[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-bernstein-ccamp-wson-impairments) 00 01 02 03 04 05 06 07 08 09 10 RFC 6566

Network Working Group                                            Y. Lee
                                                                 Huawei
                                                           G. Bernstein
                                                      Grotto Networking
                                                                  D. Li
                                                                 Huawei
                                                          G. Martinelli
                                                                  Cisco

Internet Draft
Intended status: Informational                           April 12, 2011
Expires: October 2011



    A Framework for the Control of Wavelength Switched Optical Networks
                          (WSON) with Impairments
                 draft-ietf-ccamp-wson-impairments-06.txt


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on October 12, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.




Lee & Bernstein        Expires October 12, 2011                [Page 1]


Internet-Draft    Framework for Optical Impairments          April 2011


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Abstract

   As an optical signal progresses along its path it may be altered by
   the various physical processes in the optical fibers and devices it
   encounters. When such alterations result in signal degradation, these
   processes are usually referred to as "impairments". These physical
   characteristics may be important constraints to consider when using a
   GMPLS control plane to support path setup and maintenance in
   wavelength switched optical networks.

   This document provides a framework for applying GMPLS protocols and
   the PCE architecture to support Impairment Aware Routing and
   Wavelength Assignment (IA-RWA) in wavelength switched optical
   networks.

Table of Contents


   1. Introduction...................................................3
   2. Terminology....................................................4
   3. Applicability..................................................5
   4. Impairment Aware Optical Path Computation......................6
      4.1. Optical Network Requirements and Constraints..............7
         4.1.1. Impairment Aware Computation Scenarios...............7
         4.1.2. Impairment Computation and Information Sharing
         Constraints.................................................8
         4.1.3. Impairment Estimation Process.......................10
      4.2. IA-RWA Computation and Control Plane Architectures.......11
         4.2.1. Combined Routing, WA, and IV........................13
         4.2.2. Separate Routing, WA, or IV.........................13
         4.2.3. Distributed WA and/or IV............................14
      4.3. Mapping Network Requirements to Architectures............15
   5. Protocol Implications.........................................17
      5.1. Information Model for Impairments........................17
      5.2. Routing..................................................18
      5.3. Signaling................................................19
      5.4. PCE......................................................19
         5.4.1. Combined IV & RWA...................................19

Lee & Bernstein        Expires October 12, 2011                [Page 2]


Internet-Draft    Framework for Optical Impairments          April 2011


         5.4.2. IV-Candidates + RWA.................................20
         5.4.3. Approximate IA-RWA + Separate Detailed IV...........21
   6. Security Considerations.......................................23
   7. IANA Considerations...........................................23
   8. References....................................................24
      8.1. Normative References.....................................24
      8.2. Informative References...................................25
   9. Acknowledgments...............................................26

1. Introduction

   Wavelength Switched Optical Networks (WSONs) are constructed from
   subsystems that may include Wavelength Division Multiplexed (WDM)
   links, tunable transmitters and receivers, Reconfigurable Optical
   Add/Drop Multiplexers (ROADM), wavelength converters, and electro-
   optical network elements.  A WSON is a wavelength division
   multiplexed (WDM)-based optical network in which switching is
   performed selectively based on the center wavelength of an optical
   signal.

   As an optical signal progresses along its path it may be altered by
   the various physical processes in the optical fibers and devices it
   encounters. When such alterations result in signal degradation, these
   processes are usually referred to as "impairments". Optical
   impairments accumulate along the path (without 3R regeneration)
   traversed by the signal. They are influenced by the type of fiber
   used, the types and placement of various optical devices and the
   presence of other optical signals that may share a fiber segment
   along the signal's path. The degradation of the optical signals due
   to impairments can result in unacceptable bit error rates or even a
   complete failure to demodulate and/or detect the received signal.

   In order to provision an optical connection (an optical path) through
   a WSON certain path continuity, resource availability and impairments
   constraints must be met to determine viable and optimal paths through
   the network. The determination of paths is known as Impairment Aware
   Routing and Wavelength Assignment (IA-RWA).

   Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] includes
   a set of control plane protocols that can be used to operate data
   networks ranging from packet switch capable networks, through those
   networks that use time division multiplexing, and WDM. [RFC4054]
   gives an overview of some critical optical impairments and their
   routing (path selection) implications for GMPLS. The Path Computation
   Element (PCE) architecture [RFC4655] defines functional components
   that can be used to compute and suggest appropriate paths in
   connection-oriented traffic-engineered networks.


Lee & Bernstein        Expires October 12, 2011                [Page 3]


Internet-Draft    Framework for Optical Impairments          April 2011


   This document provides a framework for applying GMPLS protocols and
   the PCE architecture to the control and operation of IA-RWA for
   WSONs.  To aid in this process this document also provides an
   overview of the subsystems and processes that comprise WSONs, and
   describes IA-RWA so that the information requirements can be
   identified to explain how the information can be modeled for use by
   GMPLS and PCE systems. This work will facilitate the development of
   protocol solution models and protocol extensions within the GMPLS and
   PCE protocol families.

