It is a wire level protocol running at the level under Remote Method Invocation (RMI) and over TCP/IP.
The Wire | Transmission Control Protocol | File Transfer Protocol | Session Initiation Protocol | User Datagram Protocol | BitTorrent (protocol) | Kyoto Protocol | Internet Protocol | Post Office Protocol | Program and System Information Protocol | The Wire (TV series) | Simple Network Management Protocol | Internet Message Access Protocol | Network File System (protocol) | Hypertext Transfer Protocol | Lightweight Directory Access Protocol | Secure Real-time Transport Protocol | Real-time Transport Protocol | Wire (band) | Wire | Simple Mail Transfer Protocol | Montreal Protocol | Communications protocol | Wireless Application Protocol | SSH File Transfer Protocol | The wire | Remote Desktop Protocol | Point-to-Point Protocol | Nicky Wire | Internet protocol |