Scalable multicomputers are based
on interconnection networks that typically provide multiple communication
routes between any given pair of processor nodes. Routes must be selected
for communication so that the load is distributed evenly among the links
and swithches to prevent congestion in the network. We describe the route
selection algorithm used in the IBM 9076 SP1 multicomputer. We then describe
a new algorithm for reducing network congestion and compare the two algorithms.