Mat-1.600 Laskennallisen tieteen ja tekniikan seminaari

13.10.2003 14.15 U356

Pasi Lassila, Tietoverkkolaboratorio
Modeling and stability of TCP-RED interaction

The window management algorithms of TCP are the most widely deployed congestion control algorithms in the Internet. However, under some circumstances TCP's mechanisms are not enough to guarantee stability of the network and so called AQM methods have been proposed for such cases as mechanisms in the network routers to gurantee stability. RED is one of the most well known of proposed AQM algorithms. We analyze the dynamic behavior of a single RED controlled buffer interacting with a large population of idealized TCP sources obeying the rules of linear increase and multiplicative decrease. A system of delay differential equations is developed that captures the time dependent behavior of the sending rate of the TCP population and the queue length(s). This provides us with a complete model for the dynamics of the system which we use to explore its equilibrium and transient behavior. For the transient behavior we can also analyze the stability and numerically explore stability boundaries as functions of the physical system parameters.