Packet filtering apparatus and method in a network system using Mobile IP

The present invention relates to a packet filtering device and method in a network system using Mobile IP, in particular, the home agent (home agent) to go through without being sent to the correspondent node from the address and the mobile node in the packet transmitted to the mobile node from the correspondent node It relates to a packet filtering device and method for reading the address of the packet. In addition, a phenomenon the invention is discarded in the relative downlink data transmitted from a node in the uplink data with the mobile node is sent to the mobile node in the correspondent node is not transmitting a packet filtering device if the firewall network correspondent node is protected It relates to a packet filtering device and method for prevention. The invention also uplink data is reasonably than by applying to recognize the packets transmitted from the packet and the mobile node is sent to the mobile node from the correspondent node to the correspondent node packet filter rules (packet filter rule), which in the protected network and to enable the transmission and downlink data transmission. Mobile IP (Mobile IP), firewall