Experimental Evaluation of Congestion Avoidance

The Internet is currently undergoing a significant change. The majority of Internet transfers have historically occurred between wired network devices. The popularity of WiFi, combined with the uptake of smartphones and tablets, has changed this assumption and the majority of Internet connections will soon utilise a wireless link. Congestion avoidance controls the rate at which packets leave a TCP sender. This research re-evaluates different congestion avoidance mechanisms over real world wired and wireless links. This paper does not assert that present mechanisms are poor, nor that wireless has never been a consideration, but that the switch to a mobile and wireless majority necessitates a review, with wireless characteristics at the forefront of design considerations. The results of this study show that TCP Cubic and TCP Hybla perform similarly and generally outperform Veno and Westwood in both wired and wireless scenarios. All tested algorithms featured large delays in 3G links. The results suggest that queuing on the 3G links added between 370ms and 570ms of delay. It is suggested that additional research into congestion avoidance and buffering mechanisms over wireless links is needed.