Modeling of Burst Assembly Process in Optical Burst-Switched Networks

We analyze burst assembly process, as the main building block of optical burst switching (OBS) paradigm. The analysis is performed for time-based, volume-based as well as hybrid burst assemblers. Under the assumption that packets arrival to the assembly buffer is Poisson, exact analytical expressions are derived for length and interdeparture time of bursts that are generated by these three classes of assembly algorithms. Furthermore, we consider the issue of generating burst traces, which arises during performance evaluation of OBS networks through discrete-event simulation. In such a simulation study a significant part of the simulation time, particularly in case of a network with a large number of ingress nodes, is used by the implementation of the burst assembly algorithms. This is due to the fact that each data burst is result of aggregating several short-length packets which in a straightforward approach have to be generated individually and afterwards ”melted” into the burst. We present a novel approach to fast generation of bursts, which is based on the analytical models developed for burst length and interdeparture time distributions as well as an efficient generation technique (composition) supporting generation of these distributions. The analysis is followed by numerical results that validate the accuracy of developed models and demonstrate the speed-up gains of using proposed burst generation algorithms.