L7 L9|
| WL2| L2 L4 L6 L10 | | WL2| L2 L4 L6 L10 |
Assume now that RWA algorithm yields WL2 and the path L2 L4 L6 L7 L9 Assume now that an RWA algorithm yields WL2 and the path L2 L4 L6 L7
for the establishment of the new LSP. L9 for the establishment of the new LSP.
A LSP request -this time from R2 to R3 - can not be fulfilled since An LSP request -- this time from R2 to R3 -- cannot be fulfilled
the only four possible paths (starting at L8 and L9) are already in since the four possible paths (starting at L8 and L9) are already in
use. use.
5.3. Resource Optimization 5.3. Resource Optimization
The preceding example gives rise to another use case: the The preceding example gives rise to another use case: the
optimization of network resources. Optimization can be achieved on a optimization of network resources. Optimization can be achieved on a
number of layers (e.g. through electrical or optical multiplexing of number of layers (e.g., through electrical or optical multiplexing of
client signals) or by re-optimizing the solutions found by a RWA client signals) or by re-optimizing the solutions found by an RWA
algorithm. algorithm.
Given the above example again, assume that a RWA algorithm should Given the above example again, assume that an RWA algorithm should
identify a path between R2 and R3. The only possible path to reach R3 identify a path between R2 and R3. The only possible path to reach
from R2 needs to use L9. L9 however is blocked by one of the LSPs R3 from R2 needs to use L9. L9, however, is blocked by one of the
from R1. LSPs from R1.
5.4. Support for Rerouting 5.4. Support for Rerouting
It is also envisioned that the extensions to GMPLS and PCE support It is also envisioned that the extensions to GMPLS and PCE support
rerouting of wavelengths in case of failures. rerouting of wavelengths in case of failures.
Assume for this discussion that the only two LSPs in use in the For this discussion, assume that the only two LSPs in use in the
system are: system are:
LSP1: WL1 L1 L3 L5 L8 LSP1: WL1 L1 L3 L5 L8
LSP2: WL2 L2 L4 L6 L7 L9 LSP2: WL2 L2 L4 L6 L7 L9
Assume furthermore that the link L5 fails. An RWA algorithm can now Furthermore, assume that the L5 fails. An RWA algorithm can now
compute the following alternate path and establish that path: compute and establish the following alternate path:
R1 -> N7 -> R2 R1 -> N7 -> R2
Level 3 regeneration will take place at N7, so that the complete path Level 3 regeneration will take place at N7, so that the complete path
looks like this: looks like this:
R1 -> L2 L4 L6 L11 L13 -> O1 -> L14 L16 L15 L12 L9 -> R2 R1 -> L2 L4 L6 L11 L13 -> O1 -> L14 L16 L15 L12 L9 -> R2
5.5. Electro-Optical Networking Scenarios 5.5. Electro-Optical Networking Scenarios
In the following various networking scenarios are considered In the following subsections, various networking scenarios are
involving regenerators, OEO switches and wavelength converters. These considered involving regenerators, OEO switches, and wavelength
scenarios can be grouped roughly by type and number of extensions to converters. These scenarios can be grouped roughly by type and
the GMPLS control plane that would be required. number of extensions to the GMPLS control plane that would be
required.
5.5.1. Fixed Regeneration Points 5.5.1. Fixed Regeneration Points
In the simplest networking scenario involving regenerators, In the simplest networking scenario involving regenerators,
regeneration is associated with a WDM link or an entire node and is regeneration is associated with a WDM link or an entire node and is
not optional, i.e., all signals traversing the link or node will be not optional; that is, all signals traversing the link or node will
regenerated. This includes OEO switches since they provide be regenerated. This includes OEO switches since they provide
regeneration on every port. regeneration on every port.
There may be input constraints and output constraints on the There may be input constraints and output constraints on the
regenerators. Hence the path selection process will need to know from regenerators. Hence, the path selection process will need to know
routing or other means the regenerator constraints so that it can the regenerator constraints from routing or other means so that it
choose a compatible path. For impairment aware routing and wavelength can choose a compatible path. For impairment-aware routing and
assignment (IA-RWA) the path selection process will also need to know wavelength assignment (IA-RWA), the path selection process will also
which links/nodes provide regeneration. Even for "regular" RWA, this need to know which links/nodes provide regeneration. Even for
regeneration information is useful since wavelength converters "regular" RWA, this regeneration information is useful since
typically perform regeneration and the wavelength continuity wavelength converters typically perform regeneration, and the
constraint can be relaxed at such a point. wavelength continuity constraint can be relaxed at such a point.
Signaling does not need to be enhanced to include this scenario since Signaling does not need to be enhanced to include this scenario since
there are no reconfigurable regenerator options on input, output or there are no reconfigurable regenerator options on input, output, or
with respect to processing. processing.
5.5.2. Shared Regeneration Pools 5.5.2. Shared Regeneration Pools
In this scenario there are nodes with shared regenerator pools within In this scenario, there are nodes with shared regenerator pools
the network in addition to fixed regenerators of the previous within the network in addition to the fixed regenerators of the
scenario. These regenerators are shared within a node and their previous scenario. These regenerators are shared within a node and
application to a signal is optional. There are no reconfigurable their application to a signal is optional. There are no
options on either input or output. The only processing option is to reconfigurable options on either input or output. The only
"regenerate" a particular signal or not. processing option is to "regenerate" a particular signal or not.
Regenerator information in this case is used in path computation to In this case, regenerator information is used in path computation to
select a path that ensures signal compatibility and IA-RWA criteria. select a path that ensures signal compatibility and IA-RWA criteria.
