Asymptotically exact decomposition approximations for open queueing networks

Two decomposition approximations are presented for mean sojourn times in open single class queueing networks. If there is a single bottleneck station, the approximations are asymptotically exact in both light and heavy traffic. When applied to a Jackson network or an M/G/1 queue, these approximations are exact for all values of the traffic intensity. They also perform reasonably well on some small examples.