Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)
draft-ietf-ccamp-rwa-wson-framework-12

The information below is for an old version of the document that is already published as an RFC
Document Type RFC Internet-Draft (ccamp WG)
Authors Wataru Imajuku  , Young Lee  , Greg Bernstein 
Last updated 2018-12-20 (latest revision 2011-02-08)
Replaces draft-ietf-ccamp-wavelength-switched-framework
Stream Internet Engineering Task Force (IETF)
Formats pdf htmlized (tools) htmlized bibtex
Stream WG state (None)
Document shepherd No shepherd assigned
IESG IESG state RFC 6163 (Informational)
Consensus Boilerplate Unknown
Telechat date
Responsible AD Adrian Farrel
Send notices to (None)
Network Working Group                                      Y. Lee (ed.) 
Internet Draft                                                   Huawei 
Intended status: Informational                       G. Bernstein (ed.) 
Expires: August 2011                                  Grotto Networking 
                                                         Wataru Imajuku 
                                                                    NTT 
 
                                                                        
                                    
                                    
                                                       February 8, 2011 
                                      
    Framework for GMPLS and PCE Control of Wavelength Switched Optical 
                              Networks (WSON)  
                draft-ietf-ccamp-rwa-wson-framework-12.txt 

Abstract 

   This document provides a framework for applying Generalized Multi-
   Protocol Label Switching (GMPLS) and the Path Computation Element 
   (PCE) architecture to the control of wavelength switched optical 
   networks (WSON).  In particular, it examines Routing and Wavelength 
   Assignment (RWA) of optical paths. 

   This document focuses on topological elements and path selection 
   constraints that are common across different WSON environments as 
   such it does not address optical impairments in any depth. 

Status of this Memo 

   This Internet-Draft is submitted to IETF 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 

 
 
 
Bernstein and Lee       Expires August 8, 2011                 [Page 1] 


Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

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

   This Internet-Draft will expire on August 8, 2011. 

Copyright Notice 

   Copyright (c) 2011 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. 

    

Table of Contents 

    
     
   1. Introduction...................................................4 
   2. Terminology....................................................5 
   3. Wavelength Switched Optical Networks...........................6 
      3.1. WDM and CWDM Links........................................6 
      3.2. Optical Transmitters and Receivers........................8 
      3.3. Optical Signals in WSONs..................................9 
         3.3.1. Optical Tributary Signals...........................10 
         3.3.2. WSON Signal Characteristics.........................10 
      3.4. ROADMs, OXCs, Splitters, Combiners and FOADMs............11 
         3.4.1. Reconfigurable Add/Drop Multiplexers and OXCs.......11 
         3.4.2. Splitters...........................................14 
         3.4.3. Combiners...........................................15 
         3.4.4. Fixed Optical Add/Drop Multiplexers.................15 
      3.5. Electro-Optical Systems..................................16 
         3.5.1. Regenerators........................................16 
         3.5.2. OEO Switches........................................19 
      3.6. Wavelength Converters....................................19 
         3.6.1. Wavelength Converter Pool Modeling..................21 
      3.7. Characterizing Electro-Optical Network Elements..........25 
         3.7.1. Input Constraints...................................26 
         3.7.2. Output Constraints..................................26 
         3.7.3. Processing Capabilities.............................27 
     

   Bernstein and Lee Expires August 8, 2011  [Page 2] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   4. Routing and Wavelength Assignment and the Control Plane.......28 
      4.1. Architectural Approaches to RWA..........................28 
         4.1.1. Combined RWA (R&WA).................................29 
         4.1.2. Separated R and WA (R+WA)...........................29 
         4.1.3. Routing and Distributed WA (R+DWA)..................30 
      4.2. Conveying information needed by RWA......................30 
   5. Modeling Examples and Control Plane Use Cases.................31 
      5.1. Network Modeling for GMPLS/PCE Control...................31 
         5.1.1. Describing the WSON nodes...........................32 
         5.1.2. Describing the links................................34 
      5.2. RWA Path Computation and Establishment...................35 
      5.3. Resource Optimization....................................36 
      5.4. Support for Rerouting....................................37 
      5.5. Electro-Optical Networking Scenarios.....................37 
         5.5.1. Fixed Regeneration Points...........................37 
         5.5.2. Shared Regeneration Pools...........................38 
         5.5.3. Reconfigurable Regenerators.........................38 
         5.5.4. Relation to Translucent Networks....................38 
   6. GMPLS and PCE Implications....................................39 
      6.1. Implications for GMPLS signaling.........................39 
         6.1.1. Identifying Wavelengths and Signals.................39 
         6.1.2. WSON Signals and Network Element Processing.........40 
         6.1.3. Combined RWA/Separate Routing WA support............40 
         6.1.4. Distributed Wavelength Assignment: Unidirectional, No 
         Converters.................................................41 
         6.1.5. Distributed Wavelength Assignment: Unidirectional, 
         Limited Converters.........................................41 
         6.1.6. Distributed Wavelength Assignment: Bidirectional, No 
         Converters.................................................41 
      6.2. Implications for GMPLS Routing...........................42 
         6.2.1. Electro-Optical Element Signal Compatibility........42 
         6.2.2. Wavelength-Specific Availability Information........43 
         6.2.3. WSON Routing Information Summary....................43 
      6.3. Optical Path Computation and Implications for PCE........45 
         6.3.1. Optical path Constraints and Characteristics........45 
         6.3.2. Electro-Optical Element Signal Compatibility........45 
         6.3.3. Discovery of RWA Capable PCEs.......................46 
   7. Security Considerations.......................................46 
   8. IANA Considerations...........................................47 
   9. Acknowledgments...............................................47 
   10. References...................................................48 
      10.1. Normative References....................................48 
      10.2. Informative References..................................49 
   11. Contributors.................................................51 
   Author's Addresses...............................................52 
   Intellectual Property Statement..................................52 
   Disclaimer of Validity...........................................53 
    
     

   Bernstein and Lee Expires August 8, 2011  [Page 3] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

1. Introduction 

   Wavelength Switched Optical Networks (WSONs) are constructed from 
   subsystems that 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 WDM-based optical network in which 
   switching is performed selectively based on the center wavelength of 
   an optical signal. 

   WSONs can differ from other types of GMPLS networks in that many 
   types of WSON nodes are highly asymmetric with respect to their 
   switching capabilities, compatibility of signal types and network 
   elements may need to be considered, and label assignment can be non-
   local. In order to provision an optical connection (an optical path) 
   through a WSON certain wavelength continuity and resource 
   availability constraints must be met to determine viable and optimal 
   paths through the WSON. The determination of paths is known as 
   Routing and Wavelength Assignment (RWA). 

   Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] includes 
   an architecture and 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, to WDM 
   networks.  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. 

   This document provides a framework for applying the GMPLS 
   architecture and protocols [RFC3945], and the PCE architecture 
   [RFC4655] to the control and operation of WSONs.  To aid in this 
   process this document also provides an overview of the subsystems and 
   processes that comprise WSONs, and describes RWA so that the 
   information requirements, both static and dynamic, 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. 

   Different WSONs such as access, metro, and long haul may apply 
   different techniques for dealing with optical impairments hence this 
   document does not address optical impairments in any depth. Note that 
   this document focuses on the generic properties of links, switches 
   and path selection constraints that occur in many types of WSONs.  
   See [WSON-Imp] for more information on optical impairments and GMPLS.  

     

   Bernstein and Lee Expires August 8, 2011  [Page 4] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

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. 

   Degree: The degree of an optical device (e.g., ROADM) is given by a 
   count of its line side ports. 

   Drop and continue: A simple multi-cast feature of some ADM where a 
   selected wavelength can be switched out of both a tributary (drop) 
   port and a line side port. 

   FOADM: Fixed Optical Add/Drop Multiplexer. 

   GMPLS: Generalized Multi-Protocol Label Switching. 

   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.  

   RWA: Routing and Wavelength Assignment. 

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

     

   Bernstein and Lee Expires August 8, 2011  [Page 5] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   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 
   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. Wavelength Switched Optical Networks 

   WSONs range in size from continent spanning long haul networks, to 
   metropolitan networks, to residential access networks. In all these 
   cases, the main concern is those properties that constrain the choice 
   of wavelengths that can be used, i.e., restrict the wavelength label 
   set, impact the path selection process, and limit the topological 
   connectivity. In addition, if electro-optical network elements are 
   used in the WSON, additional compatibility constraints may be imposed 
   by the network elements on various optical signal parameters. The 
   subsequent sections review and model some of the major subsystems of 
   a WSON with an emphasis on those aspects that are of relevance to the 
   control plane. In particular, WDM links, optical transmitters, 
   ROADMs, and wavelength converters are examined.   

   3.1. WDM and CWDM Links 

   WDM and CWDM links run over optical fibers, and optical fibers come 
   in a wide range of types that tend to be optimized for various 
   applications. Examples include access networks, metro, long haul, and 
   submarine links. International Telecommunication Union - 
   Telecommunication Standardization Sector (ITU-T) standards exist for 
   various types of fibers. Although fiber can be categorized into 
   Single mode fibers (SMF) and Multi-mode fibers (MMF), the latter are 
   typically used for short-reach campus and premise applications. SMF 
   are used for longer-reach applications and therefore are the primary 
     

   Bernstein and Lee Expires August 8, 2011  [Page 6] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   concern of this document. The following SMF fiber types are typically 
   encountered in optical networks: 

      ITU-T Standard |  Common Name  
      ------------------------------------------------------------     
      G.652 [G.652]  |  Standard SMF                              | 
      G.653 [G.653]  |  Dispersion shifted SMF                    | 
      G.654 [G.654]  |  Cut-off shifted SMF                       | 
      G.655 [G.655]  |  Non-zero dispersion shifted SMF           | 
      G.656 [G.656]  |  Wideband non-zero dispersion shifted SMF  | 
      ------------------------------------------------------------ 
    

   Typically WDM links operate in one or more of the approximately 
   defined optical bands [G.Sup39]: 

      Band     Range (nm)     Common Name    Raw Bandwidth (THz) 
      O-band   1260-1360      Original       17.5 
      E-band   1360-1460      Extended       15.1 
      S-band   1460-1530      Short          9.4 
      C-band   1530-1565      Conventional   4.4 
      L-band   1565-1625      Long           7.1 
      U-band   1625-1675      Ultra-long     5.5 
    

    
   Not all of a band may be usable, for example in many fibers that 
   support E-band there is significant attenuation due to a water 
   absorption peak at 1383nm. Hence a discontinuous acceptable 
   wavelength range for a particular link may be needed and is modeled. 
   Also some systems will utilize more than one band. This is 
   particularly true for CWDM systems.  

   Current technology subdivides the bandwidth capacity of fibers into 
   distinct channels based on either wavelength or frequency. There are 
   two standards covering wavelengths and channel spacing. ITU-T 
   Recommendation G.694.1, Spectral grids for WDM applications: DWDM 
   frequency grid [G.694.1] describes a DWDM grid defined in terms of 
   frequency grids of 12.5GHz, 25GHz, 50GHz, 100GHz, and other multiples 
   of 100GHz around a 193.1THz center frequency. At the narrowest 
   channel spacing this provides less than 4800 channels across the O 
   through U bands. ITU-T Recommendation G.694.2, Spectral grids for WDM 
   applications: CWDM wavelength grid [G.694.2] describes a CWDM grid 
   defined in terms of wavelength increments of 20nm running from 1271nm 
   to 1611nm for 18 or so channels. The number of channels is 
   significantly smaller than the 32 bit GMPLS label space defined for 
   GMPLS, see [RFC3471].  A label representation for these ITU-T grids 
   is given in [Otani] and provides a common label format to be used in 
     

   Bernstein and Lee Expires August 8, 2011  [Page 7] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   signaling optical paths. Further, these ITU-T grid based labels can 
   also be used to describe WDM links, ROADM ports, and wavelength 
   converters for the purposes of path selection. 

