Remote Authentication Dial In User Service (RADIUS) is a protocol for carrying authentication, authorization, and configuration information between a Network Access Server (NAS) and a shared Authentication Server. It uses UDP for communication and has a standardized port number of 1812. RADIUS operates on a client-server model, where the NAS acts as a client and sends user information to the RADIUS server. The server then authenticates the user and returns configuration details for the service. RADIUS supports various authentication mechanisms, including PAP, CHAP, and UNIX login. It is extensible, allowing new attributes to be added without affecting existing implementations. The protocol uses a shared secret for authentication, ensuring that passwords are encrypted and not transmitted in plain text. This enhances security by preventing unauthorized access. RADIUS packets are structured with a code, identifier, length, and authenticator. The code identifies the packet type, such as Access-Request, Access-Accept, Access-Reject, or Access-Challenge. The identifier helps match requests and responses, while the length indicates the packet size. The authenticator ensures the integrity of the packet. RADIUS supports multiple attributes, including User-Name, User-Password, CHAP-Password, NAS-IP-Address, NAS-Port, Service-Type, Framed-Protocol, Framed-IP-Address, Framed-IP-Netmask, Framed-Routing, Filter-Id, Framed-MTU, Framed-Compression, Login-IP-Host, Login-Service, and Login-TCP-Port. These attributes provide detailed information for user authentication and service configuration. The protocol includes challenge/response authentication, where the server sends a challenge to the user, and the user responds with an encrypted value. This method enhances security by ensuring that only authorized users can access the system. RADIUS also supports proxy functionality, allowing servers to forward requests to other servers for authentication. RADIUS is designed to be stateless, making it efficient and scalable. It is widely used in network authentication and access control systems, providing a secure and flexible solution for managing user access to network resources.Remote Authentication Dial In User Service (RADIUS) is a protocol for carrying authentication, authorization, and configuration information between a Network Access Server (NAS) and a shared Authentication Server. It uses UDP for communication and has a standardized port number of 1812. RADIUS operates on a client-server model, where the NAS acts as a client and sends user information to the RADIUS server. The server then authenticates the user and returns configuration details for the service. RADIUS supports various authentication mechanisms, including PAP, CHAP, and UNIX login. It is extensible, allowing new attributes to be added without affecting existing implementations. The protocol uses a shared secret for authentication, ensuring that passwords are encrypted and not transmitted in plain text. This enhances security by preventing unauthorized access. RADIUS packets are structured with a code, identifier, length, and authenticator. The code identifies the packet type, such as Access-Request, Access-Accept, Access-Reject, or Access-Challenge. The identifier helps match requests and responses, while the length indicates the packet size. The authenticator ensures the integrity of the packet. RADIUS supports multiple attributes, including User-Name, User-Password, CHAP-Password, NAS-IP-Address, NAS-Port, Service-Type, Framed-Protocol, Framed-IP-Address, Framed-IP-Netmask, Framed-Routing, Filter-Id, Framed-MTU, Framed-Compression, Login-IP-Host, Login-Service, and Login-TCP-Port. These attributes provide detailed information for user authentication and service configuration. The protocol includes challenge/response authentication, where the server sends a challenge to the user, and the user responds with an encrypted value. This method enhances security by ensuring that only authorized users can access the system. RADIUS also supports proxy functionality, allowing servers to forward requests to other servers for authentication. RADIUS is designed to be stateless, making it efficient and scalable. It is widely used in network authentication and access control systems, providing a secure and flexible solution for managing user access to network resources.