Patent ID: 7072339

Claim:
A method for performing communications between a first terminal using IPv4 as a communication protocol and a second terminal using IPv6 as a communication protocol comprising the steps of: receiving from said first terminal a first message requesting an IPv4 address as an IP address of said second terminal; sending a second message inquiring of an IP address of said second terminal to a manager apparatus which manages IPv4 address information or IPv6 address information; when receiving a third message containing a first IPv6 address possessed by said second terminal, said third message being sent from said manager apparatus in response to said second message, performing recognition that said first 12v6 address thus received differs in a protocol version from the IPv4 address requested by said first terminal; converting said first IPv6 address into an arbitrary first IPv4 address; sending a fourth message containing said first IPv4 address as an IP address of said second terminal to said first terminal, said first IPv4 address having a same protocol version as that of the IP address requested by said first terminal; receiving from said first terminal an IPv4 packet having an IPv4 header containing said first IPV4 address as a destination address and a second IPv4 address possessed by said first terminal as a source address; converting said first IPv4 address into said first IPv6 address; converting said second IPv4 address into an arbitrary second IPv6 address; converting said IPv4 header into an IPv6 header containing said first IPv6 address as a destination address and said second IPv6 address as a source address; creating from said IPv4 packet an IPv6 packet having the IPv6 header thus converted; and sending said IPv6 packet to said second terminal.