Sharing resources through advance reservation agents

We propose an architecture where clients can make advance reservations through agents responsible for advance admission control. The agents allocate resources in the routers just before they are needed for packet forwarding. In this paper we show that network resources can be shared between immediate and advance reservations without being pre-partitioned. The admission control schemes for immediate and advance reservations still operate with little interaction. Admission control decisions for immediate reservations use information about resources to be allocated for advance reservations in the near future. An important parameter in the admission control algorithm is the so called lookahead time, i.e., the point at which we actually start making resources available for approaching advance reservations by rejecting immediate requests. In our model, preemption of immediate reservations is made in cases where the admission control cannot make resources available through rejection of immediate requests. The risk of preemption can be varied by changing the lookahead time when making immediate admission control. We explore, with simulations, the effects of providing advance reservations according to this model. The results show the cost in terms of resource utilization, rejection probability and preemption probability.Godkänd; 1997; 20080411 (ysko)