On the proportional fairness of TCP Vegas

This paper concerns the fairness of TCP Vegas, a new version of TCP proposed by Brakmo et al., (1994). Firstly, we show some uncertainties in bandwidth allocation and buffer occupancy when the system is in the stable state. These uncertainties come from the using of two threshold values (α, β) in the applied innovative congestion avoidance mechanism. We propose a modification in the existing implementations of TCP Vegas to reduce the uncertainties without losing the stability. Secondly, the notion of the ideal TCP Vegas, which has no uncertainties, is defined. We prove that the ideal TCP Vegas is exactly proportionally fair in bandwidth sharing. This property of the real TCP Vegas is tested by simulation. We also show how to implement weighted proportional fairness with TCP Vegas