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, DNSsec, 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.
GkAuth is a call management system written for the GNU Gatekeeper project. It functions by connecting to the status port of the gatekeeper and collecting signals in its database. It provides Web based administration and user interface and stores its data in SQL tables. Key features include a Web-based management interface, run-time user administration (add/remove/modify user rights), prepaid/post paid/free billing, and call history.