   Many WDM links are designed to take advantage of particular fiber 
   characteristics or to try to avoid undesirable properties.  For 
   example dispersion shifted SMF [G.653] was originally designed for 
   good long distance performance in single channel systems, however 
   putting WDM over this type of fiber requires significant system 
   engineering and a fairly limited range of wavelengths. Hence the 
   following information is needed as parameters to perform basic, 
   impairment unaware, modeling of a WDM link: 

   o  Wavelength range(s): Given a mapping between labels and the ITU-T 
      grids each range could be expressed in terms of a tuple (lambda1, 
      lambda2) or (freq1, freq1) where the lambdas or frequencies can be 
      represented by 32 bit integers. 

   o  Channel spacing: Currently there are five channel spacings used in 
      DWDM systems and a single channel spacing defined for CWDM 
      systems. 

   For a particular link this information is relatively static, as 
   changes to these properties generally require hardware upgrades. Such 
   information may be used locally during wavelength assignment via 
   signaling, similar to label restrictions in MPLS or used by a PCE in 
   providing combined RWA. 

   3.2. Optical Transmitters and Receivers 

   WDM optical systems make use of optical transmitters and receivers 
   utilizing different wavelengths (frequencies). Some transmitters are 
   manufactured for a specific wavelength of operation, that is, the 
   manufactured frequency cannot be changed. First introduced to reduce 
   inventory costs, tunable optical transmitters and receivers are 
   deployed in some systems, and allow flexibility in the wavelength 
   used for optical transmission/reception.  Such tunable optics aid in 
   path selection.  

   Fundamental modeling parameters from the control plane perspective 
   optical transmitters and receivers are: 

   o  Tunable: Do the transmitter and receivers operate at variable or 
      fixed wavelength. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 8] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   o  Tuning range: This is the frequency or wavelength range over which 
      the optics can be tuned. With the fixed mapping of labels to 
      lambdas as proposed in [Otani] this can be expressed as a tuple 
      (lambda1, lambda2) or (freq1, freq2) where lambda1 and lambda2 or 
      freq1 and freq2 are the labels representing the lower and upper 
      bounds in wavelength. 

   o  Tuning time: Tuning times highly depend on the technology used. 
      Thermal drift based tuning may take seconds to stabilize, whilst 
      electronic tuning might provide sub-ms tuning times. Depending on 
      the application this might be critical. For example, thermal drift 
      might not be usable for fast protection applications. 

   o  Spectral characteristics and stability: The spectral shape of a 
      laser's emissions and its frequency stability put limits on 
      various properties of the overall WDM system. One relatively easy 
      to characterize constraint is the closest channel spacing with 
      which the transmitter can be used. 

   Note that ITU-T recommendations specify many aspects of an optical 
   transmitter. Many of these parameters, such as spectral 
   characteristics and stability, are used in the design of WDM 
   subsystems consisting of transmitters, WDM links and receivers 
   however they do not furnish additional information that will 
   influence the Label Switched Path (LSP) provisioning in a properly 
   designed system. 

   Also note that optical components can degrade and fail over time. 
   This presents the possibility of the failure of a LSP (optical path) 
   without either a node or link failure. Hence, additional mechanisms 
   may be necessary to detect and differentiate this failure from the 
   others, e.g., one doesn't want to initiate mesh restoration if the 
   source transmitter has failed, since the optical transmitter will 
   still be failed on the alternate optical path. 

   3.3. Optical Signals in WSONs 

   In WSONs the fundamental unit of switching is intuitively that of a 
   "wavelength". The transmitters and receivers in these networks will 
   deal with one wavelength at a time, while the switching systems 
   themselves can deal with multiple wavelengths at a time. Hence 
   multichannel DWDM networks with single channel interfaces are the 
   prime focus of this document as opposed to multi-channel interfaces. 
   Interfaces of this type are defined in ITU-T recommendations 
   [G.698.1] and [G.698.2]. Key non-impairment related parameters 
   defined in [G.698.1] and [G.698.2] are: 

   (a)   Minimum channel spacing (GHz) 
     

   Bernstein and Lee Expires August 8, 2011  [Page 9] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   (b)   Minimum and maximum central frequency 

   (c)   Bit-rate/Line coding (modulation) of optical tributary signals 

   For the purposes of modeling the WSON in the control plane, (a) and 
   (b) are considered as properties of the link and restrictions on the 
   GMPLS labels while (c) is a property of the "signal". 

      3.3.1. Optical Tributary Signals 

   The optical interface specifications [G.698.1], [G.698.2], and 
   [G.959.1] all use the concept of an optical tributary signal which is 
   defined as "a single channel signal that is placed within an optical 
   channel for transport across the optical network". Note the use of 
   the qualifier "tributary" to indicate that this is a single channel 
   entity and not a multichannel optical signal.  

   There are currently a number of different types of optical tributary 
   signals, which are known as "optical tributary signal classes". These 
   are currently characterized by a modulation format and bit rate range 
   [G.959.1]: 

   (a)   Optical tributary signal class NRZ 1.25G 

   (b)   Optical tributary signal class NRZ 2.5G 

   (c)   Optical tributary signal class NRZ 10G 

   (d)   Optical tributary signal class NRZ 40G 

   (e)   Optical tributary signal class RZ 40G 

   Note that with advances in technology more optical tributary signal 
   classes may be added and that this is currently an active area for 
   development and standardization. In particular at the 40G rate there 
   are a number of non-standardized advanced modulation formats that 
   have seen significant deployment including Differential Phase Shift 
   Keying (DPSK) and Phase Shaped Binary Transmission (PSBT). 

   According to [G.698.2] it is important to fully specify the bit rate 
   of the optical tributary signal. Hence it is seen that modulation 
   format (optical tributary signal class) and bit rate are key 
   parameters in characterizing the optical tributary signal. 

      3.3.2. WSON Signal Characteristics 

   An optical tributary signal referenced in ITU-T [G.698.1] and 
   [G.698.2] is referred to as the "signal" in this document. This 
     

   Bernstein and Lee Expires August 8, 2011  [Page 10] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   corresponds to the "lambda" LSP in GMPLS. For signal compatibility 
   purposes with electro-optical network elements, the following signal 
   characteristics are considered: 

  1. Optical tributary signal class (modulation format).  
  2. FEC: whether forward error correction is used in the digital stream 
     and what type of error correcting code is used. 
  3. Center frequency (wavelength).  
  4. Bit rate. 
  5. G-PID: general protocol identifier for the information format.  
    
   The first three items on this list can change as a WSON signal 
   traverses the optical network with elements that include 
   regenerators, Optical-to-Electrical (OEO) switches, or wavelength 
   converters. 
    
   Bit rate and G-PID would not change since they describe the encoded 
   bit stream. A set of G-PID values is already defined for lambda 
   switching in [RFC3471] and [RFC4328]. 
    
   Note that a number of non-standard or proprietary modulation formats 
   and FEC codes are commonly used in WSONs. For some digital bit 
   streams the presence of Forward Error Correction (FEC) can be 
   detected, e.g., in [G.707] this is indicated in the signal itself via 
   the FEC Status Indication (FSI) byte, while in [G.709] this can be 
   inferred from whether the FEC field of the Optical Channel Transport 
   Unit-k (OTUk) is all zeros or not.  
    

   3.4. ROADMs, OXCs, Splitters, Combiners and FOADMs 

   Definitions of various optical devices such as ROADMs, Optical Cross-
   connects (OXCs), splitters, combiners and Fixed Optical Add-Drop 
   Multiplexers (FOADMs) and their parameters can be found in [G.671]. 
   Only a subset of these relevant to the control plane and their non-
   impairment related properties are considered in the following 
   sections.  

      3.4.1. Reconfigurable Add/Drop Multiplexers and OXCs 

   ROADMs are available in different forms and technologies. This is a 
   key technology that allows wavelength based optical switching. A 
   classic degree-2 ROADM is shown in Figure 1. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 11] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

 
          Line side input    +---------------------+  Line side output 
                         --->|                     |---> 
                             |                     | 
                             |        ROADM        | 
                             |                     | 
                             |                     | 
                             +---------------------+ 
                                 | | | |  o o o o 
                                 | | | |  | | | | 
                                 O O O O  | | | | 
         Tributary Side:   Drop (output)  Add (input)  
    
                  Figure 1. Degree-2 unidirectional ROADM 

   The key feature across all ROADM types is their highly asymmetric 
   switching capability. In the ROADM of Figure 1, signals introduced 
   via the add ports can only be sent on the line side output port and 
   not on any of the drop ports. The term "degree" is used to refer to 
   the number of line side ports (input and output) of a ROADM, and does 
   not include the number of "add" or "drop" ports. The add and drop 
   ports are sometimes also called tributary ports. As the degree of the 
   ROADM increases beyond two it can have properties of both a switch 
   (OXC) and a multiplexer and hence it is necessary to know the 
   switched connectivity offered by such a network element to 
   effectively utilize it. A straightforward way to represent this is 
   via a "switched connectivity" matrix A where Amn = 0 or 1, depending 
   upon whether a wavelength on input port m can be connected to output 
   port n [Imajuku]. For the ROADM shown in Figure 1 the switched 
   connectivity matrix can be expressed as: 

               Input    Output Port 
               Port     #1 #2 #3 #4 #5 
                        -------------- 
               #1:      1  1  1  1  1 
               #2       1  0  0  0  0 
         A =   #3       1  0  0  0  0 
               #4       1  0  0  0  0   
               #5       1  0  0  0  0 
    
   Where input ports 2-5 are add ports, output ports 2-5 are drop ports 
   and input port #1 and output port #1 are the line side (WDM) ports. 

   For ROADMs, this matrix will be very sparse, and for OXCs the matrix 
   will be very dense. Compact encodings and examples, including high 
   degree ROADMs/OXCs, are given in [Gen-Encode]. A degree-4 ROADM is 
   shown in Figure 2. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 12] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

     
    
                      +-----------------------+   
   Line side-1    --->|                       |--->    Line side-2  
   Input (I1)         |                       |        Output (E2) 
   Line side-1    <---|                       |<---    Line side-2  
   Output  (E1)       |                       |        Input (I2) 
                      |         ROADM         |                                
   Line side-3    --->|                       |--->    Line side-4  
   Input (I3)         |                       |        Output (E4) 
   Line side-3    <---|                       |<---    Line side-4  
   Output (E3)        |                       |        Input (I4) 
                      |                       | 
                      +-----------------------+ 
                      | O    | O    | O    | O 
                      | |    | |    | |    | | 
                      O |    O |    O |    O | 
 Tributary Side:     E5 I5  E6 I6  E7 I7  E8 I8 
 
 
                  Figure 2. Degree-4 bidirectional ROADM 

 
   Note that this example is 4-degree example with one (potentially 
   multi-channel) add/drop per line side port.  

   Note also that the connectivity constraints for typical ROADM designs 
   are "bidirectional", i.e. if input port X can be connected to output 
   port Y, typically input port Y can be connected to output port X, 
   assuming the numbering is done in such a way that input X and output 
   X correspond to the same line side direction or the same add/drop 
   port. This makes the connectivity matrix symmetrical as shown below.  

