PROXY SERVER, COMMUNICATION SYSTEM, COMMUNICATION METHOD, AND PROGRAM

摘要

A proxy server in an SIP network includes the common SIP proxy server function 11, the function of determining whether an SIP request and an SIP response received by the proxy server 10 belong to a call flow encountering a failure of the working SIP server 30, and the function of, when determination is made that they belong to a call flow encountering a failure, referring to the contents of the received SIP request and SIP response to specify a destination to which the SIP request and the SIP response are to be transmitted next.