To setup an LSP that utilizes a regenerator from a node with a shared To set up an LSP that utilizes a regenerator from a node with a
regenerator pool it is necessary to indicate that regeneration is to shared regenerator pool, it is necessary to indicate that
take place at that particular node along the signal path. Such a regeneration is to take place at that particular node along the
capability currently does not exist in GMPLS signaling. signal path. Such a capability does not currently exist in GMPLS
signaling.
5.5.3. Reconfigurable Regenerators 5.5.3. Reconfigurable Regenerators
This scenario is concerned with regenerators that require This scenario is concerned with regenerators that require
configuration prior to use on an optical signal. As discussed configuration prior to use on an optical signal. As discussed
previously, this could be due to a regenerator that must be previously, this could be due to a regenerator that must be
configured to accept signals with different characteristics, for configured to accept signals with different characteristics, for
regenerators with a selection of output attributes, or for regenerators with a selection of output attributes, or for
regenerators with additional optional processing capabilities. regenerators with additional optional processing capabilities.
As in the previous scenarios it is necessary to have information As in the previous scenarios, it is necessary to have information
concerning regenerator properties for selection of compatible paths concerning regenerator properties for selection of compatible paths
and for IA-RWA computations. In addition during LSP setup it is and for IA-RWA computations. In addition, during LSP setup, it is
necessary to be able configure regenerator options at a particular necessary to be able to configure regenerator options at a particular
node along the path. Such a capability currently does not exist in node along the path. Such a capability does not currently exist in
GMPLS signaling. GMPLS signaling.
5.5.4. Relation to Translucent Networks 5.5.4. Relation to Translucent Networks
Networks that contain both transparent network elements such as Networks that contain both transparent network elements such as
reconfigurable optical add drop multiplexers (ROADMs) and electro- Reconfigurable Optical Add/Drop Multiplexers (ROADMs) and electro-
optical network elements such regenerators or OEO switches are optical network elements such as regenerators or OEO switches are
frequently referred to as translucent optical networks. frequently referred to as translucent optical networks.
Three main types of translucent optical networks have been discussed: Three main types of translucent optical networks have been discussed:
1. Transparent "islands" surrounded by regenerators. This is 1. Transparent "islands" surrounded by regenerators. This is
frequently seen when transitioning from a metro optical sub- frequently seen when transitioning from a metro optical
network to a long haul optical sub-network. subnetwork to a long-haul optical subnetwork.
2. Mostly transparent networks with a limited number of OEO 2. Mostly transparent networks with a limited number of OEO
("opaque") nodes strategically placed. This takes advantage of the ("opaque") nodes strategically placed. This takes advantage of
inherent regeneration capabilities of OEO switches. In the the inherent regeneration capabilities of OEO switches. In the
planning of such networks one has to determine the optimal planning of such networks, one has to determine the optimal
placement of the OEO switches. placement of the OEO switches.
3. Mostly transparent networks with a limited number of optical 3. Mostly transparent networks with a limited number of optical
switching nodes with "shared regenerator pools" that can be switching nodes with "shared regenerator pools" that can be
optionally applied to signals passing through these switches. optionally applied to signals passing through these switches.
These switches are sometimes called translucent nodes. These switches are sometimes called translucent nodes.
All three types of translucent networks fit within the networking All three types of translucent networks fit within the networking
scenarios of Section 5.5.1. and Section 5.5.2. above. And hence, scenarios of Sections 5.5.1 and 5.5.2. Hence, they can be
can be accommodated by the GMPLS extensions envisioned in this accommodated by the GMPLS extensions envisioned in this document.
document.
6. GMPLS and PCE Implications 6. GMPLS and PCE Implications
The presence and amount of wavelength conversion available at a The presence and amount of wavelength conversion available at a
wavelength switching interface has an impact on the information that wavelength switching interface have an impact on the information that
needs to be transferred by the control plane (GMPLS) and the PCE needs to be transferred by the control plane (GMPLS) and the PCE
architecture. Current GMPLS and PCE standards can address the full architecture. Current GMPLS and PCE standards address the full
wavelength conversion case so the following will only address the wavelength conversion case, so the following subsections will only
limited and no wavelength conversion cases. address the limited and no wavelength conversion cases.
6.1. Implications for GMPLS signaling 6.1. Implications for GMPLS Signaling
Basic support for WSON signaling already exists in GMPLS with the Basic support for WSON signaling already exists in GMPLS with the
lambda (value 9) LSP encoding type [RFC3471], or for G.709 compatible lambda (value 9) LSP encoding type [RFC3471] or for G.709-compatible
optical channels, the LSP encoding type (value = 13) "G.709 Optical optical channels, the LSP encoding type (value = 13) "G.709 Optical
Channel" from [RFC4328]. However a number of practical issues arise Channel" from [RFC4328]. However, a number of practical issues arise
in the identification of wavelengths and signals, and distributed in the identification of wavelengths and signals and in distributed
wavelength assignment processes which are discussed below. wavelength assignment processes, which are discussed below.
6.1.1. Identifying Wavelengths and Signals 6.1.1. Identifying Wavelengths and Signals
As previously stated a global fixed mapping between wavelengths and As previously stated, a global-fixed mapping between wavelengths and
labels simplifies the characterization of WDM links and WSON devices. labels simplifies the characterization of WDM links and WSON devices.
Furthermore, a mapping like the one described in [RFC6205] provides
Furthermore such a mapping as described in [Otani] provides such a
fixed mapping for communication between PCE and WSON PCCs. fixed mapping for communication between PCE and WSON PCCs.
