Burst rescheduling with wavelength and last-hop FDL reassignment in WDM optical burst switching networks

In this paper, we consider the problem of fast and efficient dynamic scheduling of bursts that belong to different classes of priority in wavelength-division multiplexing (WDM)-based optical burst switching (OBS) networks with limited optical buffers. In OBS networks, control and data components of a burst are sent separately with a time gap to ensure that resources such as wavelengths and fiber delay lines (FDLs) are reserved at various nodes before the data burst arrives. A scheduling algorithm with attractive features such as computational simplicity and efficient resource utilization is mandatory to quickly handle dynamic burst traffic and reduce burst dropping probability. While void filling algorithms achieve good burst dropping performance they are computationally complex. We propose burst rescheduling as an alternative to void filling which can do fast scheduling without requiring to examine and fill voids and at the same time can achieve good performance. Burst rescheduling uses two mechanisms known as wavelength reassignment and lasthop FDL reassignment. We develop a scheduling algorithm using the above rescheduling mechanisms called burst rescheduling with wavelength and last-hop FDL reassignment (BR-WFR) which is computationally simpler than a void filling algorithm. We then discuss the signalling overhead and feasibility of implementing burst rescheduling. Through simulation experiments we demonstrate the effectiveness of the proposed burst rescheduling algorithm.