OpenSIPS

OpenSIPS is an open source SIP server and proxy that handles voice, video, IM, presence and other SIP extensions. It serves as the core component of SIP-based VoIP solutions, addressing the need for a flexible, scalable signaling platform for carriers, telecoms and ITSPs building residential platforms, trunking, virtual PBX, session border controllers, load balancers, IMS platforms and call centers.

The product offers a modular architecture with more than 120 modules covering SIP handling, backend operations, integration and routing logic, alongside a custom scripting language for defining routing rules. Key capabilities include a SIP registrar, router/proxy, redirect server, presence agent, back-to-back user agent, IM server, SIP-to-SMS and SIP-to-XMPP gateways, load balancer/dispatcher, NAT traversal and application server. Monitoring and control are provided through MI, Event and Statistics interfaces, with an optional web control panel (OpenSIPS-CP) for provisioning, statistics and control actions. A menuconfig console assists with compile-time options and script generation.

OpenSIPS runs on most Unix-based systems and is suited to deployments requiring custom SIP routing and integration. It is distributed as open source software with stable and LTS release lines available for download, and the project accepts donations for support.