6.1.2. WSON Signals and Network Element Processing 6.1.2. WSON Signals and Network Element Processing
As discussed in Section 3.3.2. a WSON signal at any point along its As discussed in Section 3.3.2, a WSON signal at any point along its
path can be characterized by the (a) modulation format, (b) FEC, (c) path can be characterized by the (a) modulation format, (b) FEC, (c)
wavelength, (d)bit rate, and (d)G-PID. wavelength, (d) bitrate, and (e) G-PID.
Currently G-PID, wavelength (via labels), and bit rate (via bandwidth Currently, G-PID, wavelength (via labels), and bitrate (via bandwidth
encoding) are supported in [RFC3471] and [RFC3473]. These RFCs can encoding) are supported in [RFC3471] and [RFC3473]. These RFCs can
accommodate the wavelength changing at any node along the LSP and can accommodate the wavelength changing at any node along the LSP and can
thus provide explicit control of wavelength converters. thus provide explicit control of wavelength converters.
In the fixed regeneration point scenario described in Section 5.5.1. In the fixed regeneration point scenario described in Section 5.5.1,
(Fixed Regeneration Points) no enhancements are required to signaling no enhancements are required to signaling since there are no
since there are no additional configuration options for the LSP at a additional configuration options for the LSP at a node.
node.
In the case of shared regeneration pools described in Section 5.5.2. In the case of shared regeneration pools described in Section 5.5.2,
(Shared Regeneration Pools) it is necessary to indicate to a node it is necessary to indicate to a node that it should perform
that it should perform regeneration on a particular signal. Viewed regeneration on a particular signal. Viewed another way, for an LSP,
another way, for an LSP, it is desirable to specify that certain it is desirable to specify that certain nodes along the path perform
nodes along the path perform regeneration. Such a capability regeneration. Such a capability does not currently exist in GMPLS
currently does not exist in GMPLS signaling. signaling.
The case of configurable regenerators described in Section 5.5.3. The case of reconfigurable regenerators described in Section 5.5.3 is
(Reconfigurable Regenerators) is very similar to the previous except very similar to the previous except that now there are potentially
that now there are potentially many more items that can be configured many more items that can be configured on a per-node basis for an
on a per node basis for an LSP. LSP.
Note that the techniques of [RFC5420] which allow for additional LSP Note that the techniques of [RFC5420] that allow for additional LSP
attributes and their recording in a Record Route Object (RRO) object attributes and their recording in a Record Route Object (RRO) could
could be extended to allow for additional LSP attributes in an ERO. be extended to allow for additional LSP attributes in an Explicit
This could allow one to indicate where optional 3R regeneration Route Object (ERO). This could allow one to indicate where optional
should take place along a path, any modification of LSP attributes 3R regeneration should take place along a path, any modification of
such as modulation format, or any enhance processing such as LSP attributes such as modulation format, or any enhance processing
performance monitoring. such as performance monitoring.
6.1.3. Combined RWA/Separate Routing WA support 6.1.3. Combined RWA/Separate Routing WA support
In either the combined RWA or separate routing WA cases, the node In either the combined RWA case or the separate routing WA case, the
initiating the signaling will have a route from the source to node initiating the signaling will have a route from the source to
destination along with the wavelengths (generalized labels) to be destination along with the wavelengths (generalized labels) to be
used along portions of the path. Current GMPLS signaling supports an used along portions of the path. Current GMPLS signaling supports an
Explicit Route Object (ERO) and within an ERO an ERO Label subobject Explicit Route Object (ERO), and within an ERO, an ERO Label
can be used to indicate the wavelength to be used at a particular subobject can be used to indicate the wavelength to be used at a
node. In case the local label map approach is used the label sub- particular node. In case the local label map approach is used, the
object entry in the ERO has to be interpreted appropriately. label subobject entry in the ERO has to be interpreted appropriately.
6.1.4. Distributed Wavelength Assignment: Unidirectional, No 6.1.4. Distributed Wavelength Assignment: Unidirectional, No Converters
Converters
GMPLS signaling for a unidirectional optical path LSP allows for the GMPLS signaling for a unidirectional optical path LSP allows for the
use of a label set object in the Resource Reservation Protocol - use of a Label Set object in the Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) path message. The processing of the Traffic Engineering (RSVP-TE) path message. Processing of the Label
label set object to take the intersection of available lambdas along Set object to take the intersection of available lambdas along a path
a path can be performed resulting in the set of available lambda can be performed, resulting in the set of available lambdas being
being known to the destination that can then use a wavelength known to the destination, which can then use a wavelength selection
selection algorithm to choose a lambda. algorithm to choose a lambda.
6.1.5. Distributed Wavelength Assignment: Unidirectional, Limited 6.1.5. Distributed Wavelength Assignment: Unidirectional, Limited
Converters Converters
In the case of wavelength converters, nodes with wavelength In the case of wavelength converters, nodes with wavelength
converters would need to make the decision as to whether to perform converters would need to make the decision as to whether to perform
conversion. One indicator for this would be that the set of available conversion. One indicator for this would be that the set of
wavelengths which is obtained via the intersection of the incoming available wavelengths that is obtained via the intersection of the
label set and the output links available wavelengths is either null incoming Label Set and the output links available wavelengths is
or deemed too small to permit successful completion. either null or deemed too small to permit successful completion.
