End-to-end delay in localized QoS routing

Quality of service (QoS) routing has been proposed for supporting the requirements of network applications and satisfying connection constraints. A large amount of information needs to be exchanged periodically among routers. Therefore, in order to satisfy such requirements localized QoS routing algorithms have been proposed. This is where source nodes make routing decisions based on statistics collected locally. Using local information for routing avoids the overheads of exchanging global information with other nodes. In this paper we present a localized delay-based QoS routing (DBR) algorithm which relies on delay constraint that each path satisfies to make routing decisions. We also modify credit based routing (CBR) so that this uses delay instead of bandwidth. The two localized algorithms and the commonly used global shortest path algorithm (Dijkstra¿s) are compared under different delay constraints and network topologies. We demonstrated through simulation that our scheme performs better than the modified CBR under different range of workloads and system parameters and outperforms the Dijkstra scheme in all network topologies, unless unrealistically small update intervals are used.