Comparison of VoIP software

VoIP software is used to conduct telephone-like voice conversations across Internet Protocol (IP) based networks. VoIP stands for "Voice over IP". For residential markets, VoIP phone service is often cheaper than traditional public switched telephone network (PSTN) service and can remove geographic restrictions to telephone numbers, e.g. have a New York PSTN phone number in Tokyo.

For businesses, VoIP obviates separate voice and data pipelines, channelling both types of traffic through the IP network while giving the telephony user a range of advanced capabilities.

Softphones are client devices for making and receiving voice and video calls over the IP network with the standard functionality of most "original" telephones and usually allow integration with IP phones and USB phones instead of utilizing a computer's microphone and speakers (or headset). Most softphone clients run on the open Session Initiation Protocol (SIP) supporting various codecs. Skype runs on a closed proprietary network, though the network (but not the official Skype client software) also supports SIP clients. Online "Chat" programs now also incorporate voice and video communications.

Other VoIP software applications include conferencing servers, intercom systems, virtual FXOs and adapted telephony software which concurrently support VoIP and PSTN like IVR systems, dial in dictation, on hold and call recording servers.

General softphone clients

Program	Operating systems	License	Open Source?	Protocols/based upon/compatible with	Encryption	Max conference peers	Other capabilities	Latest release
AOL Instant Messenger	Mac OS, Windows	Freeware / Closed Proprietary	No	SIP (Windows ver. only), RTP	Un­known	Un­known	Video, file transfer, PC to phone, phone to PC
Avaya Application Server 5300 Soft Client	Windows	Proprietary	No	SIP, RTP,	TLS, SRTP	Un­known		2.0 (2010)
Blink	Linux, Mac OS, Windows	GPL / Free software	Yes	ICE, SIP, MSRP, RFB (VNC)	TLS, SRTP	Unlimited	IM, File Transfer, Desktop Sharing(only Mac OS), Multi-party conference, Wideband	1.8.1 (April 20, 2012)
Bria by CounterPath Corporation	Windows, Mac OS, Linux (Voice calling only)	Proprietary	No	SIP, XMPP, STUN, ICE	TLS, SRTP	6 party audio; 3 party video	Voice and HD (1280 x 720p) Video calling; IM and Presence (SIP SIMPLE and XMPP); Multiple Account Integration; Address Book Support (Mac and Windows); Company Chat Rooms; USB Support; Troubleshooting Assistant; Workgroups; Call Recording and Conferencing	3.3.2 (February 2012)
Cisco IP Communicator	Windows	Closed Proprietary	No	SCCP (Skinny), SIP, TFTP	sRTP	Un­known	Call Recording, Silent Monitoring, Multiple lines and directory numbers, Configurable speed dial, Calling name and number display, Call Waiting, Call Forward, Call Transfer, Three-Way Calling (conference), Call Park, Call Pickup, Redial, Hold, Barge, Callback, Extension Mobility, Message waiting indicator, iDivert, Meet Me conferencing, Group Pickup, Do Not Disturb,G.722 wideband, G.711a, G.711u, iLBC, G.729a, and G.729ab audio codecs	7.0.6 (Jan 2011)
