Historically, devices with network connectivity have been allowed to communicate as soon as they are plugged into the network. For enhanced security, many networks will now require that physical network devices be uniquely identified and authorized to communicate on the network before any additional network based provisioning can be done. For example, the assignment of a Certificate using the Certificate management services as described in 5.7.3.
OPC 10000-21 defines a standard process for devices to be allowed to communicate on the network so that OPC UA Applications can be installed, updated, and provisioned with Certificates over the network.