draft-ietf-ccamp-wson-impairments-03.txt   draft-ietf-ccamp-wson-impairments-04.txt 
Network Working Group Y. Lee Network Working Group Y. Lee
Internet Draft Huawei Internet Draft Huawei
G. Bernstein G. Bernstein
Grotto Networking Grotto Networking
D. Li D. Li
Huawei Huawei
G. Martinelli G. Martinelli
Cisco Cisco
Intended status: Informational July 9, 2010 Intended status: Informational October 21, 2010
Expires: November 2010 Expires: April 2011
A Framework for the Control of Wavelength Switched Optical Networks A Framework for the Control of Wavelength Switched Optical Networks
(WSON) with Impairments (WSON) with Impairments
draft-ietf-ccamp-wson-impairments-03.txt draft-ietf-ccamp-wson-impairments-04.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
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to consider when using a GMPLS control plane to support path setup to consider when using a GMPLS control plane to support path setup
and maintenance. This document discusses how the definition and and maintenance. This document discusses how the definition and
characterization of optical fiber, devices, subsystems, and network characterization of optical fiber, devices, subsystems, and network
elements contained in various ITU-T recommendations can be combined elements contained in various ITU-T recommendations can be combined
with GMPLS control plane protocols and mechanisms to support with GMPLS control plane protocols and mechanisms to support
Impairment Aware Routing and Wavelength Assignment (IA-RWA) in Impairment Aware Routing and Wavelength Assignment (IA-RWA) in
optical networks. optical networks.
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................4
1.1. Revision History..........................................4 1.1. Revision History..........................................5
2. Motivation.....................................................4 2. Motivation.....................................................5
3. Impairment Aware Optical Path Computation......................5 3. Impairment Aware Optical Path Computation......................6
3.1. Optical Network Requirements and Constraints..............6 3.1. Optical Network Requirements and Constraints..............7
3.1.1. Impairment Aware Computation Scenarios ..............7 3.1.1. Impairment Aware Computation Scenarios...............7
3.1.2. Impairment Computation and Information Sharing 3.1.2. Impairment Computation and Information Sharing
Constraints.................................................8 Constraints.................................................8
3.1.3. Impairment Estimation Functional Blocks..............9 3.1.3. Impairment Estimation Process.......................10
3.2. IA-RWA Computation and Control Plane Architectures.......11 3.2. IA-RWA Computation and Control Plane Architectures.......11
3.2.1. Combined Routing, WA, and IV........................12 3.2.1. Combined Routing, WA, and IV........................13
3.2.2. Separate Routing, WA, or IV.........................12 3.2.2. Separate Routing, WA, or IV.........................13
3.2.3. Distributed WA and/or IV............................13 3.2.3. Distributed WA and/or IV............................13
3.3. Mapping Network Requirements to Architectures............14 3.3. Mapping Network Requirements to Architectures............14
4. Protocol Implications.........................................17 4. Protocol Implications.........................................17
4.1. Information Model for Impairments........................17 4.1. Information Model for Impairments........................17
4.1.1. Properties of an Impairment Information Model.......18 4.2. Routing..................................................18
4.2. Routing..................................................19 4.3. Signaling................................................18
4.3. Signaling................................................19 4.4. PCE......................................................19
4.4. PCE......................................................20 4.4.1. Combined IV & RWA...................................19
4.4.1. Combined IV & RWA...................................20 4.4.2. IV-Candidates + RWA.................................19
4.4.2. IV-Candidates + RWA.................................20 4.4.3. Approximate IA-RWA + Separate Detailed IV...........21
4.4.3. Approximate IA-RWA + Separate Detailed IV...........22 5. Security Considerations.......................................23
5. Security Considerations.......................................24 6. IANA Considerations...........................................23
6. IANA Considerations...........................................24 7. Acknowledgments...............................................23
7. Acknowledgments...............................................24 8. References....................................................31
8. References....................................................32 8.1. Normative References.....................................31
8.1. Normative References.....................................32 8.2. Informative References...................................33
8.2. Informative References...................................34
1. Introduction 1. Introduction
As an optical signal progresses along its path it may be altered by As an optical signal progresses along its path it may be altered
the various physical processes in the optical fibers and devices it by the various physical processes in the optical fibers and
encounters. When such alterations result in signal degradation, we devices it encounters. When such alterations result in signal
usually refer to these processes as "impairments". An overview of degradation, we usually refer to these processes as "impairments".
some critical optical impairments and their routing (path selection) An overview of some critical optical impairments and their routing
implications can be found in [RFC4054]. Roughly speaking, optical (path selection) implications can be found in [RFC4054]. Roughly
impairments accumulate along the path (without 3R regeneration) speaking, optical impairments accumulate along the path (without
traversed by the signal. They are influenced by the type of fiber 3R regeneration) traversed by the signal. They are influenced by
used, the types and placement of various optical devices and the the type of fiber used, the types and placement of various optical
presence of other optical signals that may share a fiber segment devices and the presence of other optical signals that may share a
along the signal's path. The degradation of the optical signals due fiber segment along the signal's path. The degradation of the
to impairments can result in unacceptable bit error rates or even a optical signals due to impairments can result in unacceptable bit
complete failure to demodulate and/or detect the received signal. error rates or even a complete failure to demodulate and/or detect
Therefore, path selection in any WSON requires consideration of the received signal. Therefore, path selection in any WSON
optical impairments so that the signal will be propagated from the requires consideration of optical impairments so that the signal
network ingress point to the egress point with an acceptable signal will be propagated from the network ingress point to the egress
quality. point with an acceptable signal quality.
Some optical subnetworks are designed such that over any path the Some optical subnetworks are designed such that over any path the
degradation to an optical signal due to impairments never exceeds degradation to an optical signal due to impairments never exceeds
prescribed bounds. This may be due to the limited geographic extent prescribed bounds. This may be due to the limited geographic
of the network, the network topology, and/or the quality of the extent of the network, the network topology, and/or the quality of
fiber and devices employed. In such networks the path selection the fiber and devices employed. In such networks the path
problem reduces to determining a continuous wavelength from source selection problem reduces to determining a continuous wavelength
to destination (the Routing and Wavelength Assignment problem). from source to destination (the Routing and Wavelength Assignment
These networks are discussed in [WSON-Frame]. In other optical problem). These networks are discussed in [WSON-Frame]. In other
networks, impairments are important and the path selection process optical networks, impairments are important and the path selection
must be impairment-aware. process must be impairment-aware.
Although [RFC4054] describes a number of key optical impairments, a Although [RFC4054] describes a number of key optical impairments,
more complete description of optical impairments and processes can be a more complete description of optical impairments and processes
found in the ITU-T Recommendations. Appendix A of this document can be found in the ITU-T Recommendations. Appendix A of this
provides an overview of the extensive ITU-T documentation in this document provides an overview of the extensive ITU-T documentation
area. in this area.
The benefits of operating networks using the Generalized The benefits of operating networks using the Generalized
Multiprotocol Label Switching (GMPLS) control plane is described in Multiprotocol Label Switching (GMPLS) control plane is described
[RFC3945]. The advantages of using a path computation element (PCE) in [RFC3945]. The advantages of using a path computation element
to perform complex path computations are discussed in [RFC4655]. (PCE) to perform complex path computations are discussed in
[RFC4655].
Based on the existing ITU-T standards covering optical Based on the existing ITU-T standards covering optical
characteristics (impairments) and the knowledge of how the impact of characteristics (impairments) and the knowledge of how the impact
impairments may be estimated along a path, this document provides a of impairments may be estimated along a path, this document
framework for impairment aware path computation and establishment provides a framework for impairment aware path computation and
utilizing GMPLS protocols and the PCE architecture. As in the establishment utilizing GMPLS protocols and the PCE architecture.
impairment free case covered in [WSON-Frame], a number of different As in the impairment free case covered in [WSON-Frame], a number
control plane architectural options are described. of different control plane architectural options are described.
1.1. Revision History 1.1. Revision History
Changes from 00 to 01: Changes from 00 to 01:
Added discussion of regenerators to section 3. Added discussion of regenerators to section 3.
Added to discussion of interface parameters in section 3.1.3. Added to discussion of interface parameters in section 3.1.3.
Added to discussion of IV Candidates function in section 3.2. Added to discussion of IV Candidates function in section 3.2.
Changes from 01 to 02: Changes from 01 to 02:
Correct and refine use of "black link" concept based on liaison with Correct and refine use of "black link" concept based on liaison
ITU-T and WG feedback. with ITU-T and WG feedback.
Changes from 02 to 03: Changes from 02 to 03:
Insert additional information on use and considerations for Insert additional information on use and considerations for
regenerators in section 3. regenerators in section 3.
2. Motivation 2. Motivation
There are deployment scenarios for WSON networks where not all There are deployment scenarios for WSON networks where not all
possible paths will yield suitable signal quality. There are possible paths will yield suitable signal quality. There are
multiple reasons behind this choice; here below is a non-exhaustive multiple reasons behind this choice; here below is a non-
list of examples: exhaustive list of examples:
o WSON is evolving using multi-degree optical cross connects in a o WSON is evolving using multi-degree optical cross connects in a
way that network topologies are changing from rings (and way that network topologies are changing from rings (and
interconnected rings) to a full mesh. Adding network equipment interconnected rings) to a full mesh. Adding network equipment
such as amplifiers or regenerators, to make all paths feasible, such as amplifiers or regenerators, to make all paths feasible,
leads to an over-provisioned network. Indeed, even with over leads to an over-provisioned network. Indeed, even with over
provisioning, the network could still have some infeasible paths. provisioning, the network could still have some infeasible
paths.
o Within a given network, the optical physical interface may change o Within a given network, the optical physical interface may
over the network life, e.g., the optical interfaces might be change over the network life, e.g., the optical interfaces might
upgraded to higher bit-rates. Such changes could result in paths be upgraded to higher bit-rates. Such changes could result in
being unsuitable for the optical signal. Although the same paths being unsuitable for the optical signal. Although the same
considerations may apply to other network equipment upgrades, the considerations may apply to other network equipment upgrades,
optical physical interfaces are a typical case because they are the optical physical interfaces are a typical case because they
typically provisioned at various stages of the network's life span are typically provisioned at various stages of the network's
as needed by traffic demands. life span as needed by traffic demands.
o There are cases where a network is upgraded by adding new optical o There are cases where a network is upgraded by adding new
cross connects to increase network flexibility. In such cases optical cross connects to increase network flexibility. In such
existing paths will have their feasibility modified while new cases existing paths will have their feasibility modified while
paths will need to have their feasibility assessed. new paths will need to have their feasibility assessed.
o With the recent bit rate increases from 10G to 40G and 100G over a o With the recent bit rate increases from 10G to 40G and 100G over
single wavelength, WSON networks will likely be operated with a a single wavelength, WSON networks will likely be operated with
mix of wavelengths at different bit rates. This operational a mix of wavelengths at different bit rates. This operational
scenario will impose some impairment considerations due to scenario will impose some impairment considerations due to
different physical behavior of different bit rates and associated different physical behavior of different bit rates and
modulation formats. associated modulation formats.
Not having an impairment aware control plane for such networks will Not having an impairment aware control plane for such networks
require a more complex network design phase that has to also take will require a more complex network design phase that, since the
into account evolving network status in term of equipments and beginning, takes into account evolving network status in term of
traffic. Moreover, network operations such as path establishment, equipments and traffic. This could result in over-engineering the
will require significant pre-design via non-control plane processes DWDM network with additional regenerators nodes and optical
resulting in significantly slower network provisioning. amplifiers. Optical impairment awareness allows for the concept of
photonic switching where possible and provides regeneration when
it is a must. In addition, network operations such as path
establishment, will require significant pre-design via non-control
plane processes resulting in significantly slower network
provisioning.
3. Impairment Aware Optical Path Computation 3. Impairment Aware Optical Path Computation
The basic criteria for path selection is whether one can successfully The basic criteria for path selection is whether one can
transmit the signal from a transmitter to a receiver within a successfully transmit the signal from a transmitter to a receiver
prescribed error tolerance, usually specified as a maximum within a prescribed error tolerance, usually specified as a
permissible bit error ratio (BER). This generally depends on the maximum permissible bit error ratio (BER). This generally depends
nature of the signal transmitted between the sender and receiver and on the nature of the signal transmitted between the sender and
the nature of the communications channel between the sender and receiver and the nature of the communications channel between the
receiver. The optical path utilized (along with the wavelength) sender and receiver. The optical path utilized (along with the
determines the communications channel. wavelength) determines the communications channel.
