Performance Analysis of LEDBAT in the Presence of TCP-Newreno

DOI: 10.5176/978-981-08-7656-2_NTC2010-41

Authors: Amuda James Abu and Steven Gordon

Abstract:

Low Extra Delay Background Transport (LEDBAT) is a novel one-way delay Internet congestion control algorithm developed to react to congestion earlier than any ofthe loss-based TCP congestion control algorithms (e.g. TCPNewReno).A LEDBAT source quickly reduces its sending rate when the queue delay experienced in its path is greater thana fixed pre-defined target value. This paper analyses LEDBAT when it is sharing a bottleneck link with TCP. Our analysis identifies the threshold of a bottle neck buffer size that leads LEDBAT to revert to a minimum congestion window of only 1packet in the presence of TCP. That is, for some application sits through put will be too low. In addition to the fact that intra protocol unfairness among multiple LEDBAT sources may occur when using the fixed minimum LEDBAT congestion window to improve the limited LEDBAT throughput, we show that the average LEDBAT throughput is fixed even as the bottleneck link capacity increases as opposed to TCP throughput that increases proportionally. This therefore necessitates the need for a dynamic minimum congestion window in the LEDBAT algorithm.

Keywords: LEDBAT, delay-based congestion control, low priority protocols, peer-to-peer file sharing, real-time applications