     Input     Output Port 
      Port     E1 E2 E3 E4 E5 E6 E7 E8 
               ----------------------- 
         I1    0  1  1  1  0  1  0  0 
         I2    1  0  1  1  0  0  1  0 
     A = I3    1  1  0  1  1  0  0  0 
         I4    1  1  1  0  0  0  0  1 
         I5    0  0  1  0  0  0  0  0 
         I6    1  0  0  0  0  0  0  0 
         I7    0  1  0  0  0  0  0  0  
         I8    0  0  0  1  0  0  0  0 

   Where I5/E5 are add/drop ports to/from line side-3, I6/E6 are 
   add/drop ports to/from line side-1, I7/E7 are add/drop ports to/from 
   line side-2 and I8/E8 are add/drop ports to/from line side-4. Note 
     

   Bernstein and Lee Expires August 8, 2011  [Page 13] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   that diagonal elements are zero since loopback is not supported in 
   the example. If ports support loopback, diagonal elements would be 
   set to one. 

   Additional constraints may also apply to the various ports in a 
   ROADM/OXC. The following restrictions and terms may be used: 

   Colored port: an input or more typically an output (drop) port 
   restricted to a single channel of fixed wavelength.  

   Colorless port: an input or more typically an output (drop) port 
   restricted to a single channel of arbitrary wavelength. 

   In general a port on a ROADM could have any of the following 
   wavelength restrictions: 

   o  Multiple wavelengths, full range port. 

   o  Single wavelength, full range port. 

   o  Single wavelength, fixed lambda port. 

   o  Multiple wavelengths, reduced range port (for example wave band 
      switching). 

   To model these restrictions it is necessary to have two pieces of 
   information for each port: (a) number of wavelengths, (b) wavelength 
   range and spacing.  Note that this information is relatively static. 
   More complicated wavelength constraints are modeled in [WSON-Info]. 

      3.4.2. Splitters 

   An optical splitter consists of a single input port and two or more 
   output ports. The input optical signaled is essentially copied (with 
   power loss) to all output ports.  

   Using the modeling notions of Section 3.4.1. (Reconfigurable Add/Drop 
   Multiplexers and OXCs) the input and output ports of a splitter would 
   have the same wavelength restrictions. In addition a splitter is 
   modeled by a connectivity matrix Amn as follows: 

               Input    Output Port 
               Port     #1 #2 #3 ...   #N 
                        ----------------- 
         A =   #1       1  1  1  ...   1 
                
   The difference from a simple ROADM is that this is not a switched 
   connectivity matrix but the fixed connectivity matrix of the device. 
     

   Bernstein and Lee Expires August 8, 2011  [Page 14] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

      3.4.3. Combiners 

   An optical combiner is a device that combines the optical wavelengths 
   carried by multiple input ports into a single multi-wavelength output 
   port.  The various ports may have different wavelength restrictions. 
   It is generally the responsibility of those using the combiner to 
   assure that wavelength collision does not occur on the output port. 
   The fixed connectivity matrix Amn for a combiner would look like: 

               Input    Output Port 
               Port     #1  
                        --- 
               #1:      1   
               #2       1   
         A =   #3       1   
               ...      1      
               #N       1   
    
    

      3.4.4. Fixed Optical Add/Drop Multiplexers 

   A fixed optical add/drop multiplexer can alter the course of an input 
   wavelength in a preset way. In particular a given wavelength (or 
   waveband) from a line side input port would be dropped to a fixed 
   "tributary" output port. Depending on the device's construction that 
   same wavelength may or may not also be sent out the line side output 
   port.  This is commonly referred to as "drop and continue" operation.  
   There also may exist tributary input ports ("add" ports) whose 
   signals are combined with each other and other line side signals.  

   In general, to represent the routing properties of an FOADM it is 
   necessary to have both a fixed connectivity matrix Amn as previously 
   discussed and the precise wavelength restrictions for all input and 
   output ports. From the wavelength restrictions on the tributary 
   output ports, what wavelengths have been selected can be derived. 
   From the wavelength restrictions on the tributary input ports, it can 
   be seen which wavelengths have been added to the line side output 
   port. Finally from the added wavelength information and the line side 
   output wavelength restrictions it can be inferred which wavelengths 
   have been continued.  

   To summarize, the modeling methodology introduced in Section 3.4.1. 
   (Reconfigurable Add/Drop Multiplexers and OXCs) consisting of a 
   connectivity matrix and port wavelength restrictions can be used to 
   describe a large set of fixed optical devices such as combiners, 
   splitters and FOADMs. Hybrid devices consisting of both switched and 
   fixed parts are modeled in [WSON-Info]. 
     

   Bernstein and Lee Expires August 8, 2011  [Page 15] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   3.5. Electro-Optical Systems 

   This section describes how Electro-Optical Systems (e.g., OEO 
   switches, wavelength converters, and regenerators) interact with the 
   WSON signal characteristics listed in Section 3.3.2. (WSON Signal 
   Characteristics) OEO switches, wavelength converters and regenerators 
   all share a similar property: they can be more or less "transparent" 
   to an "optical signal" depending on their functionality and/or 
   implementation. Regenerators have been fairly well characterized in 
   this regard and hence their properties can be described first. 

      3.5.1. Regenerators 

   The various approaches to regeneration are discussed in ITU-T G.872 
   Annex A [G.872]. They map a number of functions into the so-called 
   1R, 2R and 3R categories of regenerators as summarized in Table 1 
   below: 

   Table 1. Regenerator functionality mapped to general regenerator 
   classes from [G.872]. 

   --------------------------------------------------------------------- 
   1R | Equal amplification of all frequencies within the amplification  
      | bandwidth. There is no restriction upon information formats. 
      +----------------------------------------------------------------- 
      | Amplification with different gain for frequencies within the  
      | amplification bandwidth. This could be applied to both single- 
      | channel and multi-channel systems. 
      +----------------------------------------------------------------- 
      | Dispersion compensation (phase distortion). This analogue  
      | process can be applied in either single-channel or multi- 
      | channel systems. 
   --------------------------------------------------------------------- 
   2R | Any or all 1R functions. Noise suppression. 
      +----------------------------------------------------------------- 
      | Digital reshaping (Schmitt Trigger function) with no clock  
      | recovery. This is applicable to individual channels and can be  
      | used for different bit rates but is not transparent to line  
      | coding (modulation). 
   -------------------------------------------------------------------- 
   3R | Any or all 1R and 2R functions. Complete regeneration of the  
      | pulse shape including clock recovery and retiming within  
      | required jitter limits. 
   -------------------------------------------------------------------- 

   From this table it is seen that 1R regenerators are generally 
   independent of signal modulation format (also known as line coding), 
   but may work over a limited range of wavelength/frequencies.  2R 
     

   Bernstein and Lee Expires August 8, 2011  [Page 16] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   regenerators are generally applicable to a single digital stream and 
   are dependent upon modulation format (line coding) and to a lesser 
   extent are limited to a range of bit rates (but not a specific bit 
   rate). Finally, 3R regenerators apply to a single channel, are 
   dependent upon the modulation format and generally sensitive to the 
   bit rate of digital signal, i.e., either are designed to only handle 
   a specific bit rate or need to be programmed to accept and regenerate 
   a specific bit rate.  In all these types of regenerators the digital 
   bit stream contained within the optical or electrical signal is not 
   modified. 

   It is common for regenerators to modify the digital bit stream for 
   performance monitoring and fault management purposes. Synchronous 
   Optical Networking (SONET), Synchronous Digital Hierarchy (SDH) and 
   Interfaces for the Optical Transport Network (G.709) all have digital 
   signal "envelopes" designed to be used between "regenerators" (in 
   this case 3R regenerators). In SONET this is known as the "section" 
   signal, in SDH this is known as the "regenerator section" signal, in 
   G.709 this is known as an OTUk.  These signals reserve a portion of 
   their frame structure (known as overhead) for use by regenerators. 
   The nature of this overhead is summarized in Table 2 below. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 17] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

       Table 2. SONET, SDH, and G.709 regenerator related overhead. 

    
    +-----------------------------------------------------------------+ 
    |Function          |       SONET/SDH      |     G.709 OTUk        | 
    |                  |       Regenerator    |                       | 
    |                  |       Section        |                       | 
    |------------------+----------------------+-----------------------| 
    |Signal            |       J0 (section    |  Trail Trace          | 
    |Identifier        |       trace)         |  Identifier (TTI)     | 
    |------------------+----------------------+-----------------------| 
    |Performance       |       BIP-8 (B1)     |  BIP-8 (within SM)    | 
    |Monitoring        |                      |                       | 
    |------------------+----------------------+-----------------------| 
    |Management        |       D1-D3 bytes    |  GCC0 (general        | 
    |Communications    |                      |  communications       | 
    |                  |                      |  channel)             | 
    |------------------+----------------------+-----------------------| 
    |Fault Management  |       A1, A2 framing |  FAS (frame alignment | 
    |                  |       bytes          |  signal), BDI(backward| 
    |                  |                      |  defect indication)BEI| 
    |                  |                      |  (backward error      | 
    |                  |                      |  indication)          | 
    +------------------+----------------------+-----------------------| 
    |Forward Error     |       P1,Q1 bytes    |  OTUk FEC             | 
    |Correction (FEC)  |                      |                       | 
    +-----------------------------------------------------------------+ 
    

   In the previous table it is seen that frame alignment, signal 
   identification, and FEC are supported. What table 2 also shows by its 
   omission is that no switching or multiplexing occurs at this layer. 
   This is a significant simplification for the control plane since 
   control plane standards require a multi-layer approach when there are 
   multiple switching layers, but not for "layering" to provide the 
   management functions of Table 2. That is, many existing technologies 
   covered by GMPLS contain extra management related layers that are 
   essentially ignored by the control plane (though not by the 
   management plane!). Hence, the approach here is to include 
   regenerators and other devices at the WSON layer unless they provide 
   higher layer switching and then a multi-layer or multi-region 
   approach [RFC5212] is called for. However, this can result in 
   regenerators having a dependence on the client signal type. 

   Hence depending upon the regenerator technology the following 
   constraints may be imposed by a regenerator device: 

              Table 3. Regenerator Compatibility Constraints. 
     

   Bernstein and Lee Expires August 8, 2011  [Page 18] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   +--------------------------------------------------------+ 
   |      Constraints            |   1R   |   2R   |   3R   |  
   +--------------------------------------------------------+ 
   | Limited Wavelength Range    |    x   |    x   |    x   | 
   +--------------------------------------------------------+ 
   | Modulation Type Restriction |        |    x   |    x   | 
   +--------------------------------------------------------+ 
   | Bit Rate Range Restriction  |        |    x   |    x   | 
   +--------------------------------------------------------+ 
   | Exact Bit Rate Restriction  |        |        |    x   | 
   +--------------------------------------------------------+ 
   | Client Signal Dependence    |        |        |    x   | 
   +--------------------------------------------------------+ 
    

   Note that the limited wavelength range constraint can be modeled for 
   GMPLS signaling with the label set defined in [RFC3471] and that the 
   modulation type restriction constraint includes FEC.  

      3.5.2. OEO Switches 

   A common place where OEO processing may take place is within WSON 
   switches that utilize (or contain) regenerators. This may be to 
   convert the signal to an electronic form for switching then 
   reconverting to an optical signal prior to output from the switch. 
   Another common technique is to add regenerators to restore signal 
   quality either before or after optical processing (switching).   In 
   the former case the regeneration is applied to adapt the signal to 
   the switch fabric regardless of whether or not it is needed from a 
   signal quality perspective.  

   In either case these optical switches have essentially the same 
   compatibility constraints as those which are described for 
   regenerators in Table 3.  

   3.6. Wavelength Converters 

   Wavelength converters take an input optical signal at one wavelength 
   and emit an equivalent content optical signal at another wavelength 
   on output. There are multiple approaches to building wavelength 
   converters. One approach is based on OEO conversion with fixed or 
   tunable optics on output. This approach can be dependent upon the 
   signal rate and format, i.e., this is basically an electrical 
   regenerator combined with a laser/receiver. Hence, this type of 
   wavelength converter has signal processing restrictions that are 

     

   Bernstein and Lee Expires August 8, 2011  [Page 19] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   essentially the same as those described for regenerators in Table 3 
   of section 3.5.1.  