The optical impairments incurred by the signal along the fiber and at The optical impairments incurred by the signal along the fiber and
each optical network element along the path determine whether the BER at each optical network element along the path determine whether
performance or any other measure of signal quality can be met for a the BER performance or any other measure of signal quality can be
signal on a particular end-to-end path. met for a signal on a particular end-to-end path. This could
include parameters such as the Q factor to correlate both linear
and non-linear parameters into one value.
The impairment-aware path calculation needs also to take into account The impairment-aware path calculation needs also to take into
when regeneration happens along the path. [WSON-Frame] introduces the account when regeneration happens along the path. [WSON-Frame]
concept of Optical translucent network that contains transparent introduces the concept of Optical translucent network that
elements and electro-optical elements such as OEO regenerations. In contains transparent elements and electro-optical elements such as
such networks a generic lightpath can go through a certain number of OEO regenerations. In such networks a generic light path can go
regeneration points. through a certain number of regeneration points.
Regeneration points could happen for two reasons: Regeneration points could happen for two reasons:
(i) wavelength conversion to assist the RWA process to avoid (i) wavelength conversion to assist the RWA process to avoid
wavelength blocking. This is the impairment free case covered wavelength blocking. This is the impairment free case covered
by[WSON-Frame]. by[WSON-Frame].
(ii) the optical signal is too degraded. This is the case when the (ii) the optical signal is too degraded. This is the case when
RWA take into consideration impairment estimation covered by this the RWA take into consideration impairment estimation covered by
document. this document.
In the latter case a lightpath can be seen as a set of transparent In the latter case a light path can be seen as a set of transparent
segments. The optical impairments calculation needs to be reset at each segments. The optical impairments calculation needs to be reset at
regeneration point so each transparent segment will have its own each regeneration point so each transparent segment will have its own
impairment evaluation. impairment evaluation.
+---+ +----+ +----+ +---+ +----+ +---+ +---+ +----+ +----+ +---+ +----+ +---+
| I |----| N1 |---| N2 |-----| R |-----| N3 |----| E | | I |----| N1 |---| N2 |-----| R |-----| N3 |----| E |
+--+ +----+ +----+ +---+ +----+ +---+ +--+ +----+ +----+ +---+ +----+ +---+
|.--------------------------.|.------------------.| |.--------------------------.|.------------------.|
Segment 1 Segment 2 Segment 1 Segment 2
Figure 1 Lightpath as a set of transparent segments Figure 1 Light path as a set of transparent segments
For example, Figure 1 represents a lightpath from node I to node E with For example, Figure 1 represents a Light path from node I to node E
a regeneration point R in between. The lightpath is from an impairment with a regeneration point R in between. It is feasible from an
validation perspective if each segment (I, N1, N2, R) and (R, N3, E) is impairment validation perspective if both segments (I, N1, N2, R) and
feasible. (R, N3, E) are feasible.
3.1. Optical Network Requirements and Constraints 3.1. Optical Network Requirements and Constraints
This section examines the various optical network requirements and This section examines the various optical network requirements and
constraints that an impairment aware optical control plane may have constraints that an impairment aware optical control plane may
to operate under. These requirements and constraints motivate the IA- have to operate under. These requirements and constraints motivate
RWA architectural alternatives to be presented in the following the IA-RWA architectural alternatives to be presented in the
section. We can break the different optical networks contexts up following section. We can break the different optical networks
along two main criteria: (a) the accuracy required in the estimation contexts up along two main criteria: (a) the accuracy required in
of impairment effects, and (b) the constraints on the impairment the estimation of impairment effects, and (b) the constraints on
estimation computation and/or sharing of impairment information. the impairment estimation computation and/or sharing of impairment
information.
3.1.1. Impairment Aware Computation Scenarios 3.1.1. Impairment Aware Computation Scenarios
A. No concern for impairments or Wavelength Continuity Constraints A. No concern for impairments or Wavelength Continuity Constraints
This situation is covered by existing GMPLS with local wavelength This situation is covered by existing GMPLS with local wavelength
(label) assignment. (label) assignment.
B. No concern for impairments but Wavelength Continuity Constraints B. No concern for impairments but Wavelength Continuity
Constraints
This situation is applicable to networks designed such that every This situation is applicable to networks designed such that every
possible path is valid for the signal types permitted on the network. possible path is valid for the signal types permitted on the
In this case impairments are only taken into account during network network. In this case impairments are only taken into account
design and after that, for example during optical path computation, during network design and after that, for example during optical
they can be ignored. This is the case discussed in [WSON-Frame] where path computation, they can be ignored. This is the case discussed
impairments may be ignored by the control plane and only optical in [WSON-Frame] where impairments may be ignored by the control
parameters related to signal compatibility are considered.. plane and only optical parameters related to signal compatibility
are considered.
C. Approximated Impairment Estimation C. Approximated Impairment Estimation
This situation is applicable to networks in which impairment effects This situation is applicable to networks in which impairment
need to be considered but there is sufficient margin such that they effects need to be considered but there is sufficient margin such
can be estimated via approximation techniques such as link budgets that they can be estimated via approximation techniques such as
and dispersion[G.680],[G.sup39]. The viability of optical paths for a link budgets and dispersion[G.680],[G.sup39]. The viability of
particular class of signals can be estimated using well defined optical paths for a particular class of signals can be estimated
approximation techniques [G.680], [G.sup39]. Note that currently only using well defined approximation techniques [G.680], [G.sup39].
linear impairments are considered. Also, adding or removing an This is the generally known as linear case where only linear
optical signal on the path will not render any of the existing effects are taken into account. Adding or removing an optical
signals in the network as non-viable. For example, one form of non- signal on the path will not render any of the existing signals in
viability is the occurrence of transients in existing links of the network as non-viable. For example, one form of non-viability
sufficient magnitude to impact the BER of those existing signals. is the occurrence of transients in existing links of sufficient
magnitude to impact the BER of those existing signals.
Much work at ITU-T has gone into developing impairment models at this Much work at ITU-T has gone into developing impairment models at
and more detailed levels. Impairment characterization of network this and more detailed levels. Impairment characterization of
elements could then may be used to calculate which paths are network elements could then may be used to calculate which paths
conformant with a specified BER for a particular signal type. In such are conformant with a specified BER for a particular signal type.
a case, we can combine the impairment aware (IA) path computation In such a case, we can combine the impairment aware (IA) path
with the RWA process to permit more optimal IA-RWA computations. computation with the RWA process to permit more optimal IA-RWA
Note, the IA path computation may also take place in a separate computations. Note, the IA path computation may also take place in
entity, i.e., a PCE. a separate entity, i.e., a PCE.
D. Detailed Impairment Computation D. Detailed Impairment Computation
This situation is applicable to networks in which impairment effects
must be more accurately computed. For these networks, a full
computation and evaluation of the impact to any existing paths needs
to be performed prior to the addition of a new path. Currently no
impairment models are available from ITU-T and this scenario is
outside the scope of this document.
3.1.2. Impairment Computation and Information Sharing Constraints This situation is applicable to networks in which impairment
effects must be more accurately computed. For these networks, a
full computation and evaluation of the impact to any existing
paths needs to be performed prior to the addition of a new path.
Currently no impairment models are available from ITU-T and this
scenario is outside the scope of this document.
In GMPLS, information used for path computation is standardized for 3.1.2. Impairment Computation and Information Sharing Constraints
distribution amongst the elements participating in the control plane
and any appropriately equipped PCE can perform path computation. For
optical systems this may not be possible. This is typically due to
only portions of an optical system being subject to standardization.
In ITU-T recommendations [G.698.1] and [G.698.2] which specify single
channel interfaces to multi-channel DWDM systems only the single
channel interfaces (transmit and receive) are specified while the
multi-channel links are not standardized. These DWDM links are
referred to as "black links" since their details are not generally
available. Note however the overall impact of a black link at the
single channel interface points is limited by [G.698.1] and
[G.698.2].
Typically a vendor might use proprietary impairment models for DWDM In GMPLS, information used for path computation is standardized
spans and to estimate the validity of optical paths. For example, for distribution amongst the elements participating in the control
models of optical nonlinearities are not currently standardized. plane and any appropriately equipped PCE can perform path
Vendors may also choose not to publish impairment details for links computation. For optical systems this may not be possible. This is
or a set of network elements in order not to divulge their optical typically due to only portions of an optical system being subject
system designs. to standardization. In ITU-T recommendations [G.698.1] and
[G.698.2] which specify single channel interfaces to multi-channel
DWDM systems only the single channel interfaces (transmit and
receive) are specified while the multi-channel links are not
standardized. These DWDM links are referred to as "black links"
since their details are not generally available. Note however the
overall impact of a black link at the single channel interface
points is limited by [G.698.1] and [G.698.2].
In general, the impairment estimation/validation of an optical path Typically a vendor might use proprietary impairment models for
for optical networks with "black links" (path) could not be performed DWDM spans and to estimate the validity of optical paths. For
by a general purpose impairment aware (IA) computation entity since example, models of optical nonlinearities are not currently
it would not have access to or understand the "black link" impairment standardized. Vendors may also choose not to publish impairment
parameters. However, impairment estimation (optical path validation) details for links or a set of network elements in order not to
could be performed by a vendor specific impairment aware computation divulge their optical system designs.
entity. Such a vendor specific IA computation, could utilize
standardized impairment information imported from other network
elements in these proprietary computations.
In the following we will use the term "black links" to describe these In general, the impairment estimation/validation of an optical
computation and information sharing constraints in optical networks. path for optical networks with "black links" (path) could not be
From the control plane perspective we have the following options: performed by a general purpose impairment aware (IA) computation
entity since it would not have access to or understand the "black
link" impairment parameters. However, impairment estimation
(optical path validation) could be performed by a vendor specific
impairment aware computation entity. Such a vendor specific IA
computation, could utilize standardized impairment information
imported from other network elements in these proprietary
computations.
A. The authority in control of the "black links" can furnish a list In the following we will use the term "black links" to describe
of all viable paths between all viable node pairs to a these computation and information sharing constraints in optical
computational entity. This information would be particularly networks. From the control plane perspective we have the following
useful as an input to RWA optimization to be performed by another options:
computation entity. The difficulty here is for larger networks
such a list of paths along with any wavelength constraints could
get unmanageably large.
B. The authority in control of the "black links" could provide a PCE A. The authority in control of the "black links" can furnish a
like entity that would furnish a list of viable paths/wavelengths list of all viable paths between all viable node pairs to a
between two requested nodes. This is useful as an input to RWA computational entity. This information would be particularly
optimizations and can reduce the scaling issue previously useful as an input to RWA optimization to be performed by
mentioned. Such a PCE like entity would not need to perform a full another computation entity. The difficulty here is for larger
RWA computation, i.e., it would not need to take into account networks such a list of paths along with any wavelength
current wavelength availability on links. Such an approach may constraints could get unmanageably large.
require PCEP extensions for both the request and response
information.
C. The authority in control of the "black links" can provide a PCE B. The authority in control of the "black links" could provide a
that performs full IA-RWA services. The difficulty is this PCE like entity that would furnish a list of viable
requires the one authority to also become the sole source of all paths/wavelengths between two requested nodes. This is useful
RWA optimization algorithms and such. as an input to RWA optimizations and can reduce the scaling
issue previously mentioned. Such a PCE like entity would not
need to perform a full RWA computation, i.e., it would not need
to take into account current wavelength availability on links.
Such an approach may require PCEP extensions for both the
request and response information.
In all the above cases it would be the responsibility of the C. The authority in control of the "black links" can provide a PCE
authority in control of the "black links" to import the shared that performs full IA-RWA services. The difficulty is this
impairment information from the other NEs via the control plane or requires the one authority to also become the sole source of
other means as necessary. all RWA optimization algorithms and such.
3.1.3. Impairment Estimation Functional Blocks In all the above cases it would be the responsibility of the
authority in control of the "black links" to import the shared
impairment information from the other NEs via the control plane or
other means as necessary.
The Impairment Estimation process can be modeled by the following 3.1.3. Impairment Estimation Process
functional blocks. These blocks are independent of any Control Plane
architecture, that is, they can be implemented by the same or by
different control plane functional blocks.
