Patent ID: 8107461

Claim:
A Session Initiation Protocol (SIP) exchange system comprising: a plurality of SIP telephones; SIP exchange equipment; and a network to which the plurality of SIP telephones and the SIP exchange equipment are connected, wherein the SIP exchange equipment includes a control part configured to: initiate a SIP call replacement sequence when i) a response is detected from a response party's SIP telephone receiving a forwarded call or a proxy response is detected from a response party's SIP telephone and ii) communication of a SIP call sequence between the response party's SIP telephone and a calling party's SIP telephone is established; and thereafter notify the calling party's SIP telephone of the response party's telephone number and notify the response party's SIP telephone of the calling party's telephone number during the SIP call replacement sequence, wherein the SIP call replacement sequence includes: transmitting an invite message from the SIP exchange equipment to each of the calling party's SIP telephone and the response party's SIP telephone; transmitting a first response message from each of the calling party's SIP telephone and the response party's SIP telephone to the SIP exchange equipment when each of the calling party's SIP telephone and the response party's SIP telephone receives the invite message; transmitting an acknowledgement response message from the SIP exchange equipment to each of the calling party's SIP telephone and the response party's SIP telephone when the SIP exchange equipment receives the first response message.