Patent ID: 7072338

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