Abstract: A system for controlling multimedia features and supplementary services in SIP based phones comprising: At least one UAC, operable to request desired data using a RDT message as an expanded SIP and check whether the data is correctly received; at least one UAS, operable to combine the requested data with information indicating whether the data is correctly transmitted, using the RDT message as the expanded SIP, and transmit the resultant data; a SIP terminal which supports two way communication with another SIP entity in real-time and also supports both signaling and media; at least a Proxy server capable of contacting at least one client or the next hop server and passes the call request further; and At least a Redirect Server capable of accepting SIP requests; and At least a Location Server capable of providing information about a caller's possible locations and redirect to the proxy servers.