2. Terminology

   Add/Drop Multiplexers (ADM): An optical device used in WDM networks
   composed of one or more line side ports and typically many tributary
   ports.

   CWDM: Coarse Wavelength Division Multiplexing.

   DWDM: Dense Wavelength Division Multiplexing.

   FOADM: Fixed Optical Add/Drop Multiplexer.

   GMPLS: Generalized Multi-Protocol Label Switching.

   IA-RWA: Impairment Aware Routing and Wavelength Assignment

   Line side: In WDM system line side ports and links typically can
   carry the full multiplex of wavelength signals, as compared to
   tributary (add or drop ports) that typically carry a few (typically
   one) wavelength signals.

   OXC: Optical cross connect. An optical switching element in which a
   signal on any input port can reach any output port.

   PCC: Path Computation Client.  Any client application requesting a
   path computation to be performed by the Path Computation Element.

   PCE: Path Computation Element.  An entity (component, application, or
   network node) that is capable of computing a network path or route
   based on a network graph and applying computational constraints.

   PCEP: PCE Communication Protocol. The communication protocol between
   a Path Computation Client and Path Computation Element.

   ROADM: Reconfigurable Optical Add/Drop Multiplexer. A wavelength
   selective switching element featuring input and output line side
   ports as well as add/drop tributary ports.


Lee & Bernstein        Expires October 12, 2011                [Page 4]


Internet-Draft    Framework for Optical Impairments          April 2011


   RWA: Routing and Wavelength Assignment.

   Transparent Network: A wavelength switched optical network that does
   not contain regenerators or wavelength converters.

   Translucent Network:  A wavelength switched optical network that is
   predominantly transparent but may also contain limited numbers of
   regenerators and/or wavelength converters.

   Tributary: A link or port on a WDM system that can carry
   significantly less than the full multiplex of wavelength signals
   found on the line side links/ports. Typical tributary ports are the
   add and drop ports on an ADM and these support only a single
   wavelength channel.

   Wavelength Conversion/Converters: The process of converting
   information bearing optical signal centered at a given wavelength to
   one with "equivalent" content centered at a different wavelength.
   Wavelength conversion can be implemented via an optical-electronic-
   optical (OEO) process or via a strictly optical process.

   WDM: Wavelength Division Multiplexing.

   Wavelength Switched Optical Networks (WSONs): WDM based optical
   networks in which switching is performed selectively based on the
   center wavelength of an optical signal.

3. Applicability

   There are deployment scenarios for WSON networks where not all
   possible paths will yield suitable signal quality. There are
   multiple reasons behind this choice; here below is a non-exhaustive
   list of examples:

   o  WSON is evolving using multi-degree optical cross connects in a
      way that network topologies are changing from rings (and
      interconnected rings) to general mesh. Adding network equipment
      such as amplifiers or regenerators, to make all paths feasible,
      leads to an over-provisioned network. Indeed, even with over
      provisioning, the network could still have some infeasible paths.

   o  Within a given network, the optical physical interface may change
      over the network life, e.g., the optical interfaces might be
      upgraded to higher bit-rates. Such changes could result in paths
      being unsuitable for the optical signal. Moreover, the optical
      physical interfaces are typically provisioned at various stages of
      the network's life span as needed by traffic demands.


Lee & Bernstein        Expires October 12, 2011                [Page 5]


Internet-Draft    Framework for Optical Impairments          April 2011


   o  There are cases where a network is upgraded by adding new optical
      cross connects to increase network flexibility. In such cases
      existing paths will have their feasibility modified while new
      paths will need to have their feasibility assessed.

   o  With the recent bit rate increases from 10G to 40G and 100G over a
      single wavelength, WSON networks will likely be operated with a
      mix of wavelengths at different bit rates. This operational
      scenario will impose impairment constraints due to different
      physical behavior of different bit rates and associated modulation
      formats.

   Not having an impairment aware control plane for such networks will
   require a more complex network design phase that takes into account
   evolving network status in term of equipments and traffic at the
   beginning stage. This could result in over-engineering the DWDM
   network with additional regenerators and optical amplifiers. In
   addition, network operations such as path establishment, will
   require significant pre-design via non-control plane processes
   resulting in significantly slower network provisioning.

4. Impairment Aware Optical Path Computation

   The basic criteria for path selection is whether one can successfully
   transmit the signal from a transmitter to a receiver within a
   prescribed error tolerance, usually specified as a maximum
   permissible bit error ratio (BER). This generally depends on the
   nature of the signal transmitted between the sender and receiver and
   the nature of the communications channel between the sender and
   receiver. The optical path utilized (along with the wavelength)
   determines the communications channel.

