Define Remote Authentication Dial In User Service (RADIUS) server
This protocol is widely used by Internet Service Providers (ISPs) and large enterprises, companies, schools and other organizations to regulate and manage access to the Internet and internal networks. Normally, these devices authentication protocol is run as a modem, digital subscriber lines Line (DSL) automatically.
The main features of the radius server can be summarized as AAA or Authentication, Authorization and Accounting. The first two "A return to allow a user to access a network. If we look at our previous example, we will come to know that a radius server can return one of three responses to the connection request - "No", which means that access to the user is denied in Anyway "Challenge" which means that the user is prompted for additional information before granting access, and "Yes", which gives the user access to the network.
Accounting refers to the radius server to perform the billing function. It refers to situations in which users are monitored in the time or the assets and recorded. This is particularly useful for those who go online billing, which is calculated on time or data transfer. The radius server receives the command to start billing, when the user logs in, and later to stop the billing, when the user logs off. radius server can now use the databases are stored remotely check the details. The communication between the user and the server is now done very encrypted, reliable channels.