Diameter is an "AAA" (Authorization, Authentication and Accounting) protocol. It is a client/server protocol used for handling service requests like subscriber validation, network resource control, wireless mobility/roaming and charging and billing applications.

The AntHill Diameter (Cpp,Ruby) project is a powerful networking library that implements Diameter protocol (RFC 3588, 4004, 4005, 4006, 4072 & 4720) and supplies different fail-over and scaling functionality. It is based on AntHill library. The library contains Diameter Encoder and Decoder as well as other utilities like Diameter DumpViewer, Diameter Shell and etc.