Disclosed herein are systems, methods, and non-transitory computer-readable storage media for splitting SIP back-to-back user agents and converting SIP communications between a back-to-back user agent server and a back-to-back user agent client to HTTP requests while preserving SIP headers. The back-to-back user agent server receives a SIP invite from a caller and converts the SIP invite to an HTTP request, wherein headers from the SIP invite are preserved in the HTTP request. The server transmits the HTTP request to a user agent client via a wide area network connection and receives, from the user agent client, an HTTP response to the HTTP request. The server converts the HTTP response to a SIP response, and transmits the SIP response to the caller, wherein the SIP response contains instructions for establishing SIP communications between the caller and a callee via a network.