Service differentiation mechanisms for variable length packets in an optical switch with recirculating FDL buffer

In this paper we focus on providing service differentiation for variable length packets. Apart from the well-known OBS approach using differentiated offsets to introduce multiple service classes, we consider a look - ahead approach allowing for later arriving high priority packets to pre -empt earlier arrived low priority packets, and a slotted control approach. All approaches attain ser- vice differentiation without any resource reservation, and are of limited complexity, to minimize packet processing requirements. Through simulation, we assess the quality of the approaches under varying loads, buffer dimensions and QoS algorithm parameters. The main criterion used is the packet loss rate per service class.