IPP uses the traditional client-server model, with clients sending IPP request messages with the MIME media type "application/ipp" in HTTP POST requests to an IPP printer. IPP request messages consist of key/value pairs using a custom binary encoding followed by an "end of attributes" tag and any document data required for the request (such as the document to be printed). The IPP response is sent back to the client in the HTTP POST response, again using the "application/ipp" MIME media type.