BACnet Secure Connect (BACnet/SC) is a new BACnet datalink, ASHRAE 135-2020 Annex AB, that provides secure message transport by using the standard IP application protocol, Secure WebSocket, which is an extension to HTTPS and runs over Transport Layer Security (TLS). BACnet/SC thereby provides a secure mechanism to authenticate and authorize a device to use the network. From a cybersecurity standpoint, mixing BACnet/IP and BACnet/SC compromises the security of the network. It is best practice to use only BACnet/SC for the entire site to safeguard a site's security, if possible. If you must connect BACnet/IP devices, it is best practice to minimize the number of BACnet/IP devices and isolate them to one engine.