Evaluation of end-to-end latency for segmented bursts in OBS networks

Abstract

In Optical Burst Switched (OBS) networks several contention resolution schemes such as wavelength conversion, fibre delay lines (FDLs), deflection routing and burst segmentation have been proposed. To provide the differential quality of service (QoS) for different classes of packets, priority-based segmented burst assembling at the edge nodes coupled with segment level transmission in the core nodes (in the event of congestion or contention) is proposed. All packets are assembled in units called segments according to two priorities, high priority (HP) and low priority (LP). HP segments are always placed at the head end of the composite burst as they are more delay sensitive, whereas the LP segments fill up at the tail end. Only in the event or anticipation of contention/ congestion occurrence, the affected section(s) of the network switch to segment transmission mode in which the composite burst is from this point decomposed into its individual segments and streamed (segment level transmission) along the same route to the destination end. The limited buffering in the core nodes will facilitate temporary buffering of the contending segments as since they are relatively smaller. The queuing at the inputs may lead to differential delays in the core nodes due to possible addition of segments from other links. This ultimately affects the inter-segment-gap between successive data segments ferrying packets of the same source thus leading to increased jittery whose magnitude may compromise the desirable QoS. In this paper we analyze inter-segment delay variations as a function of the number of nodes traversed.