An Analytical Model of TCP Performance

Abstract

The transmission control protocol (TCP) is the dominant transport layer protocol for the end-to-end control of information transfer. Accurate models of TCP performance are a key and basic step for designing, dimensioning and planning IP (Internet Protocol) networks. Packet-level simulation models do not scale with the growth of network capacities and number of users. Measurements can only be used to explore existing network scenarios or otherwise they become costly and inflexible with the growth and complexity of the Internet. This study presents a simple, fast and accurate analytical model of TCP. The model gives Internet performance metrics, assuming that only basic network parameters such as the network topology, the number of users, link capacity, distance between network nodes and router buffer sizes are known. The TCP performance model derives performance metrics which express the network quality of service. To obtain the performance metrics, TCP and network sub-models are used. A closed network of ./G//spl infin/ queues is used to develop each TCP sub-model where each queue represents a state of a TCP connection. An M/M/1/K queue is used for each network sub-model which represents the output interface of an IP router with a buffer capacity of K packets. The two sub-models are iteratively solved. Initial comparisons of our results with ns2 simulation experiments and with results from a well known TCP model show that our model is faster, simpler and gives more accurate TCP performance metrics.