Diameter

The diameter of a subset $S$ of a metric space is

The diameter of a nonempty subset $S$ of a metric space is $\mathrm{diam}(S)=\sup \{d(x,y):x,y\in S\}$. For a Euclidean circle it is the longest chord length; the same definition applies to arbitrary metric subsets.

Diameter is a protocol designed for authentication, authorization, and accounting (AAA) in computer networks. It is an evolution of the older RADIUS (Remote Authentication Dial-In User Service) protocol. Diameter offers several enhancements and improvements over RADIUS, making it more suitable for managing AAA needs in modern networks, especially in environments like telecommunications and mobile networks.