A Stateless and Light-Weight Bandwidth Management Mechanism for Elastic Traffic

Unbounded growth in the number of active flows can lead to severe service quality degradation to existing flows in a network . To guarantee minimum service quality for individual flows, specially for multimedia traffic, it is necessary to estimate and bound the number of active flows in the network. Prior work on estimating the number of active flows has been difficult without maintaining per-flow state. In this paper, we propose a light weight (not requiring per flow state) mechanism to estimate the number of active flows. This estimate is then used to determine the probability of admitting a new flow into the network with the goal of preventing extreme degradation of throughput to existing flows. The key idea here is that the number of active flows can be inferred from the frequency at which a newly arriving packet is part of the same flow as a randomly selected packet in the buffer. Since this scheme relies on information already available in the buffer, no per-flow state is maintained in the network. This mechanism requires very little per-packet processing, even less than a forwarding table lookup. Simulation results show that the proposed scheme can stabilize an overloaded network by bounding the number of active flows without significantly impairing link utilization. This scheme also gives good performance when buffer sizes are small and when the network has a mix of TCP and UDP traffic.