   Another approach performs the wavelength conversion optically via 
   non-linear optical effects, similar in spirit to the familiar 
   frequency mixing used in radio frequency systems, but significantly 
   harder to implement.  Such processes/effects may place limits on the 
   range of achievable conversion. These may depend on the wavelength of 
   the input signal and the properties of the converter as opposed to 
   only the properties of the converter in the OEO case. Different WSON 
   system designs may choose to utilize this component to varying 
   degrees or not at all. 

   Current or envisioned contexts for wavelength converters are: 

  1. Wavelength conversion associated with OEO switches and fixed or 
     tunable optics. In this case there are typically multiple 
     converters available since each use of an OEO switch can be thought 
     of as a potential wavelength converter.  

  2. Wavelength conversion associated with ROADMs/OXCs. In this case 
     there may be a limited pool of wavelength converters available. 
     Conversion could be either all optical or via an OEO method. 

  3. Wavelength conversion associated with fixed devices such as FOADMs. 
     In this case there may be a limited amount of conversion. Also in 
     this case the conversion may be used as part of optical path 
     routing. 

   Based on the above considerations, wavelength converters are modeled 
   as follows: 

   1. Wavelength converters can always be modeled as associated with 
      network elements. This includes fixed wavelength routing elements. 

   2. A network element may have full wavelength conversion capability, 
      i.e., any input port and wavelength, or a limited number of 
      wavelengths and ports. On a box with a limited number of 
      converters there also may exist restrictions on which ports can 
      reach the converters. Hence regardless of where the converters 
      actually are they can be associated with input ports. 

   3. Wavelength converters have range restrictions that are either 
      independent or dependent upon the input wavelength.  

   In WSONs where wavelength converters are sparse an optical path may 
   appear to loop or "backtrack" upon itself in order to reach a 
   wavelength converter prior to continuing on to its destination. The 
     

   Bernstein and Lee Expires August 8, 2011  [Page 20] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   lambda used on input to the wavelength converter would be different 
   from the lambda coming back from the wavelength converter. 

   A model for an individual O-E-O wavelength converter would consist 
   of: 

   o  Input lambda or frequency range. 

   o  Output lambda or frequency range. 

   

      3.6.1. Wavelength Converter Pool Modeling 

   A WSON node may include multiple wavelength converters. These are 
   usually arranged into some type of pool to promote resource sharing. 
   There are a number of different approaches used in the design of 
   switches with converter pools. However, from the point of view of 
   path computation it is necessary to know the following: 

   1. The nodes that support wavelength conversion. 

   2. The accessibility and availability of a wavelength converter to 
      convert from a given input wavelength on a particular input port 
      to a desired output wavelength on a particular output port. 

   3. Limitations on the types of signals that can be converted and the 
      conversions that can be performed. 

   To model point 2 above, a technique similar to that used to model 
   ROADMs and optical switches can be used, i.e., matrices to indicate 
   possible connectivity along with wavelength constraints for 
   links/ports. Since wavelength converters are considered a scarce 
   resource it will be desirable to include as a minimum the usage state 
   of individual wavelength converters in the pool.  

   A three stage model is used as shown schematically in Figure 3. 
   (Schematic diagram of wavelength converter pool model). This model 
   represents N input ports (fibers), P wavelength converters, and M 
   output ports (fibers). Since not all input ports can necessarily 
   reach the converter pool, the model starts with a wavelength pool 
   input matrix WI(i,p) = {0,1} where input port i can potentially reach 
   wavelength converter p.  

   Since not all wavelengths can necessarily reach all the converters or 
   the converters may have limited input wavelength range there is a set 
   of input port constraints for each wavelength converter. Currently it 
   is assumed that a wavelength converter can only take a single 
     

   Bernstein and Lee Expires August 8, 2011  [Page 21] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   wavelength on input. Each wavelength converter input port constraint 
   can be modeled via a wavelength set mechanism.  

   Next a state vector WC(j) = {0,1} dependent upon whether wavelength 
   converter j in the pool is in use. This is the only state kept in the 
   converter pool model. This state is not necessary for modeling 
   "fixed" transponder system, i.e., systems where there is no sharing.  
   In addition, this state information may be encoded in a much more 
   compact form depending on the overall connectivity structure [Gen-
   Encode]. 

   After that, a set of wavelength converter output wavelength 
   constraints is used. These constraints indicate what wavelengths a 
   particular wavelength converter can generate or are restricted to 
   generating due to internal switch structure. 

   Finally, a wavelength pool output matrix WE(p,k) = {0,1} indicating 
   whether the output from wavelength converter p can reach output port 
   k. Examples of this method being used to model wavelength converter 
   pools for several switch architectures are given in reference [Gen-
   Encode]. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 22] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

    
    
    
      I1   +-------------+                       +-------------+ E1 
     ----->|             |      +--------+       |             |-----> 
      I2   |             +------+ WC #1  +-------+             | E2 
     ----->|             |      +--------+       |             |-----> 
           | Wavelength  |                       |  Wavelength | 
           | Converter   |      +--------+       |  Converter  | 
           | Pool        +------+ WC #2  +-------+  Pool       | 
           |             |      +--------+       |             | 
           | Input       |                       |  Output     | 
           | Connection  |           .           |  Connection | 
           | Matrix      |           .           |  Matrix     | 
           |             |           .           |             | 
           |             |                       |             | 
      IN   |             |      +--------+       |             | EM 
     ----->|             +------+ WC #P  +-------+             |-----> 
           |             |      +--------+       |             | 
           +-------------+   ^               ^   +-------------+ 
                             |               | 
                             |               | 
                             |               | 
                             |               | 
    
                    Input wavelength    Output wavelength 
                    constraints for       constraints for 
                    each converter        each converter 
    
      Figure 3. Schematic diagram of wavelength converter pool model. 

   Figure 4 below shows a simple optical switch in a four wavelength 
   DWDM system sharing wavelength converters in a general shared "per 
   node" fashion.  

     

   Bernstein and Lee Expires August 8, 2011  [Page 23] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

    
                +-----------+ ___________                +------+ 
                |           |--------------------------->|      | 
                |           |--------------------------->|  C   | 
          /|    |           |--------------------------->|  o   | E1 
    I1   /D+--->|           |--------------------------->|  m   | 
        + e+--->|           |                            |  b   |====> 
   ====>| M|    |  Optical  |    +-----------+  +----+   |  i   | 
        + u+--->|   Switch  |    |  WC Pool  |  |O  S|-->|  n   | 
         \x+--->|           |    |  +-----+  |  |p  w|-->|  e   | 
          \|    |           +----+->|WC #1|--+->|t  i|   |  r   | 
                |           |    |  +-----+  |  |i  t|   +------+ 
                |           |    |           |  |c  c|   +------+ 
          /|    |           |    |  +-----+  |  |a  h|-->|      | 
    I2   /D+--->|           +----+->|WC #2|--+->|l   |-->|  C   | E2 
        + e+--->|           |    |  +-----+  |  |    |   |  o   | 
   ====>| M|    |           |    +-----------+  +----+   |  m   |====> 
        + u+--->|           |                            |  b   | 
         \x+--->|           |--------------------------->|  i   | 
          \|    |           |--------------------------->|  n   | 
                |           |--------------------------->|  e   | 
                |___________|--------------------------->|  r   | 
                +-----------+                            +------+ 
    
    Figure 4. An optical switch featuring a shared per node wavelength 
                       converter pool architecture. 

   In this case the input and output pool matrices are simply: 

              +-----+       +-----+ 
              | 1 1 |       | 1 1 | 
          WI =|     |,  WE =|     | 
              | 1 1 |       | 1 1 | 
              +-----+       +-----+ 
    
    
   Figure 5 shows a different wavelength pool architecture known as 
   "shared per fiber". In this case the input and output pool matrices 
   are simply: 

              +-----+       +-----+ 
              | 1 1 |       | 1 0 | 
          WI =|     |,  WE =|     | 
              | 1 1 |       | 0 1 | 
              +-----+       +-----+ 
    
    

     

   Bernstein and Lee Expires August 8, 2011  [Page 24] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

                +-----------+                            +------+ 
                |           |--------------------------->|      | 
                |           |--------------------------->|  C   | 
          /|    |           |--------------------------->|  o   | E1 
    I1   /D+--->|           |--------------------------->|  m   | 
        + e+--->|           |                            |  b   |====> 
   ====>| M|    |  Optical  |    +-----------+           |  i   | 
        + u+--->|   Switch  |    |  WC Pool  |           |  n   | 
         \x+--->|           |    |  +-----+  |           |  e   | 
          \|    |           +----+->|WC #1|--+---------->|  r   | 
                |           |    |  +-----+  |           +------+ 
                |           |    |           |           +------+ 
          /|    |           |    |  +-----+  |           |      | 
    I2   /D+--->|           +----+->|WC #2|--+---------->|  C   | E2 
        + e+--->|           |    |  +-----+  |           |  o   | 
   ====>| M|    |           |    +-----------+           |  m   |====> 
        + u+--->|           |                            |  b   | 
         \x+--->|           |--------------------------->|  i   | 
          \|    |           |--------------------------->|  n   | 
                |           |--------------------------->|  e   | 
                |___________|--------------------------->|  r   | 
                +-----------+                            +------+ 
    Figure 5. An optical switch featuring a shared per fiber wavelength 
                       converter pool architecture. 

    
   3.7. Characterizing Electro-Optical Network Elements 

   In this section electro-optical WSON network elements are 
   characterized by the three key functional components: input 
   constraints, output constraints and processing capabilities.  

                             WSON Network Element 
                          +-----------------------+  
          WSON Signal     |      |         |      |    WSON Signal 
                          |      |         |      | 
        --------------->  |      |         |      | -----------------> 
                          |      |         |      |    
                          +-----------------------+ 
                          <-----> <-------> <----->     
                            
                          Input   Processing Output      
    
                      Figure 6. WSON Network Element 

     

   Bernstein and Lee Expires August 8, 2011  [Page 25] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

      3.7.1. Input Constraints 

   Section 3. (Wavelength Switched Optical Networks) discussed the basic 
   properties regenerators, OEO switches and wavelength converters. From 
   these the following possible types of input constraints and 
   properties are derived: 

   1. Acceptable Modulation formats. 

   2. Client Signal (G-PID) restrictions. 

   3. Bit Rate restrictions. 

   4. FEC coding restrictions. 

   5. Configurability: (a) none, (b) self-configuring, (c) required. 

   These constraints are represented via simple lists. Note that the 
   device may need to be "provisioned" via signaling or some other means 
   to accept signals with some attributes versus others. In other cases 
   the devices maybe relatively transparent to some attributes, e.g., 
   such as a 2R regenerator to bit rate. Finally, some devices may be 
   able to auto-detect some attributes and configure themselves, e.g., a 
   3R regenerator with bit rate detection mechanisms and flexible phase 
   locking circuitry. To account for these different cases item 5 has 
   been added, which describes the devices configurability. 

   Note that such input constraints also apply to the termination of the 
   WSON signal. 

      3.7.2. Output Constraints 

   None of the network elements considered here modifies either the bit 
   rate or the basic type of the client signal. However, they may modify 
   the modulation format or the FEC code. Typically the following types 
   of output constraints are seen: 

   1. Output modulation is the same as input modulation (default). 

   2. A limited set of output modulations is available. 

   3. Output FEC is the same as input FEC code (default). 

   4. A limited set of output FEC codes is available. 

   Note that in cases (2) and (4) above, where there is more than one 
   choice in the output modulation or FEC code then the network element 

     

   Bernstein and Lee Expires August 8, 2011  [Page 26] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   will need to be configured on a per LSP basis as to which choice to 
   use. 

