    Internet Engineering Task Force (IETF)                       Y. Lee, Ed.
    Request for Comments: 6566                                        Huawei
    Category: Informational                                G. Bernstein, Ed.
    ISSN: 2070-1721                                        Grotto Networking
                                                                       D. Li
                                                                      Huawei
                                                               G. Martinelli
                                                                       Cisco
                                                                  March 2012

                         A Framework for the Control of
         Wavelength Switched Optical Networks (WSONs) with Impairments

    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 Path Computation Element (PCE) architecture to support
       Impairment-Aware Routing and Wavelength Assignment (IA-RWA) in
       wavelength switched optical networks.  Specifically, this document
       discusses key computing constraints, scenarios, and architectural
       processes: routing, wavelength assignment, and impairment validation.
       This document does not define optical data plane aspects; impairment
       parameters; or measurement of, or assessment and qualification of, a
       route; rather, it describes the architectural and information
       components for protocol solutions.

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    Status of This Memo

       This document is not an Internet Standards Track specification; it is
       published for informational purposes.

       This document is a product of the Internet Engineering Task Force
       (IETF).  It represents the consensus of the IETF community.  It has
       received public review and has been approved for publication by the
       Internet Engineering Steering Group (IESG).  Not all documents
       approved by the IESG are a candidate for any level of Internet
       Standard; see Section 2 of RFC 5741.

       Information about the current status of this document, any errata,
       and how to provide feedback on it may be obtained at
       http://www.rfc-editor.org/info/rfc6566.

    Copyright Notice

       Copyright (c) 2012 IETF Trust and the persons identified as the
       document authors.  All rights reserved.

       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.

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    Table of Contents

       1. Introduction ....................................................3
       2. Terminology .....................................................4
       3. Applicability ...................................................6
       4. Impairment-Aware Optical Path Computation .......................7
          4.1. Optical Network Requirements and Constraints ...............8
               4.1.1. Impairment-Aware Computation Scenarios ..............9
               4.1.2. Impairment Computation and
                      Information-Sharing Constraints ....................10
               4.1.3. Impairment Estimation Process ......................11
          4.2. IA-RWA Computation and Control Plane Architectures ........13
               4.2.1. Combined Routing, WA, and IV .......................15
               4.2.2. Separate Routing, WA, or IV ........................15
               4.2.3. Distributed WA and/or IV ...........................16
          4.3. Mapping Network Requirements to Architectures .............16
       5. Protocol Implications ..........................................19
          5.1. Information Model for Impairments .........................19
          5.2. Routing ...................................................20
          5.3. Signaling .................................................21
          5.4. PCE .......................................................21
               5.4.1. Combined IV & RWA ..................................21
               5.4.2. IV-Candidates + RWA ................................22
               5.4.3. Approximate IA-RWA + Separate Detailed-IV ..........24
       6. Manageability and Operations ...................................25
       7. Security Considerations ........................................26
       8. References .....................................................27
          8.1. Normative References ......................................27
          8.2. Informative References ....................................27
       9. Contributors ...................................................29

    1.  Introduction

       Wavelength Switched Optical Networks (WSONs) are constructed from
       subsystems that may include wavelength division multiplexed links,
       tunable transmitters and receivers, Reconfigurable Optical Add/Drop
       Multiplexers (ROADMs), wavelength converters, and electro-optical
       network elements.  A WSON is a Wavelength Division Multiplexing
       (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
       [G.680]) traversed by the signal.  They are influenced by the type of
       fiber used, the types and placement of various optical devices, and

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       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, a combination of path continuity, resource availability, and
       impairment constraints must be met to determine viable and optimal
       paths through the network.  The determination of appropriate paths is
       known as Impairment-Aware Routing and Wavelength Assignment (IA-RWA).

       Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] provides
       a set of control plane protocols that can be used to operate networks
       ranging from packet switch capable networks to those networks that
       use time division multiplexing and WDM.  The Path Computation Element
       (PCE) architecture [RFC4655] defines functional computation
       components that can be used in cooperation with the GMPLS control
       plane to compute and suggest appropriate paths.  [RFC4054] provides
       an overview of optical impairments and their routing (path selection)
       implications for GMPLS.  This document uses [G.680] and other ITU-T
       Recommendations as references for the optical data plane aspects.

       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 evaluation, this document provides an overview
       of the subsystems and processes that comprise WSONs and describes
       IA-RWA models based on the corresponding ITU-T Recommendations, so
       that the information requirements for use by GMPLS and PCE systems
       can be identified.  This work will facilitate the development of
       protocol extensions in support of IA-RWA within the GMPLS and PCE
       protocol families.

    2.  Terminology

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

       Black Links: Black links refer to tributary interfaces where only
          link characteristics are defined.  This approach enables
          transverse compatibility at the single-channel point using a
          direct wavelength-multiplexing configuration.

       CWDM: Coarse Wavelength Division Multiplexing

       DGD: Differential Group Delay

       DWDM: Dense Wavelength Division Multiplexing

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       FOADM: Fixed Optical Add/Drop Multiplexer

       GMPLS: Generalized Multi-Protocol Label Switching

       IA-RWA: Impairment-Aware Routing and Wavelength Assignment

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

       NEs: Network Elements

       OADMs: Optical Add/Drop Multiplexers

       OSNR: Optical Signal-to-Noise Ratio

       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 that
          a path computation 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 application of computational
          constraints.

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

       PXC: Photonic Cross-Connect

       Q-Factor: The Q-factor provides a qualitative description of the
          receiver performance.  It is a function of the optical signal-to-
          noise ratio.  The Q-factor suggests the minimum SNR (Signal-to-
          Noise Ratio) required to obtain a specific bit error rate (BER)
          for a given signal.

       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.

       RWA: Routing and Wavelength Assignment

       Transparent Network: A Wavelength Switched Optical Network that does
          not contain regenerators or wavelength converters.

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       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 an
          information-bearing optical signal centered at a given wavelength
          to information 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 WSONs where not all possible paths
       will yield suitable signal quality.  There are multiple reasons;
       below is a non-exhaustive list of examples:

       o  WSONs are evolving and are using multi-degree optical cross-
          connects in such a way that network topologies are changing from
          rings (and interconnected rings) to general mesh.  Adding network
          equipment such as amplifiers or regenerators to ensure that all
          paths are 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's life; e.g., the optical interfaces might be
          upgraded to higher bitrates.  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.

       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.

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

       Not having an impairment-aware control plane for such networks will
       require a more complex network design phase that needs to take into
       account the evolving network status in terms of equipment and traffic
       at the beginning stage.  In addition, network operations such as path
       establishment will require significant pre-design via non-control-
       plane processes, resulting in significantly slower network
       provisioning.

       It should be highlighted that the impact of impairments and use in
       determination of path viability is not sufficiently well established
       for general applicability [G.680]; it will depend on network
       implementations.  The use of an impairment-aware control plane, and
       the set of information distributed, will need to be evaluated on a
       case-by-case scenario.

    4.  Impairment-Aware Optical Path Computation

       The basic criterion 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 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.  [RFC6163] provides
       background on the concept of optical translucent networks that
       contain 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.

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       Regeneration points could happen for two reasons:

        (i) Wavelength conversion is performed in order to assist RWA in
            avoiding wavelength blocking.  This is the impairment-free case
            covered by [RFC6163].

       (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 calculation of optical impairments 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.  This 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 under which an impairment-aware optical control plane may
       have to operate.  These requirements and constraints motivate the
       IA-RWA architectural alternatives presented in Section 4.2.
       Different optical network 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.

