| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To protect a LAN from impersonation utilizing an RTP, a DoS attack, and the feeding of an unauthorized program or the like. <P>SOLUTION: A gateway is installed at the connecting point of an external IP network such as the Internet and an internal IP network such as the LAN. The transmission rate of a data packet passing through the gateway is constantly monitored whether it becomes disproportionately high as viewed from types of data notified by a call control packet before it. When the transmission rate exceeds a specified value, a succeeding packet is discarded. Therefore, it is possible to protect the LAN from the DoS attack of feeding a large amount of packets. While, regarding a packet relayed to the LAN without discarding it, analog data in the packet are destroyed with a noise pattern at a level of not affecting the audition of a person. Consequently, even if a program such as a virus is fed, it does not normally operate after passing through the gateway. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
