Drop policies and multiple edge thresholds to enhance the performance of TCP over OBS networks with retransmission

Abstract

Due to the bufferless nature of OBS networks, contention will unavoidably occur in core nodes. When the retransmission scheme is introduced into OBS networks, the bursts in the contention will be dropped selectively according to the drop policy adopted in core nodes, and retransmitted by edge nodes. In this paper, we proposed a drop policy based on Hop Number, in which the bursts with the larger total hop number will be given the higher priority in the contention. Taking the retransmission cost into account, we proposed another novel drop policy based on Hop Number Factor. Meanwhile, in edge nodes, multiple thresholds are also proposed to limit the unnecessary retransmission, and ease the deteriorated network performance. Both theoretical analyses and simulation results show that the proposed mechanisms can reduce the burst loss rate and the round trip time effectively, and improve the throughput significantly in TCP over OBS networks with retransmission.