Ekiga	Linux, (Beta Windows support), OpenSolaris	GPL / Free software	Yes	SIP, H.323, H.263, H.264/MPEG-4 AVC, STUN, Theora, Zeroconf	No	Un­known	Video, IM, LDAP, Call Forwarding, Call Transfer	Template:Latest stable software release/Ekiga
Empathy	Linux	GPL / Free software	Yes	SIP, XMPP (Jingle), ICE (STUN/TURN), Zeroconf	No	Un­known	IM, multi-user A/V, collaborative applications	45.0 (20 September 2023 (2023-09-20)) [±]
Eyeball Chat	Windows	Freeware / Closed Proprietary	No	SIP, STUN, ICE, XMPP	Yes	5	IM, Conferencing, Voice, Video and SIMPLE based presence	Windows 3.2
eyeBeam by CounterPath Corporation	Windows	Proprietary	No	SIP	TLS, SRTP	6 party audio; 3 party video	Voice and Video calling; IM and Presence (SIP SIMPLE); Import Microsoft Outlook Contacts; USB Support; Call Recording and Conferencing	1.5.20.1 (March 2010)
Gizmo5	Linux, Mac OS X, Windows, Windows Mobile Phone, Blackberry, Nokia, PDA Java	Freeware / Closed Proprietary	No	SIP, XMPP	SRTP	Un­known	Record Calls, Forward Calls, MSN IM, Windows Live Talk, Google Talk, Talk with Yahoo, Messenger, XMPP	Windows: 4.0.5.395 (23 Sep 2009), Mac OS: 4.0.0.269 (23 Sep 2009)
Google Talk	Linux, Windows, Mac OS X	Closed Proprietary (using libjingle)	No	XMPP	zRTP	Un­known	Video, chat, file transfer, voicemail, mail via "GMail Integration"	Windows Plugin: 3.19.1.13088 (May 14, 2013 (2013-05-14)) [±]
IBM Sametime	Linux, Mac OS X, Windows, mobile	Closed Proprietary	No	SIP, SIMPLE, T.120 and H.323	TLS	Un­known	IM, File transfer, Voice, Presence, Server stored contact list, HTTP tunneling, plugins, embedable in Lotus Notes	8.5.2 (08. May 2011)
iCall	Linux, Mac OS X, Windows, iOS, Android	Freeware / Closed Proprietary	No	SIP AIM ICQ XMPP Speex CELT WebM	TLS ZRTP	Unlimited	Video, file transfer, PC to phone, phone to PC, IM (MSN, AIM, ICQ, Yahoo!, XMPP, Google Talk), Voicemail	7.1.522
Messages	Mac OS X	Closed Proprietary	No	SIP AIM ICQ XMPP H263 H264	Un­known	Un­known	Integrated, PBX independent	7.0 July 25, 2012 (2012-07-25)
Jitsi	Linux, Mac OS, Windows XP/2000 (all java supported)	LGPL / Free software	Yes	SIP/SIMPLE, XMPP/Jingle	Voice encryption (SRTP and negotiation with zRTP), Signaling encryption (TLS)	Un­known	Text messaging, audio/video telephony, IPv6, call recording	2.10 (build.5550) (February 5, 2017 (2017-02-05)) [±]
KPhone	Linux (KDE)	GPL / Free software	Yes	SIP, STUN, NAPTR/SRV	SRTP	Un­known	Video, voice, IM, external Sessions, IPv6 support for UDP	1.2 (November 2008)
Linphone	Linux, Windows, Android, iPhone, BlackBerry	GPL / Free software	Yes	SIP	TLS, SRTP, zRTP	Un­known	Video, IM, STUN, IPv6	3.5.2 (Feb 17th 2012)
MicroSIP	Windows	GPL / Free software	Yes	SIP, STUN, ICE, SIMPLE	TLS, SRTP	Un­known	Video, voice, IM and Presence	3.0.14 (March 2012)
Mirial Softphone (Mirial s.u.r.l.)	Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86)	Closed Proprietary	No	SIP, H.323, RTSP	DTLS-SRTP	Un­known	H.264 Full-HD 1080p video rx/tx, Two independent lines supporting Call Control and 3-Party videoconference in Continuous Presence, G.722.1/C wideband audio, Call recording/export, DV/HDMI/Component capture, Presentation (H.239, RFC-4796), Encryption, Far End Camera Control, GPU accel (D3D and OpenGL)	7.0.24 (May 26, 2010)
