Experimental QoS performances of multimedia applications

Several QoS provisioning mechanisms such as differentiated services (Diffserv) and integrated services (Intserv) have been recently devised and applied to bring quality of service (QoS) to the Internet. This paper studies end-end QoS performances of two QoS-demanding applications using different transport protocols. Both applications are tested in a real network environment, with end-end QoS provisioning by Intserv. They use QoSockets, a new extension of QoS specification and management to the Berkeley sockets. Their performance in terms of throughput, delay, jitter, and loss are measured under a number of test cases combining several factors: (1) single or multiple flows, with or without resource reservations; (2) normal, heavy, or overloaded scenarios; (3) uni- or bi-directional streams; and (4) TCP or UDP protocols. The experimental results show that the performance of two applications with the Intserv resource reservations are significantly improved, but not always guaranteed. It is also shown that UDP applications are able to get the requested QoS while TCP applications may not because of the nature of its bi-directional traffic flow. The paper provides detailed interpretation of the results and provides generic conclusions on application QoS.