Novel queue-grouping based round-robin protocols for reducing collision of OBS ring networks

OBS ring networks inherently suffer from the resource contention due to the limited network resources and the one-way reservation. Multiple tokens with the help of control information table (CIT) have been applied to avoid the source and wavelength collision. However, the receiver collision cannot be completely avoided as tokens are processed in a distributed manner. In Round-Robin (RR) queue selection protocol, several bursts destined to the same node may be selected by different tokens simultaneously, resulting in receiver collision. Two novel medium access control (MAC) protocols, called Queue-Grouping based RR (QGRR) and Prior queue-Grouping based RR (PGRR), by scheduling RR manner within special queue groups are proposed to reduce the receiver collision. By further grouping the RR queues according to each wavelength, the probability for different bursts destined to the same node on different wavelengths overlapping in time is significantly reduced. Finally, the proposed protocols are evaluated and compared through OPNET simulator.