# Kamailio is a SIP server

Study notes. Not vendor documentation and not legal advice.

- Wikipedia says Kamailio, formerly OpenSER, is a GPL-licensed SIP server that can be a registrar, proxy, or redirect server.
- The feature list includes a SIP security firewall, least-cost routing, IMS and VoLTE, a SIP-WebRTC gateway, and MSRP relay.
- The article says a large public deployment, with several million users, is at the German ISP 1&1, and another is at sipgate.
- The documentation page links module docs for series including 6.0.x and 6.1.x, and older series.
- The wiki says its front page links documents for latest stable versions, 5.2 or newer, and points older releases elsewhere.

Place Kamailio on the SIP arrows only. Place RTP beside it, dashed. If the design needs a WebRTC gateway, cite the feature list and then confirm the module name in the version you run.