| | Media server | Asterisk | FreeSwitch | Yate | SEMS |
| | www | Asterisk.org | Freeswitch.org | Yate.null.ro | www.iptel.org/sems | | License | GPL | MPL | GPL | GPLv2+ | | Last stable rel. | 1.8.2.3 | 1.0.6 | 3.3.0 | 1.4.2 | | Operating system | Linux, Mac OS X, *BSD, Solaris, Windows | Linux, Mac OS X, *BSD, Solaris, Windows | Linux, Mac OS, FreeBSD, Windows | Linux | | Wrritten in | C | C/C++ | C++ | C/C++ | | Architecture | B2BUA | B2BUA | — | — |
| | Modular | Yes |
| | NAT traversal | No | STUN | No | — | | Authentication, authorization against database | MySQL, PostgreSQL, LDAP, Radius | MySQL, PostgreSQL, LDAP, Radius | MySQL, PostgreSQL, Radius | Diameter | | VoIP signalling protocols | SIP, H,323, SCCP, MGCP, IAX, GoogleTalk | SIP, H.323, IAX, SCCP | SIP, H.323, MGCP, IAX, Jingle | SIP | | Telephony signalling protocols | ISDN/SS7, FXS/FXO | ISDN/SS7 | ISDN/SS7, FXS/FXO, Sigtran | No | | Messaging protocol | XMPP | SIMPLE, XMPP | XMPP/Jabber | No | | Call encryption | SRTP | SRTP | No | SRTP | | Transport protocols | UDP, TCP, SCTP, TLS | UDP, TCP, SCTP, TLS | UDP, TCP, SCTP | UDP | | IPv4/IPv6 | Yes/Yes | Yes/Yes | Yes/— | Yes/— | | Web GUI | Yes | Yes | — | No | | SIMPLE | No | Yes | No | No | | SIP gateway | Yes | Yes | Yes | No | | Audio codecs | ADPCM, PCMU, PCMA, G.722, G.722.1, G.722.1 Annex C, G.723.1, G.726, G.729a, GSM, iLBC, Linear, LPC-10, Speex | CELT, G.722.1, G.722.1C, G.722, PCMU, PCMA, GSM, G.726, AAL2 and RFC 3551, G.723.1, G.729AB, AMR, iLBC, Speex, LPC-10, DVI4, SILK | GSM, speex, iLBC, AMR-NB | PCMU, PCMA, GSM, G.726, iLBCi, speex, adpcm, L16 | | Video codecs | No | Theora, H.261, H.263, H.263+, H.263++, H.264, MP4 | No | No |
| | Transcoding | Yes |
| | IVR and Announc. | Yes | Ann. |
| | Voice mail | Yes | Yes | — | Yes |
| | Audio conference | Yes |
| | Call recording | Yes | Yes | — | — |
| | IP/PBX features | Yes | No |
| | CDR | Yes | — |
| | Fax | T.30, T.38 | T.30, T.38 | — | No | | Text to speech | Yes | Yes | — | No |
| | SIP API | No |
| | Programming languages | With CGI any language, Adhersion | C/C++, Python, Perl, Lua, Java, JavaScript, Erlang, Ruby | Python | C++, Python, DSM |
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