Enhancing SCI´s fairness protocol for increased throughput

The scalable coherent interface (SCI) is a newly established IEEE standard which provides bus-like services to a network of nodes connected by very fast, unidirectional links. SCI provides an efficient flow control protocol that fairly allocates bandwidth to all nodes on the network. When global fairness is not required, it is desirable to relax its enforcement, in exchange for increased network utilization. This paper presents an extension to SCI´s fairness protocol that increases attainable throughput by enforcing fairness only among conflicting nodes. The authors present extensive simulation results and compare them to the standard SCI protocol and to the desired performance, which is derived in the paper. The comparisons show that, on average, the enhancements substantially increase the performance of the original protocol