Overview and framework for dynamic deflection contention resolution in OBS network

The OBS networks suffer from contention due to buffer less nature of transmission. Deflection Routing and Retransmission Mechanism have been proposed as potential techniques for resolving the burst contention problem. Combining deflection routing with retransmission technique outperforms both pure deflection and pure retransmission techniques to improve the performance. Previous work uses static as well as adaptive combination of deflection with retransmission for reducing burst losses due to contention. The static combination approach gives poor performance in terms of Burst loss ratio (BLR) as it attempt deflection first even if the load is high. For adaptive combination, limited hybrid deflection and retransmission (LHDR) scheme have been developed that limits the deflection. However, LHDR perform poorly when traffic is very high. This paper presents a review of these techniques. In addition, we propose a concept called dynamic hybrid retransmission in deflection routing (DHRD) to further resolve contention. Unlike, the exiting hybrid schemes our approach provide an accurate relationship between impact of network load due to retransmissions or deflection and gain in the end-to-end burst delivery rate. In this, two retransmission parameters are introduced namely, retransmission probability (D1) and persistent probability (D2) to control rate of data transmission with the help of updated values of BLR. It is expected that the proposed approach will produce better BLR performance compared to static and adaptive approaches due to use of dynamic nature of deflection with retransmission.