| APDU | Application (layer) Protocol Data Unit is a BACnet message—that is, a unit of data specified within any of the BACnet link-layer protocols. It consists of protocol control information and possibly application user data. |
| BACnet | Building Automation and Control NETworking protocol (ANSI/ASHRAE Standard 135- 2004) is an open communication protocol standard conceived by a consortium of manufacturers and system users under the auspices of ASHRAE. BACnet modles data a common set of objects, which can accessed using a standard set of services. |
| BACnet/Ethernet or B/ETH | BACnet over Ethernet, one of the original BACnet link-layer types. Since the introduction of BACnet/IP, its usage has become less common. |
| BACnet/IP or B/IP | BACnet over Ethernet IP was introduced in Annex J of the BACnet standard. It has become the most popular BACnet link-layer protocol (except in lowest-cost devices, which use MS/TP). |
| BACnet client | An operational mode for a BACnet system that makes use of a BACnet device for some particular purpose via a service request instance. |
| BACnet server | An Operational mode for a BACnet system that provides a service to a requesting client. |
| BBMD | BACnet Broadcase Management Device is a device that receives and redistributes broadcasttype BACnet messages (Who-Is, I-Am, etc.) to other B/IP devices on its own subnet and sends broadcasttype messages to BBMDs on other subnets. By having one BBMD on each subnet, a B/IP network can span subnets (between IP routers, which otherwise typically block broadcast type messages). A station supports operation as a BBMD. |
| BTL | BACnet Testing Laboratories was established by BACnet International to support the compliance and interoperability testing of BACnet products. The BACnet AWS Supervisor and BACnet OWS Supervisor are each BTL-certified. |
| Config object | A model of a physical item, process, calculation or operation in a client BACnet device where you can see all the properties of the object together. |
| COV or Cov | Change-of-Value. Characterizes the option to track data based on when a value changes rather than at a consistent interval, such as every minute, 15 minutes, etc. |
| data link layer | This is the second layer of the OSI (Open Systems Interconnection) software model. This layer works between two hosts, which are directly connected (point-to-point or broadcast). At the sending end, the data link layer converts data into bit-by-bit signals that are compatible with the hardware. At the receiving end it re-assembles the electrical signals from the hardware into recognizable information for processing. The result hides the underlying hardware details, providing the communication medium to the upper layers of the model. (www.tutorialspoint.com) |
| device instance | The logical address on an MS/TP link or IP network that matters to BACnet. This number is unique across all subnets and routed links. (www.csimn.com) |
| Device object or device component | Describes any component that represents an external device. It has several device extensions, one being the Config Device Ext. By default, this extension contains a (frozen) device object component, which represents the single BACnet device object
in that device. You cannot delete this component. You can add and delete other Config objects as needed.
On the server side, the configuration of a station’s single Local Device component under its BacnetNetwork represents the station’s device object. |
| foreign device | A device that exists on an IP subnet without a BBMD. This device can register with a BBMD on another (remote) subnet as a foreign device to explicitly receive BACnet broadcast messages. In no way does it imply any reduced functionality. |
| internetwork | To be read: inter-network. Two or more BACnet networks connected by a BACnet router, or essentially “everything on your site
that can be accessed via BACnet.”
The single BacnetNetwork in a station often represents an internetwork if any external BACnet routers exist or if it has multiple ports under its component. If the latter, the station can act as a BACnet router among its local networks. In a BACnet internetwork, each network must have a unique |
| MS/TP or MSTP | BACnet link-layer protocol is used by lower-cost devices to pass master slave / tokens over RS-485 multidrop networks. QNX-based controllers support direct MS/TP (network) trunks, one per RS-485 port (if licensed for MS/TP). |
| object identifier or object ID | A BACnet method to identify a particular object within a device using a combination of its object type and an instance number (unique for that type, within that device). In the case of the single device object (type) per BACnet device, it must have a unique instance number across the BACnet internetwork on which it is installed. |
| structured view object | A presentation-related type of object. BACnet objects generally refer to sensors, actuators, and other functional elements that make up a BACnet device. Objects fall into categories specified by the protocol. Analog input and output objects are a couple of the most commonly used objects. (www.cismn.com) |
| udp/ip | User Datagram Protocol (UDP) is a networking protocol with minimal overhead that promotes network speed and efficiency. BACnet IP uses the UDP side of the IP stack. This is appropriate since messages are typically short and independent of each other. |