Initially envisioned as a building-wide network protocol, BACnet (ANSI/ASHRAE Standard 135-1995, "Building Automation Control Network") is now being used to join buildings together on campus-wide internetworks. And there is increasing demand to interconnect BACnet systems across cities, regions, countries, and even continents.
In nearly all cases, the desire is to use an existing Internet Protocol (IP), wide-area network (WAN) already spanning the area to join the BACnet systems. However, BACnet devices and IP devices speak different protocols, different languages; one cannot simply plug them into the same network and expect them to work.