Experimental Evaluation of Less-Than-Best-Effort TCP Congestion Control Mechanisms

Abstract

Increasing use of online backup services, as well as the popularity of user-generated content, has increased the demand for bandwidth. However, traffic generated by these applications can impact on the responsiveness of delay-sensitive applications if they receive a 'fair-share' of the available bandwidth. Less-than-Best-Effort TCP congestion control mechanisms aim to allow lower-priority applications to utilise excess bandwidth with minimum impact to regular TCP traffic. We evaluated the performance of six Less-than-Best-Effort congestion control algorithms in different scenarios in a Linux testbed, only three of which had existing implementations for modern operating systems. The findings of this study suggest that Nice provides background throughput comparable to that of regular TCP, while maintaining low queuing delay, while CAIA Delay-Gradient (CDG) has the least impact on regular TCP traffic, at the expense of reduced throughput.