Bounds for Deterministic Periodic Routing Sequences

We consider the problem of routing arriving jobs to parallel queues according to a deterministic periodic routing sequence. We introduce a combinatorial notion called the unbalance for such routing sequences. This unbalance is used to obtain an upper bound for the average waiting time of the routed jobs. The best upper bound for given (optimized) routing fractions is obtained when the unbalance is minimized. The problem of minimizing the unbalance is investigated and we show how to construct sequences with small unbalance.