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WDM networks in general depend on transmitters and receivers that are precisely tuned to predetermined fmed wavelengths. Robust WDM is an approach aimed at relaxing manujkcturing and operating wavelength tolerance requirements, which will lead to cost effective implementations. In this approach, connections are based on dynamically selected wavelengths as opposed to usingfied wavei'ength channels. A station that needs a connection selecfs a wavelength during a reservation interval. The perjormance of a simplified WDM protocol with dynamic wavelength selection is modeled and analyzed for packet traffic. In this version, the reJewation intervals are assigned to stations randomly. The pegormance of the protocol is analyzed for different network parameters.

Many WDM architectures are based onJixed wavelength channels which require the lasers to be tuned to their channels accurately. Achieving this task is difJicult and costly especially in the distributed environments. Robust WDM is an approach that tolerates large laser wavelength variations, due to temperature drifts and manufacturing tolerances. A reservation-based medium access protocol is used to dynamically select the laser for communication. A token-passing based control channel assigns a reservation interval to one ofthe waiting stations. The performance of a circuit-switched Robust WDM network is considered when each node has only a limited number of lasers. The model evaluates the performance of a network for a given access pattern, specibing the channels accessible to each station. Simulation results are used to veri& the analytic results.

The perfomnce of a symmetric Robust WDM network that uses token-passing on the signaling channel and has a limited number of lasers per station is modeled and analyzed for circuit-switched connections. Robust WDM networks use a reservation interval during which all stations cease their WDM transmissions so that the station holding the token may establish a connection with its intended destination. The network performance is analyzed for different network parameters. Simulation results are used to evaluate the accuracy of the model.In recent years, wavelength division multiplexing (WDM) has emerged as the most promising solution to satisfy the increasing need for larger bandwidth [9]. WDM exploits the enormous capacity of the single mode fiber by dividing the available wavelength into smaller, more manageable, multiple wavelengths to carry out more than one transmissions at a time; thereby offering a potential aggregate throughput in Terabits per second range. It has intrigued a large number of researchers in the industry and academia resulting in prototypes such as Rainbow4 & II [lo], STARNET [4], and LIGHTNING [5].WDM architectures are based on transmitters and receivers that can be precisely tuned to predetermined, fixed wavelengths. wavelength of a laser shifts with temperature and the output power of the laser can also change even though a constant input current is applied. Wavelength and power stabilization of laser transmitters is a very critical and expensive task. For this reason the commercial exploitation of WDM systems has not made great progress. This is especially true for short-haul (SH) local area network (LAN) environment where the cost of the fiber and its installation would be considerably less in comparison to the cost of suitable transmitter sources.Robust WDM network, a network being implemented at Colorado State University and University of Colorado, is an approach that allows relaxed manufacturing and operating wavelength tolerances [ 11. Robust WDM networks can be implemented based on several different medium access protocols [7]. This paper evaluates a reservation type, token based medium access protocol for a Robust WDM network with circuit-switched connections.In [23, we modeled and analyzed a symmetric Robust WDM circuit-switched network where each station can access all the c channels of the network. In this paper, we investigate a more realistic case where each station has only a limited number of lasers (c,) and hence can access only c, channels that are randomly spread over the total network channels (c).Section 2 provides a description of Robust WDM network and the token based MAC protocol, Section 3 details the performance model, Section 4 discusses the test results and its comparison with the simulation results, and Section 5 concludes the paper.