At this point the node would need to remember that it will apply At this point, the node would need to remember that it will apply
wavelength conversion and will be responsible for assigning the wavelength conversion and will be responsible for assigning the
wavelength on the previous lambda-contiguous segment when the RSVP-TE wavelength on the previous lambda-contiguous segment when the RSVP-TE
RESV message is processed. The node will pass on an enlarged label RESV message is processed. The node will pass on an enlarged label
set reflecting only the limitations of the wavelength converter and set reflecting only the limitations of the wavelength converter and
the output link. The record route option in RSVP-TE signaling can be the output link. The record route option in RSVP-TE signaling can be
used to show where wavelength conversion has taken place. used to show where wavelength conversion has taken place.
6.1.6. Distributed Wavelength Assignment: Bidirectional, No 6.1.6. Distributed Wavelength Assignment: Bidirectional, No Converters
Converters
There are cases of a bidirectional optical path which requires the There are cases of a bidirectional optical path that require the use
use of the same lambda in both directions. The above procedure can be of the same lambda in both directions. The above procedure can be
used to determine the available bidirectional lambda set if it is used to determine the available bidirectional lambda set if it is
interpreted that the available label set is available in both interpreted that the available Label Set is available in both
directions. In bidirectional LSPs setup, according to [RFC3471] directions. According to [RFC3471], Section 4.1, the setup of
Section 4.1. (Architectural Approaches to RWA), is indicated by the bidirectional LSPs is indicated by the presence of an upstream label
presence of an upstream label in the path message. in the path message.
However, until the intersection of the available label sets is However, until the intersection of the available Label Sets is
determined along the path and at the destination node the upstream determined along the path and at the destination node, the upstream
label information may not be correct. This case can be supported label information may not be correct. This case can be supported
using current GMPLS mechanisms, but may not be as efficient as an using current GMPLS mechanisms but may not be as efficient as an
optimized bidirectional single-label allocation mechanism. optimized bidirectional single-label allocation mechanism.
6.2. Implications for GMPLS Routing 6.2. Implications for GMPLS Routing
GMPLS routing [RFC4202] currently defines an interface capability GMPLS routing [RFC4202] currently defines an interface capability
descriptor for "lambda switch capable" (LSC) which can be used to descriptor for "Lambda Switch Capable" (LSC) that can be used to
describe the interfaces on a ROADM or other type of wavelength describe the interfaces on a ROADM or other type of wavelength
selective switch. In addition to the topology information typically selective switch. In addition to the topology information typically
conveyed via an IGP, it would be necessary to convey the following conveyed via an Interior Gateway Protocol (IGP), it would be
subsystem properties to minimally characterize a WSON: necessary to convey the following subsystem properties to minimally
characterize a WSON:
1. WDM Link properties (allowed wavelengths). 1. WDM link properties (allowed wavelengths)
2. Optical transmitters (wavelength range). 2. Optical transmitters (wavelength range)
3. ROADM/FOADM Properties (connectivity matrix, port wavelength 3. ROADM/FOADM properties (connectivity matrix, port wavelength
restrictions). restrictions)
4. Wavelength converter properties (per network element, may change if 4. Wavelength converter properties (per network element, may change
a common limited shared pool is used). if a common limited shared pool is used)
This information is modeled in detail in [WSON-Info] and a compact This information is modeled in detail in [WSON-Info], and a compact
encoding is given in [WSON-Encode]. encoding is given in [WSON-Encode].
6.2.1. Electro-Optical Element Signal Compatibility 6.2.1. Electro-Optical Element Signal Compatibility
In network scenarios where signal compatibility is a concern it is In network scenarios where signal compatibility is a concern, it is
necessary to add parameters to our existing node and link models to necessary to add parameters to our existing node and link models to
take into account electro-optical input constraints, output take into account electro-optical input constraints, output
constraints, and the signal processing capabilities of a NE in path constraints, and the signal-processing capabilities of an NE in path
computations. computations.
Input constraints: Input constraints:
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)
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
included with the optical tributary signal class restrictions.
4. Acceptable G-PID list: a list of G-PIDs corresponding to the
"client" digital streams that is compatible with this device.
Note that the bit rate of the signal does not change over the LSP. 2. Acceptable FEC codes (configuration type)
This can be communicated as an LSP parameter and hence this
3. Acceptable bitrate set: a list of specific bitrates or bitrate
ranges that the device can accommodate. Coarse bitrate info is
included with the optical tributary signal-class restrictions.
4. Acceptable G-PID list: a list of G-PIDs corresponding to the
"client" digital streams that is compatible with this device
Note that the bitrate of the signal does not change over the LSP.
This can be communicated as an LSP parameter; therefore, 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
for the NE with respect to bit rate. type" for the NE with respect to bitrate.
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 (a) a network-
element wide basis, (b) a per port basis, (c) on a per regenerator element-wide basis, (b) a per-port basis, or (c) 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. and 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
layer-specific TE attributes are discussed. RWA for optical networks layer-specific TE attributes are discussed. RWA for optical networks
without wavelength converters imposes an additional requirement for without wavelength converters imposes an additional requirement for
the lambda (or optical channel) layer: that of knowing which specific the lambda (or optical channel) layer: that of knowing which specific
wavelengths are in use. Note that current DWDM systems range from 16 wavelengths are in use. Note that current DWDM systems range from 16
channels to 128 channels with advanced laboratory systems with as channels to 128 channels, with advanced laboratory systems with as
many as 300 channels. Given these channel limitations and if the many as 300 channels. Given these channel limitations, if the
approach of a global wavelength to label mapping or furnishing the approach of a global wavelength to label mapping or furnishing the
local mappings to the PCEs is taken then representing the use of local mappings to the PCEs is taken, representing the use of
wavelengths via a simple bit-map is feasible [Gen-Encode]. wavelengths via a simple bitmap is feasible [Gen-Encode].
