baresip is a bare-bones SIP user agent. It supports SIP, SDP, RTP/RTCP, and STUN/TURN/ICE, and IPv4 and IPv6, and is RFC-compliant and has portable C89 and C99 source code. A modular plugin architecture provides stdio, cons, and evdev user interfaces, celt, g711, g722, gsm, ilbc, l16, and speex audio codecs, alsa, coreaudio, gst, portaudio, oss, winwav, and mda audio drivers, speex_pp, speex_aec, speex_resamp, and sndfile audio filters, the avcodec video codec, avformat, quicktime, qtcapture, v4l, and v4l2 video sources, sdl, opengl, and x11 video display drivers, and srtp media encoding.
Billion PBX is IP phone system that uses the SIP protocol. In addition to voice calls it supports call forwarding, voicemail, callback, and much more, and features simple installation and configuration, reliability, low hardware requirements, and a flexible pricing policy. Its main features are subscriber registration by SIP Registrar and RAS protocols, call routing by SIP and H.323, call authorization, subscriber self-service, Call Data Records (CDR), embedded rating and billing, integration with external billing systems, NAT traversal, IVR, report generation, and a convenient administrative Web interface allowing remote management.
Billion Softswitch works as a switchboard in SIP/H.323 VoIP networks, proxying both signalling and media streams while performing cross-protocol conversion and even media stream transcoding. It integrates advanced call routing features as well as embedded compact billing system. It supports subscriber registration by SIP Registrar and RAS, call authorization, call data record (CDR) list maintenance, external billing system interfaces, NAT/firewall support, and report generation, and is easy to install and maintain.
HOMER is a robust, carrier-grade, scalable SIP capturing system and monitoring application with hEP, IP Proto4 (IPIP) encapsulation, and port mirroring/monitoring support right out of the box, ready to process and store large amounts of signaling with instant searches, end-to-end analysis, and drill-down capabilities for ITSPs, VoIP providers, and trunk suppliers using SIP signaling.