The first method is a method in which an administrator of one of the FWs 5 inputs setting information to the FWC 7, thereby setting, from the FWC 7, flow entries in the respective FWs 5. The administrator of one of the FWs 5 may be equal to an administrator of the FW system 1 or may be different therefrom. Note that the “administrator” may be called an “operator” or a “user”.

The administrator of, for example, one of the FWs 5 may specify, for the FWC 7, the FWs 5 to serve as flow entry setting targets and contents of flow entries to be set. The FWC 7 communicates with the specified FWs 5, thereby setting and registering the contents of flow entries in the relevant FWs 5.

An entry setting (or deletion) request message may be exemplarily used for the setting and registration (or deletion) of flow entries, performed on the FWs 5 by the FWC 7. The entry setting (or deletion) request message is an example of a control message transmitted and addressed to each of the relevant FWs 5. The “control message” is an example of a “control signal”.

FIG. 2 illustrates an example of a format of the entry setting (or deletion) request message. As exemplified in FIG. 2, the entry setting (or deletion) request message may include respective fields of a packet header, a transmission control protocol (TCP) header, and a payload.

In the payload, an identifier of the FW #x (may be called a “FW identifier”) to serve as a target of a setting (or deletion) of a flow entry and a content of the flow entry to be set (or deleted) may be set. It may be conveniently thought that “#x” corresponds to the FW identifier.