   The optical impairments incurred by the signal along the fiber and at
   each optical network element along the path determine whether the BER
   performance or any other measure of signal quality can be met for a
   signal on a particular end-to-end path.

   Impairment-aware path calculation also needs to take into account
   when regeneration is used along the path. [WSON-Frame] provides
   background on the concept of optical translucent networks which
   contains transparent elements and electro-optical elements such as
   OEO regenerations. In such networks a generic light path can go
   through a number of regeneration points.

   Regeneration points could happen for two reasons:

  (i)  wavelength conversion to assist RWA to avoid wavelength blocking.
     This is the impairment free case covered by [WSON-Frame].

Lee & Bernstein        Expires October 12, 2011                [Page 6]


Internet-Draft    Framework for Optical Impairments          April 2011


  (ii)  the optical signal without regeneration would be too degraded
     to meet end to end BER requirements. This is the case when RWA
     takes into consideration impairment estimation covered by this
     document.

In the latter case an optical path can be seen as a set of transparent
segments. The optical impairments calculation needs to be reset at each
regeneration point so each transparent segment will have its own
impairment evaluation.

   +---+    +----+   +----+     +-----+     +----+    +---+
   | I |----| N1 |---| N2 |-----| REG |-----| N3 |----| E |
   +---+    +----+   +----+     +-----+     +----+    +---+

   |<----------------------------->|<-------------------->|
           Segment 1                      Segment 2

          Figure 1 Optical path as a set of transparent segments

For example, Figure 1 represents an optical path from node I to node E
with a regeneration point REG in between. It is feasible from an
impairment validation perspective if both segments (I, N1, N2, REG) and
(REG, N3, E) are feasible.

4.1. Optical Network Requirements and Constraints

   This section examines the various optical network requirements and
   constraints that an impairment aware optical control plane may have
   to operate under. These requirements and constraints motivate the IA-
   RWA architectural alternatives to be presented in the following
   section. Different optical networks contexts can be broken into two
   main criteria: (a) the accuracy required in the estimation of
   impairment effects, and (b) the constraints on the impairment
   estimation computation and/or sharing of impairment information.

4.1.1. Impairment Aware Computation Scenarios

   A. No concern for impairments or Wavelength Continuity Constraints

   This situation is covered by existing GMPLS with local wavelength
   (label) assignment.

   B. No concern for impairments but Wavelength Continuity Constraints

   This situation is applicable to networks designed such that every
   possible path is valid for the signal types permitted on the network.
   In this case impairments are only taken into account during network
   design and after that, for example during optical path computation,

Lee & Bernstein        Expires October 12, 2011                [Page 7]


Internet-Draft    Framework for Optical Impairments          April 2011


   they can be ignored. This is the case discussed in [WSON-Frame] where
   impairments may be ignored by the control plane and only optical
   parameters related to signal compatibility are considered.

   C. Approximated Impairment Estimation

   This situation is applicable to networks in which impairment effects
   need to be considered but there is sufficient margin such that they
   can be estimated via approximation techniques such as link budgets
   and dispersion [G.680],[G.sup39]. The viability of optical paths for
   a particular class of signals can be estimated using well defined
   approximation techniques [G.680], [G.sup39]. This is the generally
   known as linear case where only linear effects are taken into
   account. Note that adding or removing an optical signal on the path
   should not render any of the existing signals in the network as non-
   viable.  For example, one form of non-viability is the occurrence of
   transients in existing links of sufficient magnitude to impact the
   BER of existing signals.

   Much work at ITU-T has gone into developing impairment models at this
   and more detailed levels. Impairment characterization of network
   elements may be used to calculate which paths are conformant with a
   specified BER for a particular signal type. In such a case, the
   impairment aware (IA) path computation can be combined with the RWA
   process to permit more optimal IA-RWA computations. Note that the IA
   path computation may also take place in a separate entity, i.e., a
   PCE.

   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.



4.1.2. Impairment Computation and Information Sharing Constraints

   In GMPLS, information used for path computation is standardized for
   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

Lee & Bernstein        Expires October 12, 2011                [Page 8]


Internet-Draft    Framework for Optical Impairments          April 2011


   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
   spans and to estimate the validity of optical paths. For example,
   models of optical nonlinearities are not currently standardized.
   Vendors may also choose not to publish impairment details for links
   or a set of network elements in order not to divulge their optical
   system designs.

   In general, the impairment estimation/validation of an optical path
   for optical networks with "black links" (path) could not be 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.

