A framework for admission control and path allocation in DiffServ networks

Abstract

We consider a Differentiated Service Domain, in which the domain administrator has to decide if to accept or to reject Bandwidth Reservation Requests (BRRs) requested by users. We first define an analytical approach and a methodology to determine the set of SLAs that can be effectively supported by a DiffServ IP network. We consider the Assured Forwarding Per Hop Behavior, and, based on the BRR probabilistic description, we derive a worst-case mathematical formulation for the overbooking probability, i.e., the probability that the traffic crossing any link of a source-destination path exceeds the link capacity. Next, we focus our attention to the problem of routing traffic arising from BRRs, i.e., the selection of paths along which traffic may flow. In particular, we show that the construction of an optimal set of paths is equivalent to the construction of a multicast tree, or a Steiner Tree, which is know to be an NP-hard problem. We therefore propose a class of simple heuristics, whose performance are assessed by simulations. Results show the effectiveness of the admission control criterium proposed, and that it is possible to increase up to 40% the amount of capacity a network provider can reserve to BRRs without violating the QoS constraints or to reduce the BRR blocking probability by a order of magnitude by using the proposed optimization algorithm.