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This paper proposes and evaluates an optimized feedback design for a backpressure-based fairness control scheme in best-effort networks. UDP applications can continuously waste shared bandwidth on undeliverable packets that are dropped in the networks before reaching the receiving end hosts. Undeliverable packets of heavily loaded receivers cause unfairness when they block deliverable packets of other receivers in the networks. The scheme can prevent the unfairness by detecting undeliverable packets at egress boundary nodes of the network, and by regulating subsequent ones at ingress boundary nodes through backpressure signals sent from egress to ingress boundary nodes. In order to minimize the number of feedback packets that contain the backpressure signals, this paper proposes a scalable backpressure scheme, in which feedback packets are sent only for undeliverable packets detected at a regular interval. Increasing the detection interval reduces the number of feedback packets, but also reduces the effectiveness of the fairness control since it weakens regulation on heavily loaded receivers. This paper also proposes an optimized design of the detection interval that can minimize the number of feedback packets while keeping fairness. Simulation results show that the proposed design achieves the expected optimization.
Date of Conference: 2002