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In order to solve the priority problem of tactical data link,a prioritized two-level polling control strategy based on exhaustive access strategy and asymmetric gated access strategy is proposed for media access control in tactical data link. In the polling control strategy, an asymmetric gated access strategy is adopted for the low priority outposts in tactical data link, and the exhaustive access strategy is adopted for the high priority outposts. When the network control site is transferred from the high priority outpost to the low priority outpost, the transmission service and the transfer query are processed in parallel to reduce the time cost during the query conversion, and the operating efficiency of the polling system is improved. The Markov chain and probabilistic generating function are used to establish the mathematical model of the polling system, which accurately resolves the expression of the average number of information packets waiting to be sent in each outpost. The approximate expression of the average waiting time for the infor¬mation packets in the outpost is resolved by using the second-order characteristic quantity approximation method of the cyclic period. The simulated results of the proposed model show that the experimental value is approximately equal to the theoretical value,and the service quality of the high-priority outpost is better than those of other outposts,indicating that the theoretical analysis is correct, and the proposed model a¬chieves the purpose of prioritizing. [ABSTRACT FROM AUTHOR]

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Considering the laige effect of MAC protocol on network performance such as throughput, packet drop rate and transmission delay, this paper developed a new multichannel MAC algorithm CRTC-MAC based on the requirements of the CR-VANET and it combined the fixed TDMA and dynamic CSMA method. The algorithm applied TDMA method when it was in fixed time-slot allocation while it utilized CSMA method when it was in dynamic time-slot allocation. Then, this paper proposed a better architecture of TDMA and CSMA based on traditional protocol to adapt the new multiple access algorithm. By optimizing the frame structure, it could reduce the extra cost which is caused by redundant data. Performance analysis and simulation results show that CRTC-MAC show certain advantages in aforementioned performance indicators. This protocol has smaller collision probability between packet of nodes and these nodes can successfully obtain their corresponding slots in few frames, thus it can improve the network performance. [ABSTRACT FROM AUTHOR]

以太网无源光网络（EPON）已经在全球得到广泛应用,光线路终端（OLT）设备是EPON的核心。由于EPON是点到多点的共享型网络,网络安全会受到威胁,保护OLT设备对整个EPON有着重要意义。文章介绍了EPON OLT设备防攻击方法,重点介绍了交换芯片在设备防攻击中扮演的重要角色,并举例说明了EPON设备如何防攻击。