Steady-state and transient-state analyses of TCP and TCP-friendly rate control mechanism using a control theoretic approach

Abstract

In recent years, various real-time applications in the Internet have been emerging with rapid increase of the network bandwidth. A real-time application traditionally uses either UDP (User Datagram Protocol) or TCP (Transmission Control Protocol) as its transport layer protocol. However, using either UDP or TCP is insufficient for most real-time applications because of lacking a smooth rate control mechanism or suffering a significant transfer delay. In the literature, several transport-layer communication protocols for real-time applications have been proposed. In this paper, among these transport-layer communication protocols, we focus on TFRC (TCP-Friendly Rate Control). Steady state performances of TCP and TFRC connections such as throughput and fairness have been throughly investigated by many researchers using simulation experiments. However, transient state properties of TCP and TFRC connections such as stability and responsiveness have not been investigated. In this paper, we therefore analyze both steady state and transient state performances of TCP and TFRC connections using a control theoretic approach. We frist model TFRC and TCP connections with different propagation delays and the active queue management mechanism of RED (Random Early Detection) router as independent discrete-time systems. By combining these discrete-time systems, we analyze steady state performance of TCP and TFRC connections such as throughput, transfer delay, and packet loss probability. We also analyze transient state performance of TCP and TFRC connections using linearization of discrete-time systems around their equilibrium points.