2008) OpenSIPS (formerly known as OpenSER ) BSD , Linux , Solaris GPL free software SIP , Jabber , XMPP SIP Registrar/Proxy, Authentication, Diameter , RADIUS , ENUM , least-cost-routing and many others. SIP Service Providers 1.4.3 pbxnsip Windows, Mac OS X, BSD , Linux Closed Proprietary SIP SRTP IP PBX,