Admission and routing control with partial information and limited buffers

Problems of admission and routing control for loss systems comprised of a controller and C down-stream servers are studied. We focus on problems in which control actions have to be taken with either delayed or with no information on the state of the down-stream servers. We first consider a problem of routing into C servers and compare the performance of two policies: a static round-robin policy, which does not wait for the delayed information at a risk of losing customers at the busy servers, and a Wait policy, that avoids losses at the servers but risks losses at the controller buffer. We identify regions in which each of the policies performs better. We then study the problem with no information on down-stream servers and propose a timer mechanism to decide when to dispatch an arriving customer. We optimize the value of the timer's parameter. Our study is accompanied with numerical investigations.