1. A method of operating a Session Initiation Protocol (SIP) server including a signaling data system and a session data system stored on a storage system and executed by a processing system, the method comprising: in the signaling data system, receiving a first SIP message having a Session Description Protocol (SDP) data set, and in response, storing the SDP data set in association with a session segment identifier and transferring a session request having the session segment identifier and not the SDP data set; in the session data system, receiving the session request having the session segment identifier and not the SDP data set, and in response, authorizing the session request and transferring a session instruction having the session segment identifier; and in the signaling data system, receiving the session instruction having the session segment identifier, and in response, identifying the SDP data set with the session segment identifier and transferring a second SIP message having the SDP data set.