Existing project upgrades/extensions BACnet network structure example

It is important to start BACnet/SC upgrades with the ALN controllers and the management workstation, creating a secure BACnet/SC logical “island” and leveraging BACnet/SC routing to interconnect with the existing BACnet/IP network. Any existing drivers on BACnet/IP are also routed to BACnet/SC.

Since BACnet/SC is only secure within the BACnet/SC logical network, any non-BACnet/SC networks must be secured using traditional methods. A plan must be put in place to replace unsecured BACnet/IP devices on the network with newly available BACnet/SC devices as application requirements evolve, or devices become obsolete.

BACnet/SC renders BBMDs obsolete within the BACnet/SC logical network (hub and nodes). Even though BACnet/SC does not require BBMDs for nodes to communicate with the hub when going across IP subnets, BBMDs are still required for any existing BACnet/IP devices on different IP subnets in the project.

When designing mixed BACnet/SC and BACnet/IP networks in large projects with several or more IP subnets where BBMDs may be needed for the BACnet/IP portion of the network, careful configuration of BACnet routing and the BBMDs’ Broadcast Distribution Table must be ensured to avoid network loops or multiple paths to the same device.