Analysis and application of congestion measures

In end-to-end congestion control protocols, sources continuously obtain feedback from the network, detect the level of congestion along their network path and adjust their sending rate accordingly. The level of congestion can be represented by the loss rate in TCP Tahoe/Reno, queuing delay in TCP Vegas or marking probability in ECN-capable protocols. We call them the congestion measures. Our aim in this paper is to generalize the congestion measures and investigate their common properties, especially the so-called "population effect", where the total congestion level tends to increase with the number of active connections. This better understanding of the congestion measures promotes the use of ECN-like router mechanisms to avoid the negative impact of population effect. We also propose the use of congestion measures in available bandwidth estimation and dynamic path selection algorithms.