Mumble	Linux, Mac OS X, iOS, Windows, Android	BSD	Yes	CELT / Speex	TLS and OCB-AES128	No max (limited only by server bandwidth and memory)	Chat with (limited) embedded HTML, Automatic Gain Control, Access Control Lists for user management, Customizable In-Game Overlay, Directional Audio, Plugin Support, Nested Channels, Echo cancellation, Logitech G15 support	1.2.3 (February 19, 2011)
Nymgo	Windows	Freeware, Proprietary, Closed	No	SIP, RTP and RTCP	Yes	No	Address Book integration,Call recording/export,Mute,On Hold, Caller ID definition,	4.1.1b (February 13, 2012)
PhonerLite	Windows	Freeware / Closed Proprietary	No	SIP	TLS, SRTP, ZRTP	8	Conferencing, call redirection, call recording	3.20 (7 August 2023 (2023-08-07)) [±]
QuteCom	Linux, Mac OS X, Windows XP/2000	GPL / Free software	Yes	SIP	SRTP, but key exchange via Everbee key Exchange which is not a Standard)	Un­known	Video, IM (MSN, AIM, ICQ, Yahoo!, XMPP, Google Talk), voicemail, wengo to phone, conferencing.	2.2.1 (22 June 2011 (2011-06-22)) [±]
Revation Communicator	Windows 2000/XP/Vista/7	Closed Proprietary	No	SIP/SIMPLE	TLS and SRTP	No max (limited by server mixing services)	Secure Multi-Party Chat/Instant Messaging, Presence, VoIP, Video, File Transfer, Desktop Sharing	5.3 (August 2011)
SFLphone	Linux	GPL3 / Free software	Yes	SIP, RTP, IAX2, STUN per account, SRV	Voice encryption (SRTP), Signaling encryption (TLS), Multiple realms authentification mechanism	Un­known	Gnome/KDE client, address book, multiple accounts, unlimited number of calls, call transfer, call hold/unhold, call recording, Multi-way conferencing	1.2.0 (July, 2012)
SightSpeed	Mac OS X, Windows	Freeware / Closed Proprietary	No	SIP, RTP,Proprietary P2P protocol	Un­known	Un­known	Video, voicemail, phone in, phone out, multiparty calling, conference recording, text messaging, NAT traversal, video mail	6.0
Skype	Linux, Mac OS X, Windows 2000/XP/Vista/7/Mobile (no longer supported), BREW, Android, iPhone, PSP	Freeware / Closed Proprietary	No	Proprietary P2P protocol; SIP users can connect to the Skype network using alternate software/hardware, but the Skype software does not support it directly	Yes	25 starting with version 3.6.0.216. 10 with 2.x	Conferencing, video, file transfer, voicemail, Skype to phone, phone to Skype, additional P2P extensions (games, whiteboard, etc...); depending on platform.	Windows, UWP 15.123.203.0 / 8 July 2024 (2024-07-08) Windows, desktop 8.123.0.203 / 8 July 2024 (2024-07-08) macOS 8.123.0.203 / 8 July 2024 (2024-07-08) Linux 8.123.0.203 / 8 July 2024 (2024-07-08) Android 8.126.0.208 / 15 August 2024 (2024-08-15) iOS 8.123.0.203 / 8 July 2024 (2024-07-08) (iPhone and iPad)
Spikko	Windows 2000/XP/Vista/7/Mobile, iPhone,	Freeware / Closed Proprietary	No	SIP	Yes	8	Conferencing, voicemail, PC to phone, phone to PC, Free international phone numbers, address book integration;	Dec 2010