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    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; after that -- for example, during optical
          path computation -- they can be ignored.  This is the case
          discussed in [RFC6163] 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 where there is a sufficient
          margin such that impairment effects can be estimated via such
          approximation techniques 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 generally known as the
          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 non-viable.
          For example, one form of non-viability is the occurrence in
          existing links of transients of sufficient magnitude to impact the
          BER of existing signals.

          Much work at ITU-T has gone into developing impairment models at
          this level and at 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.

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       D. Accurate 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 need 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-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.  However, note that 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 in order 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 in the path could not be
       performed by a general-purpose 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 IA computation entity.  Such
       a vendor-specific IA computation entity 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:

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

       2. The authority in control of the black links could provide a
          PCE-like entity 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.

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

       In all of 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 the
       following sections.

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                                                   +-----------------+
            +------------+        +-----------+    |  +------------+ |
            |            |        |           |    |  |            | |
            | Optical    |        | Optical   |    |  | Optical    | |
            | Interface  |------->| Impairment|--->|  | Channel    | |
            | (Transmit/ |        | Path      |    |  | Estimation | |
            |  Receive)  |        |           |    |  |            | |
            +------------+        +-----------+    |  +------------+ |
                                                   |        ||       |
                                                   |        ||       |
                                                   |    Estimation   |
                                                   |        ||       |
                                                   |        \/       |
                                                   |  +------------+ |
                                                   |  |  BER/      | |
                                                   |  |  Q Factor  | |
                                                   |  +------------+ |
                                                   +-----------------+

       Starting from the functional block on the left, the optical interface
       represents where the optical signal is transmitted or received and
       defines the properties at the path endpoints.  Even the impairment-
       free case, such as scenario B in Section 4.1.1, needs to consider a
       minimum set of interface characteristics.  In such a case, only a few
       parameters used to assess the signal compatibility will be taken into
       account (see [RFC6163]).  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 consider a set of interface parameters during
       the impairment validation process.

       The "Optical Impairment Path" block represents the types of
       impairments affecting a wavelength as it traverses the networks
       through links and nodes.  In the case of a network where there are no
       impairments (scenario A), this block will not be present.  Otherwise,
       this function must be implemented in some way via the control plane.
       Architectural alternatives to accomplish this are provided in
       Section 4.2.  This block implementation (e.g., through routing,
       signaling, or a 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 the case of no IA approximation,
       only the signal class compatibility will be verified.  In addition to
       a feasible/not-feasible result, it may be worthwhile for decision
       functions to consider the case in which paths would likely be
       feasible within some degree of confidence.  The optical impairments

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       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 the
       impairment validation process may lead to marking some paths as not
       feasible, while they are very likely to be, in reality, feasible.

    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 [RFC6163].  In IA-RWA, there are conceptually three general
       classes of processes to be considered: Routing (R), Wavelength
       Assignment (WA), and Impairment Validation (IV), i.e., estimation.

       Impairment validation may come in many forms and may be invoked at
       different levels of detail in the IA-RWA process.  All of the
       variations of impairment validation discussed in this section are
       based on scenario C ("Approximated Impairment Estimation") as
       discussed in Section 4.1.1.  From a process point of view, the
       following three forms of impairment validation will be considered:

       o  IV-Candidates

          In this case, an 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 paths and
          wavelengths may not actually be 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 also that this
          case includes any paths between the source and destination that
          may have been "pre-validated".

          In this case, the control plane simply makes use of candidate
          paths but does not have 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.

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       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 from a decision-making point of view.

       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 on how
          information is gathered, this may put additional requirements on
          routing protocols.  This topic will be detailed in later sections.

       o  IV-Distributed

          In the distributed IV process, approximate degradation measures
          such as OSNR, dispersion, DGD, etc., may be accumulated along the
          path via signaling.  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
          distributing optical parameters to the entire network.

       The control plane must not preclude the possibility of concurrently
       performing one or all of the above cases 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 set
       up one of those paths 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 review some of their respective
       advantages and disadvantages.

