A router-based technique to mitigate reduction of quality (RoQ) attacks

We propose a router-based technique to mitigate the stealthy reduction of quality (RoQ) attacks at the routers in the Internet. The RoQ attacks have been shown to impair the QoS sensitive VoIP and the TCP traffic in the Internet. It is difficult to detect these attacks because of their low average rates. We also show that our generalized approach can detect these attacks even if they employ the source IP address spoofing, the destination IP address spoofing, and undefined periodicity to evade several router-based detection systems. The detection system operates in two phases: in phase 1, the presence of the RoQ attack is detected from the readily available per flow information at the routers, and in phase 2, the attack filtering algorithm drops the RoQ attack packets. Assuming that the attacker uses the source IP address and the destination IP address spoofing, we propose to detect the sudden increase in the traffic load of all the expired flows within a short period. In a network without RoQ attacks, we show that the traffic load of all the expired flows is less than certain thresholds, which are derived from real Internet traffic analysis. We further propose a simple filtering solution to drop the attack packets. The filtering scheme treats the long-lived flows in the Internet preferentially, and drops the attack traffic by monitoring the queue length if the queue length exceeds a threshold percent of the queue limit. Our results show that we can successfully detect and mitigate RoQ attacks even with the source and destination IP addresses spoofed. The detection system is implemented in the ns2 simulator. In the simulations, we use the flowid field available in ns2 to implement per-flow logic, which is a combination of the source IP address, the destination IP address, the source port, and the destination port. We also discuss the real implementation of the proposed detection system. 2007 Published by Elsevier B.V.