Segment Technology of Differentiated Services Supporting in Optical Burst Switched networks

Optical Burst Switching (OBS) has been developed as an efficient switching technique to exploit the capacity provided by Dense Wavelength Division Multiplexing (DWDM) transmission technology for the next generation optical Internet. Segmentation is proposed in literatures to resolve contention, a major concern in optical burst switched networks. As far as segmentation is concerned, nearly all the methods introduced in the literatures adopt tail-dropping policy. In this paper, we will demonstrate, however, that tail-dropping policy may not be a feasible solution to resolve contention. Based upon this, a modified head-dropping solution is proposed. In this method, when the overlap part is no more than the entire contending burst arriving late, the head part of contending burst will be discarded, otherwise the entire contending burst will be dropped. In order to alleviate disorder resulted from head dropping and support Differentiated Services well, we also present a priority-based proportional mixed segment assembly technique to encapsulate burst at edge node. A burst consists of several segments, each of which is a group of same priority packets and has it’s own assembly information. We suggest that the priority-based proportional mixed segment assembly be used integrated with modified head-dropping contention resolution policy in OBS networks. The main objective of our segment scheme is to improve the utilization of resource, decrease the packet loss probability, and afford a better Differentiated Services support as well. Experiment results prove that our integrated segment scheme performs well on decreasing packet loss probability and Differentiated Services.