RADIUS uses the UDP transport protocol to communicate.
- This means Telnet cannot be used to connect to a RADIUS server to see if it’s running. Telnet uses TCP.
- RADIUS can use TCP but it is only practical between very large traffic systems.
- The use of encryption limited to authentication, as in a RADIUS server or client, results in a classification of EAR99 and is not subject to any restrictions (apart from the country and entity restrictions).
- From this document on the BIS website.