A QoS-based routing algorithm for PNNI ATM networks

Although the ATM Forum has proposed the Private Network-Network Interface (PNNI) specification to facilitate routing in ATM networks, path selection or routing algorithms that guarantee users' multiple Quality of Service (QoS) requirements remain an open issue since the PNNI protocol only provides a routing framework and does not standardize on a method of finding an appropriate path. In this paper, we propose a heuristic routing algorithm called the Backward Hierarchical Routing Algorithm (BHRA) for ATM networks, which is compliant with the PNNI protocol. BHRA uses an adaptive and iterative path search approach and takes advantage of the PNNI hierarchical network structure. It consists of three components: (1) a path selection algorithm, (2) a rerouting mechanism, and (3) inter-class resource sharing. The BHRA has been simulated using the BONeS network simulation tool and the simulation results show that call setup time is significantly reduced, and the computational overhead and call blocking probability are lower, compared to other PNNI routing algorithms. Network throughput is also improved by evenly distributing the traffic among several eligible paths. A multicast routing extension to BHRA is also presented.