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    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 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 information as discussed in [RFC6163] 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 the sharing of different types of information used in path
       computation.  This was discussed for routing, separate from WA, in
       [RFC6163].  In addition, as was discussed in Section 4.1.2, 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.

       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 improved efficiency.

       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.

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    4.2.3.  Distributed WA and/or IV

       In the non-impairment RWA situation [RFC6163], it was shown that a
       distributed 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 by routing protocols or by other means.  Therefore, 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].  The protocol encoding of the impairment-related information
       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.  The amount of information is
       reduced somewhat as potential wavelengths are discovered to be in use
       but could be a significant burden for lightly loaded networks with
       high channel counts.

    4.3.  Mapping Network Requirements to Architectures

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

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                      +-----------------------------------+
                      |   +--+     +-------+     +--+     |
                      |   |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 computation entity
          have 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

          This alternative allows separation of impairment information into
          two computation entities while still maintaining a high degree of
          potential optimality and efficiency in IA-RWA.  The IV-Candidates
          process needs to have impairment information from all optical
          network elements, while the RWA process needs to have

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          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 conducive to specialization.

       o  Routing + Distributed WA and IV

          In this alternative, a signaling protocol may be extended and
          leveraged in the wavelength assignment and impairment validation
          processes.  Although this doesn't enable as high a potential
          degree 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 the highest potential optimality and
          efficiency in IA-RWA while keeping 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.

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       o  IV-Candidates + RWA + Detailed-IV

          This alternative allows separation of approximate impairment
          information into a computation 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) the PCE
       as computation entity assuming the various process roles and
       consequences for PCEP, (c) possible extensions to signaling, and
       (d) possible extensions to routing.  This document is providing this
       evaluation to aid protocol solutions work.  The protocol
       specifications may deviate from this assessment.  The assessment of
       the impacts to the control plane for IA-RWA is summarized in
       Figure 4.

           +--------------------+-----+-----+------------+---------+
           | IA-RWA Option      | PCE | Sig | Info Model | Routing |
           +--------------------+-----+-----+------------+---------+
           |          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, most IA-RWA scenarios rely, to a greater or
       lesser extent, on a common impairment information model.  A number of
       ITU-T Recommendations cover both detailed and approximate impairment
       characteristics of fibers, a variety of devices, and a variety of
       subsystems.  An impairment model that can be used as a guideline for
       optical network elements and assessment of path viability is given
       in [G.680].

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       It should be noted that the current version of [G.680] is limited to
       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
       planned 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].

       For the case of distributed IV, this would require more than an
       impairment information model.  It would need 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,
       and effects of channel uniformity.  However, specifics of what
       intermediate results are kept and in what form would need to be
       standardized for interoperability.  As noted in [G.680], this
       information may possibly not be sufficient, and in such a case, the
       applicability would be network dependent.

    5.2.  Routing

       Different approaches to path/wavelength impairment validation give
       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 the impairment validation
       process.  This can potentially cause scalability issues, due to the
       high volume of data that need to be advertised.  Such issues can be
       addressed by separating data that need to be advertised only rarely
       from data that need to be advertised more frequently, or by adopting
       other forms of awareness solutions as described in previous sections
       (e.g., a centralized and/or external IV entity).

       In terms of scenario C in Section 4.1.1, the model defined by [G.680]
       will apply, and the routing protocol will need to gather information
       required for such computations.

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

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    5.3.  Signaling

       The largest impacts on signaling occur in the cases where distributed
       impairment validation is performed.  In this case, it is 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 whether 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 4.2, a number of computational architectural alternatives
       were given that could be used to meet the various requirements and
       constraints of Section 4.1.  Here, the focus is on 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.  This
       document provides this evaluation to aid solutions work.  The
       protocol specifications may deviate from this assessment.

    5.4.1.  Combined IV & RWA

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

       o  Traffic Engineering (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, and 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 why.  At a minimum, it is
          of interest to know if this was due to lack of wavelength
          availability, impairment considerations, or both.  The information
          to be conveyed is for further study.

