Users who have the authority to use certain parts of the system may not have the right to see everything, and businesses, for billing purposes, often want to track how long users spend in a system. RADIUS provides architectural guidance and technical implementation of RADIUS, enabling readers to design systems RADIUS -secured properly and choose products wisely. Jonathan Hassell approach is to lay the foundation of RADIUS protocol theory, then explain how to implement the protocol with a specific product (FreeRadius for Linux) Wall. - David Topics covered: How the RADIUS protocol provides authentication, authorization, and accounting (AAA services), and how it fits with other elements of network design. The author covers the protocol in theory before digging in its implementation and integration for Linux FreeRadius package with several important networking products.