Interference Effect of UDP Mixed with TCP-RED

Abstract

Multimedia applications are gaining momentum as the principal service on the Internet. Because most of multimedia service use the UDP protocol to carry the traffic over the Internet, it is very important therefore to explore the interaction between UDP and TCP protocol in the routers. In this paper, we apply the matrix-analytic approach to explore the interactive behavior between UDP and TCP protocol under RED scheme. In order to reduce the analysis complexity of RED mechanism, we chose to bypass the interactions between TCP sessions and RED mechanisms and constructed a simple queuing model for RED mechanism with UDP and TCP traffic which follow a continuous-time Markovian arrival process (MAP). The queueing model of the router with RED scheme is modelled as MAP/M/1/K. With the numerical results, we find that as the arrival rate of UDP traffic increases, the drop probability of TCP traffic will also increase under RED scheme. In practice, this effect causes TCP congestion control protocol to reduce the transmission rate of TCP traffic. This is an unfair effect for providing multimedia applications on the Internet. Based on this observation, the router in the Internet must implement some mechanisms to suppress this effect.