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.