VoIP software

Comparison of VoIP software

  • Print

This is a comparison of voice over IP (VoIP) software used to conduct telephone-like voice conversations across Internet Protocol (IP) based networks. For residential markets, voice over IP 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 PSTN phone number in a New York area code ring 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 abilities.

Softphones are client devices for making and receiving voice and video calls over the IP network with the standard functions of most original telephones and usually allow integration with VoIP phones and USB phones instead of using 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 networking protocol but additional business telephone system (PBX) software can allow a SIP based telephone system to connect to the Skype network.[1] Online chat programs now also incorporate voice and video communications.

Other VoIP software applications include conferencing servers, intercom systems, virtual foreign exchange services (FXOs) and adapted telephony software which concurrently support VoIP and public switched telephone network (PSTN) like Interactive Voice Response (IVR) systems, dial in dictation, on hold and call recording servers.

Some entries below are Web-based VoIP; most are standalone applications.

Softphone applications[edit]

Program Operating systems License Costs Protocols Codecs Encryption Max conference peers Other abilities Latest release
AudioCodes MobilityPLUS Windows, Android, iOS Proprietary ? SIP, RTP, XMPP, STUN, ICE G.722 wideband, G.711a, G.711u, iLBC, G.729a, SILK, GSM, VP8, H.264, Opus TLS, SRTP Unknown Voice, video, IM, Group chat, content sharing, SMS and MMS over IP services, native and social network contacts integration, incoming call/IM push notifications. 2014; 4 years ago (2014)
Avaya Application Server 5300 Soft Client Windows Proprietary ? SIP, RTP Unknown TLS, SRTP Unknown 2.0; 2010; 8 years ago (2010)
Blink Linux, macOS, Windows Mixed: free software versions under GNU GPLv3 + shareware versions under gplv3 with exception of including proprietary code Windows and Linux are free, macOS version is available for a fee in Mac App Store, source code is freely available ICE, SIP, MSRP, RFB (VNC), XCAP Opus, speex, G.722, GSM, iLBC, PCMU, PCMA TLS, SRTP and ZRTP on all versions, OTR/SMP on Linux and macOS only[2] No limit IM, file transfer, desktop sharing, multi-party conference, wideband Blink Qt
CSipSimple Android GPL Free SIP, ICE, STUN, TURN Opus, AMR, G.711 (u-law/a-law), speex, G.722, GSM, iLBC, G.729 (need to buy a licensed plugin), iSAC, SILK (narrow-band/wide-band/ultra wide-band) SRTP, SIP over TLS 1.0 and ZRTP Unknown SIP SIMPLE messaging, Support for IPv6, Integration with Android operating system with filters and rewriting rules 1.0.2; November 2014; 3 years ago (2014-11)
Cisco IP Communicator[3] Windows, Android Proprietary Free (for Cisco SMB Partners only) SCCP (Skinny), SIP, TFTP, HTTP (for XML Services) G.722 wideband, G.711a, G.711u, iLBC, iSAC, G.729a, G.729ab SRTP Unlimited (with bridge), 2 otherwise[4] 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, XML Services 8.6.6; April 27, 2016; 2 years ago (2016-04-27)
Discord macOS, Android, iOS, Windows, Linux Proprietary Free, Premium "Nitro" Subscription for Additional Features. ? Opus TLS 5,000 soft limit[5] IM, file sharing, in-game overlay 02.01.2018; February 1, 2018; 4 months ago (2018-02-01)
Ekiga Linux, Windows, OpenSolaris GPL Free SIP, H.323, STUN, Zeroconf, XMPP, RTP H.263, H.264/MPEG-4 AVC, Theora, iLBC, Speex, SILK, GSM, ... No Unknown Video, IM, LDAP, Call Forwarding, Call Transfer, Auto-answering, PC to phone, phone to PC, Multiple accounts, USP support, Message waiting indicator, SIMPLE-based presence etc. 4.0.1 (February 21, 2013; 5 years ago (2013-02-21)) [±][6]
