It can be configured to act as a SIP registrar, proxy or redirect server, and features presence support, RADIUS / syslog accounting and authorization, XML-RPC and JSON-RPC-based remote control, SQL and NoSQL backends, IMS / VoLTE extensions and others.

"[2]Kamailio is written in pure C with architecture-specific optimizations;[3] it can be configured for many scenarios including small-office use, enterprise PBX replacements and carrier services—it is SIP signaling server—a proxy—aiming to be used for large real-time communication services.

The largest public announced deployment with several million of users is in operation at the German ISP 1&1.

OpenSIPS is intended for installations serving thousands of calls and is IETF RFC 3261 compliant.

[7] The software was recognized by Google in 2017 with their Open Source Peer Bonus award.