Chapter 2 - Analytic Modeling of Congestion Control

Abstract

This chapter has a detailed discussion of TCP models, starting from simple models using fluid approximations to more sophisticated models using stochastic theory. The well known “square root” formula for the throughput of a TCP connection is derived and is further generalized to additive increase/multiplicative decrease (AIMD) congestion control schemes. These formulae have proven to be very useful over the years and have formed an integral part of the discovery of new congestion control protocols, as shown in Part 2 of this book. A general procedure for deriving an expression for the throughput of a congestion control algorithm is also presented. This chapter also analyzes systems with multiple parallel TCP connections and derives expressions for the throughput ratio as a function of the round trip latencies.