1. Assessing the Sensitivity of WiMAX Parameters to MAC-level DoS Attacks Juan Deng and Richard Brooks* Clemson University Abstract The research community has established that WiMAX networks suffer Denial of Service (DoS) attacks. We consider a new type of DoS attacks on WiMAX networks exploiting WiMAX system parameter. The behavior of the WiMAX MAC level protocol is sensitive to the settings of core system parameters. DoS attacks resulting from parameter misconfiguration are difficult for network operators to detect. We focus on Bandwidth Contention Resolution (BCR) aspects of the WiMAX MAC protocol. Experiments are simulated using the ns-2 simulator. Analysis of Variance (ANOVA) techniques on the resulting simulation data identify which BCR parameter combinations are crucial for configuring WiMAX to be less vulnerable to DoS attacks. We migrate the experiments to GENI WiMAX testbed to verify the results using a hardware-in-the-loop test environment. Research Objectives There are many parameters DoS attackers can exploit. Our goal is to: compare the effect of setting different values for a single parameter, learn which parameter(s) are dominant, compare the effect of important parameter interactions, and, parameter interactions are dominant. Fig. 1: Network Topology The Research efforts have resulted in the following publications: J. Deng, R. R. Brooks, J. Martin (under review), Assessing the Sensitivity of WiMAX Parameters to MAC-level DoS Attacks, International Journal of Performability Engineering. Use of Glab/GENI Infrastructure We plan to use GENI WiMAX testbed: Experiment Setup Experiment Run Measurement Collection Data Analysis Results Comparisons Future Work Verify simulation results using GENI WiMAX testbed; Verify the ns-2 WiMAX modules; Verify the performance of radio model in ns-2 is consistent with commercial settings. Experiments Design We simulate DoS attacks where attackers attempt to exploit the BCR mechanism using the ns-2 network simulator. Our simulations analyze the influence of six parameters (Table 1) on DoS attacks. Fig. 1 shows the network topology we use in the simulation, where DoS attackers are represented by ■ and SS are represented by. We use the factorial experiment design to collect data. There are in total 3 6 =729 parameter combinations. For each combination, we run 7 replicates, which gives a total of 729x7=5103 simulations. For each replicate, we measure the average traffic throughput and average traffic loss rate of all SSs. 1 st DFG/GENI Doctoral Consortium, San Juan, PR March 13 th -15 th, 2011 Parameters Values lowmediumhigh Frame_duration (X1)0.0040.010.02 Number_of_attackers/SSs (X2) 20/8050/5080/20 Dos_backoff_start (X3)135 Dos_request_retry (X4)246 Bw_backoff_start (X5)135 Bw_request_retry (X6)246 Table 1: Parameter Values Experiment Results We apply ANOVA on the throughput data. Table 2 shows the results, which suggest:  X1 explains about 21% of the variability, while X6 accounts for another 31%.  The most significant 2 nd order effect is the interaction between X1 and X6, which accounts for an additional 18%.  All 3 rd order interactions are not significant. X1 and X6 together explain over 70% of the total variability. Therefore, the average throughput of all SSs is determined mainly by these two parameters. Table 2: ANOVA Results Fig. 5: 3D Plot of (X1, X6, throughput)Fig. 3: Box Plot of Throughput corresponding to X1 Fig. 4: Box Plot of Throughput corresponding to X6 Fig. 2: PDF of Throughput