2.9.6 Connections and Peers

Despite the fact that RADIUS uses the connectionless UDP transport, the concept of a RADIUS connection is helpful to facilitate understanding RSR operation. From the point of view of RADIUS peers connecting to DSR, the DSR can act either as a RADIUS server (to RADIUS clients) or as a RADIUS client (towards RADIUS servers). We can generally think of a RADIUS peer as defined by its IP address and (optional) port and a RADIUS connection as an association of source IP address + (optional) ports and recipient IP address + port, where either the source or the recipient would be represented by DSR.

In RADIUS, specific recipient ports are typically associated with specific services - for example, Authentication, Accounting, and Change of Authorization would each have their own distinct ports. This means that on a given connection, requests always flow in one direction and the responses in the other. There are two types of DSR RADIUS connections:

• Client connection: remote IP + port combined with local (DSR) IP + port range. These are connections towards servers.
• Server connection: remote IP combined with local (DSR) IP + port. These are the connections towards clients.