TeamViewer	Linux, Windows, Mac OS X, iOS, Android	Freeware (personal use only) Closed / Proprietary	No	?	AES256	?	?	7
TeamSpeak	Linux, Windows, Mac OS X, FreeBSD, Android, iOS	Freeware Closed / Proprietary	No	CELT / Speex	Yes (Optional)	Unlimited (depending on server bandwidth and memory)	Simultaneous Server Conferencing with Tabs, 3D Sound Effects, Scalable Permissions System, Firewall Friendly File Transfers, In-Game Overlay for DirectX & OpenGL Games, Global Public Server List, Plugin System	3.0.6
Telephone	Mac OS X 10.5	BSD / Free Software	Yes	SIP, STUN, ICE	No	Un­known	Address Book integration	1.0.2 (April 30, 2011 (2011-04-30))
Tokbox	Mac OS X, Windows XP/2000/Vista	Freeware / Closed Proprietary	No	Un­known	Un­known	Un­known	Video calling, video conferencing, chat, IM (MSN, AIM, Yahoo!, Google Talk)	Un­known
Toktumi Unlimited / Line2 Pro	Windows XP/Vista/7, Mac OS X, iOS, Android	Freeware / Closed Proprietary	No	Proprietary with SIP core	Un­known	20	Conferencing, voicemail, caller ID, call-waiting, address book integration; auto-attendant, call-forwarding	Windows: August 2010 / OS X: October 2010
Tru App	Windows 2000/XP/Vista/7, Mac OS X, Linux iOS, Android, Symbian, BlackBerry OS,	Freeware / Closed Proprietary	No	SIP, XMPP	Un­known	Un­known	Chat, file transfer, voicemail, inbound numbers, integration with GTalk, Microsoft Live, Skype
Twinkle	Linux	GPL / Free software	Yes	SIP	SRTP, ZRTP	Un­known	Conferencing, chat, file transfer, Firefox integration, call redirection, voicemail, support of VoIP-to-Phone services	1.10.3 (February 19, 2022 (2022-02-19)) [±]
Vbuzzer	Windows 2000/XP/Vista	Freeware / Closed Proprietary	No	SIP	TLS	Un­known	IM (MSN), voicemail, personalized voice greeting.	2.0.282
Ventrilo	Mac OS X, Windows	Freeware / Closed Proprietary	No		No	Un­known	Conferencing, chat, text-to-speech	3.0.8
Voice Operator Panel	Windows 2000/XP/Vista	Closed Proprietary	No	SIP, RTP	Un­known	Un­known	Call forwarding, Call transfer, Call recording, Presence, Outlook integration, Windows Messenger/MSN/Live integration, CRM, Built-in web browser & e-mailer, LDAP, APS.	1.3.2
Wirofon	Windows XP/Vista/7, Android, iOS	Closed Proprietary	No	SIP, RTP	Un­known	Un­known	Audio & Video, Intuitive UI, PC to mobile, mobile to PC
X-Lite	Mac OS, Windows, (Linux)	Freeware / Closed Proprietary	No	SIP, STUN, ICE	No	Un­known	IM, single login account, for Windows and Mac also Conferencing, Video and SIMPLE based presence	Windows / Mac OS: 4.1 / Linux: Discontinued
Yahoo! Messenger	Mac OS (8, 9, X), Windows, (Linux/FreeBSD version not VoIP capable)	Freeware / Closed Proprietary	No	SIP (using TLS) and RTP (media)	Un­known	Un­known	Video, file transfer, PC to phone, phone to PC
Yate	Linux, Mac OS, Windows	GPL / Free software	Yes	SIP, IAX, H.323, XMPP
Zfone	Linux, Mac OS X, Windows	Freeware / Viewable source Proprietary (includes time bomb provision)	No	SIP, RTP	SRTP, ZRTP	Un­known		Beta 2008-09-04 (Linux 0.9.224), (Mac OS 0.9.246), (Windows 0.9.206)

