RadSec
From FreeRADIUS Wiki
RadSec is a RADIUS extension developed by Open Systems Consultants Pty Ltd and implemented in Radiator 3.11 and onwards. It provides a TCP or SCTP connection between a RADIUS client and a RADIUS server. It allows any type of radius request to be proxied from the AuthBy RADSEC to the ServerRADSEC and then handled as configured in the RadSec server. Replies will be carried back to the RadSec client and thence to the original requester. It was designed to work as similarly to standard RADIUS as possible.
RadSec connections can optionally be encrypted with TLS and optionally require mutual authentication of client and server using PKI certificates.
FreeRADIUS does not yet support RadSec although support is planned for the future.