A Dynamic Algorithm for Stabilising LEDBAT Congestion Window

Low Extra Delay Background Transport (LEDBAT) is a delay-based Internet congestion control mechanism developed to allow fair and efficient data transfer when delay-sensitive and file sharing applications co-exist in networks. A LEDBAT source increases its congestion window until a fixed, pre-defined target queue delay is experienced. This paper analyses LEDBAT congestion control showing that the current algorithm, although quickly reaching a steady state (i.e. target delay reached), results in large oscillations of congestion window and queue delay once in steady state. We therefore propose a dynamic calculation of the congestion window gain once in steady state, and show that the proposed modification stabilises the congestion window while still meeting the fairness and efficiency goals of LEDBAT.