Visualising interactions between TCP's congestion and flow control algorithms

Abstract

The Transmission Control Protocol, TCP, is used in over 90% of the traffic on the Internet. The effect of the protocol itself on the efficiency and fairness of Internet traffic is accordingly the focus of much study. In particular, the tight timeliness constraints required by Web traffic require that TCP should not unnecessarily introduce delay. TCP continues to evolve, and insights into its behaviour are of great potential value. The work reported offers novel approaches to understanding the subtle interactions between TCP's congestion control and flow control algorithms across a wide range of transfer sizes and congestion regimes. A model of TCP's behaviour is described in the form of a program used to generate data sets. These are then processed to generate 3D graphics that are used to visualise the model. This leads to a re-evaluation of TCP's congestion control algorithms within the context of high bandwidth WANs and a high level of multiplexing. As new access technologies are deployed and more users acquire high bandwidth access to the Internet, the limitation imposed by the needs of competing traffic will reinforce the importance of the fair distribution of network resources.