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    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 IV-Candidates
       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 could be added to one of a number of
       previously defined entities.  This later option requires that the RWA
       entity 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):

          The RWA-Coord PCE is responsible for interacting with the PCC and
          for utilizing the IV-Candidates PCE as needed during RWA
          computations.  In particular, it needs to know that it is to use
          the IV-Candidates PCE to obtain a 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 IV-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 need not take into account current link
          wavelength utilization, but this is not prohibited.  The
          IV-Candidates PCE is only required to interact with the RWA PCE as
          indicated above, and not the initiating PCC.  Note: The
          RWA-Coord PCE is also a PCC with respect to the IV-Candidate.

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          o  TE Database requirements: WSON topology and switching
             capabilities, and WSON impairment information (no information
             link wavelength utilization required).

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

       In step (a), the PCC requests a path that meets 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-Coord PCE requests up to
       K candidate paths between nodes A and Z, and associated acceptable
       wavelengths.  The term "K candidate paths" is associated with the k
       shortest path algorithm.  It refers to an algorithm that finds
       multiple k short paths connecting the source and the destination in a
       graph allowing repeated vertices and edges in the paths.  See details
       in [Eppstein].

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       In step (c), the IV-Candidates PCE returns this list to the
       RWA-Coord 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-Coord 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
       the PCC, it is possible to keep the interactions with this separate
       IV-Detailed PCE very simple.  Note that, from a message flow
       perspective, there is some inefficiency as a result of separating the
       IV-Candidates PCE from the IV-Detailed PCE in order to achieve a high
       degree of potential optimality.

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

       o  IV-Detailed PCE to RWA-Coord PCE reply: The reply is essentially a
          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 the cause or to
          quantify the failure, e.g., so that a judgment can be made
          regarding whether to try a different signal or adjust signal
          parameters.

       Figure 6 shows a sequence diagram for the interactions corresponding
       to the process shown in Figure 3(b).  This involves interactions
       between the PCC, RWA PCE (acting as coordinator), IV-Candidates PCE,
       and IV-Detailed PCE.

       In step (a), the PCC requests a path that meets 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-Coord 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

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       the RWA-Coord 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-Coord PCE requests 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-Coord PCE.  Finally,
       in step (f), the RWA-Coord PCE returns the final results (either a
       path and wavelength, or a cause for the failure to compute a path and
       wavelength) to the PCC.

                    +----------+      +--------------+      +------------+
        +---+       |RWA-Coord |      |IV-Candidates |      |IV-Detailed |
        |PCC|       |   PCE    |      |     PCE      |      |    PCE     |
        +-+-+       +----+-----+      +------+-------+      +-----+------+
          |.._   (a)     |                   |                    |
          |   ``--.__    |                   |                    |
          |          `-->|                   |                    |
          |              |        (b)        |                    |
          |              |--....____         |                    |
          |              |          ````---.>|                    |
          |              |                   |                    |
          |              |         (c)  __..-|                    |
          |              |     __..---''     |                    |
          |              |<--''              |                    |
          |              |                                        |
          |              |...._____          (d)                  |
          |              |         `````-----....._____           |
          |              |                             `````----->|
          |              |                                        |
          |              |                 (e)          _____.....+
          |              |          _____.....-----'''''          |
          |              |<----'''''                              |
          |     (f)   __.|                                        |
          |    __.--''   |
          |<-''          |
          |              |

         Figure 6.  Sequence Diagram for the Interactions between the PCC,
               RWA-Coord PCE, IV-Candidates PCE, and IV-Detailed PCE

    6.  Manageability and Operations

       The issues concerning manageability and operations are beyond the
       scope of this document.  The details of manageability and operational
       issues will have to be deferred to future protocol implementations.

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       On a high level, the GMPLS-routing-based architecture discussed in
       Section 5.2 may have to deal with how to resolve potential scaling
       issues associated with disseminating a large amount of impairment
       characteristics of the network elements and links.