+-----------------+ The Impairment Estimation Process can be modeled through the
+------------+ +-----------+ | +------------+ | following functional blocks. These blocks are independent from any
| | | | | | | | Control Plane architecture, that is, they can be implemented by
| Optical | | Optical | | | Optical | | the same or by different control plane functions as detailed in
| Interface |------->| Path |--->| | Channel | | following sections.
| (Transmit/ | | | | | Estimation | |
| Receive) | | | | | | |
+------------+ +-----------+ | +------------+ |
| || |
| || |
| Estimation |
| || |
| \/ |
| +------------+ |
| | BER / | |
| | Q Factor | |
| +------------+ |
+-----------------+
Starting from functional block on the left the Optical Interface +-----------------+
represents where the optical signal is transmitted or received and +------------+ +-----------+ | +------------+ |
defines the properties at the end points path. For WSON even the case | | | | | | | |
with no IA has to consider a minimum set of interface | Optical | | Optical | | | Optical | |
characteristics. As an example, the document [G.698.1] reports the | Interface |------->| Impairment|--->| | Channel | |
full set of those parameters for certain interfaces. In this function | (Transmit/ | | Path | | | Estimation | |
only a significant subset of those parameters would be considered. In | Receive) | | | | | | |
addition transmit and receive interface might consider a different +------------+ +-----------+ | +------------+ |
subset of properties. In term of GMPLS, [WSON-Comp] provides a | || |
minimum set of parameters to characterize the interface. During an | || |
impairment estimation process these parameters may be sufficient or | Estimation |
not depending on the accepted level of approximation (Section 3.1.1). | || |
| \/ |
| +------------+ |
| | BER / | |
| | Q Factor | |
| +------------+ |
+-----------------+
The block "Optical Path" represents all kinds of impairments Starting from functional block on the left the Optical Interface
affecting a wavelength as it traverses the networks through links and represents where the optical signal is transmitted or received and
nodes. In the case where the control plane has no IA this block will defines the properties at the end points path. Even the no-
not be present. Otherwise, this function must be implemented in some impairment case like scenario B in section 3.1.1 needs to consider
way via the control plane. Options for this will be given in the next a minimum set of interface characteristics. In such case only few
section on control plane architectural alternatives. parameters to assess the signal compatibility will be taken into
account (see [WSON-Frame]). For the impairment-awareness case
signal compatibility these parameters may be sufficient or not
depending on the accepted level of approximation (scenarios C and
D). This functional block highlights the need to consider a set of
interface parameters during an Impairment Validation Process.
The last block implements the decision function for path feasibility. The block "Optical Impairment Path" represents all kinds of
Depending on the IA level of approximation this function can be more impairments affecting a wavelength as it traverses the networks
or less complex. For example in case of no IA only the signal class through links and nodes. In the case where the control plane has
compatibility will be verified. no IV this block will not be present. Otherwise, this function
must be implemented in some way via the control plane. Options for
this will be given in the next section architectural alternatives.
This block implementation (e.g. through routing, signaling or PCE)
may influence the way the control plane distributes impairment
information within the network.
3.2. IA-RWA Computation and Control Plane Architectures The last block implements the decision function for path
feasibility. Depending on the IA level of approximation this
function can be more or less complex. For example in case of no IA
only the signal class compatibility will be verified. In addition
to feasible/not-feasible result, it may be worth for decision
functions to consider the case in which paths can be likely-to-be-
feasible within some degree of confidence. The optical impairments
are usually not fixed values as they may vary within ranges of
values according to the approach taken in the physical modeling
(worst-case, statistical or based on typical values). For example,
the utilization of the worst-case value for each parameter within
impairment validation process may lead to marking some paths as
not-feasible while they are very likely to be feasible in reality.
From a control plane point of view optical impairments are additional 3.2. IA-RWA Computation and Control Plane Architectures
constraints to the impairment-free RWA process described in [WSON-
Frame]. In impairment aware routing and wavelength assignment (IA-
RWA), there are conceptually three general classes of processes to be
considered: Routing (R), Wavelength Assignment (WA), and Impairment
Validation (estimation) (IV).
Impairment validation may come in many forms, and maybe invoked at From a control plane point of view optical impairments are
different levels of detail in the IA-RWA process. From a process additional constraints to the impairment-free RWA process
point of view we will consider the following three forms of described in [WSON-Frame]. In impairment aware routing and
impairment validation: wavelength assignment (IA-RWA), there are conceptually three
general classes of processes to be considered: Routing (R),
Wavelength Assignment (WA), and Impairment Validation (estimation)
(IV).
o IV-Candidates Impairment validation may come in many forms, and maybe invoked at
different levels of detail in the IA-RWA process. From a process
point of view we will consider the following three forms of
impairment validation:
In this case an Impairment Validation (IV) process furnishes a set of o IV-Candidates
paths between two nodes along with any wavelength restrictions such
that the paths are valid with respect to optical impairments. These
paths and wavelengths may not be actually available in the network
due to its current usage state. This set of paths would be returned
in response to a request for a set of at most K valid paths between
two specified nodes. Note that such a process never directly
discloses optical impairment information. Note that that this case
includes any paths between source and destination that may have been
"pre-validated".
In this case the control plane simply makes use of candidate paths In this case an Impairment Validation (IV) process furnishes a set
but does not know any optical impairment information. Another option of paths between two nodes along with any wavelength restrictions
is when the path validity is assessed within the control plane. The such that the paths are valid with respect to optical impairments.
following cases highlight this situation. These paths and wavelengths may not be actually available in the
network due to its current usage state. This set of paths would be
returned in response to a request for a set of at most K valid
paths between two specified nodes. Note that such a process never
directly discloses optical impairment information. Note that that
this case includes any paths between source and destination that
may have been "pre-validated".
o IV-Approximate Verification In this case the control plane simply makes use of candidate paths
but does not know any optical impairment information. Another
option is when the path validity is assessed within the control
plane. The following cases highlight this situation.
Here approximation methods are used to estimate the impairments o IV-Approximate Verification
experienced by a signal. Impairments are typically approximated by
linear and/or statistical characteristics of individual or combined
components and fibers along the signal path.
o IV-Detailed Verification Here approximation methods are used to estimate the impairments
experienced by a signal. Impairments are typically approximated by
linear and/or statistical characteristics of individual or
combined components and fibers along the signal path.
In this case an IV process is given a particular path and wavelength o IV-Detailed Verification
through an optical network and is asked to verify whether the overall
quality objectives for the signal over this path can be met. Note
that such a process never directly discloses optical impairment
information.
o IV-Centralized In this case an IV process is given a particular path and
wavelength through an optical network and is asked to verify
whether the overall quality objectives for the signal over this
path can be met. Note that such a process never directly discloses
optical impairment information.
In this case impairments to a path are computed at a single entity. The next two cases refer to the way an impairment validation
The information concerning impairments may still be gathered from computation can be performed.
network elements however.
o IV-Distributed o IV-Centralized
In the distributed IV process, impairment approximate degradation In this case impairments to a path are computed at a single
measures such as OSNR, dispersion, DGD, etc. are accumulated along entity. The information concerning impairments may still be
the path via a signaling like protocol. When the accumulated measures gathered from network elements however. Depending how information
reach the destination node a decision on the impairment validity of are gathered this may put requirements on routing protocols. This
the path can be made. Note that such a process would entail revealing will be detailed in following sections.
an individual network element's impairment information.
The Control Plane however must not preclude the possibility to o IV-Distributed
operate any or all the above cases concurrently in the same network.
For example there could be cases where a certain number of paths are
already pre-validates (IV-Candidates) so the control plane may setup
one of those path without requesting any impairment validation
procedure. On the same network however the control plane may compute
a path outside the set of IV-Candidates for which an impairment
evaluation can be necessary.
The following subsections present three major classes of IA-RWA path In the distributed IV process, impairment approximate degradation
computation architectures and their respective advantages and measures such as OSNR, dispersion, DGD, etc. are accumulated along
disadvantages. the path via a signaling like protocol. Each node on the path may
already perform some part of the impairment computation (i.e.
distributed). When the accumulated measures reach the destination
node a decision on the impairment validity of the path can be
made. Note that such a process would entail revealing an
individual network element's impairment information but it does
not generally require spreading optical parameters at network
level.
3.2.1. Combined Routing, WA, and IV The Control Plane must not preclude the possibility to operate one
or all the above cases concurrently in the same network. For
example there could be cases where a certain number of paths are
already pre-validates (IV-Candidates) so the control plane may
setup one of those path without requesting any impairment
validation procedure. On the same network however the control
plane may compute a path outside the set of IV-Candidates for
which an impairment evaluation can be necessary.
From the point of view of optimality, the "best" IA-RWA solutions can The following subsections present three major classes of IA-RWA
be achieved if the path computation entity (PCE) can path computation architectures and their respective advantages and
conceptually/algorithmically combine the processes of routing, disadvantages.
wavelength assignment and impairment validation.
Such a combination can take place if the PCE is given: (a) the 3.2.1. Combined Routing, WA, and IV
impairment-free WSON network information as discussed in [WSON-Frame]
and (b) impairment information to validate potential paths.
3.2.2. Separate Routing, WA, or IV From the point of view of optimality, the "best" IA-RWA solutions
can be achieved if the path computation entity (PCE) can
conceptually/algorithmically combine the processes of routing,
wavelength assignment and impairment validation.
Separating the processes of routing, WA and/or IV can reduce the need Such a combination can take place if the PCE is given: (a) the
for sharing of different types of information used in path impairment-free WSON network information as discussed in [WSON-
computation. This was discussed for routing separate from WA in Frame] and (b) impairment information to validate potential paths.
[WSON-Frame]. In addition, as will be discussed in the section on 3.2.2. Separate Routing, WA, or IV
network contexts some impairment information may not be shared and
this may lead to the need to separate IV from RWA. In addition, as
also discussed in the section on network contexts, if IV needs to be
done at a high level of precision it may be advantageous to offload
this computation to a specialized server.
The following conceptual architectures belong in this general Separating the processes of routing, WA and/or IV can reduce the
category: need for sharing of different types of information used in path
computation. This was discussed for routing separate from WA in
[WSON-Frame]. In addition, as will be discussed in the section on
network contexts some impairment information may not be shared and
this may lead to the need to separate IV from RWA. In addition,
as also discussed in the section on network contexts, if IV needs
to be done at a high level of precision it may be advantageous to
offload this computation to a specialized server.
o R+WA+IV -- separate routing, wavelength assignment, and impairment The following conceptual architectures belong in this general
validation. category:
o R + (WA & IV) -- routing separate from a combined wavelength o R+WA+IV -- separate routing, wavelength assignment, and
assignment and impairment validation process. Note that impairment impairment validation.
validation is typically wavelength dependent hence combining WA
with IV can lead to efficiencies.
o (RWA)+IV - combined routing and wavelength assignment with a o R + (WA & IV) -- routing separate from a combined wavelength
separate impairment validation process. assignment and impairment validation process. Note that
impairment validation is typically wavelength dependent hence
combining WA with IV can lead to efficiencies.
Note that the IV process may come before or after the RWA processes. o (RWA)+IV - combined routing and wavelength assignment with a
If RWA comes first then IV is just rendering a yes/no decision on the separate impairment validation process.
selected path and wavelength. If IV comes first it would need to
furnish a list of possible (valid with respect to impairments) routes
and wavelengths to the RWA processes.
3.2.3. Distributed WA and/or IV Note that the IV process may come before or after the RWA
processes. If RWA comes first then IV is just rendering a yes/no
decision on the selected path and wavelength. If IV comes first it
would need to furnish a list of possible (valid with respect to
impairments) routes and wavelengths to the RWA processes.
In the non-impairment RWA situation [WSON-Frame] it was shown that a 3.2.3. Distributed WA and/or IV
distributed wavelength assignment (WA) process carried out via
signaling can eliminate the need to distribute wavelength
availability information via an IGP. A similar approach can allow for
the distributed computation of impairment effects and avoid the need
to distribute impairment characteristics of network elements and
links via route protocols or by other means. An example of such an
approach is given in [Martinelli] and utilizes enhancements to RSVP
signaling to carry accumulated impairment related information.
