In a connection-oriented communication method using a connection-type protocol typified by TCP (Transmission Control Protocol), end-to-end connection between a communication device and a correspondent communication device is first established, and then data is sequentially transmitted via the connection. The connection is released when the data transmission is completed. This type of communication method is characterized in that once a circuit (or a session) is established between communication devices; the same circuit is dedicated to the data transmission until the session is completed.
A communication carrier, which provides a packet communication service by way of connection-oriented communication, charges one of the parties on the basis of an amount of data transmitted and received during a connection period from when the connection is established until the connection is released. For example, in a case that a communication terminal requests a content server to deliver content to the terminal, a connection is first established between the communication terminal and the content server. The communication terminal transmits a content request message via the established connection to the content server, and, in response to the request message from the communication terminal, the content server delivers content to the communication terminal via the same connection. The connection is released after the communication terminal receives the content. The carrier operating the packet communication service performs a billing process, after obtaining information required for billing, on the basis of data transmitted or received via the connection, with the data including the request message sent from the communication terminal to the content server and the content delivered to the communication terminal.
In such connection-oriented communication, however, there exists a problem in that communication may be discontinued before data transmission is complete. This may occur as a result of an instruction issued by one of the communicating devices or as a result of a failure of a connection link. In the case that communication is discontinued following issuance of a request message, requested content can not be fully delivered from a content server to a requesting terminal; and consequently a carrier operating the packet communication service may not be able to obtain information required for billing, as a result of which it becomes impossible for a communication charge relative to the request message to be collected.