Abstract – 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 exa...