A distributed impairment validation for a prescribed network path In the non-impairment RWA situation [WSON-Frame] it was shown that
requires that the effects of impairments can be calculated by a distributed wavelength assignment (WA) process carried out via
approximate models with cumulative quality measures such as those in signaling can eliminate the need to distribute wavelength
[G.680]. availability information via an IGP. A similar approach can allow
for the distributed computation of impairment effects and avoid
the need to distribute impairment characteristics of network
elements and links via route protocols or by other means. An
example of such an approach is given in [Martinelli] and utilizes
enhancements to RSVP signaling to carry accumulated impairment
related information. So the following conceptual options belong to
this category:
For such a system to be interoperable the various impairment measures o RWA+D(IV) - Combined routing and wavelength assignment and
to be accumulated would need to be agreed upon. Section 9 of [G.680] distributed impairment validation.
can be useful in deriving such cumulative measures but doesn't
explicitly state how a distributed computation would take place. For
example in the computation of the optical signal to noise ratio along
a path (see equation 9-3 of [G.680]) one could accumulate the linear
sum terms and convert to the optical signal to noise ratio (OSNR) in
(dBs) at the destination or one could convert in and out of the OSNR
in (dBs) at each intermediate point along the path.
If distributed WA is being done at the same time as distributed IV o R + D(WA & IV) -- routing separate from a distributed wavelength
then we may need to accumulate impairment related information for all assignment and impairment validation process.
wavelengths that could be used. This is somewhat winnowed down as
potential wavelengths are discovered to be in use, but could be a
significant burden for lightly loaded high channel count networks.
3.3. Mapping Network Requirements to Architectures A distributed impairment validation for a prescribed network path
requires that the effects of impairments can be calculated by
approximate models with cumulative quality measures such as those
in [G.680]. For such a system to be interoperable the various
impairment measures to be accumulated would need to be agreed
according to [G.680].
In Figure 2 we show process flows for three main architectural If distributed WA is being done at the same time as distributed IV
alternatives to IA-RWA when approximate impairment validation then we may need to accumulate impairment related information for
suffices. In Figure 3 we show process flows for two main all wavelengths that could be used. This is somewhat winnowed down
architectural alternatives when detailed impairment verification is as potential wavelengths are discovered to be in use, but could be
required. a significant burden for lightly loaded high channel count
networks.
+-----------------------------------+ 3.3. Mapping Network Requirements to Architectures
| +--+ +-------+ +--+ |
| |IV| |Routing| |WA| |
| +--+ +-------+ +--+ |
| |
| Combined Processes |
+-----------------------------------+
(a)
+--------------+ +----------------------+ In Figure 2 we show process flows for three main architectural
| +----------+ | | +-------+ +--+ | alternatives to IA-RWA when approximate impairment validation
| | IV | | | |Routing| |WA| | suffices. In Figure 3 we show process flows for two main
| |candidates| |----->| +-------+ +--+ | architectural alternatives when detailed impairment verification
| +----------+ | | Combined Processes | is required.
+--------------+ +----------------------+
(b)
+-----------+ +----------------------+ +-----------------------------------+
| +-------+ | | +--+ +--+ | | +--+ +-------+ +--+ |
| |Routing| |------->| |WA| |IV| | | |IV| |Routing| |WA| |
| +-------+ | | +--+ +--+ | | +--+ +-------+ +--+ |
+-----------+ | Distributed Processes| | |
+----------------------+ | Combined Processes |
(c) +-----------------------------------+
Figure 2 Process flows for the three main approximate impairment (a)
+--------------+ +----------------------+
| +----------+ | | +-------+ +--+ |
| | IV | | | |Routing| |WA| |
| |candidates| |----->| +-------+ +--+ |
| +----------+ | | Combined Processes |
+--------------+ +----------------------+
(b)
+-----------+ +----------------------+
| +-------+ | | +--+ +--+ |
| |Routing| |------->| |WA| |IV| |
| +-------+ | | +--+ +--+ |
+-----------+ | Distributed Processes|
+----------------------+
(c)
Figure 2 Process flows for the three main approximate impairment
architectural alternatives. architectural alternatives.
The advantages, requirements and suitability of these options are as The advantages, requirements and suitability of these options are
follows: as follows:
o Combined IV & RWA process o Combined IV & RWA process
This alternative combines RWA and IV within a single computation This alternative combines RWA and IV within a single computation
entity enabling highest potential optimality and efficiency in IA- entity enabling highest potential optimality and efficiency in IA-
RWA. This alternative requires that the computational entity knows RWA. This alternative requires that the computational entity knows
impairment information as well as non-impairment RWA information. impairment information as well as non-impairment RWA information.
This alternative can be used with "black links", but would then need This alternative can be used with "black links", but would then
to be provided by the authority controlling the "black links". need to be provided by the authority controlling the "black
links".
o IV-Candidates + RWA process o IV-Candidates + RWA process
This alternative allows separation of impairment information into two This alternative allows separation of impairment information into
computational entities while still maintaining a high degree of two computational entities while still maintaining a high degree
potential optimality and efficiency in IA-RWA. The candidates IV of potential optimality and efficiency in IA-RWA. The candidates
process needs to know impairment information from all optical network IV process needs to know impairment information from all optical
elements, while the RWA process needs to know non-impairment RWA network elements, while the RWA process needs to know non-
information from the network elements. This alternative can be used impairment RWA information from the network elements. This
with "black links", but the authority in control of the "black links" alternative can be used with "black links", but the authority in
would need to provide the functionality of the IV-candidates process. control of the "black links" would need to provide the
Note that this is still very useful since the algorithmic areas of IV functionality of the IV-candidates process. Note that this is
and RWA are very different and prone to specialization. still very useful since the algorithmic areas of IV and RWA are
very different and prone to specialization.
o Routing + Distributed WA and IV o Routing + Distributed WA and IV
In this alternative a signaling protocol is extended and leveraged in In this alternative a signaling protocol is extended and leveraged
the wavelength assignment and impairment validation processes. in the wavelength assignment and impairment validation processes.
Although this doesn't enable as high a potential degree of optimality Although this doesn't enable as high a potential degree of
of optimality as (a) or (b), it does not require distribution of optimality of optimality as (a) or (b), it does not require
either link wavelength usage or link/node impairment information. distribution of either link wavelength usage or link/node
Note that this is most likely not suitable for "black links". impairment information. Note that this is most likely not suitable
for "black links".
+-----------------------------------+ +------------+ +-----------------------------------+ +------------+
| +-----------+ +-------+ +--+ | | +--------+ | | +-----------+ +-------+ +--+ | | +--------+ |
| | IV | |Routing| |WA| | | | IV | | | | IV | |Routing| |WA| | | | IV | |
| |approximate| +-------+ +--+ |---->| |Detailed| | | |approximate| +-------+ +--+ |---->| |Detailed| |
| +-----------+ | | +--------+ | | +-----------+ | | +--------+ |
| Combined Processes | | | | Combined Processes | | |
+-----------------------------------+ +------------+ +-----------------------------------+ +------------+
(a) (a)
+--------------+ +----------------------+ +------------+ +--------------+ +----------------------+ +------------+
| +----------+ | | +-------+ +--+ | | +--------+ | | +----------+ | | +-------+ +--+ | | +--------+ |
| | IV | | | |Routing| |WA| |---->| | IV | | | | IV | | | |Routing| |WA| |---->| | IV | |
| |candidates| |----->| +-------+ +--+ | | |Detailed| | | |candidates| |----->| +-------+ +--+ | | |Detailed| |
| +----------+ | | Combined Processes | | +--------+ | | +----------+ | | Combined Processes | | +--------+ |
+--------------+ +----------------------+ | | +--------------+ +----------------------+ | |
(b) +------------+ (b) +------------+
Figure 3 Process flows for the two main detailed impairment Figure 3 Process flows for the two main detailed impairment
validation architectural options. validation architectural options.
The advantages, requirements and suitability of these detailed The advantages, requirements and suitability of these detailed
validation options are as follows: validation options are as follows:
o Combined approximate IV & RWA + Detailed-IV o Combined approximate IV & RWA + Detailed-IV
This alternative combines RWA and approximate IV within a single This alternative combines RWA and approximate IV within a single
computation entity enabling highest potential optimality and computation entity enabling highest potential optimality and
efficiency in IA-RWA; then has a separate entity performing detailed efficiency in IA-RWA; then has a separate entity performing
impairment validation. In the case of "black links" the authority detailed impairment validation. In the case of "black links" the
controlling the "black links" would need to provide all authority controlling the "black links" would need to provide all
functionality. functionality.
o Candidates-IV + RWA + Detailed-IV o Candidates-IV + RWA + Detailed-IV
This alternative allows separation of approximate impairment This alternative allows separation of approximate impairment
information into a computational entity while still maintaining a information into a computational entity while still maintaining a
high degree of potential optimality and efficiency in IA-RWA; then a high degree of potential optimality and efficiency in IA-RWA; then
separate computation entity performs detailed impairment validation. a separate computation entity performs detailed impairment
Note that detailed impairment estimation is not standardized. validation. Note that detailed impairment estimation is not
standardized.
4. Protocol Implications 4. Protocol Implications
The previous IA-RWA architectural alternatives and process flows make The previous IA-RWA architectural alternatives and process flows
differing demands on a GMPLS/PCE based control plane. In this section make differing demands on a GMPLS/PCE based control plane. In this
we discuss the use of (a) an impairment information model, (b) PCE as section we discuss the use of (a) an impairment information model,
computational entity assuming the various process roles and (b) PCE as computational entity assuming the various process roles
consequences for PCEP, (c)any needed extensions to signaling, and (d) and consequences for PCEP, (c)any needed extensions to signaling,
extensions to routing. The impacts to the control plane for IA-RWA and (d) extensions to routing. The impacts to the control plane
are summarized in Figure 4. for IA-RWA are summarized in Figure 4.
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| IA-RWA Option |PCE |Sig |Info Model| Routing| | IA-RWA Option |PCE |Sig |Info Model| Routing|
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| Combined |Yes | No | Yes | Yes | | Combined |Yes | No | Yes | Yes |
| IV & RWA | | | | | | IV & RWA | | | | |
+-------------------+----+----+----------+--------+- +-------------------+----+----+----------+--------+-
| IV-Candidates |Yes | No | Yes | Yes | | IV-Candidates |Yes | No | Yes | Yes |
| + RWA | | | | | | + RWA | | | | |
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| Routing + |No | Yes| Yes | No | | Routing + |No | Yes| Yes | No |
|Distributed IV, RWA| | | | | |Distributed IV, RWA| | | | |
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
| Detailed IV |Yes | No | Yes | Yes | | Detailed IV |Yes | No | Yes | Yes |
+-------------------+----+----+----------+--------+ +-------------------+----+----+----------+--------+
Figure 4 IA-RWA architectural options and control plane impacts. Figure 4 IA-RWA architectural options and control plane impacts.
4.1. Information Model for Impairments 4.1. Information Model for Impairments
As previously discussed all IA-RWA scenarios to a greater or lesser As previously discussed all IA-RWA scenarios to a greater or
extent rely on a common impairment information model. A number of lesser extent rely on a common impairment information model. A
ITU-T recommendations cover detailed as well as approximate number of ITU-T recommendations cover detailed as well as
impairment characteristics of fibers and a variety of devices and approximate impairment characteristics of fibers and a variety of
subsystems. A well integrated impairment model for optical network devices and subsystems. A well integrated impairment model for
elements is given in [G.680] and is used to form the basis for an optical network elements is given in [G.680] and is used to form
optical impairment model in a companion document [Imp-Info]. the basis for an optical impairment model in a companion document
[Imp-Info].
It should be noted that the current version of [G.680] is limited to It should be noted that the current version of [G.680] is limited
the networks composed of a single WDM line system vendor combined to the networks composed of a single WDM line system vendor
with OADMs and/or PXCs from potentially multiple other vendors, this combined with OADMs and/or PXCs from potentially multiple other
is known as situation 1 and is shown in Figure 1-1 of [G.680]. It is vendors, this is known as situation 1 and is shown in Figure 1-1
planed in the future that [G.680] will include networks incorporating of [G.680]. It is planed in the future that [G.680] will include
line systems from multiple vendors as well as OADMs and/or PXCs from networks incorporating line systems from multiple vendors as well
potentially multiple other vendors, this is known as situation 2 and as OADMs and/or PXCs from potentially multiple other vendors, this
is shown in Figure 1-2 of [G.680]. is known as situation 2 and is shown in Figure 1-2 of [G.680].
