A study of ECN effects on long-lived TCP connections using red and drop tail gateway mechanisms

Abstract

Rapid growth of Internet traffic and the increase of new user applications authorize the development of new internet infrastructure. Congestion remains the major problem that affects the Internet service quality. Avoiding packet drops keeps network bandwidth and permits congestion signals to be propagated faster. Sending congestion information is essential to the network performance. Using Explicit Congestion Notification (ECN) to notify the source about the network congestion can result in sending congestion signal faster so that the sender can reduce its congestion window sooner which leads to better network utilization. When ECN is enabled on routers, they mark packets instead of dropping them. ECN mechanism does not require creation of additional transfer at the router and can be applied in the data path of routers. . In this article, we study the behavior of ECN-capable TCP and examine the effect of ECN on long-lived TCP connections using Random Early Detection (RED) and Drop tail gateway mechanisms. We estimate the gain introduced by ECN, in terms of throughput, with different sets of number of TCP users and a point of congestion. Our analysis and simulations results show that the use of ECN over long-lived TCP connections sharing a bottleneck can improve the overall throughput, having less loss, less delay time, and better network utilization