freeDiameter is a implementation of the Diameter protocol specified in RFC3588. Diameter is a protocol for carrying Authentication, Authorization and Accounting information. It is an evolution of the widely-deployed RADIUS protocol. freeDiameter also implements the changes to the Diameter protocol introduced by the rfc3588bis Internet Draft (work in progress). freeDiameter is open-source and released under a BSD compatible license. It is mainly written in the C language, which provides excellent performance and small memory footprint.