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.¹ 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.

Contents 1 General softphone clients 2 Mobile phones 3 Frameworks and libraries 4 Server software 5 See also 6 References

General softphone clients

Program	Operating systems	License	Protocols/based upon/compatible with	Encryption	Max conference peers	Other capabilities	Latest release
AOL Instant Messenger	Linux, Mac OS, Windows	Freeware / Closed Proprietary	SIP (Windows ver. only), RTP	Unknown	Unknown	Video, file transfer, PC to phone, phone to PC
Blink	Mac OS X	GPL / Free software	SIP, MSRP, RFB (VNC)	sRTP, TLS	Unknown	IM, File Transfer, Desktop Sharing	0.15.0
Brosix	Windows	Freeware / Closed Proprietary		Unknown	Unknown	Text chat, File transfer, Video chat, Screen-shot, Screen-sharing, Whiteboard, Voice mail, Co-browse	2.0.2
Cisco IP Communicator	Windows	Closed Proprietary	SCCP (Skinny), SIP, TFTP	sRTP	Unknown		7.0.3 (Aug 2009)
CommuniGate Pro	Linux/BSD, Solaris, Mac OS X, Windows, AIX, HPUX	Closed Proprietary	SIP, XIMSS Protocol	TLS/SSL and SASL	Unknown	Multi-party conference, IM, Video, VideoMail, Presence	5.2.x (October-2008)
CounterPath X-Lite	Linux, Mac OS, Windows	Freeware / Closed Proprietary	SIP, STUN, ICE	Yes	Unknown	IM, single login account, for Windows and Mac also Conferencing, Video and SIMPLE based presence]	Windows / Mac OS: 3.0 / Linux: 2.0
Ekiga	Linux, (Beta Windows support), OpenSolaris	GPL / Free software	SIP, H.323, H.263, H.264/MPEG-4 AVC, STUN, Theora, Zeroconf	No	Unknown	Video, IM, LDAP, Call Forwarding, Call Transfer	3.2.7  (May 31, 2010)
Empathy	Linux	GPL / Free software	SIP, XMPP (Jingle), ICE (STUN/TURN), Zeroconf	No	Unknown	IM, multi-user A/Vcitation needed, collaborative applications	2.28.2 (2009-12-14)
Gizmo5	Linux, Mac OS X, Windows, Windows Mobile Phone, Blackberry, Nokia, PDA Java	Freeware / Closed Proprietary	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	Windows	Closed Proprietary (using libjingle)	XMPP	Unknown	Unknown	Video, chat, file transfer, voicemail, mail via "GMail Integration"	1.0.0.104
iChat	Mac OS X	Closed Proprietary	SIP AIM ICQ XMPP H263 H264	Unknown	Unknown	Integrated, PBX independent	January 2007
KPhone	Linux (KDE)	GPL / Free software	SIP, STUN, NAPTR/SRV	SRTP	Unknown	Video, voice, IM, external Sessions, IPv6 support for UDP	1.2 (November 2008)
Linphone	Linux, Windows	GPL / Free software	SIP	Unknown	Unknown	Video, IM, STUN, IPv6	3.3.3 (Apr 2010)
Lotus Sametime	Linux, Mac OS X, Windows, mobile	Closed Proprietary	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 2	8.5 (22. December 2009)
Mercuro IMS Client	Windows XP/Vista/Mobile	Closed Proprietary	SIP, XCAP, MSRP, NAPTR/SRV, Dhcp, RTP, H263, H264	TLS-Ipsec	Unknown	Voice/Video Calls, Presence, Instant messaging, File transfer, Remote Contact Storage	4.0
Mirial Softphone (Mirial s.u.r.l.)	Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86)	Closed Proprietary	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, Windows	BSD	CELT / Speex	TLS and OCB-AES128	No max (limited only by server bandwidth and memory)	Chat with (limited) embedded HTML, ACLs for user management, Customizable In-Game Overlay, Directional Audio, Plugin Support, Nested Channels, Echo cancellation, Logitech G15 support	1.2.2 (February 9, 2010)
OctroTalk	Symbian, Windows Mobile, Windows	Shareware / Closed Proprietary	SIP, (XMPP, STUN, ICE, Libjingle and RTP (media)	TLS and SASL	Unknown	VoIP, SIP calling, Video conference/chat, live video streaming, P2P file transfer, instant messaging	2.14 (February 17, 2009)
QuteCom	Linux, Mac OS X, Windows XP/2000	GPL / Free software	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 RC3  (2008-12-18)
Revation Communicator	Windows 2000/XP/Vista/7	Closed Proprietary	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	5.0 (April 2010)
SFLphone	Linux	GPL3 / Free software	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	0.9.8 (April 23rd 2010)
SightSpeed	Mac OS X, Windows	Freeware / Closed Proprietary	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
SIP Communicator	Linux, Mac OS, Windows XP/2000 (all java supported)	LGPL / Free software	SIP/SIMPLE, XMPP	Voice encryption (SRTP and negotiation with zRTP), Signaling encryption (TLS)	Unknown	Text messaging, audio/video telephony, IPv6	1.0-alpha3-nightly.build.2772  (June 28, 2010; 2 months ago (2010-06-28))
Skype	Linux, Mac OS X, Windows 2000/XP/Vista/7/Mobile (no longer supported), BREW, iPhone, PSP	Freeware / Closed Proprietary	Proprietary P2P protocol; SIP users can connect to the Skype network using alternate software/hardware, but the Skype software does not support it directly1	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.	4.2.0.187 (Windows) 2.8.0.851 (Mac OS X) 2.0.1 (iOS) 2.1.0.81 beta 2 (Linux)  (6 September 2010; 0 days ago (2010-09-06) (Windows) 10 February 2010; 6 months ago (2010-02-10) (Mac OS X) 21 January 2010; 7 months ago (2010-01-21) (Linux))
