The existing Random Early Detection (RED) algo-

rithm and its variants are found vulnerable to emerging attacks,especially the Low-rate Denial-of-Service (LDoS) attacks. In this

letter we propose a Robust RED (RRED) algorithm to improve the TCP throughput against LDoS attacks. The basic idea behind

the RRED is to detect and fi lter out attack packets before a normal RED algorithm is applied to incoming fl ows. We conduct

a set of simulations to evaluate the performance of the proposed RRED algorithm. The results show that, compared to existing

RED-like algorithms, the RRED algorithm nearly fully preserves the TCP throughput in the presence of LDoS attacks.