Optical burst switching was conceived to provide an efficient solution for sending high-speed bursty traffic over WDM networks75-82 Traffic is considered as being bursty if there are long idle times between the busy periods in which a large number of packets arrive form users. This format is typical of data traffic in contrast to voice traffic which is characterized by a more continuous bit stream nature. There are two advantages to OBS Fist it offers the high bandwidth and packet-sized granularity of optical packet switched networks without the need for complex optical buffering. Second. It provides the low packet-processing overhead that is characteristic of wavelength-routed networks. Thus the performance characteristic of OBS lie between those of a wavelength-routed network and an optical packet-switched network
In the OBS network concept, a collection of optical burst switched are interconnected with WDM link to form the central core of the network. Devices called edge routers collect traffic flows form various sources at the periphery of a WDM network, as illustrated in Fig 13.36. The flows then are sorted into different classes according to their destination address and grouped in variable-sized elementary switching units called burst. The characteristics of an edge router play a critical role in an OBS system since the overall network performance depends on how a burst is assembled based on particular types of traffic statistics.