| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent unauthorized access from a network to a terminal. <P>SOLUTION: If virus is contained in a signaling packet received from an external terminal, that signal packet is discarded. If it is not evident that virus is contained, unnecessary parts are deleted and the signaling packet is transferred to an internal terminal in response to a polling signal. A port number described in an acknowledgement packet received from the internal terminal is transformed into other port number. If a session packet received from an external terminal conforms to a predetermined protocol, the port number undergoes inverse transformation before being transferred to the internal terminal. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