The case of distributed impairment validation actually requires a bit The case of distributed impairment validation actually requires a
more than an impairment information model. In particular, it needs a bit more than an impairment information model. In particular, it
common impairment "computation" model. In the distributed IV case one needs a common impairment "computation" model. In the distributed
needs to standardize the accumulated impairment measures that will be IV case one needs to standardize the accumulated impairment
conveyed and updated at each node. Section 9 of [G.680] provides measures that will be conveyed and updated at each node. Section 9
guidance in this area with specific formulas given for OSNR, residual of [G.680] provides guidance in this area with specific formulas
dispersion, polarization mode dispersion/polarization dependent loss, given for OSNR, residual dispersion, polarization mode
effects of channel uniformity, etc... However, specifics of what dispersion/polarization dependent loss, effects of channel
intermediate results are kept and in what form would need to be uniformity, etc... However, specifics of what intermediate results
standardized. are kept and in what form would need to be standardized.
4.1.1. Properties of an Impairment Information Model 4.2. Routing
In term of information model there are a set of property that needs Different approaches to path/wavelength impairment validation
to be defined for each optical parameters that need to be in some way gives rise to different demands placed on GMPLS routing protocols.
considered within an impairment aware control plane. In the case where approximate impairment information is used to
validate paths GMPLS routing may be used to distribute the
impairment characteristics of the network elements and links based
on the impairment information model previously discussed.
The properties will help to determine how the control plane can deal Depending on the computational alternative the routing protocol
with it depending also on the above control plane architectural may need to advertise information necessary to impairment
options. In some case properties value will help to indentify the validation process. This can potentially cause scalability issues
level of approximation supported by the IV process. due to the high amount of data that need to be advertised. Such
issue can be addressed separating data that need to be advertised
rarely and data that need to be advertised more frequently or
adopting other form of awareness solutions described in previous
sections (e.g. centralized and/or external IV entity).
o Time Dependency. This will identify how the impairment may vary In term of approximated scenario (see Section 3.1.1. ) the model
along the time. There could be cases where there's no time defined by [G.680] will apply and routing protocol will need to
dependency, while in other cases there is need of an impairment gather information required for such computation.
re-evaluation after a certain time. In some cases a level of
approximation will consider an impairment that has time dependency
as constant.
o Wavelength Dependency. This property will identify if an In the case of distributed-IV no new demands would be placed on
impairment value can be considered as constant over all the the routing protocol.
wavelength spectrum of interest or if it has different values.
Also in this case a detailed impairment evaluation might lead to
consider the exact value while an approximation IV might take a
constant value for all wavelengths.
o Linearity. As impairments are representation of physical effects 4.3. Signaling
there are some that have a linear behavior while other are non
linear. Linear impairments are in general easy to consider while a
non linear will require the knowledge of the full path to be
evaluated. An approximation level could only consider linear
effects or approximate non-linear impairments in linear ones.
o Multi-Channel. There are cases where an impairments take different The largest impacts on signaling occur in the cases where
values depending on the aside wavelengths already in place. In distributed impairment validation is performed. In this we need to
this case a dependency among different LSP is introduced. An accumulate impairment information as previously discussed. In
approximation level can neglect or not the effects on neighbor addition, since the characteristics of the signal itself, such as
LSPs. modulation type, can play a major role in the tolerance of
impairments, this type of information will need to be implicitly
or explicitly signaled so that an impairment validation decision
can be made at the destination node.
o Value range. An impairment that has to be considered by a It remains for further study if it may be beneficial to include
computational element will needs a representation in bits. So additional information to a connection request such as desired
depending on the impairments different types can be considered egress signal quality (defined in some appropriate sense) in non-
form integer to real numbers as well as a fixed set of values. distributed IV scenarios.
This information is important in term of protocol definition and
level of approximation introduced by the number representation.
4.2. Routing 4.4. PCE
Different approaches to path/wavelength impairment validation gives In section 3.3. we gave a number of computation architectural
rise to different demands placed on GMPLS routing protocols. In the alternatives that could be used to meet the various requirements
case where approximate impairment information is used to validate and constraints of section 3.1. Here we look at how these
paths GMPLS routing may be used to distribute the impairment alternatives could be implemented via either a single PCE or a set
characteristics of the network elements and links based on the of two or more cooperating PCEs, and the impacts on the PCEP
impairment information model previously discussed. In the case of protocol.
distributed-IV no new demands would be placed on the routing
protocol.
4.3. Signaling 4.4.1. Combined IV & RWA
The largest impacts on signaling occur in the cases where distributed In this situation, shown in Figure 2(a), a single PCE performs all
impairment validation is performed. In this we need to accumulate the computations needed for IA-RWA.
impairment information as previously discussed. In addition, since
the characteristics of the signal itself, such as modulation type,
can play a major role in the tolerance of impairments, this type of
information will need to be implicitly or explicitly signaled so that
an impairment validation decision can be made at the destination
node.
It remains for further study if it may be beneficial to include o TE Database Requirements
additional information to a connection request such as desired egress
signal quality (defined in some appropriate sense) in non-distributed
IV scenarios.
4.4. PCE WSON Topology and switching capabilities, WSON WDM link
wavelength utilization, and WSON impairment information
In section 3.3. we gave a number of computation architectural o PCC to PCE Request Information
alternatives that could be used to meet the various requirements and
constraints of section 3.1. Here we look at how these alternatives
could be implemented via either a single PCE or a set of two or more
cooperating PCEs, and the impacts on the PCEP protocol.
4.4.1. Combined IV & RWA Signal characteristics/type, required quality, source node,
destination node
In this situation, shown in Figure 2(a), a single PCE performs all o PCE to PCC Reply Information
the computations needed for IA-RWA.
o TE Database Requirements If the computations completed successfully then the PCE returns
the path and its assigned wavelength. If the computations could
not complete successfully it would be potentially useful to know
the reason why. At a very crude level we'd like to know if this
was due to lack of wavelength availability or impairment
considerations or a bit of both. The information to be conveyed
is for further study.
WSON Topology and switching capabilities, WSON WDM link wavelength 4.4.2. IV-Candidates + RWA
utilization, and WSON impairment information
o PCC to PCE Request Information In this situation, shown in Figure 2(b), we have two separate
processes involved in the IA-RWA computation. This requires at
least two cooperating PCEs: one for the Candidates-IV process and
another for the RWA process. In addition, the overall process
needs to be coordinated. This could be done with yet another PCE
or we can add this functionality to one of previously defined
PCEs. We choose this later option and require the RWA PCE to also
act as the overall process coordinator. The roles,
responsibilities and information requirements for these two PCEs
are given below.
Signal characteristics/type, required quality, source node, RWA and Coordinator PCE (RWA-Coord-PCE):
destination node
o PCE to PCC Reply Information Responsible for interacting with PCC and for utilizing Candidates-
PCE as needed during RWA computations. In particular it needs to
know to use the Candidates-PCE to obtain potential set of routes
and wavelengths.
If the computations completed successfully then the PCE returns o TE Database Requirements
the path and its assigned wavelength. If the computations could
not complete successfully it would be potentially useful to know
the reason why. At a very crude level we'd like to know if this
was due to lack of wavelength availability or impairment
considerations or a bit of both. The information to be conveyed is
for further study.
4.4.2. IV-Candidates + RWA WSON Topology and switching capabilities and WSON WDM link
wavelength utilization (no impairment information).
In this situation, shown in Figure 2(b), we have two separate o PCC to RWA-PCE request: same as in the combined case.
processes involved in the IA-RWA computation. This requires at least
two cooperating PCEs: one for the Candidates-IV process and another
for the RWA process. In addition, the overall process needs to be
coordinated. This could be done with yet another PCE or we can add
this functionality to one of previously defined PCEs. We choose this
later option and require the RWA PCE to also act as the overall
process coordinator. The roles, responsibilities and information
requirements for these two PCEs are given below.
RWA and Coordinator PCE (RWA-Coord-PCE): o RWA-PCE to PCC reply: same as in the combined case.
Responsible for interacting with PCC and for utilizing Candidates-PCE o RWA-PCE to IV-Candidates-PCE request
as needed during RWA computations. In particular it needs to know to
use the Candidates-PCE to obtain potential set of routes and
wavelengths.
o TE Database Requirements The RWA-PCE asks for a set of at most K routes along with
acceptable wavelengths between nodes specified in the original
PCC request.
WSON Topology and switching capabilities and WSON WDM link o IV-Candidates-PCE reply to RWA-PCE
wavelength utilization (no impairment information).
o PCC to RWA-PCE request: same as in the combined case. The Candidates-PCE returns a set of at most K routes along with
acceptable wavelengths between nodes specified in the RWA-PCE
request.
o RWA-PCE to PCC reply: same as in the combined case. IV-Candidates-PCE:
o RWA-PCE to IV-Candidates-PCE request The IV-Candidates-PCE is responsible for impairment aware path
computation. It needs not take into account current link
wavelength utilization, but this is not prohibited. The
Candidates-PCE is only required to interact with the RWA-PCE as
indicated above and not the PCC.
The RWA-PCE asks for a set of at most K routes along with acceptable o TE Database Requirements
wavelengths between nodes specified in the original PCC request.
o IV-Candidates-PCE reply to RWA-PCE WSON Topology and switching capabilities and WSON impairment
information (no information link wavelength utilization
required).
The Candidates-PCE returns a set of at most K routes along with In Figure 5 we show a sequence diagram for the interactions
acceptable wavelengths between nodes specified in the RWA-PCE between the PCC, RWA-PCE and IV-Candidates-PCE.
request.
IV-Candidates-PCE: +---+ +-------------+ +-----------------
+
|PCC| |RWA-Coord-PCE| |IV-Candidates-
PCE|
+-+-+ +------+------+ +---------+-------
+
...___ (a) | |
| ````---...____ | |
| ```-->| |
| | |
| |--..___ (b) |
| | ```---...___ |
| | ```---->|
| | |
| | |
| | (c) ___...|
| | ___....---'''' |
| |<--'''' |
| | |
| | |
| (d) ___...| |
| ___....---''' | |
|<--''' | |
| | |
| | |
The IV-Candidates-PCE is responsible for impairment aware path Figure 5 Sequence diagram for the interactions between PCC, RWA-
computation. It needs not take into account current link Coordinating-PCE and the IV-Candidates-PCE.
wavelength utilization, but this is not prohibited. The
Candidates-PCE is only required to interact with the RWA-PCE as
indicated above and not the PCC.
o TE Database Requirements In step (a) the PCC requests a path meeting specified quality
constraints between two nodes (A and Z) for a given signal
represented either by a specific type or a general class with
associated parameters. In step (b) the RWA-Coordinating-PCE
requests up to K candidate paths between nodes A and Z and
associated acceptable wavelengths. In step (c) The IV-Candidates-
PCE returns this list to the RWA-Coordinating PCE which then uses
this set of paths and wavelengths as input (e.g. a constraint) to
its RWA computation. In step (d) the RWA-Coordinating-PCE returns
the overall IA-RWA computation results to the PCC.
WSON Topology and switching capabilities and WSON impairment 4.4.3. Approximate IA-RWA + Separate Detailed IV
information (no information link wavelength utilization required).
In Figure 5 we show a sequence diagram for the interactions between In Figure 3 we showed two cases where a separate detailed
the PCC, RWA-PCE and IV-Candidates-PCE. impairment validation process could be utilized. We can place the
detailed validation process into a separate PCE. Assuming that a
different PCE assumes a coordinating role and interacts with the
PCC we can keep the interactions with this separate IV-Detailed-
PCE very simple.
+---+ +-------------+ +-----------------+ IV-Detailed-PCE:
|PCC| |RWA-Coord-PCE| |IV-Candidates-PCE|
+-+-+ +------+------+ +---------+-------+
...___ (a) | |
| ````---...____ | |
| ```-->| |
| | |
| |--..___ (b) |
| | ```---...___ |
| | ```---->|
| | |
| | |
| | (c) ___...|
| | ___....---'''' |
| |<--'''' |
| | |
| | |
| (d) ___...| |
| ___....---''' | |
|<--''' | |
| | |
| | |
Figure 5 Sequence diagram for the interactions between PCC, RWA- o TE Database Requirements
Coordinating-PCE and the IV-Candidates-PCE.
