The RADIUS client, often a NAS (BNG/UGW, etc.), plays a crucial role in the subscribers session. It passes user information to designated RADIUS servers and acts on the returned response, giving you, as a network administrator or engineer, the power to manage and control user access. RADIUS servers are the backbone of the system. They receive user connection requests, authenticate the user, and then return the configuration information necessary for the client to deliver service to the user.

The request messages to the radius server and the response messages from the radius server contain information defined using attributes. These attributes would differ based on the authentication method used by the customer device connecting to the RADIUS client (NAS/BNG). The RADIUS server response would need to be crafted explicitly based on the subscriber's limitations, quotas, capabilities, and supported attributes by the radius client. These attributes differ from BNG/NAS vendor to vendor and in terms of use cases.

Client profiles are used to identify RADIUS client types; examples are Cisco, Juniper, H3C, Huawei, Mikrotik, etc. Attributes per service are assigned to client profiles, and RADIUS clients are assigned to these profiles. Based on the specific service assigned to the subscriber, we can then identify which attributes are for which RADIUS client.