6.2.3. WSON Routing Information Summary 6.2.3. WSON Routing Information Summary
The following table summarizes the WSON information that could be The following table summarizes the WSON information that could be
conveyed via GMPLS routing and attempts to classify that information conveyed via GMPLS routing and attempts to classify that information
as to its static or dynamic nature and whether that information would according to its static or dynamic nature and its association with
tend to be associated with either a link or a node. either a link or a node.
Information Static/Dynamic Node/Link Information Static/Dynamic Node/Link
------------------------------------------------------------------ ------------------------------------------------------------------
Connectivity matrix Static Node Connectivity matrix Static Node
Per port wavelength restrictions Static Node(1) Per-port wavelength restrictions Static Node(1)
WDM link (fiber) lambda ranges Static Link WDM link (fiber) lambda ranges Static Link
WDM link channel spacing Static Link WDM link channel spacing Static Link
Optical transmitter range Static Link(2) Optical transmitter range Static Link(2)
Wavelength conversion capabilities Static(3) Node Wavelength conversion capabilities Static(3) Node
Maximum bandwidth per wavelength Static Link Maximum bandwidth per wavelength Static Link
Wavelength availability Dynamic(4) Link Wavelength availability Dynamic(4) Link
Signal compatibility and processing Static/Dynamic Node Signal compatibility and processing Static/Dynamic Node
Notes: Notes:
1. These are the per port wavelength restrictions of an optical 1. These are the per-port wavelength restrictions of an optical
device such as a ROADM and are independent of any optical device such as a ROADM and are independent of any optical
constraints imposed by a fiber link. constraints imposed by a fiber link.
2. This could also be viewed as a node capability. 2. This could also be viewed as a node capability.
3. This could be dynamic in the case of a limited pool of converters 3. This could be dynamic in the case of a limited pool of converters
where the number available can change with connection where the number available can change with connection
establishment. Note it may be desirable to include regeneration establishment. Note that it may be desirable to include
capabilities here since OEO converters are also regenerators. regeneration capabilities here since OEO converters are also
regenerators.
4. Not necessarily needed in the case of distributed wavelength 4. This is not necessarily needed in the case of distributed
assignment via signaling. wavelength assignment via signaling.
While the full complement of the information from the previous table While the full complement of the information from the previous table
is needed in the Combined RWA and the separate Routing and WA is needed in the Combined RWA and the separate Routing and WA
architectures, in the case of Routing + distributed WA via signaling architectures, in the case of Routing + Distributed WA via Signaling,
only the following information is needed: only the following information is needed:
Information Static/Dynamic Node/Link Information Static/Dynamic Node/Link
------------------------------------------------------------------ ------------------------------------------------------------------
Connectivity matrix Static Node Connectivity matrix Static Node
Wavelength conversion capabilities Static(3) Node Wavelength conversion capabilities Static(3) Node
Information models and compact encodings for this information is Information models and compact encodings for this information are
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 Communication Protocol (PCEP) defines
necessary to support both sequential [RFC5440] and global concurrent the procedures necessary to support both sequential [RFC5440] and
path computations (PCE-GCO) [RFC5557]. The PCEP is well positioned to Global Concurrent Optimization (GCO) path computations [RFC5557].
support WSON-enabled RWA computation with some protocol enhancement. With some protocol enhancement, the PCEP is well positioned to
support WSON-enabled RWA computation.
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
requests are encountered: requests are encountered:
o Batch optimization, multiple optical paths requested at one time o Batch optimization, multiple optical paths requested at one time
(PCE-GCO). (PCE-GCO)
o Optical path(s) and backup optical path(s) requested at one time o Optical path(s) and backup optical path(s) requested at one time
(PCEP). (PCEP)
o Single optical path requested at a time (PCEP). o Single optical path requested at a time (PCEP)
PCEP and PCE-GCO can be readily enhanced to support all of the PCEP and PCE-GCO can be readily enhanced to support all of the
potential models of RWA computation. potential models of RWA computation.
Optical path constraints include: Optical path constraints include:
o Bidirectional Assignment of wavelengths. o Bidirectional assignment of wavelengths
o Possible simultaneous assignment of wavelength to primary and o Possible simultaneous assignment of wavelength to primary and
backup paths. backup paths
o Tuning range constraint on optical transmitter. o Tuning range constraint on optical transmitter
6.3.2. Electro-Optical Element Signal Compatibility 6.3.2. Electro-Optical Element Signal Compatibility
When requesting a path computation to PCE, the PCC should be able to When requesting a path computation to PCE, the PCC should be able to
indicate the following: indicate the following:
o The G-PID type of an LSP. o The G-PID type of an LSP
o The signal attributes at the transmitter (at the source): (i) o The signal attributes at the transmitter (at the source): (i)
modulation type; (ii) FEC type. modulation type, (ii) FEC type
o The signal attributes at the receiver (at the sink): (i) o The signal attributes at the receiver (at the sink): (i)
modulation type; (ii) FEC type. modulation type, (ii) FEC type
The PCE should be able to respond to the PCC with the following: The PCE should be able to respond to the PCC with the following:
o The conformity of the requested optical characteristics associated o The conformity of the requested optical characteristics associated
with the resulting LSP with the source, sink and NE along the LSP. with the resulting LSP with the source, sink, and NE along the LSP
o Additional LSP attributes modified along the path (e.g., o Additional LSP attributes modified along the path (e.g.,
modulation format change, etc.). modulation format change)
6.3.3. Discovery of RWA Capable PCEs 6.3.3. Discovery of RWA-Capable PCEs
The algorithms and network information needed for RWA are somewhat The algorithms and network information needed for RWA are somewhat
specialized and computationally intensive hence not all PCEs within a specialized and computationally intensive; hence, not all PCEs within
domain would necessarily need or want this capability. Hence, it a domain would necessarily need or want this capability. Therefore,
would be useful via the mechanisms being established for PCE it would be useful to indicate that a PCE has the ability to deal
discovery [RFC5088] to indicate that a PCE has the ability to deal with RWA via the mechanisms being established for PCE discovery
with RWA. Reference [RFC5088] indicates that a sub-TLV could be [RFC5088]. [RFC5088] indicates that a sub-TLV could be allocated for
allocated for this purpose. this purpose.
