A note on the hypercube model

We consider a variation of the hypercube model in which there are N distinguishable servers and R types of customers. Customers that find all servers busy (blocked customers) are lost. When service times are exponentially distributed and customers arrive according to independent Poisson streams, we show that the policy which always assigns customers to the fastest available server minimizes the long-run average number of lost customers. Furthermore, we derive an upper bound for the blocking probability and the long-run average number of customers lost.