两次更新NAV防止信道抢占攻击的研究

文章根据IEEE 802.11的规定,为了避免信号干扰,采用一种基于NAV的虚拟介质监听技术.协议中要求节点在探测到RTS/CTS数据包之后利用其中的Duration域设置自己的NAV时间,然后开始倒计时直到NAV内时间耗尽.在NAV内时间还未结束之前,节点认为信道处于忙碌状态,既不会向网络中别的节点发进数据包,也不会尝试去监听信道.基于上述理论,可以伪造Duration域的数值,使其长于正常数据包需要占用信道的时间,以此影响网络的质量和性能.IEEE 802.11中同时规定,接收节点在收到Data数据包后,需要发送ACK数据包给发送节点作为数据包成功发送的标志.在此过程中,设计接收节点在发送Data数据包之后再次更新一跳范围内的所有节点NAV为正常值,发送节点在收到ACK数据包后,也更新一跳范围内的所有节点NAV为正常值.以此来防止恶意占用信道的攻击.

Researching on Anti-Occupying Channel by Setting NAV Twice

In order to avoid signal interference, there’s a virtual media monitoring technology based on NAV been mentioned in IEEE 802.11 protocol. Protocol requires all the nodes set their NAV according to the DURATION field which in RTS/CTS Packets’ header when they detect RTS/CTS in the medium. Once they set up the NAV, they will start the countdown until the time in NAV runs out. In the agreement, when the time in NAV is not over, the nodes will conjecture that the channel is busy, so they won’t try to forward or send packets to the other nodes listen to the channel neither. Base on the above theory, attack node could false the value of DURATION field in RTS packets which far longer than normal to transfer a packet in the channel. This will affect the network performance. IEEE 802.11 prescribe that once the receiving node receives DATA packet, it need to send an ACK packet to the sending node as a signal of DATA packet sending successfully. There can be some new steps to avoid the attack like： Once the receiving node receives the DATA packet, it needs to correct the neighbors’ NAV to the normal value. Once the sending node receives ACK packet, it also needs to correct its neighbors’ NAV.