Patent ID: 7441248

Claim:
A data transfer device having a function of compressing data to be transferred and decompressing received data, comprising: a request receiving unit configured to receive from a requesting device a request message that requests a requested device to send desired data; an analysis unit configured to analyze whether the request message received by the request receiving unit includes a prescribed header indicating a presence of another data transfer device having the function; a storing unit configured to store therein information indicating whether the request message includes the prescribed header or not; a request transfer unit configured to transfer the request message without making any change when the prescribed header is included in the request message, and attach the prescribed header to the request message and then transfer the request message when the prescribed header is not included in the request message; a reply receiving unit configured to receive a reply message corresponding to the request message; a checking unit configured to refer to the storing unit and check whether the prescribed header was included in the request message corresponding to the reply message received by the reply receiving unit; and a reply transfer unit configured to transfer to the requesting device the reply message according to a result of checking by the checking unit, wherein the reply transfer unit transfers to the requesting device the reply message without making any change when the checking unit checks that the prescribed header was included.