Media access protocols for a scalable optical interconnection network

Hierarchical optical interconnection networks have the potential of solving the communication bottleneck that has evolved in parallel processing systems due to big increases in processor speeds. Hierarchical Optical Ring Interconnection Network (HORN) is one network architecture that was proposed to provide scalability to a larger number of processing nodes (PNs) with low latency and high bandwidth. In HORN PNs are arranged in rings and those rings are grouped together hierarchically in higher level rings. While collisions of data from multiple sources in hierarchical networks like HORN are reduced by separating nodes spatially and by wavelength, they can´t be prevented completely and a media access (MAC) protocols must be used to that end. An in depth analysis of five collision-free, single hop protocols is performed in terms of average delay and system throughput. The protocols analyzed are: time division multiple access (TDMA), TDMA with arbitration, FatMAC, DMON, and token hierarchical optical ring network (THORN). The first four protocols are documented in the literature but the fifth, THORN, was developed expressly for HORN. While all the protocols support the scalability objectives of HORN, THORN is shown to have the lowest delay and a throughput comparable to the other four protocols