      3.7.3. Processing Capabilities 

   A general WSON network element (NE) can perform a number of signal 
   processing functions including: 

     (A) Regeneration (possibly different types). 

     (B) Fault and Performance Monitoring.  

     (C) Wavelength Conversion.   

     (D) Switching.   

    

   An NE may or may not have the ability to perform regeneration (of the 
   one of the types previously discussed). In addition some nodes may 
   have limited regeneration capability, i.e., a shared pool, which may 
   be applied to selected signals traversing the NE. Hence to describe 
   the regeneration capability of a link or node it is necessary to have 
   at a minimum: 

   1. Regeneration capability: (a)fixed, (b) selective, (c) none. 

   2. Regeneration type: 1R, 2R, 3R. 

   3. Regeneration pool properties for the case of selective 
      regeneration (input and output restrictions, availability). 

   Note that the properties of shared regenerator pools would be 
   essentially the same as that of wavelength converter pools modeled in 
   section 3.6.1. (Wavelength Pool Convertor Modeling). 

   Item (B), fault and performance monitoring, is typically outside the 
   scope of the control plane. However, when the operations are to be 
   performed on an LSP basis or on part of an LSP then the control plane 
   can be of assistance in their configuration. Per LSP, per node, fault 
   and performance monitoring examples include setting up a "section 
   trace" (a regenerator overhead identifier) between two nodes, or 
   intermediate optical performance monitoring at selected nodes along a 
   path. 

    

     

   Bernstein and Lee Expires August 8, 2011  [Page 27] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

4. Routing and Wavelength Assignment and the Control Plane 

   From a control plane perspective, a wavelength-convertible network 
   with full wavelength-conversion capability at each node can be 
   controlled much like a packet MPLS-labeled network or a circuit-
   switched Time-division multiplexing (TDM) network with full time slot 
   interchange capability is controlled.  In this case, the path 
   selection process needs to identify the Traffic Engineered (TE) links 
   to be used by an optical path, and wavelength assignment can be made 
   on a hop-by-hop basis. 

   However, in the case of an optical network without wavelength 
   converters, an optical path needs to be routed from source to 
   destination and must use a single wavelength that is available along 
   that path without "colliding" with a wavelength used by any other 
   optical path that may share an optical fiber. This is sometimes 
   referred to as a "wavelength continuity constraint".  

   In the general case of limited or no wavelength converters the 
   computation of both the links and wavelengths is known as RWA. 

   The inputs to basic RWA are the requested optical path's source and 
   destination, the network topology, the locations and capabilities of 
   any wavelength converters, and the wavelengths available on each 
   optical link. The output from an algorithm providing RWA is an 
   explicit route through ROADMs, a wavelength for optical transmitter, 
   and a set of locations (generally associated with ROADMs or switches) 
   where wavelength conversion is to occur and the new wavelength to be 
   used on each component link after that point in the route. 

   It is to be noted that the choice of specific RWA algorithm is out of 
   the scope for this document. However there are a number of different 
   approaches to dealing with RWA algorithm that can affect the division 
   of effort between path computation/routing and signaling. 

    

   4.1. Architectural Approaches to RWA 

   Two general computational approaches are taken to performing RWA. 
   Some algorithms utilize a two-step procedure of path selection 
   followed by wavelength assignment, and others perform RWA in a 
   combined fashion.   

   In the following, three different ways of performing RWA in 
   conjunction with the control plane are considered. The choice of one 
   of these architectural approaches over another generally impacts the 
   demands placed on the various control plane protocols. The approaches 
     

   Bernstein and Lee Expires August 8, 2011  [Page 28] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   are provided for reference purposes only, and other approaches are 
   possible.  

      4.1.1. Combined RWA (R&WA) 

   In this case, a unique entity is in charge of performing routing and 
   wavelength assignment. This approach relies on a sufficient knowledge 
   of network topology, of available network resources and of network 
   nodes' capabilities. This solution is compatible with most known RWA 
   algorithms, and in particular those concerned with network 
   optimization. On the other hand, this solution requires up-to-date 
   and detailed network information.  

   Such a computational entity could reside in two different places:  

   o  In a PCE which maintains a complete and updated view of network 
      state and provides path computation services to nodes (PCCs). 

   o  In an ingress node, in which case all nodes have the R&WA 
      functionality and network state is obtained by a periodic flooding 
      of information provided by the other nodes. 

      4.1.2. Separated R and WA (R+WA) 

   In this case, one entity performs routing, while a second performs 
   wavelength assignment. The first entity furnishes one or more paths 
   to the second entity which will perform wavelength assignment and 
   final path selection. 

   As the entities computing the path and the wavelength assignment are 
   separated, this constrains the class of RWA algorithms that may be 
   implemented. Although it may seem that algorithms optimizing a joint 
   usage of the physical and wavelength paths are excluded from this 
   solution, many practical optimization algorithms only consider a 
   limited set of possible paths, e.g., as computed via a k-shortest 
   path algorithm. Hence, while there is no guarantee that the selected 
   final route and wavelength offers the optimal solution, by allowing 
   multiple routes to pass to the wavelength selection process 
   reasonable optimization can be performed. 

   The entity performing the routing assignment needs the topology 
   information of the network, whereas the entity performing the 
   wavelength assignment needs information on the network's available 
   resources and specific network node capabilities.  

    

     

   Bernstein and Lee Expires August 8, 2011  [Page 29] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

      4.1.3. Routing and Distributed WA (R+DWA) 

   In this case, one entity performs routing, while wavelength 
   assignment is performed on a hop-by-hop, distributed manner along the 
   previously computed path. This mechanism relies on updating of a list 
   of potential wavelengths used to ensure conformance with the 
   wavelength continuity constraint. 

   As currently specified, the GMPLS protocol suite signaling protocol 
   can accommodate such an approach. GMPLS, per [RFC3471], includes 
   support for the communication of the set of labels (wavelengths) that 
   may be used between nodes via a Label Set. When conversion is not 
   performed at an intermediate node, a hop generates the Label Set it 
   sends to the next hop based on the intersection of the Label Set 
   received from the previous hop and the wavelengths available on the 
   node's switch and ongoing interface. The generation of the outgoing 
   Label Set is up to the node local policy (even if one expects a 
   consistent policy configuration throughout a given transparency 
   domain). When wavelength conversion is performed at an intermediate 
   node, a new Label Set is generated. The egress node selects one label 
   in the Label Set which it received; additionally the node can apply 
   local policy during label selection. GMPLS also provides support for 
   the signaling of bidirectional optical paths. 

   Depending on these policies a wavelength assignment may not be found 
   or one may be found that consumes too many conversion resources 
   relative to what a dedicated wavelength assignment policy would have 
   achieved. Hence, this approach may generate higher blocking 
   probabilities in a heavily loaded network. 

   This solution may be facilitated via signaling extensions which ease 
   its functioning and possibly enhance its performance with respect to 
   blocking probability. Note that this approach requires less 
   information dissemination than the other techniques described.  

   The first entity may be a PCE or the ingress node of the LSP.  

   4.2. Conveying information needed by RWA 

   The previous sections have characterized WSONs and optical path 
   requests. In particular, high level models of the information used by 
   RWA process were presented. This information can be viewed as either 
   relatively static, i.e., changing with hardware changes (including 
   possibly failures), or relatively dynamic, i.e., those that can 
   change with optical path provisioning. The time requirement in which 
   an entity involved in RWA process needs to be notified of such 
   changes is fairly situational. For example, for network restoration 

     

   Bernstein and Lee Expires August 8, 2011  [Page 30] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   purposes, learning of a hardware failure or of new hardware coming 
   online to provide restoration capability can be critical. 

   Currently there are various methods for communicating RWA relevant 
   information, these include, but are not limited to:  

   o  Existing control plane protocols, i.e., GMPLS routing and 
      signaling. Note that routing protocols can be used to convey both 
      static and dynamic information.  

   o  Management protocols such as NetConf, SNMPv3, CLI, and CORBA.  

   o  Directory services and accompanying protocols. These are typically 
      used for the dissemination of relatively static information. 
      Directory services are not suited to manage information in dynamic 
      and fluid environments.  

   o  Other techniques for dynamic information, e.g., sending 
      information directly from NEs to PCE to avoid flooding. This would 
      be useful if the number of PCEs is significantly less than number 
      of WSON NEs. There may be other ways to limit flooding to 
      "interested" NEs. 

   Possible mechanisms to improve scaling of dynamic information 
      include: 

   o  Tailor message content to WSON. For example the use of wavelength 
      ranges, or wavelength occupation bit maps. 

   o  Utilize incremental updates if feasible. 

5. Modeling Examples and Control Plane Use Cases 

   This section provides examples of the fixed and switched optical node 
   and wavelength constraint models of Section 3. and use cases for WSON 
   control plane path computation, establishment, rerouting, and 
   optimization.  

   5.1. Network Modeling for GMPLS/PCE Control 

   Consider a network containing three routers (R1 through R3), eight 
   WSON nodes (N1 through N8) and 18 links (L1 through L18) and one OEO 
   converter (O1) in a topology shown below.  

    

     

   Bernstein and Lee Expires August 8, 2011  [Page 31] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

                    +--+    +--+             +--+       +--------+ 
               +-L3-+N2+-L5-+  +--------L12--+N6+--L15--+   N8   + 
               |    +--+    |N4+-L8---+      +--+       ++--+---++ 
               |            |  +-L9--+|                  |  |   | 
   +--+      +-+-+          ++-+     ||                  | L17 L18 
   |  ++-L1--+   |           |      ++++      +----L16---+  |   | 
   |R1|      | N1|           L7     |R2|      |             |   | 
   |  ++-L2--+   |           |      ++-+      |            ++---++ 
   +--+      +-+-+           |       |        |            +  R3 | 
               |    +--+    ++-+     |        |            +-----+ 
               +-L4-+N3+-L6-+N5+-L10-+       ++----+ 
                    +--+    |  +--------L11--+ N7  + 
                            +--+             ++---++ 
                                              |   | 
                                             L13 L14 
                                              |   | 
                                             ++-+ | 
                                             |O1+-+ 
                                             +--+ 
    
     Figure 7. Routers and WSON nodes in a GMPLS and PCE Environment. 

      5.1.1. Describing the WSON nodes 

   The eight WSON nodes described in Figure 7 have the following 
   properties: 

   o  Nodes N1, N2, N3 have FOADMs installed and can therefore only 
      access a static and pre-defined set of wavelengths. 

   o  All other nodes contain ROADMs and can therefore access all 
      wavelengths. 

   o  Nodes N4, N5, N7 and N8 are multi-degree nodes, allowing any 
      wavelength to be optically switched between any of the links. Note 
      however, that this does not automatically apply to wavelengths 
      that are being added or dropped at the particular node.  

   o  Node N4 is an exception to that: This node can switch any 
      wavelength from its add/drop ports to any of its output links (L5, 
      L7 and L12 in this case). 

   o  The links from the routers are only able to carry one wavelength 
      with the exception of links L8 and L9 which are capable to 
      add/drop any wavelength. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 32] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   o  Node N7 contains an OEO transponder (O1) connected to the node via 
      links L13 and L14. That transponder operates in 3R mode and does 
      not change the wavelength of the signal. Assume that it can 
      regenerate any of the client signals, however only for a specific 
      wavelength. 

   Given the above restrictions, the node information for the eight 
   nodes can be expressed as follows: (where ID == identifier, SCM == 
   switched connectivity matrix, and FCM == fixed connectivity matrix). 

