In this paper we evaluate the effectiveness of Random Early Detection (RED) over traffic types categorized as nonadaptive, fragile and robust, according to their responses to congestion. We point out that RED allows unfair bandwidth sharing when a mixture of the three traffic types shares a link This urlfairness is caused by the fact that at any given time RED imposes the same loss rate on all jlows, regardless of their bandwidths. We propose Fair Random Early Drop (FRED), a modified version of RED. FRED uses per-active-jlow accounting to impose 011 each flow a loss rate that depends on the flow's buffer use. We sl~ow that FRED provides better protection than RED for adaptive uragile and robust) flows. In addition, FRED is able to isolate non-adaptive greedy trafic more effectively. Finally we present a "two-packet-buffer" gateway mechanism to support a large number of f7ows without incurring additional queueing delays inside the network These improvements are demonstrated by simulations of TCP and UDP traffic. FRED does not make any assumptions about queueing architecture: it will work with a FIFO gateway. FRED's peractive-jlow accounting uses memory in proportion to the total number of b@fers used: a FRED gateway maintains state only for flows for which it has packets buffered, not for all flows that traverse the gateway,
Flow random early detection (FRED) REF was motivated by the unfair bandwidth sharing of RED gateways.
Dynamics of random early detection
SIGCOMM '97
Computer Science