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What does a BACnet topology look like?

BACnet topology BACnet architecture MS/TP and IP

What defines a BACnet network? There are certain essentials you can expect to find on a basic BACnet network, according to KMC Controls: “A simple network requires only two or more controllers, an operator workstation and network wiring.”

There are many physical topologies that can be used to design your BACnet/IP networks. The really important part to understand about the BACnet topology is its logical architecture, though: the way that data actually travels from device to device. There’s a basic hierarchy that most BACnet systems follow.

Essentially, a Building Management System (BMS) connects to a data aggregator. That aggregator connects to different zones or applications via MS/TP connections, or to different IP devices via IP connections. Data is shared from the zones or devices, up to the aggregator and BMS. Simple!

BACnet topology BACnet architecture MS/TP and IP

The devices will all be assigned a MAC address and BACnet device instance number and, in the case of an MS/TP network, they’ll be configured with the same baud rate. In a BACnet/IP network, of course, you’ll have IP addresses and will need a BACnet Broadcast Management Device (BBMD), as well. (Learn more about BBMDs.)

There are also flat networks, which are not divided into subnetworks or “hierarchies” with individual switches. This design is used to reduce costs, since purchasing switches can become quite pricey. Flat networks do work well on home or very small business networks. The larger your network, though, the less feasible flat networks become. They’re susceptible to speed and scalability issues.

If you’re looking for additional information, be sure to check out Bill Swan’s guide to internetworking with BACnet and BACnet International’s tutorial.

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