     

   Bernstein and Lee Expires August 8, 2011  [Page 33] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   +ID+SCM                    +FCM                    + 
   |  |   |L1 |L2 |L3 |L4 |   |   |L1 |L2 |L3 |L4 |   | 
   |  |L1 |0  |0  |0  |0  |   |L1 |0  |0  |1  |0  |   | 
   |N1|L2 |0  |0  |0  |0  |   |L2 |0  |0  |0  |1  |   | 
   |  |L3 |0  |0  |0  |0  |   |L3 |1  |0  |0  |1  |   | 
   |  |L4 |0  |0  |0  |0  |   |L4 |0  |1  |1  |0  |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L3 |L5 |   |   |   |   |L3 |L5 |   |   |   | 
   |N2|L3 |0  |0  |   |   |   |L3 |0  |1  |   |   |   | 
   |  |L5 |0  |0  |   |   |   |L5 |1  |0  |   |   |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L4 |L6 |   |   |   |   |L4 |L6 |   |   |   | 
   |N3|L4 |0  |0  |   |   |   |L4 |0  |1  |   |   |   | 
   |  |L6 |0  |0  |   |   |   |L6 |1  |0  |   |   |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L5 |L7 |L8 |L9 |L12|   |L5 |L7 |L8 |L9 |L12| 
   |  |L5 |0  |1  |1  |1  |1  |L5 |0  |0  |0  |0  |0  | 
   |N4|L7 |1  |0  |1  |1  |1  |L7 |0  |0  |0  |0  |0  | 
   |  |L8 |1  |1  |0  |1  |1  |L8 |0  |0  |0  |0  |0  | 
   |  |L9 |1  |1  |1  |0  |1  |L9 |0  |0  |0  |0  |0  | 
   |  |L12|1  |1  |1  |1  |0  |L12|0  |0  |0  |0  |0  | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L6 |L7 |L10|L11|   |   |L6 |L7 |L10|L11|   | 
   |  |L6 |0  |1  |0  |1  |   |L6 |0  |0  |1  |0  |   | 
   |N5|L7 |1  |0  |0  |1  |   |L7 |0  |0  |0  |0  |   | 
   |  |L10|0  |0  |0  |0  |   |L10|1  |0  |0  |0  |   | 
   |  |L11|1  |1  |0  |0  |   |L11|0  |0  |0  |0  |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L12|L15|   |   |   |   |L12|L15|   |   |   | 
   |N6|L12|0  |1  |   |   |   |L12|0  |0  |   |   |   | 
   |  |L15|1  |0  |   |   |   |L15|0  |0  |   |   |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L11|L13|L14|L16|   |   |L11|L13|L14|L16|   | 
   |  |L11|0  |1  |0  |1  |   |L11|0  |0  |0  |0  |   | 
   |N7|L13|1  |0  |0  |0  |   |L13|0  |0  |1  |0  |   | 
   |  |L14|0  |0  |0  |1  |   |L14|0  |1  |0  |0  |   | 
   |  |L16|1  |0  |1  |0  |   |L16|0  |0  |1  |0  |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |  |   |L15|L16|L17|L18|   |   |L15|L16|L17|L18|   | 
   |  |L15|0  |1  |0  |0  |   |L15|0  |0  |0  |1  |   | 
   |N8|L16|1  |0  |0  |0  |   |L16|0  |0  |1  |0  |   | 
   |  |L17|0  |0  |0  |0  |   |L17|0  |1  |0  |0  |   | 
   |  |L18|0  |0  |0  |0  |   |L18|1  |0  |1  |0  |   | 
   +--+---+---+---+---+---+---+---+---+---+---+---+---+ 
    
      5.1.2. Describing the links 

   For the following discussion some simplifying assumptions are made: 
     

   Bernstein and Lee Expires August 8, 2011  [Page 34] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

    
   o   It is assumed that the WSON node support a total of four 
      wavelengths designated WL1 through WL4. 

   o   It is assumed that the impairment feasibility of a path or path 
      segment is independent from the wavelength chosen. 

   For the discussion of RWA operation to build LSPs between two 
   routers, the wavelength constraints on the links between the routers 
   and the WSON nodes as well as the connectivity matrix of these links 
   needs to be specified: 

   +Link+WLs supported    +Possible output links+ 
   | L1 | WL1             | L3                  | 
   +----+-----------------+---------------------+ 
   | L2 | WL2             | L4                  | 
   +----+-----------------+---------------------+ 
   | L8 | WL1 WL2 WL3 WL4 | L5 L7 L12           | 
   +----+-----------------+---------------------+ 
   | L9 | WL1 WL2 WL3 WL4 | L5 L7 L12           | 
   +----+-----------------+---------------------+ 
   | L10| WL2             | L6                  | 
   +----+-----------------+---------------------+ 
   | L13| WL1 WL2 WL3 WL4 | L11 L14             | 
   +----+-----------------+---------------------+ 
   | L14| WL1 WL2 WL3 WL4 | L13 L16             | 
   +----+-----------------+---------------------+ 
   | L17| WL2             | L16                 | 
   +----+-----------------+---------------------+ 
   | L18| WL1             | L15                 | 
   +----+-----------------+---------------------+ 
    

   Note that the possible output links for the links connecting to the 
   routers is inferred from the switched connectivity matrix and the 
   fixed connectivity matrix of the Nodes N1 through N8 and is show here 
   for convenience, i.e., this information does not need to be repeated. 

   5.2. RWA Path Computation and Establishment  

   The calculation of optical impairment feasible routes is outside the 
   scope of this document. In general optical impairment feasible routes 
   serve as an input to RWA algorithm. 

   For the example use case shown here, assume the following feasible 
   routes: 

     

   Bernstein and Lee Expires August 8, 2011  [Page 35] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   +Endpoint 1+Endpoint 2+Feasible Route        + 
   |  R1      | R2       | L1 L3 L5 L8          | 
   |  R1      | R2       | L1 L3 L5 L9          | 
   |  R1      | R2       | L2 L4 L6 L7 L8       | 
   |  R1      | R2       | L2 L4 L6 L7 L9       | 
   |  R1      | R2       | L2 L4 L6 L10         | 
   |  R1      | R3       | L1 L3 L5 L12 L15 L18 | 
   |  R1      | N7       | L2 L4 L6 L11         | 
   |  N7      | R3       | L16 L17              | 
   |  N7      | R2       | L16 L15 L12 L9       | 
   |  R2      | R3       | L8 L12 L15 L18       | 
   |  R2      | R3       | L8 L7 L11 L16 L17    | 
   |  R2      | R3       | L9 L12 L15 L18       | 
   |  R2      | R3       | L9 L7 L11 L16 L17    | 
    
   Given a request to establish a LSP between R1 and R2 RWA algorithm 
   finds the following possible solutions: 

   +WL  + Path          + 
   | WL1| L1 L3 L5 L8   | 
   | WL1| L1 L3 L5 L9   | 
   | WL2| L2 L4 L6 L7 L8| 
   | WL2| L2 L4 L6 L7 L9| 
   | WL2| L2 L4 L6 L10  | 
    

   Assume now that RWA algorithm yields WL1 and the Path L1 L3 L5 L8 for 
   the requested LSP. 

   Next, another LSP is signaled from R1 to R2. Given the established 
   LSP using WL1, the following table shows the available paths: 

   +WL  + Path          + 
   | WL2| L2 L4 L6 L7 L9| 
   | WL2| L2 L4 L6 L10  |  

   Assume now that RWA algorithm yields WL2 and the path L2 L4 L6 L7 L9 
   for the establishment of the new LSP. 

   A LSP request -this time from R2 to R3 - can not be fulfilled since 
   the only four possible paths (starting at L8 and L9) are already in 
   use. 

   5.3. Resource Optimization 

   The preceding example gives rise to another use case: the 
   optimization of network resources. Optimization can be achieved on a 
   number of layers (e.g. through electrical or optical multiplexing of 
     

   Bernstein and Lee Expires August 8, 2011  [Page 36] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   client signals) or by re-optimizing the solutions found by a RWA 
   algorithm. 

   Given the above example again, assume that a RWA algorithm should 
   identify a path between R2 and R3. The only possible path to reach R3 
   from R2 needs to use L9. L9 however is blocked by one of the LSPs 
   from R1.  

   5.4. Support for Rerouting 

   It is also envisioned that the extensions to GMPLS and PCE support 
   rerouting of wavelengths in case of failures. 

   Assume for this discussion that the only two LSPs in use in the 
   system are: 

   LSP1: WL1 L1 L3 L5 L8 

   LSP2: WL2 L2 L4 L6 L7 L9 

   Assume furthermore that the link L5 fails. An RWA algorithm can now 
   compute the following alternate path and establish that path: 

   R1 -> N7 -> R2 

   Level 3 regeneration will take place at N7, so that the complete path 
   looks like this: 

   R1 -> L2 L4 L6 L11 L13 -> O1 -> L14 L16 L15 L12 L9 -> R2 

   5.5. Electro-Optical Networking Scenarios 

   In the following various networking scenarios are considered 
   involving regenerators, OEO switches and wavelength converters. These 
   scenarios can be grouped roughly by type and number of extensions to 
   the GMPLS control plane that would be required. 

      5.5.1. Fixed Regeneration Points 

   In the simplest networking scenario involving regenerators, 
   regeneration is associated with a WDM link or an entire node and is 
   not optional, i.e., all signals traversing the link or node will be 
   regenerated. This includes OEO switches since they provide 
   regeneration on every port. 

   There may be input constraints and output constraints on the 
   regenerators. Hence the path selection process will need to know from 
   routing or other means the regenerator constraints so that it can 
     

   Bernstein and Lee Expires August 8, 2011  [Page 37] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   choose a compatible path. For impairment aware routing and wavelength 
   assignment (IA-RWA) the path selection process will also need to know 
   which links/nodes provide regeneration. Even for "regular" RWA, this 
   regeneration information is useful since wavelength converters 
   typically perform regeneration and the wavelength continuity 
   constraint can be relaxed at such a point. 

   Signaling does not need to be enhanced to include this scenario since 
   there are no reconfigurable regenerator options on input, output or 
   with respect to processing. 

      5.5.2. Shared Regeneration Pools 

   In this scenario there are nodes with shared regenerator pools within 
   the network in addition to fixed regenerators of the previous 
   scenario. These regenerators are shared within a node and their 
   application to a signal is optional. There are no reconfigurable 
   options on either input or output. The only processing option is to 
   "regenerate" a particular signal or not. 

   Regenerator information in this case is used in path computation to 
   select a path that ensures signal compatibility and IA-RWA criteria. 

   To setup an LSP that utilizes a regenerator from a node with a shared 
   regenerator pool it is necessary to indicate that regeneration is to 
   take place at that particular node along the signal path. Such a 
   capability currently does not exist in GMPLS signaling.  

      5.5.3. Reconfigurable Regenerators 

   This scenario is concerned with regenerators that require 
   configuration prior to use on an optical signal. As discussed 
   previously, this could be due to a regenerator that must be 
   configured to accept signals with different characteristics, for 
   regenerators with a selection of output attributes, or for 
   regenerators with additional optional processing capabilities.  

   As in the previous scenarios it is necessary to have information 
   concerning regenerator properties for selection of compatible paths 
   and for IA-RWA computations. In addition during LSP setup it is 
   necessary to be able configure regenerator options at a particular 
   node along the path. Such a capability currently does not exist in 
   GMPLS signaling. 

      5.5.4. Relation to Translucent Networks 

   Networks that contain both transparent network elements such as 
   reconfigurable optical add drop multiplexers (ROADMs) and electro-
     

   Bernstein and Lee Expires August 8, 2011  [Page 38] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   optical network elements such regenerators or OEO switches are 
   frequently referred to as translucent optical networks.  

