Setting up a Desigo project with BACnet/SC devices is like setting up a project with BACnet/IP and/or BACnet/MSTP devices.
Multi-vendor projects, however, require additional coordination among the parties on digital certificates: End-to-end BACnet/SC communication does not work unless all certificates are properly in place, from all vendors, and on all devices. This of course may result in considerable coordination among the parties during engineering and commissioning.
The IT-domain is aware of similar bootstrapping problems involving cybersecurity, so we can expect to see similar mitigation principles applied to BACnet/SC project bootstrapping: The most common approach is to start system engineering in an unsecured (here by BACnet/IP) state and switch the entire system to secure mode in one step at the very end of commissioning (here by BACnet/SC).
On Desigo-only projects, this is not an issue: BACnet/SC devices can bootstrap directly to BACnet/SC during engineering. ABT Site is BACnet/SC native and has its own corresponding BACnet/SC certificate pair to allow the tool to properly authenticate BACnet/SC devices on a project. We forgo a more detailed description of the Desigo-only project here since the use case is fairly straightforward and does not differ much from the older BACnet/IP engineering case and concentrate instead on setting up a project on more complex multi-vendor projects, starting with BACnet/IP and then switching to BACnet/SC:
- Set up a new project in ABT Site.
- Populate it with devices.
- Start engineering the devices, including BACnet/SC devices, on a BACnet/IP datalink.
- Define whether a BACnet/SC device is a hub or node.
- Link each node to its hub.
- Supply root and operational certificates to all BACnet/SC devices.
- Structure BACnet devices on the BACnet networks.
- Check all system limits.
- Check the maximum number of nodes per hub.
Devices using different BACnet datalinks automatically form separate BACnet networks. The BACnet router interconnects these networks to form one BACnet internetwork.
BACnet/SC, BACnet/IP, and BACnet/MSTP devices co-exist on real world projects and most projects require BACnet routers. BACnet/SC hubs are the natural choice for connecting the BACnet/SC network to other non-BACnet/SC networks. Desigo BACnet/SC hubs also include built-in BACnet routers to simplify project planning.
The planning process logically breaks down the project into BACnet networks that are interconnected by BACnet routing and splits up the site on larger projects in line with the building, floor, and plants to retain as much traffic as possible within a single BACnet network.
See Functions in a building automation and control system.
On very large projects, even BACnet networks shaped along functional lines, are too large and need to be further split up into multiple BACnet networks. This is, however, independent of the actual BACnet datalink and thus, not specific to BACnet/SC networks. Reasons for splitting up networks might include:
- IT requirements to structure underlying IP subnets into a smaller number of devices.
See Primary versus failover hubs - The BACnet network consists of more than ~200 devices.
- The BACnet/SC network exceeds the limits for a single BACnet hub.
These are not hard requirements, for example, BACnet/SC networks can easily cross over multiple underlying IP subnets and several BACnet/SC hubs and be combined to form a single common BACnet/SC network but current best practice is to plan the boundaries in BACnet network by building, floor, or plant, underlying IP subnets and size.
Initial project setup with ABT Site starts with BACnet/IP
Key
1 | Engineering laptop |
2 | Hub |
3 | Unsecured BACnet/IP |
Final project setup with ABT Site disables BACnet/IP ports
Key
1 | Engineering laptop |
2 | Hub |
3 | Nodes - Secured |
4 | Unsecured BACnet/IP |
Example structure of a small project with mixed BACnet/IP and BACnetSC networks
