Deflection Routing Method Using Link Reflection Latency in Optical Packet Switched Networks

摘要

A main issue for the realization of Optical Packet Switched (OPS) networks is the resolution of packet contention due to the lack of RAM-like optical buffer. Although an optical buffer using Fiber Delay Line (FDL) has been proposed as alternative, its capacity is extremely limited. For this reason, several studies have been challenged on this problem. One approach is a deflection routing. It is widely used in electronic packet switched networks or optical burst switched (OBS) networks. However, in the OPS networks, packet length is short, thus, speed limitation for route look-up is significantly stringent. If the network topology is geometric such as a Manhattan Street Network (MSN), a hop-by-hop routing can be implemented by simple optical logic devices without an electronic routing table, but if the topology is non-geometric, it is hard to implement the deflection routing electronically or optically. Another approach is a reflection routing. It is easy to implement, but its packet loss probability is inferior to that of the deflection routing. In this paper, we propose a packet contention resolution scheme that is based on the reflection routing and furthermore enables to detour the reflected packet to alternate path if its primary path is under congestion. Our method enables to alleviate the time limitation for alternate path setting by using the packet reflection latency and to improve the performance of packet loss probability. We evaluate the performance of the proposed method to confirm its effectiveness.