Quality-of-Service differentiation and fairness in Optical Burst-Switched networks

A mechanism that is often proposed for Quality-of-Service differentiation in Optical Burst-Switched networks is offset-time management. In this paper we identify and explain some undesired characteristics of this. mechanism. The most important finding is that the burst drop probability differentiation that is attained for a given offset-time value strongly depends on the distribution of the burst durations. Hence control of the differentiation is difficult, since the distribution of burst durations is subject to changes all the time, depending on the traffic conditions at the edge of the OBS network. We also found that offset-time management slightly increases the unfairness within the lower priority classes, in the sense that longer bursts are dropped more frequently than shorter ones.