   In the following the term "black links" will be used to describe
   these computation and information sharing constraints in optical
   networks. From the control plane perspective the following options
   are considered:

   1. The authority in control of the "black links" can furnish a list
      of all viable paths between all viable node pairs to a
      computational entity. This information would be particularly
      useful as an input to RWA optimization to be performed by another
      computation entity. The difficulty here is for larger networks
      such a list of paths along with any wavelength constraints could
      get unmanageably large.

   2. The authority in control of the "black links" could provide a PCE
      like entity that would furnish a list of viable paths/wavelengths
      between two requested nodes. This is useful 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.



Lee & Bernstein        Expires October 12, 2011                [Page 9]


Internet-Draft    Framework for Optical Impairments          April 2011


   3. The authority in control of the "black links" can provide a PCE
      that performs full IA-RWA services. The difficulty is this
      requires the one authority to also become the sole source of all
      RWA optimization algorithms and such.

   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.

4.1.3. Impairment Estimation Process

   The Impairment Estimation Process can be modeled through the
   following 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 functions as detailed in following
   sections.

                                              +-----------------+
       +------------+        +-----------+    |  +------------+ |
       |            |        |           |    |  |            | |
       | Optical    |        | Optical   |    |  | Optical    | |
       | Interface  |------->| Impairment|--->|  | Channel    | |
       | (Transmit/ |        | Path      |    |  | 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. Even the no-impairment
   case like scenario B in section 4.1.1 needs to consider a minimum set
   of interface characteristics. In such case only a few parameters used
   to assess the signal compatibility will be taken into account (see
   [WSON-Frame]). For the impairment-aware case 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


Lee & Bernstein        Expires October 12, 2011               [Page 10]


Internet-Draft    Framework for Optical Impairments          April 2011


   consider a set of interface parameters during an Impairment
   Validation Process.

   The block "Optical Impairment Path" represents all kinds of
   impairments affecting a wavelength as it traverses the networks
   through links and nodes. In the case where the control plane has 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 on 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.

   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 worthwhile 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.



4.2. IA-RWA Computation and Control Plane Architectures

   From a control plane point of view optical impairments are additional
   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
   different levels of detail in the IA-RWA process. From a process
   point of view the following three forms of impairment validation will
   be considered:

   o  IV-Candidates

   In this case an Impairment Validation (IV) process furnishes a set of
   paths between two nodes along with any wavelength restrictions such
   that the paths are valid with respect to optical impairments. These

Lee & Bernstein        Expires October 12, 2011               [Page 11]


Internet-Draft    Framework for Optical Impairments          April 2011


   paths and wavelengths may not be actually available in the network
   due to its current usage state. This set of paths could 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
   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.



   o  IV-Approximate 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.

   o  IV-Detailed Verification

   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.

   The next two cases refer to the way an impairment validation
   computation can be performed.

   o  IV-Centralized

   In this case impairments to a path are computed at a single entity.
   The information concerning impairments, however, may still be
   gathered from network elements. Depending how information is gathered
   this may put additional requirements on routing protocols. This will
   be detailed in later sections.

   o  IV-Distributed

   In the distributed IV process, approximate degradation measures such
   as OSNR, dispersion, DGD, etc. are accumulated along 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

Lee & Bernstein        Expires October 12, 2011               [Page 12]


Internet-Draft    Framework for Optical Impairments          April 2011


   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 distributing optical
   parameters to the entire network.

   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-
   validated (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
   computation architectures and reviews some of their respective
   advantages and disadvantages.

4.2.1. Combined Routing, WA, and IV

   From the point of view of optimality, reasonably good 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.

   Such a combination can take place if the PCE is given: (a) the
   impairment-free WSON network information as discussed in [WSON-Frame]
   and (b) impairment information to validate potential paths.

4.2.2. Separate Routing, WA, or IV

   Separating the processes of routing, WA and/or IV can reduce the 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 was discussed some impairment
   information may not be shared and this may lead to the need to
   separate IV from RWA.  In addition, 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
   category:

   o  R+WA+IV -- separate routing, wavelength assignment, and impairment
      validation.




Lee & Bernstein        Expires October 12, 2011               [Page 13]


Internet-Draft    Framework for Optical Impairments          April 2011


   o  R + (WA & IV) -- routing separate from a combined wavelength
      assignment and impairment validation process. Note that impairment
      validation is typically wavelength dependent hence combining WA
      with IV can lead to efficiencies.

   o  (RWA)+IV - combined routing and wavelength assignment with a
      separate impairment validation process.

   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.

4.2.3. Distributed WA and/or IV

   In the non-impairment RWA situation [WSON-Frame] it was shown that a
   distributed wavelength assignment (WA) process carried out via
   signaling can eliminate the need to distribute wavelength
   availability information via an interior gateway protocol (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 routing 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:

   o  RWA + D(IV) - Combined routing and wavelength assignment and
      distributed impairment validation.

   o  R + D(WA & IV) -- routing separate from a distributed wavelength
      assignment and impairment validation process.

