Dynamic buffer management based on rate estimation in IP networks

Abstract

While traffic volume of real-time applications is rapidly increasing, cur-rent routers do not guarantee the minimum QoS values of fairness and drop packets in random fashion. If routers provide a minimum QoS, less delays, more fairness, and smoother sending rates, TCP-Friendly Rate Control can be adopted for real-time applications. We propose a dynamic buffer management scheme that meets the requirements described above, and can be applied to TCP flow and to data flow for transfer of real-time applications. The proposed scheme consists of a virtual threshold function, an accurate and stable per-flow rate estimation, a per-flow exponential drop probability, and a dropping strategy that guarantees fairness when there are many flows. Moreover, we introduce a practical definition of active flows to reduce the overhead coming from maintaining per-flow states. Introduction of a virtual threshold function that divides router operation into three modes helps routers support more flows than RED, FRED and DRR with the same buffer size. Moreover, we introduce Fair Drop that guarantees fairness even when there are so many flows that each flow can buffer less than one packet in average in a router buffer.