Maximizing Throughput for Optical Burst Switching Networks

Abstract

Abstract-A key problem in Optical Burst Switching (OBS) is to schedule as many bursts as possible on wavelength channels so that the throughput is maximized and the burst loss is minimized. Currently, most of the research on OBS (e.g., burst scheduling and assembly algorithms) has been concentrated on reducing burst loss in an "average-case" sense. Little effort has been devoted to understanding the worst-case performance. Since OBS itself is an open-loop control system, it may often exhibit a worst-case behavior when adversely synchronized, thus a poor worst-case performance can lead to an unacceptable system-wide performance. In this paper, we use competitive analysis to analyze the worstcase performance of a large set of scheduling algorithms, called best-effort online scheduling algorithms, for OBS networks, and establish a number of interesting upper and lower bounds on the performance of such algorithms. Our analysis shows that the performance of any best-effort online algorithm is closely related to a few factors, such as the range of offset time, burst length ratio, scheduling algorithm, and number of data channels. A surprising discovery is that the worst-case performance of any best-effort online scheduling algorithm is primarily determined by the maximum to minimum burst length ratio, followed by the range of offset time. Furthermore, if all bursts have the same burst length and offset time, all best-effort online scheduling algorithms generate the same optimal solution, regardless how different they may look like. Our analysis can also be extended to some non-besteffort online scheduling algorithms, such as the well-known Horizon algorithm, and establish similar bounds. Based on the analytic results, we give guidelines for several widely discussed OBS problems, including burst assembly, offset time setting and scheduling algorithm design, and propose a new channel reservation protocol called VFO to improve the worst-case performance. Our simulation shows that it is quite often for an online scheduling algorithm to exhibit its (near) worst-case performance. Thus improving the worst-case performance is essential. Our simulation also suggests that VFO reduces the average burst loss rate by as much as 35%.

Research in optical burst switching within the e-Photon/ONe network of excellence

“…In the bufferless case, we can observe that both OTD and BP offer the same loss performance for the HP class, however BP shows better behavior for both LP and the total traffic. This is due to the scheduling, which, according to [49], suffers performance degradation due to the variable offset-times in the OTD mechanism.…”

“…More specifically, the BD-W and BD-B mechanisms may be recommended in order to boost the HP performance of the BP technique since it does not impact significantly the performance of the LP class. Finally, BLD should not be used with OTD because of the sensitivity of the OTD mechanism to scheduling operation that suffers performance degradation if bursts of different lengths are scheduled [49].…”

Optimizing offset times in Optical Burst Switching networks with variable Burst Control Packets sojourn times

“…Such complexity orders serve to characterize the asymptotic behavior of the scheduler, that has a variable service time. In [15], prior scheduling algorithms are studied and it is stated that since OBS networks are open loop systems, they may often exhibit a worst-case performance. The same work also shows that the burst processing time is not constant, but a function of the scheduling algorithm and the traffic load.…”

“…In this section we analyze a case with constant service time and variable waiting time in queue. The constant service time assumption has also been suggested in [15], as a worst case upper bound. It will be assumed that the SCU incorporates a buffer, i.e., the SCU rate is not the peak BCP rate.…”

Accounting Information Systems Genetic Algorithms for All-Optical Shared Fiber-Delay-Line Packet Switches

“…J. Karol, 1993;S. Y. Liew, 2005), or the wavelengths of the contended packets are required to be converted to other and unused wavelengths in order to avoid communication conflict (J. Li, 2007). In this paper, we focus using the buffering approach, though both contention resolution schemes, buffering and wavelength conversion, can be applied at the same time to obtain a hybrid solution (Z.…”