Communication method between communication networks

An exchange apparatus in communications with a first communication network and a second communication network that differs from the first communication network, the exchange apparatus comprising:

• means for transmitting a first packet to a first telephone terminal being part of the first communication network and a second telephone terminal being part of the second communication network, the first packet being used to determine if an intermediary device, which alters source address information of packets transmitted therefrom, is situated between the exchange apparatus and at least one of the first telephone terminal and the second telephone terminal;
• an interface unit to receive a second packet from the second telephone terminal, the second packet comprises a header area including a source address information;
• a control unit to determine that the source address information has been changed from an original address used in the second communication network to a changed address used in the first communication network by comparing whether the original address contained in the data area of the second packet differs from the source address information contained within the header area of the second packet;
• and
• a memory to store the changed address contained in the header area being associated with the terminal in accordance with the determination by the control unit.

A computerized communication method, comprising:

• transmitting a first packet to a plurality of terminals including a first telephone terminal of a first communication network and a second telephone terminal of a second communication network, the first packet being used to determine if an intermediary device that is adapted to alter source address information within packets transmitted therefrom is situated between the exchange apparatus and at least one of the first telephone terminal and the second telephone terminal;
• receiving a packet from the second telephone terminal in response to the first packet, the packet including a source address information therein;
• determining that the source address information had been changed from an original address used in the second communication network to a changed address used in the first communication address by comparing content within a header area and a data area of the packet;
• storing the changed address being associated with the second telephone terminal upon determining that the source address information has been changed to the changed address;
• and
• providing the source address information including the changed address to the first telephone terminal to enable communications between the first telephone terminal of the first communication network and the second telephone terminal of the second communication network, using the source address information.