Mobile phones

Program	Operating systems	License	Protocols/based upon/compatible with	Encryption	Other capabilities	Latest release
Acrobits Softphone by Acrobits	Android, iOS	Proprietary	No	SIP,	TLS, SRTP, ]], ZRTP	0 (does not support conferencing)	VOIP over wifi or 3G, supports codecs G.711, G.722, iLBC, GSM and G.729 can be added by in-app purchase. iOS only - Push Notifications, video, number rewriting, address book matching, sms for betamax providers and pennytel	Acrobits Softphone (iOS) 5.2, Acrobits Softphone (android) 3.20
Amivox	Java ME, Android, BlackBerry RIM, iPhone, many mobile browsers	Web based / Proprietary	SIP, GSM, CDMA, WiMax, WiFi, Facebook	Un­known	Allows to send voice messages as a micro-call, as SMS, as Email or to post them on to Facebook	2.0
Bria by CounterPath Corporation	iPhone iOS 4.3+, Android v2.2+	Proprietary	SIP	TLS, SRTP	VoIP over Wi-Fi or 3G/4G; Audio codecs G.711, G.722, iLBC, GSM and SILK, with option to purchase G.729; Multiple languages; Option to purchase Video Calls add-on with H.264 codec and Messaging and Presence add-on which uses XMPP and SIP SIMPLE protocols.	2.1.3 (iPhone), 2.0.3 (Android)
CSipSimple	Android v1.6+	GPL	SIP	SRTP / ZRTP / TLS (using special builds)	VoIP over Wi-Fi or mobile data; Audio codecs G.711, Speex, GSM, iLBC, G.722, AMR, iSAC, SILK, CODEC2, G.726, G.722.1; Conference; Android integration with filtering/rewriting rules	0.03-01 (November 2011)
Gizmo5 Mobile	Windows Mobile (non-native, only through SJPhone), Motorola, Nokia, Blackberry, Java PDA's, Sony Ericsson, Samsung	Freeware	SIP, AIM, iChat, XMPP, MSN, Yahoo	Yes	Online Phone over Edge, UMTS, 3G, Call Land and Cell phone, Voicemail, AOL, iChat, XMPP, Yahoo! Messenger, Windows Live	1.15 (as of May '08)
Groundwire by Acrobits	Android, iOS	Proprietary	No	SIP	TLS, SRTP, ZRTP	Unlimited	Groundwire voip over wifi or 3G, supports audio codecs G.711, G.722, iLBC, GSM and G.729 can be added. SMS through SIP SIMPLE, multi line, call conferencing, transfer and attended transfer, voicemail. iOS only - Push Notifications, video, number rewriting, address book matching, sms for betamax providers and pennytel	Groundwire (iOS) 2.4, Groundwire (android) 3.21
iCall Mobile	iOS v4.3+	Freeware / Proprietary	SIP AIM ICQ XMPP Speex CELT WebM	TLS ZRTP	VoIP over Wi-Fi or 3G, SMS, Voicemail, AOL, Facebook, XMPP, Yahoo! Messenger, Windows Live	2.0.1 (as of Apr '12)
Jajah Mobile Web	Symbian OS, Windows Mobile (version unknown)	web based service, Call back,no download		Un­known
Line2	iOS (iPhone & iPad), Android	Freeware / Proprietary	Proprietary with SIP core	Un­known	Tri-mode calling (cellular, 3G/4G data, WiFi), SMS over IP, visual voicemail, 20-person conference calls, auto-attendant, call-forwarding	1.0.4 Android, 3.2.1 iOS
Sipdroid	Android	GPL	SIP	Un­known	Uses wifi, 3G or EDGE	2.7
Truphone	Nokia-Symbian, iPhone, Android, Blackberry	Freeware / Proprietary	SIP	Un­known	WiFi VoIP out & in, SMS over IP, call-through & call-back, connection management, provisioning	4.0 Symbian, 1.11.1 iPhone
Vopium	Symbian, Java ME, Android, BlackBerry RIM, iPhone, Windows Mobile 2003 SE and higher, iPhone (selected models)	Freeware / Proprietary	SIP, GSM, MSN, Skype, Yahoo, AOL, ICQ, Google Talk, Facebook & Twitter,	Un­known	WiFi VoIP, GSM call-trough, SMS over IP, least cost routing, Synchronisation/back-up of mobile contacts and calendar	2.0
Windows Mobile 6	Windows Mobile 6 Professional/Standard	Proprietary	SIP to publicly and non-publicly routable servers	Un­known	WiFi Mobile VoIP	6.1
X-PRO for Pocket PC	Windows Mobile 2003 (earlier versions support Windows PocketPC 2002)	Proprietary, discontinued in April 2007	SIP	Un­known	Supported devices: AudioVox Maestro, Compaq/HP iPAQ: 365x, 37xx, 385x, 395x, hx4700, Dell Axim X51, X51v, Toshiba e550, e570. iPAQ 545x and Toshiba e7xx are not supported.	2.2

Frameworks and libraries

Program	Operating systems	License	Protocols/based upon/compatible with	Encryption	Other capabilities	Key and target markets	Latest release
Tapioca	Linux	GPL / Free software	Telepathy (software)	Un­known			0.3.9 (June 12, 2006)
Telepathy/Farstream	Linux, Mac OS X, Windows	LGPL / Free software	SIP, XMPP (Jingle), ICE (STUN/TURN), UPnP	None yet	Multi-user A/V conferencing, IM, collaborative applications	Mobile devices (Maemo), Linux Desktop	spec 0.17.8 (24-Jul-2008)
OPAL	Windows, Linux (including embedded variants), Mac OS X	MPL / Free software	SIP, H.323, IAX2, CAPI, VXML	Real Soon Now	Multi-user A/V conferencing, IM, IVR	Softphones, Softswitches, Telephony application servers	3.10.3 (14-Oct-2011)

