Kamailio (formerly OpenSER) is a high-performance SIP (RFC3261) server with a flexible architecture and many extensions. The server implements proxy, registrar, redirect, and location SIP/VoIP services. It has support for UDP, TCP, TLS, and SCTP transport layers, ENUM, AAA via database, RADIUS, DIAMETER, gateways to SMS and XMPP, least cost routing, load balancing, NAT traversal, and call processing language. Kamailio implements SIMPLE presence and instant messaging extensions, and includes an embedded XCAP server and MSRP relay. It can be also used as a routing SIP sever for WebRTC via WebSocket.
SIREMIS is a Web management interface for Kamailio (OpenSER). It features subscriber, database aliases, and speed dial management; location table view; dispatcher, prefix-domain translation, and least cost routing management; access control lists (user groups) and permissions management; accounting records, missed calls, and call data records view; hash table, dial plan table, and user preferences table management; and offline message storage view. It is developed on top of a framework (PHP/Web2.0/AJAX), and has XML metadata-driven extensions and an MVC architecture.