   Distributed impairment validation for a prescribed network path
   requires that the effects of impairments be calculated by approximate
   models with cumulative quality measures such as those given in
   [G.680]. For such a system to be interoperable the exact encoding of
   the techniques from [G.680] would need to be agreed upon.

   If distributed WA is being done at the same time as distributed IV
   then it is necessary to accumulate impairment related information for
   all 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.




Lee & Bernstein        Expires October 12, 2011               [Page 14]


Internet-Draft    Framework for Optical Impairments          April 2011


4.3. Mapping Network Requirements to Architectures

   Figure 2 shows process flows for three main architectural
   alternatives to IA-RWA when approximate impairment validation
   suffices. Figure 3 shows process flows for two main architectural
   alternatives when detailed impairment verification is required.


                  +-----------------------------------+
                  |   +--+     +-------+     +--+     |
                  |   |IV|     |Routing|     |WA|     |
                  |   +--+     +-------+     +--+     |
                  |                                   |
                  |        Combined Processes         |
                  +-----------------------------------+
                                  (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.

   The advantages, requirements and suitability of these options are as
   follows:

   o  Combined IV & RWA process

   This alternative combines RWA and IV within a single computation
   entity enabling highest potential optimality and efficiency in IA-
   RWA. This alternative requires that the computational entity knows
   impairment information as well as non-impairment RWA information.
   This alternative can be used with "black links", but would then need
   to be provided by the authority controlling the "black links".

   o  IV-Candidates + RWA process

Lee & Bernstein        Expires October 12, 2011               [Page 15]


Internet-Draft    Framework for Optical Impairments          April 2011


   This alternative allows separation of impairment information into two
   computational entities while still maintaining a high degree of
   potential optimality and efficiency in IA-RWA. The candidates IV
   process needs to know impairment information from all optical network
   elements, while the RWA process needs to know non-impairment RWA
   information from the network elements. This alternative can be used
   with "black links", but the authority in control of the "black links"
   would need to provide the functionality of the IV-candidates process.
   Note that this is still very useful since the algorithmic areas of IV
   and RWA are very different and prone to specialization.

   o  Routing + Distributed WA and IV

   In this alternative a signaling protocol is extended and leveraged in
   the wavelength assignment and impairment validation processes.
   Although this doesn't enable as high a potential degree of optimality
   of optimality as (a) or (b), it does not require distribution of
   either link wavelength usage or link/node impairment information.
   Note that this is most likely not suitable for "black links".



          +-----------------------------------+     +------------+
          | +-----------+  +-------+    +--+  |     | +--------+ |
          | |    IV     |  |Routing|    |WA|  |     | |  IV    | |
          | |approximate|  +-------+    +--+  |---->| |Detailed| |
          | +-----------+                     |     | +--------+ |
          |        Combined Processes         |     |            |
          +-----------------------------------+     +------------+
                                   (a)

    +--------------+      +----------------------+     +------------+
    | +----------+ |      | +-------+    +--+    |     | +--------+ |
    | |    IV    | |      | |Routing|    |WA|    |---->| |  IV    | |
    | |candidates| |----->| +-------+    +--+    |     | |Detailed| |
    | +----------+ |      |  Combined Processes  |     | +--------+ |
    +--------------+      +----------------------+     |            |
                                   (b)                 +------------+
        Figure 3 Process flows for the two main detailed impairment
                     validation architectural options.

   The advantages, requirements and suitability of these detailed
   validation options are as follows:

   o  Combined approximate IV & RWA + Detailed-IV

   This alternative combines RWA and approximate IV within a single
   computation entity enabling highest potential optimality and

Lee & Bernstein        Expires October 12, 2011               [Page 16]


Internet-Draft    Framework for Optical Impairments          April 2011


   efficiency in IA-RWA; then has a separate entity performing detailed
   impairment validation. In the case of "black links" the authority
   controlling the "black links" would need to provide all
   functionality.

   o  Candidates-IV + RWA + Detailed-IV

   This alternative allows separation of approximate impairment
   information into a computational entity while still maintaining a
   high degree of potential optimality and efficiency in IA-RWA; then a
   separate computation entity performs detailed impairment validation.
   Note that detailed impairment estimation is not standardized.

5. Protocol Implications

   The previous IA-RWA architectural alternatives and process flows make
   differing demands on a GMPLS/PCE based control plane. This section
   discusses the use of (a) an impairment information model, (b) PCE as
   computational entity assuming the various process roles and
   consequences for PCEP, (c) any needed extensions to signaling, and
   (d) extensions to routing. The impacts to the control plane for IA-
   RWA are summarized in Figure 4.