Server software

Program	Operating systems	License	Protocols/based upon/compatible with	Encryption	Other capabilities	Key and target markets	Latest release
3CX Phone System	Microsoft Windows	Closed	SIP	TLS, SRTP	Voice and Video IP telephony, Voice and Video conferencing, voice mail and instant messaging	25,000 - 50,000 users	11 (Jul 2012)
AS5300	Linux, Windows Server 2003	Closed	SIP, UNIStim, MLPP	SSL, TLS, SRTP, SDESC	Voice and Video IP telephony, Voice and Video conferencing, voice mail and instant messaging	1,000 - 25,000 users	1.0 (Jan 2008)
Asterisk PBX	Linux/BSD, Mac OS X, Solaris	GPL / Free software	SIP, H.323, IAX	TLS, SRTP	VoIP Gateway, voicemail, basic accounting (can be expanded by interface with ODBC-compliant database), billing, conferencing, hot-desking, IVR trees with conditional logic, call queuing, automated call distribution	Enthusiasts, developers, enterprise users (capacity dependent on server design, scalable across multiple servers)	21.3.1 (17 May 2024 (2024-05-17)) 20.5.0 LTS (18 October 2023 (2023-10-18)) 19.8.1 (7 July 2023 (2023-07-07)) 18.20.0 LTS (18 October 2023 (2023-10-18))
CallMax Softswitch	Linux	Closed Proprietary	SIP, H.323	SSL, TLS, HTTPS	Integrated billing, Residential/Hosted IP PBX, Multilevel IVR menu, Calling card platform, Callshop module, DID-numbers, SIP Trunking, Authorization by SIP, PIN, ANI, IP address and login/password	SIP Service Providers, VoIP service providers, IP PBX Users, Other Class 5 softswitch users	2.12 (January 2012)
Cisco Unified Communications Manager	Linux	Proprietary	SIP, SCCP, MGCP, H.323	SSL, TLS, SRTP	SIP Registrar/Proxy, Authentication	Enterprise users	8.5
ClearSea (Mirial s.u.r.l.)	Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86), iOS (iPhone 3S+, iPad 2), Android	Closed Proprietary	SIP, H.323		H.239 presentation,H.224, H.281 (FECC), Acts as a Session Border Controller, H.323/SIP endpoint autodiscovery on local LAN, Support user authentication with external databases / LDAP,Centralized Contacts Directory, User Groups management, Video IVR for dialing endpoint extensions, Ajax-powered web-based administration console, ClearSea desktop client one-step installation via HTTP browser, Automatic provisioning, configuration and secure authentication of ClearSea client based on user credentials	Desktop video conferencing users, Enterprises, Educational and Healthcare organizations	1.0.3 (April 30, 2010)
CommuniGate Pro	Linux/BSD, Mac OS X, Windows, Solaris, HPUX, AIX	Closed Proprietary	SIP, XIMSS Protocol, XMPP	SSL, TLS,	SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others...	Mobile Operators, ISP's, and SaaS providers	5.4c1 (January 2011)
Elastix	Linux	GPL / Free software	SIP, IAX, H323, XMPP		Unified communication server that also supports chat, mail and fax.	Capacity dependent on server design, scalable across multiple servers	2.0.3
FreeSWITCH	Linux/BSD, Mac OS X, Solaris, Windows	Mozilla Public License / Free software / Open source	SIP, NAT-PMP, STUN, SIMPLE, XMPP, Google Talk (Jingle), IAX, H.323, MRCP, RSS, Skype	TLS, SRTP, ZRTP	Recording, Voicemail, Conferencing, RADIUS, ENUM, IM Proxy, Streaming, Media gateway, Soft-PBX, IVR (modular)	Large soft-switch users, home PBX users, softphone users	1.0.6 (April 16, 2010)
