RADIUS Communication

C.

Source: TIPTON, Harold.

F.

& KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 2, 2001, CRC Press, NY, Page 33.

RADIUS (Remote Authentication Dial-In User Service) is a protocol that provides centralized authentication, authorization, and accounting (AAA) management for users who connect and use network resources. It is commonly used in large organizations, such as universities or corporations, to manage network access for remote users.

RADIUS uses UDP (User Datagram Protocol) for communication between clients and servers. UDP is a connectionless protocol that provides no guarantees of delivery, ordering, or duplicate protection. However, it is a fast and lightweight protocol that is well-suited for RADIUS's requirements, which typically involve small packets of data exchanged between the client and server.

TCP (Transmission Control Protocol) is a connection-oriented protocol that provides reliable, ordered, and error-checked delivery of data between applications. It is not used by RADIUS for communication between clients and servers.

SSL (Secure Sockets Layer) is a cryptographic protocol that provides secure communication over a network. It is commonly used in web browsers for secure transactions, such as online banking or e-commerce. However, it is not used by RADIUS for communication between clients and servers.

SSH (Secure Shell) is a cryptographic network protocol that provides secure communication between networked devices. It is commonly used for remote access to servers and other devices. However, it is not used by RADIUS for communication between clients and servers.

Therefore, the correct answer to the question is C. UDP.