Recent progress on objective functions in PCE [RFC5541] would allow Recent progress on objective functions in PCE [RFC5541] would allow
the operators to flexibly request differing objective functions per operators to flexibly request differing objective functions per their
their need and applications. For instance, this would allow the need and applications. For instance, this would allow the operator
operator to choose an objective function that minimizes the total to choose an objective function that minimizes the total network cost
network cost associated with setting up a set of paths concurrently. associated with setting up a set of paths concurrently. This would
This would also allow operators to choose an objective function that also allow operators to choose an objective function that results in
results in a most evenly distributed link utilization. the most evenly distributed link utilization.
This implies that PCEP would easily accommodate wavelength selection This implies that PCEP would easily accommodate a wavelength
algorithm in its objective function to be able to optimize the path selection algorithm in its objective function to be able to optimize
computation from the perspective of wavelength assignment if chosen the path computation from the perspective of wavelength assignment if
by the operators. chosen by the operators.
7. Security Considerations 7. Security Considerations
This document has no requirement for a change to the security models This document does not require changes to the security models within
within GMPLS and associated protocols. That is the OSPF-TE, RSVP-TE, GMPLS and associated protocols. That is, the OSPF-TE, RSVP-TE, and
and PCEP security models could be operated unchanged. PCEP security models could be operated unchanged.
However satisfying the requirements for RWA using the existing However, satisfying the requirements for RWA using the existing
protocols may significantly affect the loading of those protocols. protocols may significantly affect the loading of those protocols.
This may make the operation of the network more vulnerable to denial This may make the operation of the network more vulnerable to denial-
of service attacks. Therefore additional care maybe required to of-service attacks. Therefore, additional care maybe required to
ensure that the protocols are secure in the WSON environment. ensure that the protocols are secure in the WSON environment.
Furthermore the additional information distributed in order to Furthermore, the additional information distributed in order to
address RWA represents a disclosure of network capabilities that an address RWA represents a disclosure of network capabilities that an
operator may wish to keep private. Consideration should be given to operator may wish to keep private. Consideration should be given to
securing this information. For a general discussion on MPLS and GMPLS securing this information. For a general discussion on MPLS- and
related security issues, see the MPLS/GMPLS security framework GMPLS-related security issues, see the MPLS/GMPLS security framework
[RFC5920]. [RFC5920].
8. IANA Considerations 8. Acknowledgments
This document makes no request for IANA actions.
9. Acknowledgments
The authors would like to thank Adrian Farrel for many helpful The authors would like to thank Adrian Farrel for many helpful
comments that greatly improved the contents of this draft. comments that greatly improved the contents of this document.
This document was prepared using 2-Word-v2.0.template.dot. 9. References
10. References 9.1. Normative References
10.1. Normative References [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, January 2003.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
(GMPLS) Signaling Functional Description", RFC 3471, Switching (GMPLS) Signaling Resource ReserVation
January 2003. Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol- Switching (GMPLS) Architecture", RFC 3945, October
Traffic Engineering (RSVP-TE) Extensions", RFC 3473, 2004.
January 2003.
[RFC3945] Mannie, E. "Generalized Multi-Protocol Label Switching [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
(GMPLS) Architecture", RFC 3945, October 2004. Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4202, October 2005.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support [RFC4328] Papadimitriou, D., Ed., "Generalized Multi-Protocol
of Generalized Multi-Protocol Label Switching (GMPLS)", RFC Label Switching (GMPLS) Signaling Extensions for G.709
4202, October 2005. Optical Transport Networks Control", RFC 4328, January
2006.
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Switching (GMPLS) Signaling Extensions for G.709 Optical Computation Element (PCE)-Based Architecture", RFC
Transport Networks Control", RFC 4328, January 2006. 4655, August 2006.
[RFC4655] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and
Element (PCE)-Based Architecture ", RFC 4655, August 2006. R. Zhang, "OSPF Protocol Extensions for Path
Computation Element (PCE) Discovery", RFC 5088, January
2008.
[RFC5088] J.L. Le Roux, J.P. Vasseur, Yuichi Ikejiri, and Raymond [RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL.,
Zhang, "OSPF protocol extensions for Path Computation Vigoureux, M., and D. Brungard, "Requirements for
Element (PCE) Discovery", January 2008. GMPLS-Based Multi-Region and Multi-Layer Networks
(MRN/MLN)", RFC 5212, July 2008.
[RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux, [RFC5557] Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path
M., and D. Brungard, "Requirements for GMPLS-Based Multi- Computation Element Communication Protocol (PCEP)
Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July Requirements and Protocol Extensions in Support of
2008. Global Concurrent Optimization", RFC 5557, July 2009.
[RFC5557] Y. Lee, J.L. Le Roux, D. King, and E. Oki, "Path [RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and
Computation Element Communication Protocol (PCECP) A. Ayyangarps, "Encoding of Attributes for MPLS LSP
Requirements and Protocol Extensions In Support of Global Establishment Using Resource Reservation Protocol
Concurrent Optimization", RFC 5557, July 2009. Traffic Engineering (RSVP-TE)", RFC 5420, February
2009.
[RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A. [RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Ayyangarps, "Encoding of Attributes for MPLS LSP Computation Element (PCE) Communication Protocol
Establishment Using Resource Reservation Protocol Traffic (PCEP)", RFC 5440, March 2009.
Engineering (RSVP-TE)", RFC 5420, February 2009.
[RFC5440] J.P. Vasseur and J.L. Le Roux (Editors), "Path Computation [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Element (PCE) Communication Protocol (PCEP)", RFC 5440, May Objective Functions in the Path Computation Element
2009. Communication Protocol (PCEP)", RFC 5541, June 2009.
[RFC5541] J.L. Le Roux, J.P. Vasseur, and Y. Lee, "Encoding of 9.2. Informative References
Objective Functions in Path Computation Element (PCE)
communication and discovery protocols", RFC 5541, July
2009.
10.2. Informative References [Gen-Encode] Bernstein, G., Lee, Y., Li, D., and W. Imajuku,
"General Network Element Constraint Encoding for GMPLS
Controlled Networks", Work in Progress, December 2010.
[Gen-Encode] G. Bernstein, Y. Lee, D. Li, and W. Imajuku, "General [G.652] ITU-T Recommendation G.652, "Characteristics of a
Network Element Constraint Encoding for GMPLS Controlled single-mode optical fibre and cable", November 2009.
Networks", draft-ietf-ccamp-general-constraint-encode, work
in progress.
[G.652] ITU-T Recommendation G.652, Characteristics of a single-mode [G.653] ITU-T Recommendation G.653, "Characteristics of a
optical fibre and cable, June 2005. dispersion-shifted single-mode optical fibre and
cable", July 2010.
[G.653] ITU-T Recommendation G.653, Characteristics of a dispersion- [G.654] ITU-T Recommendation G.654, "Characteristics of a cut-
shifted single-mode optical fibre and cable, December 2006. off shifted single-mode optical fibre and cable", July
2010.
[G.654] ITU-T Recommendation G.654, Characteristics of a cut-off [G.655] ITU-T Recommendation G.655, "Characteristics of a non-
shifted single-mode optical fibre and cable, December 2006. zero dispersion-shifted single-mode optical fibre and
cable", November 2009.
[G.655] ITU-T Recommendation G.655, Characteristics of a non-zero [G.656] ITU-T Recommendation G.656, "Characteristics of a fibre
dispersion-shifted single-mode optical fibre and cable, and cable with non-zero dispersion for wideband optical
March 2006. transport", July 2010.
[G.656] ITU-T Recommendation G.656, Characteristics of a fibre and [G.671] ITU-T Recommendation G.671, "Transmission
cable with non-zero dispersion for wideband optical characteristics of optical components and subsystems",
transport, December 2006. January 2009.
[G.671] ITU-T Recommendation G.671, Transmission characteristics of [G.694.1] ITU-T Recommendation G.694.1, "Spectral grids for WDM
optical components and subsystems, January 2005. applications: DWDM frequency grid", June 2002.
[G.694.1] ITU-T Recommendation G.694.1, "Spectral grids for WDM [G.694.2] ITU-T Recommendation G.694.2, "Spectral grids for WDM
applications: DWDM frequency grid", June, 2002. applications: CWDM wavelength grid", December 2003.
[G.872] ITU-T Recommendation G.872, Architecture of optical [G.698.1] ITU-T Recommendation G.698.1, "Multichannel DWDM
transport networks, November 2001. applications with single-channel optical interfaces",
November 2009.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network [G.698.2] ITU-T Recommendation G.698.2, "Amplified multichannel
Physical Layer Interfaces, March 2006. dense wavelength division multiplexing applications
with single channel optical interfaces ", November
2009.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM [G.707] ITU-T Recommendation G.707, "Network node interface for
applications: DWDM frequency grid, June 2002. the synchronous digital hierarchy (SDH)", January 2007.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM [G.709] ITU-T Recommendation G.709, "Interfaces for the Optical
applications: CWDM wavelength grid, December 2003. Transport Network (OTN)", December 2009.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and [G.872] ITU-T Recommendation G.872, "Architecture of optical
engineering considerations, February 2006. transport networks", November 2001.
[G.Sup43] ITU-T Series G Supplement 43, Transport of IEEE 10G base-R [G.959.1] ITU-T Recommendation G.959.1, "Optical transport
in optical transport networks (OTN), November 2006. network physical layer interfaces", November 2009.
[Imajuku] W. Imajuku, Y. Sone, I. Nishioka, S. Seno, "Routing [G.Sup39] ITU-T Series G Supplement 39, "Optical system design
Extensions to Support Network Elements with Switching and engineering considerations", December 2008.
Constraint", work in progress: draft-imajuku-ccamp-rtg-
switching-constraint.
