Optimal call admission control under packet and call level QoS constraints and effect of buffering

Abstract

SUMMARYFor a single network switch allocating link bandwidth to connections of a single class, an optimal call admission control (CAC) policy is found by the solution of a linear programming (LP) problem. Our optimization differs from previous work in that we include the effect of an output buffer in the switch for the temporary storage of packets bound for transmittal across the link. We find a policy that is optimal in the sense of minimizing call blocking subject to a packet level quality of service (QoS) requirement that limits the packet loss ratio. Such a policy's call blocking probability, if it is small enough to satisfy a call level QoS requirement, then establishes the feasibility of satisfying both the packet and call level QoS requirements for a given call request rate. We show with a previously described example that the addition of even a small output buffer can significantly increase the range of call request rates for which there exists a feasible policy, i.e. one that satisfies both QoS requirements. Also presented is an upper bound, valid for any fixed buffer size, on the range of call request rates for which there exists a feasible CAC policy.