Patent ID: 8422503

Claim:
An address translator, for use between an IP (Internet Protocol) network and a further network, for carrying out address translation between a private address and a global address of a source address or a destination address included in a header of a packet, the private address being the address of a first node on the further network and the global address being the address of a second node on the IP network, said address translator comprising: interface means for receiving and transferring a packet from the IP network or the further network; and an address translation processor for inserting address translation information in a header area of the received packet at a network layer level and for using the address translation information to carry out the address translation at the network layer level, wherein said address translation processor rewrites, if the packet is to be transferred to the second node from the first node, the source address field of the header area from the private address of the first node to the global address of the first node, and then inserts the address translation information including the private address of the first node in an option field of the header area, and wherein said address translator additionally rewrites, if the packet is to be transferred from the second node to the first node, the destination address field of the header area from the global address of the second node to the private address of the first node inserted in the option field on the basis of the address translation information, and then deletes the address translation information inserted in the option field.