Patent ID: 7496089

Claim:
A network including: at least a session initiation protocol (SIP) terminal which performs communication by an SIP for realizing connection type communication to perform the communication while confirming connection to a target in an Internet protocol (IP) network; and a private branch exchange which performs a call connection process between the terminals, the network comprising: an SIP system protocol control module incorporated as one of component groups of the private branch exchange and constituted into the module using a mechanism of a back to back user agent (B2BUA) which operates as an acting user agent of a process of the SIP; and an additional service providing module which is incorporated as one of the component groups of the private branch exchange and which provides additional services of the private branch exchange in response to a key operation of the SIP terminal, the key operation causing an output of a hooking operation or a tone indication, wherein no software change is required for the SIP terminal in order to utilize the additional services on the network.