Empathy Linux GPL Free SIP, XMPP (Jingle), ICE (STUN-TURN), Zeroconf Unknown No Unknown IM, multi-user A/V,[7] collaborative applications 3.12.12[8] (May 13, 2016; 2 years ago (2016-05-13)) [±]
Eyeball Chat Windows Proprietary Free SIP, STUN, ICE, XMPP Unknown Yes 5[9] IM, Conferencing, Voice, Video and SIMPLE based presence Windows 3.2; 2009; 9 years ago (2009)
eyeBeam Windows Proprietary ? SIP-SIMPLE Unknown TLS, SRTP 6 party audio; 3 party video Voice and Video calling; IM; Import Microsoft Outlook Contacts; USB Support; Call Recording and Conferencing 1.5.20.1; March 2010; 8 years ago (2010-03)
Google+ Hangouts Linux, Windows, macOS, Android, iOS Proprietary (using libjingle) Free XMPP H.264/SVC, H.264/AVC, H.263 and VP8 SRTP 10 Video, chat, screen sharing, with additional tools available as "Hangout Apps". Google Chrome Web Store extension
2013.626.1614.1 (July 9, 2013; 4 years ago (2013-07-09)) [±] [10]
IBM Sametime Linux, macOS, Windows, mobile Proprietary ? SIP-SIMPLE, T.120 H.323 TLS Unknown IM, File transfer, Voice, Presence, Server stored contact list, HTTP tunneling, plugins, embedable in Lotus Notes[11] 8.5.2; May 8, 2011; 7 years ago (2011-05-08)
iCall Linux, macOS, Windows, iOS, Android Proprietary Free SIP, AIM, ICQ, XMPP Speex, CELT, WebM TLS, ZRTP No limit Video, file transfer, PC to phone, phone to PC, IM (MSN, AIM, ICQ, Yahoo!, XMPP, Google Talk), Voicemail 7.1.522
Jitsi Linux, macOS, Windows (all java supported). Experimental Android builds are also available.[12] Apache Free SIP-SIMPLE, XMPP-Jingle STUN ICE, TURN SILK, G.722, Speex, Opus, G.711 (PCMU/PCMA), iLBC, GSM, G.729, H.264, H.263, VP8 ZRTP, SRTP, OTR, TLS Unknown Text messaging, audio-video telephony, IPv6 (often broken,[13] P2P not supported[14]), call recording, 64-bit 2.10 (build.5550) (February 5, 2017; 16 months ago (2017-02-05)) [±]
KPhone Linux (KDE) GPL Free SIP, STUN, NAPTR-SRV Unknown SRTP Unknown Video, voice, IM, external Sessions, IPv6 support for UDP 1.2 (November 2008)
Kiax ver.2 Linux (KDE), Windows GPL Free IAX Speex, G711, GSM, iLBC No Unknown Multiple calls, DTMF, Hold, Resume, HTTP API 2.1-Beta2 April 26, 2013; 5 years ago (2013-04-26)[15][16]
Librestream Onsight Connect Windows, Android, iOS Proprietary ? SIP, RTP, STUN G.711, H.264, MPEG, and others TLS, SRTP Unknown Voice, video, conferencing, image sharing, incoming call/IM push notifications. February 27, 2018; 3 months ago (2018-02-27)
Linphone Linux, Windows, macOS, Android, iPhone, BlackBerry GPL Free SIP Speex, Opus, G711, GSM, G.722, VP8 (WebM), H263, MPEG4, Theora and H264 (plugin) TLS, SRTP, ZRTP Unknown Video, IM, STUN, IPv6 (disables IPv4 support when enabled, P2P supported only by version 3.5.1-2) 3.11.1; March 10, 2017; 15 months ago (2017-03-10)
Messages macOS Proprietary Free, only MacOS and iOS SIP AIM ICQ XMPP H263, H264 Unknown Unknown Integrated, PBX independent 7.0; July 25, 2012; 5 years ago (2012-07-25)
MicroSIP Windows GPL Free SIP, STUN, ICE, SIMPLE Speex, iLBC, GSM, G.711, G.722, G.729, SILK, Linear PCM TLS, SRTP Unknown Video, voice, IM and Presence 3.18.3 March 2018; 3 months ago (2018-03)
Mirial Softphone (Mirial s.u.r.l.) Windows 2000-XP-2003-Vista-7 (including 64-bit versions), macOS (x86) Proprietary not free SIP, RTSP H.323 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; 8 years ago (2010-05-26), discontinued
Mumble Linux, macOS, iOS, Windows, Android New BSD license Free ICE CELT, Speex, Opus TLS and OCB-AES128 No max (limited only by server bandwidth and memory) Chat with (limited) embedded HTML, Automatic Gain Control, very low latency, Access Control Lists for user management, Customizable In-Game Overlay for OpenGL and DirectX, Directional Audio, Plugin Support, Nested Channels, Echo cancellation for headset free use, Global Public Server List, Logitech G15 support, Push-To-Talk and Voice-Activation 1.2.19; January 27, 2017; 16 months ago (2017-01-27)
