A framework for dynamically selecting gain in LEDBAT algorithm for high speed networks

Low Extra Delay Background Transport (LEDBAT) congestion control algorithm has been developed as an alternative for Internet applications that use multiple TCP connections. To allow efficient data transfer when no other traffic exists, a LEDBAT source saturates a bottleneck link while maintaining the access router queue delay at or below a pre-defined target. The source rapidly reduces its sending rate upon the arrival of a new traffic. This paper analyses the relationship between LEDBAT performance and the congestion window gain inhigh-speed access networks. We develop mathematical models, validated with simulations, which show high values of gain are necessary otherwise a LEDBAT source will take a long time to reach optimal sending rate (steady state), underutilizing the bottleneck link. However our analysis also shows that, once in steady state, with a high gain a LEDBAT source can induce jitter into real-time applications and also achieve sub-optimal sending rates. Therefore, we propose a novel framework for dynamically selecting a gain during a LEDBAT connection. Unlike LEDBAT using a fixed gain, our framework achieves a better trade-off between throughput for the LEDBAT source and fairness with other sources. It also provides the ability to tune LEDBAT depending on requirements (throughput or fairness).