        +-------------------+----+----+----------+--------+
        | IA-RWA Option     |PCE |Sig |Info Model| Routing|
        +-------------------+----+----+----------+--------+
        |          Combined |Yes | No |  Yes     |  Yes   |
        |          IV & RWA |    |    |          |        |
        +-------------------+----+----+----------+--------+-
        |     IV-Candidates |Yes | No |  Yes     |  Yes   |
        |         + RWA     |    |    |          |        |
        +-------------------+----+----+----------+--------+
        |    Routing +      |No  | Yes|  Yes     |  No    |
        |Distributed IV, RWA|    |    |          |        |
        +-------------------+----+----+----------+--------+

     Figure 4 IA-RWA architectural options and control plane impacts.



5.1. Information Model for Impairments

   As previously discussed all IA-RWA scenarios to a greater or lesser
   extent rely on a common impairment information model. A number of
   ITU-T recommendations cover detailed as well as approximate
   impairment characteristics of fibers and a variety of devices and
   subsystems. A well integrated impairment model for optical network

Lee & Bernstein        Expires October 12, 2011               [Page 17]


Internet-Draft    Framework for Optical Impairments          April 2011


   elements is given in [G.680] and is used to form 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
   the networks composed of a single WDM line system vendor combined
   with OADMs and/or PXCs from potentially multiple other vendors, this
   is known as situation 1 and is shown in Figure 1-1 of [G.680]. It is
   planed in the future that [G.680] will include networks incorporating
   line systems from multiple vendors as well as OADMs and/or PXCs from
   potentially multiple other vendors, this 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
   more than an impairment information model. In particular, it needs a
   common impairment "computation" model. In the distributed IV case one
   needs to standardize the accumulated impairment measures that will be
   conveyed and updated at each node. Section 9 of [G.680] provides
   guidance in this area with specific formulas given for OSNR, residual
   dispersion, polarization mode dispersion/polarization dependent loss,
   effects of channel uniformity, etc... However, specifics of what
   intermediate results are kept and in what form would need to be
   standardized.



5.2. Routing

   Different approaches to path/wavelength impairment validation gives
   rise to different demands placed on GMPLS routing protocols. 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.

   Depending on the computational alternative the routing protocol may
   need to advertise information necessary to impairment validation
   process. This can potentially cause scalability issues 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).

   In term of approximated scenario (see Section 4.1.1. ) the model
   defined by [G.680] will apply and routing protocol will need to
   gather information required for such computation.



Lee & Bernstein        Expires October 12, 2011               [Page 18]


Internet-Draft    Framework for Optical Impairments          April 2011


   In the case of distributed-IV no new demands would be placed on the
   routing protocol.

5.3. Signaling

   The largest impacts on signaling occur in the cases where distributed
   impairment validation is performed. In this case, it ie necessary to
   accumulate 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
   additional information to a connection request such as desired egress
   signal quality (defined in some appropriate sense) in non-distributed
   IV scenarios.

5.4. PCE

   In section 4.3. a number of computation architectural alternatives
   were given that could be used to meet the various requirements and
   constraints of section 4.1.  Here the focus is how these alternatives
   could be implemented via either a single PCE or a set of two or more
   cooperating PCEs, and the impacts on the PCEP protocol.

5.4.1. Combined IV & RWA

   In this situation, shown in Figure 2(a), a single PCE performs all
   the computations needed for IA-RWA.

   o  TE Database Requirements: WSON Topology and switching
      capabilities, WSON WDM link wavelength utilization, and WSON
      impairment information

   o  PCC to PCE Request Information: Signal characteristics/type,
      required quality, source node, destination node

   o  PCE to PCC Reply Information: 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 it is of interest 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.



Lee & Bernstein        Expires October 12, 2011               [Page 19]


Internet-Draft    Framework for Optical Impairments          April 2011


5.4.2. IV-Candidates + RWA

   In this situation, as shown in Figure 2(b), two separate processes
   are involved in the IA-RWA computation. This requires two cooperating
   path computation entities: 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 this
   functionality can be added to one of previously defined entities.
   This later option requires the RWA entity to also act as the overall
   process coordinator. The roles, responsibilities and information
   requirements for these two entities when instantiated as PCEs are
   given below.

   RWA and Coordinator PCE (RWA-Coord-PCE):

   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.

   o  TE Database Requirements: WSON Topology and switching capabilities
      and WSON WDM link wavelength utilization (no impairment
      information).

   o  PCC to RWA-PCE request: same as in the combined case.

   o  RWA-PCE to PCC reply: same as in the combined case.

   o  RWA-PCE to IV-Candidates-PCE request: The RWA-PCE asks for a set
      of at most K routes along with acceptable wavelengths between
      nodes specified in the original PCC request.

   o  IV-Candidates-PCE reply to RWA-PCE: The Candidates-PCE returns a
      set of at most K routes along with acceptable wavelengths between
      nodes specified in the RWA-PCE request.