Nymgo Windows, Android, iOS Proprietary Free SIP, RTP and RTCP Unknown Yes No Address Book integration, Call recording/export, Mute, On Hold, Caller ID definition 4.2.9; March 2013; 5 years ago (2013-03)
oovoo macOS, iOS, Windows, Android Proprietary Free SIP, RTP and RTCP Unknown Yes 12 Address Book integration, Call recording/export, Mute, On Hold, Caller ID definition 4.2.9; March 2013; 5 years ago (2013-03)
Phoner Windows Proprietary Free SIP, TAPI, CAPI G.711a, G.711u, G.722, G.726, G.729, GSM, iLBC, speex, Opus TLS, SRTP, ZRTP 8 Conferencing, call redirection, call recording 3.20 (13 April 2018; 2 months ago (2018-04-13)) [±][17]
PhonerLite Windows Proprietary Free SIP G.711a, G.711u, G.722, G.726, G.729, GSM, iLBC, speex, Opus TLS, SRTP, ZRTP 8 Conferencing, call redirection, call recording 2.64 (21 June 2018; 2 days ago (2018-06-21)) [±][18]
QuteCom Linux, macOS, Windows XP-2000 GPL Free SIP G.711, G.729, iLBC, AMR-NB, G.722, Speex, AMR-WB (G.722.2), H.263, H.263+, H.264, Dirac[19] 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; 7 years ago (2011-06-22)[20]) [±]
Ring Linux, macOS, Windows, Android (all beta) GPL3 Free SIP, RTP, IAX2, STUN per account, SRV, DHT, P2P Audio: Opus, Speex, G.722, G.711, GSM, VP8, G.729, iLBC. Video: H.264, H.263, VP8, MPEG-4 Voice encryption (SRTP with SDES or ZRTP) and signaling encryption (TLS), multiple realms authentication mechanism No limit Blockchain ID-management, Gnome-KDE client, address book, multiple accounts, unlimited call number, call transfer, call hold-unhold, call recording, multi-way conferencing 1.0; July 21, 2017; 10 months ago (2017-07-21)
Roger Wilco GameSpy Windows Proprietary ? Proprietary ? ? ? ? 2001; 17 years ago (2001)
Skype Linux(with limited functionality),[21] macOS, Windows 2000-XP-Vista-7-Mobile (unsupported), BREW, Windows Phone , Android, iPhone, PSP Proprietary Free Proprietary P2P protocol [a] SILK TLS 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 12.1813.286.0 / 22 March 2018; 3 months ago (2018-03-22)[22]
Windows, desktop 8.22.0.2 / 21 May 2018; 33 days ago (2018-05-21)[23][24]
macOS 8.22.0.2 / 21 May 2018; 33 days ago (2018-05-21)[23][24]
Linux 8.22.0.2 / 21 May 2018; 33 days ago (2018-05-21)[25][24]
Android 6 and later 8.22.0.2 / 21 May 2018; 33 days ago (2018-05-21)[26][27]
iOS & watchOS 8.22.0.7 / 21 May 2018; 33 days ago (2018-05-21)[28][27]
TeamSpeak Linux, Windows, macOS, FreeBSD, Android, iOS Proprietary Free Unknown CELT, Speex, Opus[29] Yes 32 unlicensed, 512 with non-profit license, 2000 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 3.1.8
TeamTalk Linux, Windows, macOS, Android, iOS, Raspbian Proprietary Free Proprietary Opus, Speex, WebM No 1000 Video, file sharing, desktop sharing, stream media files (MP3, AVI) 5.1.3; May 2016; 2 years ago (2016-05)
TeamViewer Linux, Windows, macOS, iOS, Android[30] Proprietary Free (personal use only) Unknown Unknown AES256 Unknown Unknown
Windows (desktop app) 13.1.3629 / April 4, 2018; 2 months ago (2018-04-04)[31]
macOS 13.1.2991 / March 21, 2018; 3 months ago (2018-03-21)[32]
Linux 13.1.8286 / May 30, 2018; 24 days ago (2018-05-30)[33]
Android 13.0.8183 / December 21, 2017; 5 months ago (2017-12-21)[34]
iOS 13.0.89402 / November 28, 2017; 6 months ago (2017-11-28)[35]
Windows (UWP app) 13.0.100.0[36]
BlackBerry OS 12.0.0.6394 / February 1, 2017; 16 months ago (2017-02-01)[37]
Chrome OS 13.0.281 / October 30, 2017; 7 months ago (2017-10-30)[38]
Telephone macOS 10.10.2 BSD Free SIP, STUN, ICE Unknown No Unknown Address Book integration 1.1.4; March 6, 2012; 6 years ago (2012-03-06)
Toktumi Unlimited, Line2 Pro Windows XP-Vista-7, macOS, iOS, Android Proprietary Free Proprietary with SIP core Unknown Unknown 20 Conferencing, voicemail, caller ID, call-waiting, address book integration; auto-attendant, call-forwarding Windows; August 2010; 7 years ago (2010-08); macOS; October 2010; 7 years ago (2010-10)
