Which protocol combines authentication and authorization into a single process and operates over UDP?

The protocol that combines authentication and authorization into a single process while operating over UDP is Remote Authentication Dial-In User Service, commonly known as RADIUS.

RADIUS serves as a client-server protocol that centralizes the management of user credentials for network services. When a user attempts to access a network, RADIUS first authenticates their identity by verifying provided credentials, such as usernames and passwords, against a central database. Subsequently, it authorizes the user's access levels and permissions, permitting or denying their access based on established policies. This two-step process is seamlessly integrated within the RADIUS protocol, allowing for both authentication and authorization to occur in a single transaction, making it efficient for real-time applications.

Operating over UDP is particularly advantageous for scenarios where speed is vital, such as in dial-in or remote access situations, allowing for quicker packet processing, although it comes at the cost of less reliable delivery compared to TCP, which uses acknowledgments.

Other options don't fit the criteria as effectively. For instance, while Secure Sockets Layer (SSL) is focused on securing connections and data transmissions, it does not combine authentication and authorization in the same manner as RADIUS. Similarly, TACACS+ does offer both functions but operates over TCP rather than UDP. Hypertext Transfer