  IV-Candidates-PCE:

   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
   initiating PCC. (Note: RWA-Coord PCE is also a PCC with respect to
   the IV-Candidate)

   o  TE Database Requirements: WSON Topology and switching capabilities
      and WSON impairment information (no information link wavelength
      utilization required).

Lee & Bernstein        Expires October 12, 2011               [Page 20]


Internet-Draft    Framework for Optical Impairments          April 2011


   Figure 5 shows a sequence diagram for the interactions between the
   PCC, RWA-Coord PCE and IV-Candidates PCE.


    +---+                +-------------+          +-----------------+
    |PCC|                |RWA-Coord PCE|          |IV-Candidates PCE|
    +-+-+                +------+------+          +---------+-------+
       ...___     (a)            |                           |
       |     ````---...____      |                           |
       |                   ```-->|                           |
       |                         |                           |
       |                         |--..___    (b)             |
       |                         |       ```---...___        |
       |                         |                   ```---->|
       |                         |                           |
       |                         |                           |
       |                         |           (c)       ___...|
       |                         |       ___....---''''      |
       |                         |<--''''                    |
       |                         |                           |
       |                         |                           |
       |          (d)      ___...|                           |
       |      ___....---'''      |                           |
       |<--'''                   |                           |
       |                         |                           |
       |                         |                           |

     Figure 5 Sequence diagram for the interactions between PCC, RWA-
                Coordinating-PCE and the IV-Candidates-PCE.

   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.

5.4.3. Approximate IA-RWA + Separate Detailed IV

   Previously Figure 3 showed two cases where a separate detailed
   impairment validation process could be utilized. It is possible to
   place the detailed validation process into a separate PCE. Assuming
   that a different PCE assumes a coordinating role and interacts with


Lee & Bernstein        Expires October 12, 2011               [Page 21]


Internet-Draft    Framework for Optical Impairments          April 2011


   the PCC it is possible to keep the interactions with this separate
   IV-Detailed-PCE very simple.

   IV-Detailed-PCE:

   o  TE Database Requirements: The IV-Detailed-PCE will need optical
      impairment information, WSON topology, and possibly WDM link
      wavelength usage information. This document puts no restrictions
      on the type of information that may be used in these computations.

   o  Coordinating-PCE to IV-Detailed-PCE request: The coordinating-PCE
      will furnish signal characteristics, quality requirements, path
      and wavelength to the IV-Detailed-PCE.

   o  IV-Detailed-PCE to Coordinating-PCE reply: 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.

   Figure 6 shows a sequence diagram for the interactions for the
   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
   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.









Lee & Bernstein        Expires October 12, 2011               [Page 22]


Internet-Draft    Framework for Optical Impairments          April 2011


                +----------+      +--------------+      +------------+
    +---+       |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.



6. Security Considerations

   This document discusses a number of control plane architectures that
   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.

7. IANA Considerations

   This draft does not currently require any consideration from IANA.




Lee & Bernstein        Expires October 12, 2011               [Page 23]


Internet-Draft    Framework for Optical Impairments          April 2011


8. References

8.1. Normative References

   [G.650.1] ITU-T Recommendation G.650.1, Definitions and test methods
             for linear, deterministic attributes of single-mode fibre
             and cable, June 2004.

   [G.650.2] ITU-T Recommendation G.650.2, Definitions and test methods
             for statistical and non-linear related attributes of
             single-mode fibre and cable, July 2007.

   [G.650.3] ITU-T Recommendation G.650.3

   [G.652] ITU-T Recommendation G.652, Characteristics of a single-mode
             optical fibre and cable, June 2005.

   [G.653] ITU-T Recommendation G.653, Characteristics of a dispersion-
             shifted single-mode optical fibre and cable, December 2006.

   [G.654] ITU-T Recommendation G.654, Characteristics of a cut-off
             shifted single-mode optical fibre and cable, December 2006.

   [G.655] ITU-T Recommendation G.655, Characteristics of a non-zero
             dispersion-shifted single-mode optical fibre and cable,
             March 2006.

   [G.656] ITU-T Recommendation G.656, Characteristics of a fibre and
             cable with non-zero dispersion for wideband optical
             transport, December 2006.

   [G.661]  ITU-T Recommendation G.661, Definition and test methods for
             the relevant generic parameters of optical amplifier
             devices and subsystems, March 2006.

   [G.662]  ITU-T Recommendation G.662, Generic characteristics of
             optical amplifier devices and subsystems, July 2005.

   [G.671]  ITU-T Recommendation G.671, Transmission characteristics of
             optical components and subsystems, January 2005.

   [G.680]  ITU-T Recommendation G.680, Physical transfer functions of
             optical network elements, July 2007.