In step (a) the PCC requests a path meeting specified quality The IV-Detailed-PCE will need optical impairment information, WSON
constraints between two nodes (A and Z) for a given signal topology, and possibly WDM link wavelength usage information.
represented either by a specific type or a general class with This document puts no restrictions on the type of information
associated parameters. In step (b) the RWA-Coordinating-PCE requests that may be used in these computations.
up to K candidate paths between nodes A and Z and associated
acceptable wavelengths. In step (c) The IV-Candidates-PCE returns
this list to the RWA-Coordinating PCE which then uses this set of
paths and wavelengths as input (e.g. a constraint) to its RWA
computation. In step (d) the RWA-Coordinating-PCE returns the overall
IA-RWA computation results to the PCC.
4.4.3. Approximate IA-RWA + Separate Detailed IV o Coordinating-PCE to IV-Detailed-PCE request
In Figure 3 we showed two cases where a separate detailed impairment The coordinating-PCE will furnish signal characteristics, quality
validation process could be utilized. We can place the detailed requirements, path and wavelength to the IV-Detailed-PCE.
validation process into a separate PCE. Assuming that a different PCE
assumes a coordinating role and interacts with the PCC we can keep
the interactions with this separate IV-Detailed-PCE very simple.
IV-Detailed-PCE: o IV-Detailed-PCE to Coordinating-PCE reply
o TE Database Requirements The reply is essential an yes/no decision as to whether the
requirements could actually be met. In the case where the
impairment validation fails it would be helpful to convey
information related to cause or quantify the failure, e.g., so a
judgment can be made whether to try a different signal or adjust
signal parameters.
The IV-Detailed-PCE will need optical impairment information, WSON In Figure 6 we show a sequence diagram for the interactions for
topology, and possibly WDM link wavelength usage information. This the process shown in Figure 3(b). This involves interactions
document puts no restrictions on the type of information that may between the PCC, RWA-PCE (acting as coordinator), IV-Candidates-
be used in these computations. PCE and the IV-Detailed-PCE.
o Coordinating-PCE to IV-Detailed-PCE request In step (a) the PCC requests a path meeting specified quality
constraints between two nodes (A and Z) for a given signal
represented either by a specific type or a general class with
associated parameters. In step (b) the RWA-Coordinating-PCE
requests up to K candidate paths between nodes A and Z and
associated acceptable wavelengths. In step (c) The IV-Candidates-
PCE returns this list to the RWA-Coordinating PCE which then uses
this set of paths and wavelengths as input (e.g. a constraint) to
its RWA computation. In step (d) the RWA-Coordinating-PCE request
a detailed verification of the path and wavelength that it has
computed. In step (e) the IV-Detailed-PCE returns the results of
the validation to the RWA-Coordinating-PCE. Finally in step (f)IA-
RWA-Coordinating PCE returns the final results (either a path and
wavelength or cause for the failure to compute a path and
wavelength) to the PCC.
The coordinating-PCE will furnish signal characteristics, quality +----------+ +--------------+ +------------
requirements, path and wavelength to the IV-Detailed-PCE. +
+---+ |RWA-Coord | |IV-Candidates | |IV-Detailed
|
|PCC| | PCE | | PCE | | PCE
|
+-+-+ +----+-----+ +------+-------+ +-----+------
+
|.._ (a) | | |
| ``--.__ | | |
| `-->| | |
| | (b) | |
| |--....____ | |
| | ````---.>| |
| | | |
| | (c) __..-| |
| | __..---'' | |
| |<--'' | |
| | |
| |...._____ (d) |
| | `````-----....._____ |
| | `````----->|
| | |
| | (e) _____.....+
| | _____.....-----''''' |
| |<----''''' |
| (f) __.| |
| __.--'' |
|<-'' |
| |
Figure 6 Sequence diagram for the interactions between PCC, RWA-
Coordinating-PCE, IV-Candidates-PCE and IV-Detailed-PCE.
o IV-Detailed-PCE to Coordinating-PCE reply 5. Security Considerations
The reply is essential an yes/no decision as to whether the This document discusses a number of control plane architectures
requirements could actually be met. In the case where the that incorporate knowledge of impairments in optical networks. If
impairment validation fails it would be helpful to convey such architecture is put into use within a network it will by its
information related to cause or quantify the failure, e.g., so a nature contain details of the physical characteristics of an
judgment can be made whether to try a different signal or adjust optical network. Such information would need to be protected from
signal parameters. intentional or unintentional disclosure.
In Figure 6 we show a sequence diagram for the interactions for the 6. IANA Considerations
process shown in Figure 3(b). This involves interactions between the
PCC, RWA-PCE (acting as coordinator), IV-Candidates-PCE and the IV-
Detailed-PCE.
In step (a) the PCC requests a path meeting specified quality This draft does not currently require any consideration from IANA.
constraints between two nodes (A and Z) for a given signal
represented either by a specific type or a general class with
associated parameters. In step (b) the RWA-Coordinating-PCE requests
up to K candidate paths between nodes A and Z and associated
acceptable wavelengths. In step (c) The IV-Candidates-PCE returns
this list to the RWA-Coordinating PCE which then uses this set of
paths and wavelengths as input (e.g. a constraint) to its RWA
computation. In step (d) the RWA-Coordinating-PCE request a detailed
verification of the path and wavelength that it has computed. In step
(e) the IV-Detailed-PCE returns the results of the validation to the
RWA-Coordinating-PCE. Finally in step (f)IA-RWA-Coordinating PCE
returns the final results (either a path and wavelength or cause for
the failure to compute a path and wavelength) to the PCC.
+----------+ +--------------+ +------------+ 7. Acknowledgments
+---+ |RWA-Coord | |IV-Candidates | |IV-Detailed |
|PCC| | PCE | | PCE | | PCE |
+-+-+ +----+-----+ +------+-------+ +-----+------+
|.._ (a) | | |
| ``--.__ | | |
| `-->| | |
| | (b) | |
| |--....____ | |
| | ````---.>| |
| | | |
| | (c) __..-| |
| | __..---'' | |
| |<--'' | |
| | |
| |...._____ (d) |
| | `````-----....._____ |
| | `````----->|
| | |
| | (e) _____.....+
| | _____.....-----''''' |
| |<----''''' |
| (f) __.| |
| __.--'' |
|<-'' |
| |
Figure 6 Sequence diagram for the interactions between PCC, RWA-
Coordinating-PCE, IV-Candidates-PCE and IV-Detailed-PCE.
5. Security Considerations This document was prepared using 2-Word-v2.0.template.dot.
This document discusses a number of control plane architectures that APPENDIX A: Overview of Optical Layer ITU-T Recommendations
incorporate knowledge of impairments in optical networks. If such
architecture is put into use within a network it will by its nature
contain details of the physical characteristics of an optical
network. Such information would need to be protected from intentional
or unintentional disclosure.
6. IANA Considerations For optical fiber, devices, subsystems and network elements the
ITU-T has a variety of recommendations that include definitions,
characterization parameters and test methods. In the following we
take a bottom up survey to emphasize the breadth and depth of the
existing recommendations. We focus on digital communications over
single mode optical fiber.
This draft does not currently require any consideration from IANA. A.1. Fiber and Cables
7. Acknowledgments Fibers and cables form a key component of what from the control
plane perspective could be termed an optical link. Due to the wide
range of uses of optical networks a fairly wide range of fiber
types are used in practice. The ITU-T has three main
recommendations covering the definition of attributes and test
methods for single mode fiber:
This document was prepared using 2-Word-v2.0.template.dot. o Definitions and test methods for linear, deterministic
attributes of single-mode fibre and cable [G.650.1]
APPENDIX A: Overview of Optical Layer ITU-T Recommendations o Definitions and test methods for statistical and non-linear
related attributes of single-mode fibre and cable [G.650.2]
For optical fiber, devices, subsystems and network elements the ITU-T o Test methods for installed single-mode fibre cable sections
has a variety of recommendations that include definitions, [G.650.3]
characterization parameters and test methods. In the following we
take a bottom up survey to emphasize the breadth and depth of the
existing recommendations. We focus on digital communications over
single mode optical fiber.
A.1. Fiber and Cables General Definitions[G.650.1]: Mechanical Characteristics
(numerous), Mode field characteristics(mode field, mode field
diameter, mode field centre, mode field concentricity error, mode
field non-circularity), Glass geometry characteristics, Chromatic
dispersion definitions (chromatic dispersion, group delay,
chromatic dispersion coefficient, chromatic dispersion slope,
zero-dispersion wavelength, zero-dispersion slope), cut-off
wavelength, attenuation. Definition of equations and fitting
coefficients for chromatic dispersion (Annex A). [G.650.2]
polarization mode dispersion (PMD) - phenomenon of PMD, principal
states of polarization (PSP), differential group delay (DGD), PMD
value, PMD coefficient, random mode coupling, negligible mode
coupling, mathematical definitions in terms of Stokes or Jones
vectors. Nonlinear attributes: Effective area, correction factor
k, non-linear coefficient (refractive index dependent on
intensity), Stimulated Billouin scattering.
Fibers and cables form a key component of what from the control plane Tests defined [G.650.1]: Mode field diameter, cladding diameter,
perspective could be termed an optical link. Due to the wide range of core concentricity error, cut-off wavelength, attenuation,
uses of optical networks a fairly wide range of fiber types are used chromatic dispersion. [G.650.2]: test methods for polarization
in practice. The ITU-T has three main recommendations covering the mode dispersion. [G.650.3] Test methods for characteristics of
definition of attributes and test methods for single mode fiber: fibre cable sections following installation: attenuation, splice
loss, splice location, fibre uniformity and length of cable
sections (these are OTDR based), PMD, Chromatic dispersion.
o Definitions and test methods for linear, deterministic attributes With these definitions a variety of single mode fiber types are
of single-mode fibre and cable [G.650.1] defined as shown in the table below:
o Definitions and test methods for statistical and non-linear ITU-T Standard | Common Name
related attributes of single-mode fibre and cable [G.650.2] ------------------------------------------------------------
o Test methods for installed single-mode fibre cable sections G.652 [G.652] | Standard SMF |
[G.650.3] G.653 [G.653] | Dispersion shifted SMF |
G.654 [G.654] | Cut-off shifted SMF |
G.655 [G.655] | Non-zero dispersion shifted SMF |
G.656 [G.656] | Wideband non-zero dispersion shifted SMF |
------------------------------------------------------------
General Definitions[G.650.1]: Mechanical Characteristics (numerous), A.2. Devices
Mode field characteristics(mode field, mode field diameter, mode
field centre, mode field concentricity error, mode field non-
circularity), Glass geometry characteristics, Chromatic dispersion
definitions (chromatic dispersion, group delay, chromatic dispersion
coefficient, chromatic dispersion slope, zero-dispersion wavelength,
zero-dispersion slope), cut-off wavelength, attenuation. Definition
of equations and fitting coefficients for chromatic dispersion (Annex
A). [G.650.2] polarization mode dispersion (PMD) - phenomenon of PMD,
principal states of polarization (PSP), differential group delay
(DGD), PMD value, PMD coefficient, random mode coupling, negligible
mode coupling, mathematical definitions in terms of Stokes or Jones
vectors. Nonlinear attributes: Effective area, correction factor k,
non-linear coefficient (refractive index dependent on intensity),
Stimulated Billouin scattering.
Tests defined [G.650.1]: Mode field diameter, cladding diameter, core A.2.1. Optical Amplifiers
concentricity error, cut-off wavelength, attenuation, chromatic
dispersion. [G.650.2]: test methods for polarization mode dispersion.
[G.650.3] Test methods for characteristics of fibre cable sections
following installation: attenuation, splice loss, splice location,
fibre uniformity and length of cable sections (these are OTDR based),
PMD, Chromatic dispersion.
