Virtual Path Assignment and Virtual Circuit Routing in ATM Networks

The use of virtual paths in ATM networks reduces the call set-up delays, simplifies the hardware in the transit nodes and provides simple virtual circuit admission control. However, it also reduces the degree of capacity sharing and thus, increases the call blocking rate. We consider the following problem: given a network topology, link capacity of each physical link and traffic requirement of each origin-destination pair, we want to jointly determine the following four design variables: (1) the pairs of nodes that should have virtual paths, (2) the route of each virtual path, (3) the bandwidth assigned to each virtual path, and (4) the routing assignment for each virtual circuit (call), to minimize the expected call blocking rate subject to call set-up time constraints. or, alternately, to minimize the call set-up delay subject to the expected call blocking rate constraints. The problem is formulated as a nonlinear nondifferentiable combinatorial optimization problem. We also present simplified formulations for networks with abundant capacity or with limited capacity (two special cases of the general problem). Algorithms for solving the two special cases are proposed and implemented. We present computational results and make comparisons of different schemes.