Performance Analysis of Burst Assembly under Self-Similar Traffic with Measured WAN Packet Size Distribution

Studied in this paper is the convergence performance of three typical burst assembly mechanisms in optical burst-switching (OBS) networks, namely threshold-based, timer-based, and hybrid assembly algorithms. Burst assembly is an important function implemented at edge nodes in optical burst switching (OBS) networks. It can reduce the switching burden and overheads at the optical layer, by aggregating multiple packets from client networks to create a larger optical burst for transmission through the OBS network. Furthermore, burst assembly designed properly can reduce the self-similarity of traffic as traffic shaper. The main challenge in designing burst assembly is to balance the several opposing objectives: first, increasing the burst size; second, maintaining acceptable assembly delay introduced during burst assembly; thirdly, reducing the self-similarity as possible in case of self-similar traffic. Vital parameters, such as optical burst size and assembly delay, are examined by simulations under self-similar input traffic with a measured WAN packet size distribution. The balance between the burst size and the assembly delay for hybrid assembly is also discussed. The results show that the assembly threshold always keeps the burst size near the threshold while the assembly time-limit makes the burst size scattered and even split into multiple peaks when the incoming IP packet size is discrete. In addition, the self-similarity of input traffic has little impact on the burst size and the assembly delay for all three mechanisms. For hybrid assembly, when one of the assembly threshold and the assembly time-limit parameters is fixed, the burst size and the assembly delay are hard to improve by adjusting the other parameter when greater than a certain value