With these definitions a variety of single mode fiber types are Optical amplifiers greatly extend the transmission distance of
defined as shown in the table below: optical signals in both single channel and multi channel (WDM)
subsystems. The ITU-T has the following recommendations:
ITU-T Standard | Common Name o Definition and test methods for the relevant generic parameters
------------------------------------------------------------ of optical amplifier devices and subsystems [G.661]
G.652 [G.652] | Standard SMF |
G.653 [G.653] | Dispersion shifted SMF |
G.654 [G.654] | Cut-off shifted SMF |
G.655 [G.655] | Non-zero dispersion shifted SMF |
G.656 [G.656] | Wideband non-zero dispersion shifted SMF |
------------------------------------------------------------
A.2. Devices o Generic characteristics of optical amplifier devices and
subsystems [G.662]
A.2.1. Optical Amplifiers o Application related aspects of optical amplifier devices and
subsystems [G.663]
Optical amplifiers greatly extend the transmission distance of o Generic characteristics of Raman amplifiers and Raman amplified
optical signals in both single channel and multi channel (WDM) subsystems [G.665]
subsystems. The ITU-T has the following recommendations:
o Definition and test methods for the relevant generic parameters of Reference [G.661] starts with general classifications of optical
optical amplifier devices and subsystems [G.661] amplifiers based on technology and usage, and include a near
exhaustive list of over 60 definitions for optical amplifier
device attributes and parameters. In references [G.662] and
[G.665] we have characterization of specific devices, e.g.,
semiconductor optical amplifier, used in a particular setting,
e.g., line amplifier. For example reference[G.662] gives the
following minimum list of relevant parameters for the
specification of an optical amplifier device used as line
amplifier in a multichannel application:
o Generic characteristics of optical amplifier devices and a) Channel allocation.
subsystems [G.662]
o Application related aspects of optical amplifier devices and b) Total input power range.
subsystems [G.663]
o Generic characteristics of Raman amplifiers and Raman amplified c) Channel input power range.
subsystems [G.665]
Reference [G.661] starts with general classifications of optical d) Channel output power range.
amplifiers based on technology and usage, and include a near
exhaustive list of over 60 definitions for optical amplifier device
attributes and parameters. In references [G.662] and [G.665] we have
characterization of specific devices, e.g., semiconductor optical
amplifier, used in a particular setting, e.g., line amplifier. For
example reference[G.662] gives the following minimum list of relevant
parameters for the specification of an optical amplifier device used
as line amplifier in a multichannel application:
a) Channel allocation. e) Channel signal-spontaneous noise figure.
b) Total input power range. f) Input reflectance.
c) Channel input power range. g) Output reflectance.
d) Channel output power range. h) Maximum reflectance tolerable at input.
e) Channel signal-spontaneous noise figure. i) Maximum reflectance tolerable at output.
f) Input reflectance. j) Maximum total output power.
g) Output reflectance. k) Channel addition/removal (steady-state) gain response.
h) Maximum reflectance tolerable at input. l) Channel addition/removal (transient) gain response.
i) Maximum reflectance tolerable at output. m) Channel gain.
j) Maximum total output power. n) Multichannel gain variation (inter-channel gain difference).
k) Channel addition/removal (steady-state) gain response. o) Multichannel gain-change difference (inter-channel gain-change
difference).
l) Channel addition/removal (transient) gain response. p) Multichannel gain tilt (inter-channel gain-change ratio).
m) Channel gain. q) Polarization Mode Dispersion (PMD).
n) Multichannel gain variation (inter-channel gain difference). A.2.2. Dispersion Compensation
o) Multichannel gain-change difference (inter-channel gain-change In optical systems two forms of dispersion are commonly
difference). encountered [RFC4054] chromatic dispersion and polarization mode
dispersion (PMD). There are a number of techniques and devices
used for compensating for these effects. The following ITU-T
recommendations characterize such devices:
p) Multichannel gain tilt (inter-channel gain-change ratio). o Characteristics of PMD compensators and PMD compensating
receivers [G.666]
q) Polarization Mode Dispersion (PMD). o Characteristics of Adaptive Chromatic Dispersion Compensators
[G.667]
A.2.2. Dispersion Compensation The above furnish definitions as well as parameters and
characteristics. For example in [G.667] adaptive chromatic
dispersion compensators are classified as being receiver,
transmitter or line based, while in [G.666] PMD compensators are
only defined for line and receiver configurations. Parameters that
are common to both PMD and chromatic dispersion compensators
include: line fiber type, maximum and minimum input power, maximum
and minimum bit rate, and modulation type. In addition there are a
great many parameters that apply to each type of device and
configuration.
In optical systems two forms of dispersion are commonly encountered A.2.3. Optical Transmitters
[RFC4054] chromatic dispersion and polarization mode dispersion
(PMD). There are a number of techniques and devices used for
compensating for these effects. The following ITU-T recommendations
characterize such devices:
o Characteristics of PMD compensators and PMD compensating receivers The definitions of the characteristics of optical transmitters can
[G.666] be found in references [G.957], [G.691], [G.692] and [G.959.1]. In
addition references [G.957], [G.691], and [G.959.1] define
specific parameter values or parameter ranges for these
characteristics for interfaces for use in particular situations.
o Characteristics of Adaptive Chromatic Dispersion Compensators We generally have the following types of parameters
[G.667]
The above furnish definitions as well as parameters and Wavelength related: Central frequency, Channel spacing, Central
characteristics. For example in [G.667] adaptive chromatic dispersion frequency deviation[G.692].
compensators are classified as being receiver, transmitter or line
based, while in [G.666] PMD compensators are only defined for line
and receiver configurations. Parameters that are common to both PMD
and chromatic dispersion compensators include: line fiber type,
maximum and minimum input power, maximum and minimum bit rate, and
modulation type. In addition there are a great many parameters that
apply to each type of device and configuration.
A.2.3. Optical Transmitters Spectral characteristics of the transmitter: Nominal source type
(LED, MLM lasers, SLM lasers) [G.957], Maximum spectral width,
Chirp parameter, Side mode suppression ratio, Maximum spectral
power density [G.691].
The definitions of the characteristics of optical transmitters can be Power related: Mean launched power, Extinction ration, Eye pattern
found in references [G.957], [G.691], [G.692] and [G.959.1]. In mask [G.691], Maximum and minimum mean channel output power
addition references [G.957], [G.691], and [G.959.1] define specific [G.959.1].
parameter values or parameter ranges for these characteristics for
interfaces for use in particular situations.
We generally have the following types of parameters A.2.4. Optical Receivers
Wavelength related: Central frequency, Channel spacing, Central References [G.959.1], [G.691], [G.692] and [G.957], define optical
frequency deviation[G.692]. receiver characteristics and [G.959.1], [G.691] and [G.957]give
specific values of these parameters for particular interface types
and network contexts.
Spectral characteristics of the transmitter: Nominal source type The receiver parameters include:
(LED, MLM lasers, SLM lasers) [G.957], Maximum spectral width, Chirp
parameter, Side mode suppression ratio, Maximum spectral power
density [G.691].
Power related: Mean launched power, Extinction ration, Eye pattern Receiver sensitivity: minimum value of average received power to
mask [G.691], Maximum and minimum mean channel output power achieve a 1x10-10 BER [G.957] or 1x10-12 BER [G.691]. See [G.957]
[G.959.1]. and [G.691] for assumptions on signal condition.
A.2.4. Optical Receivers Receiver overload: Receiver overload is the maximum acceptable
value of the received average power for a 1x10.10 BER [G.957] or a
1x10-12 BER [G.691].
References [G.959.1], [G.691], [G.692] and [G.957], define optical Receiver reflectance: "Reflections from the receiver back to the
receiver characteristics and [G.959.1], [G.691] and [G.957]give cable plant are specified by the maximum permissible reflectance
specific values of these parameters for particular interface types of the receiver measured at reference point R."
and network contexts.
The receiver parameters include: Optical path power penalty: "The receiver is required to tolerate
an optical path penalty not exceeding X dB to account for total
degradations due to reflections, intersymbol interference, mode
partition noise, and laser chirp."
Receiver sensitivity: minimum value of average received power to When dealing with multi-channel systems or systems with optical
achieve a 1x10-10 BER [G.957] or 1x10-12 BER [G.691]. See [G.957] and amplifiers we may also need:
[G.691] for assumptions on signal condition.
Receiver overload: Receiver overload is the maximum acceptable value Optical signal-to-noise ratio: "The minimum value of optical SNR
of the received average power for a 1x10.10 BER [G.957] or a 1x10-12 required to obtain a 1x10-12 BER."[G.692]
BER [G.691].
Receiver reflectance: "Reflections from the receiver back to the Receiver wavelength range: "The receiver wavelength range is
cable plant are specified by the maximum permissible reflectance of defined as the acceptable range of wavelengths at point Rn. This
the receiver measured at reference point R." range must be wide enough to cover the entire range of central
frequencies over the OA passband." [G.692]
Optical path power penalty: "The receiver is required to tolerate an Minimum equivalent sensitivity: "This is the minimum sensitivity
optical path penalty not exceeding X dB to account for total that would be required of a receiver placed at MPI-RM in
degradations due to reflections, intersymbol interference, mode multichannel applications to achieve the specified maximum BER of
partition noise, and laser chirp." the application code if all except one of the channels were to be
removed (with an ideal loss-less filter) at point MPI-RM."
[G.959.1]
When dealing with multi-channel systems or systems with optical A.3. Components and Subsystems
amplifiers we may also need:
Optical signal-to-noise ratio: "The minimum value of optical SNR Reference [G.671] "Transmission characteristics of optical
required to obtain a 1x10-12 BER."[G.692] components and subsystems" covers the following components:
Receiver wavelength range: "The receiver wavelength range is defined o optical add drop multiplexer (OADM) subsystem;
as the acceptable range of wavelengths at point Rn. This range must
be wide enough to cover the entire range of central frequencies over
the OA passband." [G.692]
Minimum equivalent sensitivity: "This is the minimum sensitivity that o asymmetric branching component;
would be required of a receiver placed at MPI-RM in multichannel
applications to achieve the specified maximum BER of the application
code if all except one of the channels were to be removed (with an
ideal loss-less filter) at point MPI-RM." [G.959.1]
A.3. Components and Subsystems o optical attenuator;
Reference [G.671] "Transmission characteristics of optical components o optical branching component (wavelength non-selective);
and subsystems" covers the following components:
o optical add drop multiplexer (OADM) subsystem; o optical connector;
o asymmetric branching component; o dynamic channel equalizer (DCE);
o optical attenuator; o optical filter;
o optical branching component (wavelength non-selective); o optical isolator;
o optical connector; o passive dispersion compensator;
o dynamic channel equalizer (DCE); o optical splice;
o optical filter;
o optical isolator; o optical switch;
o passive dispersion compensator; o optical termination;
o optical splice; o tuneable filter;
o optical wavelength multiplexer (MUX)/demultiplexer (DMUX);
o optical switch; - coarse WDM device;
o optical termination; - dense WDM device;
o tuneable filter; - wide WDM device.
o optical wavelength multiplexer (MUX)/demultiplexer (DMUX); Reference [G.671] then specifies applicable parameters for these
components. For example an OADM subsystem will have parameters
such as: insertion loss (input to output, input to drop, add to
output), number of add, drop and through channels, polarization
dependent loss, adjacent channel isolation, allowable input power,
polarization mode dispersion, etc...
- coarse WDM device; A.4. Network Elements
- dense WDM device; The previously cited ITU-T recommendations provide a plethora of
definitions and characterizations of optical fiber, devices,
components and subsystems. Reference [G.Sup39] "Optical system
design and engineering considerations" provides useful guidance on
the use of such parameters.
- wide WDM device. In many situations the previous models while good don't encompass
the higher level network structures that one typically deals with
in the control plane, i.e, "links" and "nodes". In addition such
models include the full range of network applications from
planning, installation, and possibly day to day network
operations, while with the control plane we are generally
concerned with a subset of the later. In particular for many
control plane applications we are interested in formulating the
total degradation to an optical signal as it travels through
multiple optical subsystems, devices and fiber segments.
Reference [G.671] then specifies applicable parameters for these In reference [G.680] "Physical transfer functions of optical
components. For example an OADM subsystem will have parameters such networks elements", a degradation function is currently defined
as: insertion loss (input to output, input to drop, add to output), for the following optical network elements: (a) DWDM Line segment,
number of add, drop and through channels, polarization dependent (b) Optical Add/Drop Multiplexers (OADM), and (c) Photonic cross-
loss, adjacent channel isolation, allowable input power, polarization connect (PXC). The scope of [G.680] is currently for optical
mode dispersion, etc... networks consisting of one vendors DWDM line systems along with
another vendors OADMs or PXCs.
A.4. Network Elements The DWDM line system of [G.680] consists of the optical fiber,
line amplifiers and any embedded dispersion compensators.
