The BACnet protocol governs:
- Electrical signal parameters.
- The addressing system.
- Network access methods (Master-Slave, Peer-to-Peer).
- Error-checking procedures.
- Flow control procedures.
- Message sequencing, the segmentation system, and checkpoints.
- Presentation format (packaging, encryption).
- Message format.
BACnet Objects
Each object in a BACnet network is characterized by a set of "properties" that describe its behavior or control its operation.
Any device in a BACnet network is described as a set of standard objects, and the number of identical objects making up a device is unlimited.
The BACnet standard defines the following classes of application tasks performed by devices:
- alarms and events;
- file access;
- object access;
- remote device management;
- virtual terminal.
These classes of application tasks are described by a set of Services executed by a given task class.
Transport Layer
In addition to the application layer, the BACnet protocol describes the available local network options. Initially, the protocol allowed the use of the following network technologies:
- Ethernet;
- ARCNET;
- Master-Slave/Token Passing (MS/TP);
- Point-to-Point (PTP);
- LonTalk.
These options provide different network characteristics, covering the specific needs of particular applications.
Communication with proprietary networks requires specialized gateways that, when repackaging BACnet messages, must also "translate" them into the language of the corresponding proprietary protocol.
For communication over IP networks, BACnet provides 2 operating modes:
- tunneling of IP messages;
- use of BACnet/IP.
Standards
- International standard ISO/IEC 164845.
- American standard ANSI/ASHRAE 1351995.