   Three main types of translucent optical networks have been discussed: 

   1. Transparent "islands" surrounded by regenerators. This is 
      frequently seen when transitioning from a metro optical sub-
      network to a long haul optical sub-network. 

   2. Mostly transparent networks with a limited number of OEO 
      ("opaque") nodes strategically placed. This takes advantage of the 
      inherent regeneration capabilities of OEO switches. In the 
      planning of such networks one has to determine the optimal 
      placement of the OEO switches.  

   3. Mostly transparent networks with a limited number of optical 
      switching nodes with "shared regenerator pools" that can be 
      optionally applied to signals passing through these switches. 
      These switches are sometimes called translucent nodes.  

   All three types of translucent networks fit within the networking 
   scenarios of Section 5.5.1.  and Section 5.5.2.  above. And hence, 
   can be accommodated by the GMPLS extensions envisioned in this 
   document.  

6. GMPLS and PCE Implications 

   The presence and amount of wavelength conversion available at a 
   wavelength switching interface has an impact on the information that 
   needs to be transferred by the control plane (GMPLS) and the PCE 
   architecture. Current GMPLS and PCE standards can address the full 
   wavelength conversion case so the following will only address the 
   limited and no wavelength conversion cases. 

   6.1. Implications for GMPLS signaling 

   Basic support for WSON signaling already exists in GMPLS with the 
   lambda (value 9) LSP encoding type [RFC3471], or for G.709 compatible 
   optical channels, the LSP encoding type (value = 13) "G.709 Optical 
   Channel" from [RFC4328]. However a number of practical issues arise 
   in the identification of wavelengths and signals, and distributed 
   wavelength assignment processes which are discussed below.  

      6.1.1. Identifying Wavelengths and Signals 

   As previously stated a global fixed mapping between wavelengths and 
   labels simplifies the characterization of WDM links and WSON devices. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 39] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   Furthermore such a mapping as described in [Otani] provides such a 
   fixed mapping for communication between PCE and WSON PCCs. 

      6.1.2. WSON Signals and Network Element Processing 

   As discussed in Section 3.3.2.  a WSON signal at any point along its 
   path can be characterized by the (a) modulation format, (b) FEC, (c) 
   wavelength, (d)bit rate, and (d)G-PID.  

   Currently G-PID, wavelength (via labels), and bit rate (via bandwidth 
   encoding) are supported in [RFC3471] and [RFC3473]. These RFCs can 
   accommodate the wavelength changing at any node along the LSP and can 
   thus provide explicit control of wavelength converters. 

   In the fixed regeneration point scenario described in Section 5.5.1. 
   (Fixed Regeneration Points) no enhancements are required to signaling 
   since there are no additional configuration options for the LSP at a 
   node. 

   In the case of shared regeneration pools described in Section 5.5.2.  
   (Shared Regeneration Pools) it is necessary to indicate to a node 
   that it should perform regeneration on a particular signal. Viewed 
   another way, for an LSP, it is desirable to specify that certain 
   nodes along the path perform regeneration.  Such a capability 
   currently does not exist in GMPLS signaling. 

   The case of configurable regenerators described in Section 5.5.3. 
   (Reconfigurable Regenerators) is very similar to the previous except 
   that now there are potentially many more items that can be configured 
   on a per node basis for an LSP.  

   Note that the techniques of [RFC5420] which allow for additional LSP 
   attributes and their recording in a Record Route Object (RRO) object 
   could be extended to allow for additional LSP attributes in an ERO. 
   This could allow one to indicate where optional 3R regeneration 
   should take place along a path, any modification of LSP attributes 
   such as modulation format, or any enhance processing such as 
   performance monitoring. 

      6.1.3. Combined RWA/Separate Routing WA support 

   In either the combined RWA or separate routing WA cases, the node 
   initiating the signaling will have a route from the source to 
   destination along with the wavelengths (generalized labels) to be 
   used along portions of the path. Current GMPLS signaling supports an 
   Explicit Route Object (ERO) and within an ERO an ERO Label subobject 
   can be used to indicate the wavelength to be used at a particular 

     

   Bernstein and Lee Expires August 8, 2011  [Page 40] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   node. In case the local label map approach is used the label sub-
   object entry in the ERO has to be interpreted appropriately. 

      6.1.4. Distributed Wavelength Assignment: Unidirectional, No 
         Converters 

   GMPLS signaling for a unidirectional optical path LSP allows for the 
   use of a label set object in the Resource Reservation Protocol - 
   Traffic Engineering (RSVP-TE) path message. The processing of the 
   label set object to take the intersection of available lambdas along 
   a path can be performed resulting in the set of available lambda 
   being known to the destination that can then use a wavelength 
   selection algorithm to choose a lambda.  

      6.1.5. Distributed Wavelength Assignment: Unidirectional, Limited 
         Converters 

   In the case of wavelength converters, nodes with wavelength 
   converters would need to make the decision as to whether to perform 
   conversion. One indicator for this would be that the set of available 
   wavelengths which is obtained via the intersection of the incoming 
   label set and the output links available wavelengths is either null 
   or deemed too small to permit successful completion. 

   At this point the node would need to remember that it will apply 
   wavelength conversion and will be responsible for assigning the 
   wavelength on the previous lambda-contiguous segment when the RSVP-TE 
   RESV message is processed. The node will pass on an enlarged label 
   set reflecting only the limitations of the wavelength converter and 
   the output link. The record route option in RSVP-TE signaling can be 
   used to show where wavelength conversion has taken place. 

      6.1.6. Distributed Wavelength Assignment: Bidirectional, No 
         Converters 

   There are cases of a bidirectional optical path which requires the 
   use of the same lambda in both directions. The above procedure can be 
   used to determine the available bidirectional lambda set if it is 
   interpreted that the available label set is available in both 
   directions. In bidirectional LSPs setup, according to [RFC3471] 
   Section 4.1. (Architectural Approaches to RWA), is indicated by the 
   presence of an upstream label in the path message.  

   However, until the intersection of the available label sets is 
   determined along the path and at the destination node the upstream 
   label information may not be correct.   This case can be supported 
   using current GMPLS mechanisms, but may not be as efficient as an 

     

   Bernstein and Lee Expires August 8, 2011  [Page 41] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   optimized bidirectional single-label allocation mechanism. 
    

   6.2. Implications for GMPLS Routing 

   GMPLS routing [RFC4202] currently defines an interface capability 
   descriptor for "lambda switch capable" (LSC) which can be used to 
   describe the interfaces on a ROADM or other type of wavelength 
   selective switch. In addition to the topology information typically 
   conveyed via an IGP, it would be necessary to convey the following 
   subsystem properties to minimally characterize a WSON: 

  1. WDM Link properties (allowed wavelengths). 

  2. Optical transmitters (wavelength range). 

  3. ROADM/FOADM Properties (connectivity matrix, port wavelength 
     restrictions). 

  4. Wavelength converter properties (per network element, may change if 
     a common limited shared pool is used). 

   This information is modeled in detail in [WSON-Info] and a compact 
   encoding is given in [WSON-Encode]. 

      6.2.1. Electro-Optical Element Signal Compatibility  

   In network scenarios where signal compatibility is a concern it is 
   necessary to add parameters to our existing node and link models to 
   take into account electro-optical input constraints, output 
   constraints, and the signal processing capabilities of a NE in path 
   computations. 

   Input constraints: 

  1. Permitted optical tributary signal classes: A list of optical 
     tributary signal classes that can be processed by this network 
     element or carried over this link. (configuration type) 
  2. Acceptable FEC codes. (configuration type) 
  3. Acceptable Bit Rate Set: a list of specific bit rates or bit rate 
     ranges that the device can accommodate. Coarse bit rate info is 
     included with the optical tributary signal class restrictions. 
  4. Acceptable G-PID list: a list of G-PIDs corresponding to the 
     "client" digital streams that is compatible with this device. 
    

     

   Bernstein and Lee Expires August 8, 2011  [Page 42] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   Note that the bit rate of the signal does not change over the LSP. 
   This can be communicated as an LSP parameter and hence this 
   information would be available for any NE that needs to use it for 
   configuration. Hence it is not necessary to have "configuration type" 
   for the NE with respect to bit rate. 

   Output constraints: 

   1. Output modulation: (a)same as input, (b) list of available types 

   2. FEC options: (a) same as input, (b) list of available codes 

   Processing capabilities: 

   1. Regeneration: (a) 1R, (b) 2R, (c) 3R, (d)list of selectable 
      regeneration types 

   2. Fault and performance monitoring: (a) G-PID particular 
      capabilities, (b) optical performance monitoring capabilities. 

   Note that such parameters could be specified on an (a) Network 
   element wide basis, (b) a per port basis, (c) on a per regenerator 
   basis.  Typically such information has been on a per port basis; see 
   the GMPLS interface switching capability descriptor [RFC4202]. 

      6.2.2. Wavelength-Specific Availability Information 

   For wavelength assignment it is necessary to know which specific 
   wavelengths are available and which are occupied if a combined RWA 
   process or separate WA process is run as discussed in sections 4.1.1. 
   4.1.2.  This is currently not possible with GMPLS routing.  

   In the routing extensions for GMPLS [RFC4202], requirements for 
   layer-specific TE attributes are discussed. RWA for optical networks 
   without wavelength converters imposes an additional requirement for 
   the lambda (or optical channel) layer: that of knowing which specific 
   wavelengths are in use. Note that current DWDM systems range from 16 
   channels to 128 channels with advanced laboratory systems with as 
   many as 300 channels. Given these channel limitations and if the 
   approach of a global wavelength to label mapping or furnishing the 
   local mappings to the PCEs is taken then representing the use of 
   wavelengths via a simple bit-map is feasible [Gen-Encode].  

      6.2.3. WSON Routing Information Summary 

   The following table summarizes the WSON information that could be 
   conveyed via GMPLS routing and attempts to classify that information 

     

   Bernstein and Lee Expires August 8, 2011  [Page 43] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   as to its static or dynamic nature and whether that information would 
   tend to be associated with either a link or a node. 

    

      Information                         Static/Dynamic       Node/Link 
      ------------------------------------------------------------------ 
      Connectivity matrix                 Static               Node 
      Per port wavelength restrictions    Static               Node(1) 
      WDM link (fiber) lambda ranges      Static               Link 
      WDM link channel spacing            Static               Link 
      Optical transmitter range           Static               Link(2) 
      Wavelength conversion capabilities  Static(3)            Node 
      Maximum bandwidth per wavelength    Static               Link 
      Wavelength availability             Dynamic(4)           Link 
      Signal compatibility and processing Static/Dynamic       Node 
    
   Notes: 

   1. These are the per port wavelength restrictions of an optical 
      device such as a ROADM and are independent of any optical 
      constraints imposed by a fiber link. 

   2. This could also be viewed as a node capability. 

   3. This could be dynamic in the case of a limited pool of converters 
      where the number available can change with connection 
      establishment. Note it may be desirable to include regeneration 
      capabilities here since OEO converters are also regenerators. 

   4. Not necessarily needed in the case of distributed wavelength 
      assignment via signaling. 

   While the full complement of the information from the previous table 
   is needed in the Combined RWA and the separate Routing and WA 
   architectures, in the case of Routing + distributed WA via signaling 
   only the following information is needed: 

      Information                         Static/Dynamic       Node/Link 
      ------------------------------------------------------------------ 
      Connectivity matrix                 Static               Node 
      Wavelength conversion capabilities  Static(3)            Node 
    

   Information models and compact encodings for this information is 
   provided in [WSON-Info], [Gen-Encode] and [WSON-Encode]. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 44] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

    
    
   6.3. Optical Path Computation and Implications for PCE 

   As previously noted RWA can be computationally intensive. Such 
   computationally intensive path computations and optimizations were 
   part of the impetus for the PCE architecture [RFC4655]. 

