Experimental QoS Performances of Multimedia Applications

To bring QoS to the Internet, several better-thanbest-effort network services have been recently devised with significant efforts. The goal of this paper is to measure the effective performances of existing applications after incorporating QoS, and to understand what are the effects of provisioning QoS in the applications. Our experiments use two kinds of existing multimedia applications: UDP-based NetVideo and TCP-based DIRM. QoSockets is the Berkeley socket extension for the specification of QoS requirements and the management of QoS performances in a distributed environment. We replace their socket APIs with QoSockets and test them in real network environments that include programs written in C/C++ and Java on Solaris/SPARC and Linux/X86 platforms and two sub-networks connected by two routers. We also introduce an additional program TG to create UDP or TCP reference traffic for comparisons. We use the integrated service (IS) to provide QoS for both applications, and examine their QoS performances (throughput, loss, delay and jitter) in a number of cases: (1) single and multiple, reserved and unreserved flows; (2) normal, heavy and overloaded traffic; (3) oneand two-way streams; and (4) TCP and UDP communications. The experimental data shows that QoS performances of the two applications through resource reservations are significantly improved but slightly different for DIRM (which suffers the complexities of TCP and its own system). We summarize the experimental results and derive some generic conclusions on providing QoS for existing distributed applications.