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- 저자 : Shao-Ping Hung (검색결과 3 건)
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Mitigating SYN flooding Attack and ARP Spoofing in SDN Data Plane
Ting-Yu Lin,Jhen-Ping Wu,Pei-Hsuan Hung,Ching-Hsuan Shao,Yu-Ting Wang,Yun-Zhan Cai,Meng-Hsun Tsai 한국통신학회 2020 한국통신학회 APNOMS Vol.2020 No.09
As the number of network devices increases rapidly, it becomes more and more difficult to defend network attacks. Large-scaled attacks, such as SYN flooding, may lead to heavy burden to the switches as well as the controller in a software defined network (SDN). In this paper, we investigate the SYN flooding and Address Resolution Protocol (ARP) spoofing attacks in SDN, and then propose mechanisms to address these two attacks. We also present a new scheme to detect SYN flooding by using only a few forwarding rules. Moreover, we utilize the Programming Protocol-independent Packet Processors (P4) technique to mitigate the burden of the controller.
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Yi-Jen Chiu,Szu-Lin Su,Shao-Ping Hung 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
Direct conversion receiver is widely utilized in today’s communication system. However, it usually faces a common problem of front-end distortions such as IQ imbalance and frequency offset. When treated separately, effective algorithms exist for estimating and compensating for IQ imbalance as well as frequency offset. With both effects present, such algorithms do not lead to useful estimates of the related parameters. OFDM is sensitive to nonidealities in the receiver front-end. This leads either to stringent front-end specifications and, thus, an expensive device, or large performance degradations. A good summary, Guanbin [1] discusses the transmitter calibration briefly and proposes an estimation technique for calculating the imbalance parameters. For the IEEE 802.11a OFDM standard, Tubbax observe that additional effects from OFDM channel estimation and correction can affect the IQ correction circuits and proposes a smoothing procedure to compensate. The above procedure is not effective when the CFO is too small. This paper extends the previous results mentioned above by developing a simple and adaptive least-square (LS) algorithm to estimate and compensate for IQ imbalance assuming the IQ imbalance compensation is not affected by the CFO, then the CFO is estimated using any of several conventional algorithms. With the additional requirement of a known periodic training sequence (see Su and Chiu ) this process extends the results of to practical cases when CFO is small. Our compensation scheme eliminates the IQ imbalance based on one OFDM symbol and performs well in the presence of CFO. The compensation scheme has fast convergence and small residual degradations. The solution is implemented with an adaptive filter to adjust the parameters of estimation and is computationally relatively inexpensive. With the proposed method as shown in Fig. 1, we can estimate the effect of IQ imbalance without knowing CFO exactly by means of an repetitive training sequence as depicted in Fig.2. Two set of I/Q mismatch parameters, (εr=1.5㏈, ?φr=1.5˚) and (εr=3㏈, ?φr=3˚), are used in the simulations. Fig. 3 shows the performance comparison between the systems with and without I/Q imbalance compensation. It shows that the proposed algorithm can give a satisfactory performance for CFO > 5㎑. To reduce the drawback of high sensitivity under low CFO channel, we modify the adaptive scheme and the fine IQ estimation method to solve the problem of performance degradation when CFO is small. Therefore, our IQ imbalance estimation/compensation scheme potentially leads to low-cost and low-complexity receivers. The simulation results show that the modified scheme can achieve much better performance as shown in Fig. 4.
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