Which protocol is primarily used for authentication, authorization, and accounting in Cisco ISE?

The primary protocol used for authentication, authorization, and accounting in Cisco Identity Services Engine (ISE) is RADIUS. RADIUS, which stands for Remote Authentication Dial-In User Service, is widely utilized in network access scenarios. It functions as a client-server protocol that provides centralized Authentication, Authorization, and Accounting services for users who connect and use a network service.

In the context of Cisco ISE, RADIUS is crucial as it facilitates secure communication between network devices and the ISE server for validating users' credentials (authentication), determining their permissions (authorization), and tracking their activity (accounting). This is particularly important in environments that require compliance and regulation, as RADIUS helps enforce policies consistently across various network segments and devices.

Other protocols like SSH and SFTP are mainly used for secure communication and file transfer, respectively, and do not serve the functions of authentication and authorization in the same capacity as RADIUS does. HTTP, while essential for web communications and accessing web interfaces, does not inherently provide the necessary access control and tracking features that RADIUS offers for network access management. Thus, RADIUS stands out as the most suitable protocol for these functions within Cisco ISE.