Integrating path computation and precomputation for quality-of-service provisioning

QoS provisioning involves reserving resources along a suitable path through the network for the entire lifetime of a connection. To assess the suitability of the possible paths, their QoS metrics which indicate the available resources, should be computed. The QoS metrics can be computed on-demand after the arrival of a QoS connection request or precomputed. On-demand path computation is superior to path precomputation in that suitable paths may be determined using most up to date network state. However, the delay incurred in determining a suitable path on demand may be unacceptable. Path precomputation overcomes the drawback of long delay of on-demand path computation. In addition, path precomputation may be preferred over on-demand path computation for scalability issues, whet? the number of expected QoS connection requests is very large. Typically, path precomputation needs to be performed frequently, for different k-constrained routing problems, and from each source node to every possible destination node, which causes excessive consumption of resources. The overheads associated with typical on-demand and path precomputation techniques become unacceptable when routing inter-domain connections, and hence these techniques have been used almost exclusively in the context of intra-domain connections. The present paper describes an effective QoS provisioning technique which integrates path computation and precomputation intelligently in order to exploit the advantages offered by both these approaches. A novel reverse path precomputation technique which reduces the overheads associated with the precomputation process is also described. The presented QoS provisioning technique is suitable for provisioning both intra-domain and inter-domain connections.