An evaluation of wavelength reservation protocol with delayed link state information

Previous studies on routing and wavelength assignment algorithms assumed that the global link state information is obtained without delays. However, in distributed lightpath establishment, the probability of request blocking strongly depends on both the accuracy of the global link state information and the distributed protocol for wavelength reservation. In this paper, we evaluate how the frequency of link state information exchange affects the blocking probability in lightpath establishment. The evaluation is performed based on forward and backward reservation protocols in three network topologies. Simulation results show that while the forward reservation protocol is greatly affected by the frequency of link state information exchange and the amount of this information, the backward reservation protocol does not need as detailed information about the link state and as frequent link state exchange for routing as does the forward protocol.