Effairness: A Metric for Congestion Control Evaluation in Dynamic Networks

This paper examines the problem of congestion control evaluation in dynamic networks. We determine a source of deficiencies for existing metrics of congestion control performance – the existing metrics are defined with respect to ideal allocations that do not represent short-term efficiency and fairness of network usage in dynamic environments. We introduce the concept of an effair allocation, a dynamic ideal allocation that specifies optimal efficiency and fairness at every timescale. This concept has a general applicability; in particular, it applies to networks that provide both unicast and multicast services. Another desirable property of the effair allocation is its dependence on the communication needs and capabilities of applications. We design an algorithm that accounts for network delays and computes the effair allocation as a series of static ideal allocations. Using the notion of effair allocation as a foundation, we define a new metric of effairness that shows how closely the actual delivery times match the delivery times under the effair allocation.