GNU Bayonne	GNU/Linux, ??	GNU GPL	SIP (GNU Bayonne 2), ??	??	"free, scalable, media independent software environment for development and deployment of telephony solutions for use with current and next generation telephone networks"
GNU Gatekeeper	Linux/FreeBSD, Mac OS X, Windows XP/2000/Vista/Windows 7	GPLv2 / Free software	H.323	H.235	H.460.18 firewall traversal, Routing, Accounting	video conferencing, VoIP carriers large and small	2.3.2, May 25, 2010
MediaCore Softswitch	Linux	Closed Proprietary	H.323, SIP	SSL, TLS, HTTPS	Dynamic routing mechanism, integrated billing, SIP-H.323 protocol converter, Transcoding - codec converter module, Guardian - revenue assurance module, SBC functionality, full and media proxy	Transit VoIP services providers, VoIP wholesale carriers	2.24 (December 2011)
Murmur	Linux/BSD, Mac OS X, Windows	BSD / GPLv2	CELT / Speex	TLS	Chat with (limited) embedded HTML, ACLs for user management, Customizable In-Game Overlay, Directional Audio, Plugin Support, Nested Channels	Individuals to Small and medium enterprise (25-5000 users)	1.2.3 (February 19, 2011)
Mysipswitch	Linux	BSD / Free software / Open source	SIP, Ajax	SSL	SIP proxy server which allows the use of multiple SIP accounts with a single SIP login	Individuals	August 2007
Objectworld UC Server	Windows XP/2003/2008	Closed Proprietary	SIP		IP PBX, personal assistants, IVR, automated phone provisioning, fax server, unified messaging, Outlook, Exchange and Lotus Domino/Notes integration, conferencing, outbound dialing	Small and medium enterprise (25-2000 users)	4.4.2 (May 2009)
Kamailio/OpenSIPS (formerly known as OpenSER)	Linux/BSD, Solaris	GPL / Free software	SIP, XMPP		SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, least-cost-routing and many others.	SIP Service Providers	3.0.0 (January 2010)
snom ONE (formerly pbxnsip)	Linux/BSD, Mac OS X, Windows	Closed Proprietary	SIP	SRTP	IP PBX, presence indication, IVR, automated phone provisioning, fax server, unified messaging, Outlook, Exchange integration, conferencing, outbound dialing	Small and medium enterprise (25-256 users)	3.3.1.3177 (April 2009)
Revation LinkLive	Windows server / Linux	Closed Proprietary	SIP	TLS, SRTP	Secure Unified Communications, Presence, Instant Messaging/Chat, VoIP, Video, Desktop Sharing, File Sharing, IVR, PBX, Voicemail, ACD, Email Server	SIP Service Providers	5.3 (August 2011)
SIP Express Router (SER)	Linux/BSD, Solaris	GPL / Free software	SIP		SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others...	SIP Service Providers	2.0.0 Ottendorf
sipX ECS IP PBX	Linux	L-GPL / Open source	Native SIP Call Control	HTTPS, TLS	Full redundancy (HA), plug & play management including phones and gateways, fully featured	Enterprises between 200 and 10,000 users, multi-site	4.4, April 2012
Unison	Linux	Closed Proprietary	SIP, XMPP, IMAP, SMTP, CalDAV	SSL, TLS	Unified messaging, IP PBX, IVR, instant messaging, calendar server, LDAP server, E-mail server	Small and medium enterprise (25-256 users)	3.0, February 2010
vzRoom	Windows	Closed Proprietary	SIP	SSL, TLS, AES	Instant Messaging/Chat, VoIP, Video, Desktop Sharing, Video Sharing, whiteboard, File Sharing, scheduler, recording	Individual to small and medium enterprise (2-1,000 users)	0.8.8.735, November 2010
Yate	Linux, Mac OS, Windows	GPL / Free software	SIP, IAX, H.323, XMPP

See also

• Voice over IP
• Mobile VoIP
• Secure communication
• Softphone
• Video conference
• List of SIP software