   The Path Computation Element Protocol (PCEP) defines the procedures 
   necessary to support both sequential [RFC5440] and global concurrent 
   path computations (PCE-GCO) [RFC5557]. The PCEP is well positioned to 
   support WSON-enabled RWA computation with some protocol enhancement.  

   Implications for PCE generally fall into two main categories: (a) 
   optical path constraints and characteristics, (b) computation 
   architectures. 

      6.3.1. Optical path Constraints and Characteristics 

   For the varying degrees of optimization that may be encountered in a 
   network the following models of bulk and sequential optical path 
   requests are encountered: 

   o  Batch optimization, multiple optical paths requested at one time 
      (PCE-GCO).  

   o  Optical path(s) and backup optical path(s) requested at one time 
      (PCEP). 

   o  Single optical path requested at a time (PCEP). 

   PCEP and PCE-GCO can be readily enhanced to support all of the 
   potential models of RWA computation.  

   Optical path constraints include: 

   o  Bidirectional Assignment of wavelengths. 

   o  Possible simultaneous assignment of wavelength to primary and 
      backup paths.  

   o  Tuning range constraint on optical transmitter. 

      6.3.2. Electro-Optical Element Signal Compatibility  

   When requesting a path computation to PCE, the PCC should be able to 
   indicate the following: 

     

   Bernstein and Lee Expires August 8, 2011  [Page 45] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   o  The G-PID type of an LSP.  

   o  The signal attributes at the transmitter (at the source): (i) 
      modulation type; (ii) FEC type. 

   o  The signal attributes at the receiver (at the sink): (i) 
      modulation type; (ii) FEC type. 

   The PCE should be able to respond to the PCC with the following: 

   o  The conformity of the requested optical characteristics associated 
      with the resulting LSP with the source, sink and NE along the LSP.  

   o  Additional LSP attributes modified along the path (e.g., 
      modulation format change, etc.).  

    

      6.3.3. Discovery of RWA Capable PCEs 

   The algorithms and network information needed for RWA are somewhat 
   specialized and computationally intensive hence not all PCEs within a 
   domain would necessarily need or want this capability.  Hence, it 
   would be useful via the mechanisms being established for PCE 
   discovery [RFC5088] to indicate that a PCE has the ability to deal 
   with RWA. Reference [RFC5088] indicates that a sub-TLV could be 
   allocated for this purpose. 

   Recent progress on objective functions in PCE [RFC5541] would allow 
   the operators to flexibly request differing objective functions per 
   their need and applications. For instance, this would allow the 
   operator to choose an objective function that minimizes the total 
   network cost associated with setting up a set of paths concurrently. 
   This would also allow operators to choose an objective function that 
   results in a most evenly distributed link utilization.  

   This implies that PCEP would easily accommodate wavelength selection 
   algorithm in its objective function to be able to optimize the path 
   computation from the perspective of wavelength assignment if chosen 
   by the operators.  

7. Security Considerations 

   This document has no requirement for a change 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 RWA using the existing 
     

   Bernstein and Lee Expires August 8, 2011  [Page 46] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   protocols may significantly affect the loading of those protocols. 
   This may make the operation of the network more vulnerable to denial 
   of service attacks. Therefore additional care maybe required to 
   ensure that the protocols are secure in the WSON environment.  
    
   Furthermore the additional information distributed in order to 
   address RWA 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]. 

8. IANA Considerations 

   This document makes no request for IANA actions. 

9. Acknowledgments 

   The authors would like to thank Adrian Farrel for many helpful 
   comments that greatly improved the contents of this draft. 

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

     

   Bernstein and Lee Expires August 8, 2011  [Page 47] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

10. References 

   10.1. Normative References 

   [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching 
             (GMPLS) Signaling Functional Description", RFC 3471, 
             January 2003. 

   [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label 
             Switching (GMPLS) Signaling Resource ReserVation Protocol-
             Traffic Engineering (RSVP-TE) Extensions", RFC 3473, 
             January 2003. 

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

   [RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support 
             of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 
             4202, October 2005. 

   [RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label 
             Switching (GMPLS) Signaling Extensions for G.709 Optical 
             Transport Networks Control", RFC 4328, January 2006. 

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

   [RFC5088] J.L. Le Roux, J.P. Vasseur, Yuichi Ikejiri, and Raymond 
             Zhang, "OSPF protocol extensions for Path Computation 
             Element (PCE) Discovery", January 2008. 

   [RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux, 
             M., and D. Brungard, "Requirements for GMPLS-Based Multi-
             Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July 
             2008. 

   [RFC5557] Y. Lee, J.L. Le Roux, D. King, and E. Oki, "Path 
             Computation Element Communication Protocol (PCECP) 
             Requirements and Protocol Extensions In Support of Global 
             Concurrent Optimization", RFC 5557, July 2009. 

   [RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A. 
             Ayyangarps, "Encoding of Attributes for MPLS LSP 
             Establishment Using Resource Reservation Protocol Traffic 
             Engineering (RSVP-TE)", RFC 5420, February 2009. 

     

   Bernstein and Lee Expires August 8, 2011  [Page 48] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   [RFC5440] J.P. Vasseur and J.L. Le Roux (Editors), "Path Computation 
             Element (PCE) Communication Protocol (PCEP)", RFC 5440, May 
             2009.  

   [RFC5541] J.L. Le Roux, J.P. Vasseur, and Y. Lee, "Encoding of 
             Objective Functions in Path Computation Element (PCE) 
             communication and discovery protocols", RFC 5541, July 
             2009. 

    

   10.2. Informative References 

   [Gen-Encode] G. Bernstein, Y. Lee, D. Li, and W. Imajuku, "General 
             Network Element Constraint Encoding for GMPLS Controlled 
             Networks", draft-ietf-ccamp-general-constraint-encode, work 
             in progress. 

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

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

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

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

     

   Bernstein and Lee Expires August 8, 2011  [Page 49] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

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

   [G.Sup43] ITU-T Series G Supplement 43, Transport of IEEE 10G base-R 
             in optical transport networks (OTN), November 2006. 

   [Imajuku] W. Imajuku, Y. Sone, I. Nishioka, S. Seno, "Routing 
             Extensions to Support Network Elements with Switching 
             Constraint", work in progress: draft-imajuku-ccamp-rtg-
             switching-constraint. 

   [Otani]  T. Otani, H. Guo, K. Miyazaki, D. Caviglia, "Generalized 
             Labels of Lambda-Switching Capable Label Switching Routers 
             (LSR)", work in progress: draft-ietf-ccamp-gmpls-g-694-
             lambda-labels, work in progress. 

   [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS             
             Networks", RFC 5920, July 2010.[Otani]T. Otani, H. Guo, K. 
             Miyazaki, D. Caviglia, "Generalized Labels of Lambda-
             Switching Capable Label Switching Routers (LSR)", work in 
             progress: draft-otani-ccamp-gmpls-g-694-lambda-labels, work 
             in progress. 

   [WSON-Encode]  G. Bernstein, Y. Lee, D. Li, and W. Imajuku, "Routing 
             and Wavelength Assignment Information Encoding for 
             Wavelength Switched Optical Networks", draft-ietf-ccamp-
             rwa-wson-encode, work in progress.  

   [WSON-Imp]  Y. Lee, G. Bernstein, D. Li, G. Martinelli, "A Framework 
             for the Control of Wavelength Switched Optical Networks 
             (WSON) with Impairments", draft-ietf-ccamp-wson-
             impairments, work in progress.  

   [WSON-Info] Y. Lee, G. Bernstein, D. Li, W. Imajuku, "Routing and 
             Wavelength Assignment Information for Wavelength Switched 
             Optical Networks", draft-bernstein-ccamp-wson-info, work in 
             progress 

    

     

   Bernstein and Lee Expires August 8, 2011  [Page 50] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

11.  Contributors 

   Snigdho Bardalai 
   Fujitsu 
    
   Email: Snigdho.Bardalai@us.fujitsu.com 
    
   Diego Caviglia  
   Ericsson 
   Via A. Negrone 1/A 16153 
   Genoa Italy 
    
   Phone: +39 010 600 3736 
   Email: diego.caviglia@(marconi.com, ericsson.com) 
    
   Daniel King 
   Old Dog Consulting 
   UK 
    
   Email: daniel@olddog.co.uk 
    
    
   Itaru Nishioka 
   NEC Corp. 
   1753 Simonumabe, Nakahara-ku 
   Kawasaki, Kanagawa 211-8666 
   Japan 
    
   Phone: +81 44 396 3287 
   Email: i-nishioka@cb.jp.nec.com 
    
   Lyndon Ong 
   Ciena 
    
   Email: Lyong@Ciena.com 
    
   Pierre Peloso 
   Alcatel-Lucent 
   Route de Villejust, 91620 Nozay 
   France 
    
   Email: pierre.peloso@alcatel-lucent.fr 
    
   Jonathan Sadler 
   Tellabs 
   Email: Jonathan.Sadler@tellabs.com 
    
   Dirk Schroetter 
     

   Bernstein and Lee Expires August 8, 2011  [Page 51] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   Cisco 
   Email: dschroet@cisco.com 
    
   Jonas Martensson 
   Acreo 
   Electrum 236 
   16440 Kista, Sweden 
    
   Email:Jonas.Martensson@acreo.se 
    
    
    
Author's Addresses 

   Greg M. Bernstein (ed.) 
   Grotto Networking 
   Fremont California, USA 
       
   Phone: (510) 573-2237 
   Email: gregb@grotto-networking.com 
    

   Young Lee (ed.) 
   Huawei Technologies 
   1700 Alma Drive, Suite 100 
   Plano, TX 75075 
   USA 
    
   Phone: (972) 509-5599 (x2240) 
   Email: ylee@huawei.com 
    
    
   Wataru Imajuku 
   NTT Network Innovation Labs 
   1-1 Hikari-no-oka, Yokosuka, Kanagawa 
   Japan 
    
   Phone: +81-(46) 859-4315 
   Email: imajuku.wataru@lab.ntt.co.jp 
    
    
 

Intellectual Property Statement 

   The IETF Trust takes no position regarding the validity or scope of 
   any Intellectual Property Rights or other rights that might be 
   claimed to pertain to the implementation or use of the technology 
     

   Bernstein and Lee Expires August 8, 2011  [Page 52] 



Internet-Draft   Wavelength Switched Optical Networks     February 2011 
    

   described in any IETF Document or the extent to which any license 
   under such rights might or might not be available; nor does it 
   represent that it has made any independent effort to identify any 
   such rights.  

   Copies of Intellectual Property disclosures made to the IETF 
   Secretariat and any assurances of licenses to be made available, or 
   the result of an attempt made to obtain a general license or 
   permission for the use of such proprietary rights by implementers or 
   users of this specification can be obtained from the IETF on-line IPR 
   repository at http://www.ietf.org/ipr 

   The IETF invites any interested party to bring to its attention any 
   copyrights, patents or patent applications, or other proprietary 
   rights that may cover technology that may be required to implement 
   any standard or specification contained in an IETF Document. Please 
   address the information to the IETF at ietf-ipr@ietf.org. 

Disclaimer of Validity 

   All IETF Documents and the information contained therein are provided 
   on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE 
   REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE 
   IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL 
   WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY 
   WARRANTY THAT THE USE OF THE INFORMATION THEREIN WILL NOT INFRINGE 
   ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS 
   FOR A PARTICULAR PURPOSE. 

Acknowledgment 

   Funding for the RFC Editor function is currently provided by the 
   Internet Society. 

    

    

     

   Bernstein and Lee Expires August 8, 2011  [Page 53]