       From a scaling point of view, the GMPLS-signaling-based architecture
       discussed in Section 5.3 would be more scalable than other
       alternatives, as this architecture would avoid the dissemination of a
       large amount of data to the networks.  This benefit may come,
       however, at the expense of potentially inefficient use of network
       resources.

       The PCE-based architectures discussed in Section 5.4 would have to
       consider operational complexity when implementing options that
       require the use of multiple PCE servers.  The most serious case is
       the option discussed in Section 5.4.3 ("Approximate IA-RWA + Separate
       Detailed-IV").  The combined IV & RWA option (which was discussed in
       Section 5.4.1), on the other hand, is simpler to operate than are
       other alternatives, as one PCE server handles all functionality;
       however, this option may suffer from a heavy computation and
       processing burden compared to other alternatives.

       Interoperability may be a hurdle to overcome when trying to agree on
       some impairment parameters, especially those that are associated with
       the black links.  This work has been in progress in ITU-T and needs
       some more time to mature.

    7.  Security Considerations

       This document discusses a number of control plane architectures that
       incorporate knowledge of impairments in optical networks.  If such an
       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, similar to other network
       information used within intra-domain protocols.

       This document does not require changes to the security models within
       GMPLS and associated protocols.  That is, the OSPF-TE, RSVP-TE, and
       PCEP security models could be operated unchanged.  However,
       satisfying the requirements for impairment information dissemination
       using the existing protocols may significantly affect the loading of
       those protocols and may make the operation of the network more
       vulnerable to active attacks such as injections, impersonation, and
       man-in-the-middle attacks.  Therefore, additional care may be
       required to ensure that the protocols are secure in the impairment-
       aware WSON environment.

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       Furthermore, the additional information distributed in order to
       address impairment information represents a disclosure of network
       capabilities that an operator may wish to keep private.
       Consideration should be given to securing this information.  For a
       general discussion on MPLS- and GMPLS-related security issues, see
       the MPLS/GMPLS security framework [RFC5920] and, in particular, text
       detailing security issues when the control plane is physically
       separated from the data plane.

    8.  References

    8.1.  Normative References

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

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

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

    8.2.  Informative References

       [Eppstein]  Eppstein, D., "Finding the k shortest paths", 35th IEEE
                   Symposium on Foundations of Computer Science, Santa Fe,
                   pp. 154-165, 1994.

       [G.698.1]   ITU-T Recommendation G.698.1, "Multichannel DWDM
                   applications with single-channel optical interfaces",
                   November 2009.

       [G.698.2]   ITU-T Recommendation G.698.2, "Amplified multichannel
                   dense wavelength division multiplexing applications with
                   single channel optical interfaces", November 2009.

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

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

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    RFC 6566            Framework for Optical Impairments         March 2012

       [RFC5920]   Fang, L., Ed., "Security Framework for MPLS and GMPLS
                   Networks", RFC 5920, July 2010.

       [RFC6163]   Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
                   "Framework for GMPLS and Path Computation Element (PCE)
                   Control of Wavelength Switched Optical Networks (WSONs)",
                   RFC 6163, April 2011.

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    9.  Contributors

       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
       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

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    RFC 6566            Framework for Optical Impairments         March 2012

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

       EMail: daniele.ceccarelli@ericsson.com

       Elisa Bellagamba
       Ericsson
       Farogatan 6
       Kista  164 40
       Sweden

       EMail: elisa.bellagamba@ericsson.com

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

       EMail: diego.caviglia@ericsson.com

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    RFC 6566            Framework for Optical Impairments         March 2012

    Authors' Addresses

       Young Lee (editor)
       Huawei Technologies
       5340 Legacy Drive, Building 3
       Plano, TX  75024
       USA

       Phone: (469) 277-5838
       EMail: leeyoung@huawei.com

       Greg M. Bernstein (editor)
       Grotto Networking
       Fremont, CA
       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

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