   [G.691]  ITU-T Recommendation G.691, Optical interfaces for
             multichannel systems with optical amplifiers, November
             1998.


Lee & Bernstein        Expires October 12, 2011               [Page 24]


Internet-Draft    Framework for Optical Impairments          April 2011


   [G.692]  ITU-T Recommendation G.692, Optical interfaces for single
             channel STM-64 and other SDH systems with optical
             amplifiers, March 2006.

   [G.872]  ITU-T Recommendation G.872, Architecture of optical
             transport networks, November 2001.

   [G.957]  ITU-T Recommendation G.957, Optical interfaces for
             equipments and systems relating to the synchronous digital
             hierarchy, March 2006.

   [G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network
             Physical Layer Interfaces, March 2006.

   [G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM
             applications: DWDM frequency grid, June 2002.

   [G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM
             applications: CWDM wavelength grid, December 2003.

   [G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM
             applications with Single-Channel optical interface,
             December 2006.

   [G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM
             applications with Single-Channel optical interface, July
             2007.

   [G.Sup39] ITU-T Series G Supplement 39, Optical system design and
             engineering considerations, February 2006.

   [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
             Switching (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other
             Constraints on Optical Layer Routing", RFC 4054, May 2005.

   [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation
             Element (PCE)-Based Architecture", RFC 4655, August 2006.

8.2. Informative References

   [WSON-Frame] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS
             and PCE Control of Wavelength Switched Optical Networks",
             work in progress: draft-ietf-ccamp-wavelength-switched-
             framework.



Lee & Bernstein        Expires October 12, 2011               [Page 25]


Internet-Draft    Framework for Optical Impairments          April 2011


   [Imp-Info]  G. Bernstein, Y. Lee, D. Li, "A Framework for the Control
             and Measurement of Wavelength Switched Optical Networks
             (WSON) with Impairments", work in progress: draft-
             bernstein-wson-impairment-info.

   [Martinelli]   G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS
             Signaling Extensions for Optical Impairment Aware Lightpath
             Setup", Work in Progress: draft-martinelli-ccamp-optical-
             imp-signaling.



9. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.

   Copyright (c) 2011 IETF Trust and the persons identified as authors
   of the code. All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

   o  Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

   o  Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the
      distribution.

   o  Neither the name of Internet Society, IETF or IETF Trust, nor the
      names of specific contributors, may be used to endorse or promote
      products derived from this software without specific prior written
      permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


Lee & Bernstein        Expires October 12, 2011               [Page 26]


Internet-Draft    Framework for Optical Impairments          April 2011


Authors' Addresses


   Young Lee (ed.)
   Huawei Technologies
   1700 Alma Drive, Suite 100
   Plano, TX 75075
   USA

   Phone: (972) 509-5599 (x2240)
   Email: ylee@huawei.com


   Greg M. Bernstein (ed.)
   Grotto Networking
   Fremont California, USA

   Phone: (510) 573-2237
   Email: gregb@grotto-networking.com


   Dan Li
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28973237
   Email: danli@huawei.com


   Giovanni Martinelli
   Cisco
   Via Philips 12
   20052 Monza, Italy

   Phone: +39 039 2092044
   Email: giomarti@cisco.com

   Contributor's Addresses

   Ming Chen
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28973237

Lee & Bernstein        Expires October 12, 2011               [Page 27]


Internet-Draft    Framework for Optical Impairments          April 2011


   Email: mchen@huawei.com

   Rebecca Han
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28973237
   Email: hanjianrui@huawei.com

   Gabriele Galimberti
   Cisco
   Via Philips 12,
   20052 Monza, Italy

   Phone: +39 039 2091462
   Email: ggalimbe@cisco.com

   Alberto Tanzi
   Cisco
   Via Philips 12,
   20052 Monza, Italy

   Phone: +39 039 2091469
   Email: altanzi@cisco.com

   David Bianchi
   Cisco
   Via Philips 12,
   20052 Monza, Italy

   Email: davbianc@cisco.com

   Moustafa Kattan
   Cisco
   Dubai  500321
   United Arab Emirates

   Email: mkattan@cisco.com

   Dirk Schroetter
   Cisco

   Email: dschroet@cisco.com

   Daniele Ceccarelli
   Ericsson

Lee & Bernstein        Expires October 12, 2011               [Page 28]


Internet-Draft    Framework for Optical Impairments          April 2011


   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy

   Email: daniele.ceccarelli@ericsson.com

   Elisa Bellagamba
   Ericsson
   Farogatan 6,
   Kista   164 40
   Sweeden

   Email: elisa.bellagamba@ericcson.com

   Diego Caviglia
   Ericsson
   Via A. negrone 1/A
   Genova - Sestri Ponente
   Italy

   Email: diego.caviglia@ericcson.com




























Lee & Bernstein        Expires October 12, 2011               [Page 29]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/