On the Fair Coexistence of Loss- and Delay-Based TCP

This paper presents and develops a novel delay-based additive increase, multiplicative decrease (AIMD) congestion control algorithm. The main features of the proposed solution include: 1) low standing queues and delay in homogeneous environments (with delay-based flows only); 2) fair coexistence of delay- and loss-based flows in heterogeneous environments; 3) delay-based flows behave as loss-based flows when loss-based flows are present in the network; otherwise they revert to delay-based operation. It is also shown that these properties can be achieved without any appreciable increase in network loss rate over that which would be present in a comparable network of standard TCP flows (loss-based AIMD). To demonstrate the potential of the presented algorithm, both analytical and simulation results are provided in a range of different network scenarios. These include stability and convergence results in general multiple-bottleneck networks and a number of simulation scenarios to demonstrate the utility of the proposed scheme. In particular, we show that networks employing our algorithm have the features of networks in which RED AQM´s are deployed. Furthermore, in a wide range of situations (including high-speed scenarios), we show that low delay is achieved irrespective of the queueing algorithm employed in the network, with only sender-side modification to the basic AIMD algorithm.