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.