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This paper revisits burst contention resolution problems in optical burst switching (OBS) networks from the viewpoint of network utility maximization. Burst collision occurs when two or more bursts access the same wavelength simultaneously, and the occurrence becomes more frequent as the offered load increases. In particular, when the network is overloaded, no contention resolution scheme would effectively avoid the collision without the help of congestion control. We formulate a joint optimization problem where two variables, the length and the time at which each burst is injected into the network, are jointly optimized in order to maximize aggregate utility while minimizing burst loss. A distributed algorithm is also developed, which explicitly reveals how burst contention resolution and congestion control must interact. The simulation results show that the joint control decouples throughput performance from burst loss performance so that burst loss ratio does not increase as network throughput increases. This is not the case in conventional contention resolution schemes where burst loss ratio increases as network throughput increases so that achievable network throughput is limited. Our work is the first attempt to the joint design of congestion and contention control and might lead to an interesting development in OBS research.
Date of Publication: Sept.1, 2009