[Otani] T. Otani, H. Guo, K. Miyazaki, D. Caviglia, "Generalized [Imajuku] Imajuku, W., Sone, Y., Nishioka, I., and S. Seno,
Labels of Lambda-Switching Capable Label Switching Routers "Routing Extensions to Support Network Elements with
(LSR)", work in progress: draft-ietf-ccamp-gmpls-g-694- Switching Constraint", Work in Progress, July 2007.
lambda-labels, work in progress.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS [RFC6205] Otani, T., Ed. and D. Li, Ed., "Generalized Labels of
Networks", RFC 5920, July 2010.[Otani]T. Otani, H. Guo, K. Lambda-Switch Capable (LSC) Label Switching Routers",
Miyazaki, D. Caviglia, "Generalized Labels of Lambda- RFC 6205, March 2011.
Switching Capable Label Switching Routers (LSR)", work in
progress: draft-otani-ccamp-gmpls-g-694-lambda-labels, work
in progress.
[WSON-Encode] G. Bernstein, Y. Lee, D. Li, and W. Imajuku, "Routing [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
and Wavelength Assignment Information Encoding for Networks", RFC 5920, July 2010.
Wavelength Switched Optical Networks", draft-ietf-ccamp-
rwa-wson-encode, work in progress.
[WSON-Imp] Y. Lee, G. Bernstein, D. Li, G. Martinelli, "A Framework [WSON-Encode] Bernstein, G., Lee, Y., Li, D., and W. Imajuku,
for the Control of Wavelength Switched Optical Networks "Routing and Wavelength Assignment Information Encoding
(WSON) with Impairments", draft-ietf-ccamp-wson- for Wavelength Switched Optical Networks", Work in
impairments, work in progress. Progress, March 2011.
[WSON-Info] Y. Lee, G. Bernstein, D. Li, W. Imajuku, "Routing and [WSON-Imp] Lee, Y., Bernstein, G., Li, D., and G. Martinelli, "A
Wavelength Assignment Information for Wavelength Switched Framework for the Control of Wavelength Switched
Optical Networks", draft-bernstein-ccamp-wson-info, work in Optical Networks (WSON) with Impairments", Work in
progress Progress, April 2011.
11. Contributors [WSON-Info] Bernstein, G., Lee, Y., Li, D., and W. Imajuku,
"Routing and Wavelength Assignment Information Model
for Wavelength Switched Optical Networks", Work in
Progress, July 2008.
Contributors
Snigdho Bardalai Snigdho Bardalai
Fujitsu Fujitsu
EMail: Snigdho.Bardalai@us.fujitsu.com
Email: Snigdho.Bardalai@us.fujitsu.com
Diego Caviglia Diego Caviglia
Ericsson Ericsson
Via A. Negrone 1/A 16153 Via A. Negrone 1/A 16153
Genoa Italy Genoa
Italy
Phone: +39 010 600 3736 Phone: +39 010 600 3736
Email: diego.caviglia@(marconi.com, ericsson.com) EMail: diego.caviglia@marconi.com, diego.caviglia@ericsson.com
Daniel King Daniel King
Old Dog Consulting Old Dog Consulting
UK UK
EMail: daniel@olddog.co.uk
Email: daniel@olddog.co.uk
Itaru Nishioka Itaru Nishioka
NEC Corp. NEC Corp.
1753 Simonumabe, Nakahara-ku 1753 Simonumabe, Nakahara-ku
Kawasaki, Kanagawa 211-8666 Kawasaki, Kanagawa 211-8666
Japan Japan
Phone: +81 44 396 3287 Phone: +81 44 396 3287
Email: i-nishioka@cb.jp.nec.com EMail: i-nishioka@cb.jp.nec.com
Lyndon Ong Lyndon Ong
Ciena Ciena
EMail: Lyong@Ciena.com
Email: Lyong@Ciena.com
Pierre Peloso Pierre Peloso
Alcatel-Lucent Alcatel-Lucent
Route de Villejust, 91620 Nozay Route de Villejust, 91620 Nozay
France France
EMail: pierre.peloso@alcatel-lucent.fr
Email: pierre.peloso@alcatel-lucent.fr
Jonathan Sadler Jonathan Sadler
Tellabs Tellabs
Email: Jonathan.Sadler@tellabs.com EMail: Jonathan.Sadler@tellabs.com
Dirk Schroetter Dirk Schroetter
Cisco Cisco
Email: dschroet@cisco.com EMail: dschroet@cisco.com
Jonas Martensson Jonas Martensson
Acreo Acreo
Electrum 236 Electrum 236
16440 Kista, Sweden 16440 Kista
Sweden
Email:Jonas.Martensson@acreo.se EMail: Jonas.Martensson@acreo.se
Author's Addresses
Greg M. Bernstein (ed.)
Grotto Networking
Fremont California, USA
Phone: (510) 573-2237 Authors' Addresses
Email: gregb@grotto-networking.com
Young Lee (ed.) Young Lee (editor)
Huawei Technologies Huawei Technologies
1700 Alma Drive, Suite 100 1700 Alma Drive, Suite 100
Plano, TX 75075 Plano, TX 75075
USA USA
Phone: (972) 509-5599 (x2240) Phone: (972) 509-5599 (x2240)
Email: ylee@huawei.com EMail: ylee@huawei.com
Greg M. Bernstein (editor)
Grotto Networking
Fremont, CA
USA
Phone: (510) 573-2237
EMail: gregb@grotto-networking.com
Wataru Imajuku Wataru Imajuku
NTT Network Innovation Labs NTT Network Innovation Labs
1-1 Hikari-no-oka, Yokosuka, Kanagawa 1-1 Hikari-no-oka, Yokosuka, Kanagawa
Japan Japan
Phone: +81-(46) 859-4315 Phone: +81-(46) 859-4315
Email: imajuku.wataru@lab.ntt.co.jp EMail: wataru.imajuku@ieee.org
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