TeamSpeak	Linux, Windows, Mac OS X (unofficial)	Freeware Closed / Proprietary		No	Unknown	Conferencing	2.0.32.60
Telephone	Mac OS X 10.5	BSD / Free Software	SIP, STUN, ICE	No	Unknown	Address Book integration	0.14.0
Tokbox	Mac OS X, Windows XP/2000/Vista	Freeware / Closed Proprietary	Unknown	Unknown	Unknown	Video calling, video conferencing, chat, IM (MSN, AIM, Yahoo!, Google Talk)	Unknown
Tpad	Windows 2000/XP/Vista	Freeware / Closed Proprietary	SIP, STUN	Unknown	Unknown	Call Forwarding, PC to PSTN, PSTN to PC, Voicemail to email	3.0.1
Twinkle	Linux	GPL / Free software	SIP	SRTP, ZRTP	Unknown	Conferencing, chat, file transfer, Firefox integration, call redirection, voicemail, support of VoIP-to-Phone services	1.4.2  (2009-02-25)
Vbuzzer	Windows 2000/XP/Vista	Freeware / Closed Proprietary	SIP	TLS	Unknown	IM (MSN), voicemail, personalized voice greeting.	2.0.282
Ventrilo	Mac OS X, Windows	Freeware / Closed Proprietary		No	Unknown	Conferencing, chat, text-to-speech	3.0.5
Voice Operator Panel	Windows 2000/XP/Vista	Closed Proprietary	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
VoxOx	Windows, Mac OS X XP/Vista/7	Freeware / GPL3	XMPP	SRTP	Unknown	Calling, conferencing, video, virtual personal assistant, file transfer, voicemail, text message, fax, email, record calls, forward calls - Universal Communicator with support for: AIM, Windows Live, Yahoo Messenger, ICQ, Jabber, Google Talk, Facebook, MySpace, Twitter, Skype	2.0.6
Windows Live Messenger (Windows Live Call)	Windows	Freeware / Closed Proprietary		Unknown	Unknown
Yahoo! Messenger	Mac OS (8, 9, X), Windows, (Linux/FreeBSD version not VoIP capable)	Freeware / Closed Proprietary	SIP (using TLS) and RTP (media)	Unknown	Unknown	Video, file transfer, PC to phone, phone to PC
Zfone	Linux, Mac OS X, Windows	Freeware / Viewable source Proprietary (includes time bomb provision)	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
fring	Symbian 8.x and 9.x, Windows Mobile 5 and 6, iPhone, Maemo, Android	Proprietary	SIP to publicly routable servers only, not to non-publicly routable SIP Servers, Google Talk, MSN Messenger, Twitter, ICQ, AIM, Yahoo	?E	?OC	4.1.12 (Jan 15, 2010) [S60]
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)
IMSDroid	Android	GPL	SIP	?E	WiFi, EDGE or 3G High Quality Voice/Video Call, SMS over IP, XCAP, Presence, IM	1.0.0 (July 29, 2010)
Jajah Mobile Web	Symbian OS, Windows Mobile (version unknown)	web based service, no download3		?E	?OC
Sipdroid	Android	GPL	SIP	?E	Uses wifi, 3G or EDGE
Truphone	Nokia-Symbian, iPhone, Android, Blackberry	Freeware / Proprietary	SIP	?E	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,	?E	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	?E	WiFi Mobile VoIP	6.1
X-PRO for Pocket PC	Windows Mobile 2003 (earlier versions support Windows PocketPC 2002)	Proprietary, discontinued in April 20074	SIP	?E	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.5	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)	?E	?OC		0.3.9 (June 12, 2006)
Telepathy/Farsight	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)

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	8.0 (Oct 2009)
AS5300	Linux, Windows Server 2003	Closed	SIP, UNIStim, MLPP	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		VoIP Gateway, voicemail, basic accounting (can be expanded by interface with ODBC-compliant database), 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)	1.6.2.6 (March 2010)
Cisco Unified Communications Manager	Linux	Proprietary	SIP, SCCP, MGCP, H.323	SSL, TLS, SRTP	SIP Registrar/Proxy, Authentication	Enterprise users	8.0.2
ClearSea (Mirial s.u.r.l.)	Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86)	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	Proprietary	SIP, XMPP	SSL, TLS,	SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others...	Mobile Operators, ISP's, and SaaS providers	5.2.x October 2008
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	1.6 October 2009
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 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
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)	1.2.0 (December 11, 2009)
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)
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	5.0.22 (August 2010)
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	4.2, April 2010
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

See also

• Voice over IP
• Mobile VoIP
• Secure communication
• Softphone
• Video conference

References