An exploitation of the proper classification of conventional call processing states into categories, each category corresponding to one of the call states of the SIP finite-state machine, yields simplified design, implementation, and operation of heterogeneous call processing. The method may be implemented on a server computer or other computing device. In an outside air shut-off container according to the present invention, an inert gas is supplied between an O-ring, which hermetically seals a process chamber and a cover member, and the outside air while a gas passage formed between the O-ring and the outside air is covered with a sealing cover.