This enumerated field selects whether the switch's OpenFlow control channel to the controller uses plain TCP or an encrypted TLS connection, defaulting to tcp. An administrator changes it to tls when network policy requires the OpenFlow control traffic to be encrypted rather than sent in cleartext. For example, in a security-sensitive deployment, an admin sets rlOpenFlowProtocolType to tls so the switch-to-controller session is protected against eavesdropping.