Network of single-server queues with dependent service times

A network of single-server nodes fed by customers of several classes is considered. Each customer is equipped with the random work to be done for completing service. The distribution of this work and the rate of its decreasing during the service depend on the node, the class of the customer, the queue contents and the residual work loads of the customers at the node. The service discipline is last-come-first-served preemptive-resume. For both open and closed network, the stationary distribution is derived. In general, this distribution is not a product form. For the open network, sufficient conditions yielding the product form are given. For both open and closed network, sufficient invariance conditions are found.