TACACS and RADIUS Comparison - Cisco Systems

1. RADIUS uses UDP while TACACS+ uses TCP
2. RADIUS encrypts only the password. TACACS+ encrypts the entire body of the packet but leaves a standard TACACS+ header.
3. RADIUS combines authentication and authorization. TACACS+ uses the AAA architecture
4. TACACS+ offers multiprotocol support.
5. TACACS+ provides two methods to control the authorization of router commands on a per-user or per-group basis.

Remote Authentication Dial In User Service (RADIUS)
Terminal Access Controller Access-Control System Plus (TACACS+)
Authentication, Authorization and Accounting