If a communication path is formed between SIP servers (#1) and (#3), an SIP server (#2) for performing the relay therebetween receives an INVITE signal from the SIP server (#1) and gives up describing track information on the SIP server (#2) itself in the Via header and Record-Route header of the INVITE signal and transfers the signal to the SIP server (#3). After the INVITE signal transferred in this way, the signal transmitted/received between the SIP servers (#1) and (#3) does not include the track information of the SIP server (#2) and is thus transmitted/received without going through the SIP server (#2).
