On ordered scheduling for optical burst switching

Optical burst switching (OBS) is a promising optical networking paradigm for efficient transport of bursty IP traffic over wavelength division multiplexing (WDM) optical Internet networks. In OBS, the header of a burst is sent in advance of the data burst to reserve a wavelength channel at each optical switching node along the path. The nodes use a scheduling algorithm to assign wavelengths to incoming bursts. Our work is motivated from the observation that existing scheduling algorithms assign a wavelength to a burst when its header arrives at the node. Thus, information about other bursts whose headers arrive later is not available when the scheduling decision is made. This leads to suboptimal scheduling decisions and unnecessary burst dropping. The key idea in our proposed algorithm, Ordered Scheduling, is to defer making the scheduling decision until just before the burst arrival in order to have full knowledge about other bursts. The effectiveness of the proposed algorithm is studied through simulation and the computational complexity and signalling overhead are analysed.