Similarly the OADM/PXC network element may consist of the basic
OADM component and optionally included optical amplifiers. The
parameters for these optical network elements (ONE) are given
under the following circumstances:
The previously cited ITU-T recommendations provide a plethora of o General ONE without optical amplifiers
definitions and characterizations of optical fiber, devices, o General ONE with optical amplifiers
components and subsystems. Reference [G.Sup39] "Optical system design
and engineering considerations" provides useful guidance on the use
of such parameters.
In many situations the previous models while good don't encompass the o OADM without optical amplifiers
higher level network structures that one typically deals with in the
control plane, i.e, "links" and "nodes". In addition such models
include the full range of network applications from planning,
installation, and possibly day to day network operations, while with
the control plane we are generally concerned with a subset of the
later. In particular for many control plane applications we are
interested in formulating the total degradation to an optical signal
as it travels through multiple optical subsystems, devices and fiber
segments.
In reference [G.680] "Physical transfer functions of optical networks o OADM with optical amplifiers
elements", a degradation function is currently defined for the
following optical network elements: (a) DWDM Line segment, (b)
Optical Add/Drop Multiplexers (OADM), and (c) Photonic cross-connect
(PXC). The scope of [G.680] is currently for optical networks
consisting of one vendors DWDM line systems along with another
vendors OADMs or PXCs.
The DWDM line system of [G.680] consists of the optical fiber, line o Reconfigurable OADM (ROADM) without optical amplifiers
amplifiers and any embedded dispersion compensators. Similarly the
OADM/PXC network element may consist of the basic OADM component and
optionally included optical amplifiers. The parameters for these
optical network elements (ONE) are given under the following
circumstances:
o General ONE without optical amplifiers o ROADM with optical amplifiers
o General ONE with optical amplifiers o PXC without optical amplifiers
o OADM without optical amplifiers o PXC with optical amplifiers
o OADM with optical amplifiers 8. References
o Reconfigurable OADM (ROADM) without optical amplifiers 8.1. Normative References
o ROADM with optical amplifiers [G.650.1] ITU-T Recommendation G.650.1, Definitions and test
methods for linear, deterministic attributes of single-
mode fibre and cable, June 2004.
o PXC without optical amplifiers [650.2] ITU-T Recommendation G.650.2, Definitions and test
methods for statistical and non-linear related
attributes of single-mode fibre and cable, July 2007.
o PXC with optical amplifiers [650.3] ITU-T Recommendation G.650.3
8. References [G.652] ITU-T Recommendation G.652, Characteristics of a single-
mode optical fibre and cable, June 2005.
8.1. Normative References [G.653] ITU-T Recommendation G.653, Characteristics of a
dispersion-shifted single-mode optical fibre and cable,
December 2006.
[G.650.1] ITU-T Recommendation G.650.1, Definitions and test methods [G.654] ITU-T Recommendation G.654, Characteristics of a cut-off
for linear, deterministic attributes of single-mode fibre shifted single-mode optical fibre and cable, December
and cable, June 2004. 2006.
[650.2] ITU-T Recommendation G.650.2, Definitions and test methods [G.655] ITU-T Recommendation G.655, Characteristics of a non-zero
for statistical and non-linear related attributes of dispersion-shifted single-mode optical fibre and cable,
single-mode fibre and cable, July 2007. March 2006.
[650.3] ITU-T Recommendation G.650.3 [G.656] ITU-T Recommendation G.656, Characteristics of a fibre and
cable with non-zero dispersion for wideband optical
transport, December 2006.
[G.652] ITU-T Recommendation G.652, Characteristics of a single-mode [G.661] ITU-T Recommendation G.661, Definition and test methods
optical fibre and cable, June 2005. for the relevant generic parameters of optical amplifier
devices and subsystems, March 2006.
[G.653] ITU-T Recommendation G.653, Characteristics of a dispersion- [G.662] ITU-T Recommendation G.662, Generic characteristics of
shifted single-mode optical fibre and cable, December 2006. optical amplifier devices and subsystems, July 2005.
[G.654] ITU-T Recommendation G.654, Characteristics of a cut-off [G.671] ITU-T Recommendation G.671, Transmission characteristics
shifted single-mode optical fibre and cable, December 2006. of optical components and subsystems, January 2005.
[G.655] ITU-T Recommendation G.655, Characteristics of a non-zero [G.680] ITU-T Recommendation G.680, Physical transfer functions
dispersion-shifted single-mode optical fibre and cable, of optical network elements, July 2007.
March 2006.
[G.656] ITU-T Recommendation G.656, Characteristics of a fibre and [G.691] ITU-T Recommendation G.691, Optical interfaces for
cable with non-zero dispersion for wideband optical multichannel systems with optical amplifiers, November
transport, December 2006. 1998.
[G.661] ITU-T Recommendation G.661, Definition and test methods for [G.692] ITU-T Recommendation G.692, Optical interfaces for single
the relevant generic parameters of optical amplifier channel STM-64 and other SDH systems with optical
devices and subsystems, March 2006. amplifiers, March 2006.
[G.662] ITU-T Recommendation G.662, Generic characteristics of [G.872] ITU-T Recommendation G.872, Architecture of optical
optical amplifier devices and subsystems, July 2005. transport networks, November 2001.
[G.671] ITU-T Recommendation G.671, Transmission characteristics of [G.957] ITU-T Recommendation G.957, Optical interfaces for
optical components and subsystems, January 2005. equipments and systems relating to the synchronous
digital hierarchy, March 2006.
[G.680] ITU-T Recommendation G.680, Physical transfer functions of [G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network
optical network elements, July 2007. Physical Layer Interfaces, March 2006.
[G.691] ITU-T Recommendation G.691, Optical interfaces for [G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM
multichannel systems with optical amplifiers, November applications: DWDM frequency grid, June 2002.
1998.
[G.692] ITU-T Recommendation G.692, Optical interfaces for single [G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM
channel STM-64 and other SDH systems with optical applications: CWDM wavelength grid, December 2003.
amplifiers, March 2006.
[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 interface,
December 2006.
[G.957] ITU-T Recommendation G.957, Optical interfaces for [G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel
equipments and systems relating to the synchronous digital DWDM applications with Single-Channel optical interface,
hierarchy, March 2006. July 2007.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network [G.Sup39] ITU-T Series G Supplement 39, Optical system design and
Physical Layer Interfaces, March 2006. engineering considerations, February 2006.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
applications: DWDM frequency grid, June 2002. Switching (GMPLS) Architecture", RFC 3945, October 2004.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and
applications: CWDM wavelength grid, December 2003. Other Constraints on Optical Layer Routing", RFC 4054,
May 2005.
[G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
applications with Single-Channel optical interface, Computation Element (PCE)-Based Architecture", RFC 4655,
December 2006. August 2006.
[G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM [WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for
applications with Single-Channel optical interface, July GMPLS and PCE Control of Wavelength Switched Optical
2007. Networks", work in progress: draft-ietf-ccamp-
wavelength-switched-framework-02.txt, March 2009.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and 8.2. Informative References
engineering considerations, February 2006.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label [Imp-Info] G. Bernstein, Y. Lee, D. Li, "A Framework for the
Switching (GMPLS) Architecture", RFC 3945, October 2004. Control and Measurement of Wavelength Switched Optical
Networks (WSON) with Impairments", work in progress:
draft-bernstein-wson-impairment-info.
[RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other [Martinelli] G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS
Constraints on Optical Layer Routing", RFC 4054, May 2005. Signaling Extensions for Optical Impairment Aware
Lightpath Setup", Work in Progress: draft-martinelli-
ccamp-optical-imp-signaling-02.txt, February 2008.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation [WSON-Comp] G. Bernstein, Y. Lee, Ben Mack-Crane, "WSON Signal
Element (PCE)-Based Architecture", RFC 4655, August 2006. Characteristics and Network Element Compatibility
Constraints for GMPLS", work in progress: draft-
bernstein-ccamp-wson-signal.
[WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for GMPLS Author's Addresses
and PCE Control of Wavelength Switched Optical Networks",
work in progress: draft-ietf-ccamp-wavelength-switched-
framework-02.txt, March 2009.
8.2. Informative References Greg M. Bernstein (ed.)
Grotto Networking
Fremont California, USA
[Imp-Info] G. Bernstein, Y. Lee, D. Li, "A Framework for the Control Phone: (510) 573-2237
and Measurement of Wavelength Switched Optical Networks Email: gregb@grotto-networking.com
(WSON) with Impairments", work in progress: draft-
bernstein-wson-impairment-info.
[Martinelli] G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS Young Lee (ed.)
Signaling Extensions for Optical Impairment Aware Lightpath Huawei Technologies
Setup", Work in Progress: draft-martinelli-ccamp-optical- 1700 Alma Drive, Suite 100
imp-signaling-02.txt, February 2008. Plano, TX 75075
USA
[WSON-Comp] G. Bernstein, Y. Lee, Ben Mack-Crane, "WSON Signal Phone: (972) 509-5599 (x2240)
Characteristics and Network Element Compatibility Email: ylee@huawei.com
Constraints for GMPLS", work in progress: draft-bernstein-
ccamp-wson-signal.
Author's Addresses Dan Li
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Greg M. Bernstein (ed.) Phone: +86-755-28973237
Grotto Networking Email: danli@huawei.com
Fremont California, USA Giovanni Martinelli
Cisco
Via Philips 12
20052 Monza, Italy
Phone: (510) 573-2237 Phone: +39 039 2092044
Email: gregb@grotto-networking.com Email: giomarti@cisco.com
Young Lee (ed.) Contributor's Addresses
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075
USA
Phone: (972) 509-5599 (x2240) Ming Chen
Email: ylee@huawei.com Huawei Technologies Co., Ltd.
Dan Li F3-5-B R&D Center, Huawei Base,
Huawei Technologies Co., Ltd. Bantian, Longgang District
F3-5-B R&D Center, Huawei Base, Shenzhen 518129 P.R.China
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237 Phone: +86-755-28973237
Email: danli@huawei.com Email: mchen@huawei.com
Giovanni Martinelli Rebecca Han
Cisco Huawei Technologies Co., Ltd.
Via Philips 12 F3-5-B R&D Center, Huawei Base,
20052 Monza, Italy Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +39 039 2092044 Phone: +86-755-28973237
Email: giomarti@cisco.com Email: hanjianrui@huawei.com
Contributor's Addresses Gabriele Galimberti
Cisco
Via Philips 12,
20052 Monza, Italy
Ming Chen Phone: +39 039 2091462
Huawei Technologies Co., Ltd. Email: ggalimbe@cisco.com
F3-5-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28973237 Alberto Tanzi
Email: mchen@huawei.com Cisco
Via Philips 12,
20052 Monza, Italy
Rebecca Han Phone: +39 039 2091469
Huawei Technologies Co., Ltd. Email: altanzi@cisco.com
F3-5-B R&D Center, Huawei Base, David Bianchi
Bantian, Longgang District Cisco
Shenzhen 518129 P.R.China Via Philips 12,
20052 Monza, Italy
Phone: +86-755-28973237 Email: davbianc@cisco.com
Email: hanjianrui@huawei.com
Gabriele Galimberti
Cisco
Via Philips 12,
20052 Monza, Italy
Phone: +39 039 2091462 Moustafa Kattan
Email: ggalimbe@cisco.com Cisco
Dubai 500321
United Arab Emirates
Alberto Tanzi Email: mkattan@cisco.com
Cisco
Via Philips 12,
20052 Monza, Italy
Phone: +39 039 2091469 Dirk Schroetter
Email: altanzi@cisco.com Cisco
David Bianchi Email: dschroet@cisco.com
Cisco
Via Philips 12,
20052 Monza, Italy
Email: davbianc@cisco.com Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Moustafa Kattan Email: daniele.ceccarelli@ericsson.com
Cisco
Email: mkattan@cisco.com Elisa Bellagamba
Ericsson
Farogatan 6,
Kista 164 40
Sweeden
Dirk Schroetter Email: elisa.bellagamba@ericcson.com
Cisco
Email: dschroet@cisco.com Diego Caviglia
Ericsson
Via A. negrone 1/A
Genova - Sestri Ponente
Italy
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DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
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We thank Chen Ming of DICONNET Project who provided valuable Acknowledgment
information relevant to this document.
We'd also like to thank Deborah Brungard for editorial and technical We thank Chen Ming of DICONNET Project who provided valuable
assistance. information relevant to this document.
We'd also like to thank Deborah Brungard for editorial and
technical assistance.
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