TCP's Influence on Interactive Multimedia Traffic
Bent Jarle Lorentzen · NORA - Norwegian Open Research Archives · 2008
Interactive multimedia traffic is usually a stream of packets containing voice, video a combination of these. Because of the user interaction, there is a high vulnerability to latency, jitter and packet loss. In this thesis, we have investigated TCP’s influence (FTP and HTTP traffic) on interactive multimedia traffic through numerous simulations in the network simulator NS-2. Our findings include what types and amounts of traffic are required to disrupt an interactive multimedia stream. We have also done a thorough investigation into what kind of changes to endpoint and network variables make the greatest difference in TCP’s influence on this kind of traffic. The changes made in the endpoints that affected TCP’s influence on the VoIP traffic were the choice of transport protocol and the rate of the VoIP calls. Silence suppression made a little effect for the worse, i.e., it reduced the VoIP bandwidth consumption, but the received quality was reduced due to higher loss. The change of queuing methods from tail-drop to RED made the packet loss for the VoIP call drop to almost zero. The increase in queue length improved on the packet loss, but it also introduced higher latency. The distance to the bottleneck proved to have no effect at all. Our simulations in the 100Mbps version of our network shows that our results are valid for higher bandwidth as well. Our results indicate that the network has to be quite badly congested before serious disruption occurs for the VoIP application.