Tox Linux, macOS, Windows, Android, FreeBSD GPL Free Tox, VP8 Opus, NaCl Unknown Voice, video, instant messaging, file transfers Unknown
Tru App Windows 2000-XP-Vista-7, macOS, Linux
iOS, Android, Symbian, BlackBerry OS,		 Proprietary Free SIP, XMPP Unknown Unknown Unknown Chat, file transfer, voicemail, inbound numbers, integration with GTalk, Microsoft Live, Skype
Tuenti Android, iPhone, Windows Phone Proprietary Free WebRTC, SIP, XMPP iLBC, Opus Yes ? Voice, video, Instant messaging, group chat, photo and video sharing, SMS and MMS, native and social network contacts integration, incoming call/IM push notifications.
Twinkle Linux GPL Free SIP G.711 A-law μ-law, G.726, GSM, iLBC, Speex narrow wide ultrawide SRTP, ZRTP 3 Conferencing, chat, file transfer, Firefox integration, call redirection, voicemail, support of VoIP-to-Phone services 1.10.0 (July 15, 2016; 22 months ago (2016-07-15)) [±]
Ventrilo macOS, Windows, iOS, Android Proprietary Free Unknown Unknown No 8 Conferencing, chat, text-to-speech 3.0.8
Viber Linux,[b] macOS,[b] Windows,[b] Android, Bada, BlackBerry OS, iOS, Series 40, Symbian, Windows Phone Proprietary ? Unknown Unknown Yes[41] Unknown Varies by platform: Text, picture and video messaging on all, voice calling only on iPhone, Android and Microsoft's Windows Phone
  • Android:
    8.7.0.6 (April 26, 2018; 58 days ago (2018-04-26)[42]) [±]
  • iOS:
    8.7.1 (April 21, 2018; 2 months ago (2018-04-21)[43]) [±]
  • Windows Mobile:
    6.6.1 (April 26, 2018; 58 days ago (2018-04-26)[44]) [±]
  • BlackBerry 10 OS:
    4.3.0.728 (April 23, 2014; 4 years ago (2014-04-23)[45]) [±]
Voice Operator Panel Windows 2000-XP-Vista Proprietary ? SIP, RTP Unknown Unknown Unknown Call forwarding, call transfer, call recording, presence, Outlook integration, Windows Messenger-MSN-Live integration, CRM, built-in web browser, emailer, LDAP, APS. 1.3.2
Vyke iPhone, Android Proprietary Free SIP Unknown TLS, SRTP Unknown P2P calls, instant messaging, text messaging, incoming calls, incoming messaging, voicemail, international mobile phone numbers, push notifications, address book integration; iOS September 2016; 1 year ago (2016-09); Android August 2016; 1 year ago (2016-08)
Wire Linux, Windows, macOS, iOS, Android, Web GPLv3 Free ? Template:Opus (audio), VP8 (video) DTLS, SRTP[46] 10[47] End-to-end encryption by default for everything, instant messaging, video call, video group call, file sharing, GIF sharing, push to talk, edit message, delete message (on both side), timed messages, doodling, identity verification, screen sharing (desktop only) ?
X-Lite macOS, Windows Proprietary Free SIP, STUN, ICE, TURN H.263, H.263+, G.711, iLBC, Speex No 3 VoIP over WiFi, 3G, 4G, video, instant messaging, presence (SIP SIMPLE), call waiting, call hold, call forwarding, voice mail, message waiting indication, 3 way conferencing, contacts integration, background noise reduction (BNR), automatic gain control (AGC) Windows: 4.9.2, macOS: 4.9.2; December 2015; 2 years ago (2015-12)
Yahoo! Messenger Classic Mac OS (8, 9), macOS, Windows, (Linux, FreeBSD version VoIP incapable) Proprietary Free SIP (using TLS) and RTP (media) Unknown Unknown Unknown Video, file transfer, PC to phone, phone to PC Windows: 11.5.0.228; May 31, 2012; 6 years ago (2012-05-31)
Mac: 3.0.1; July 20, 2011; 6 years ago (2011-07-20)
Linux: 1.0.6; September 2003; 14 years ago (2003-09)
SunOS 5.7: 0.99.17-1; September 2003; 14 years ago (2003-09)
Solaris 8: 1.0.4; September 2003; 14 years ago (2003-09)
FreeBSD 4-5: 1.0.4; September 2003; 14 years ago (2003-09)
iOS: 2.2.6; July 12, 2012; 5 years ago (2012-07-12)
Yate Client Linux, macOS, Windows GPL Free SIP, IAX, XMPP, H.323 G.711a, G.711u, GSM 06.10, iLBC, Speex, G.723, G.726, G.728, G.729 SRTP, maybe ZRTP? Unknown 4.3; January 2013; 5 years ago (2013-01)
Zfone Linux, macOS, Windows Viewable source Includes time bomb provision SIP, RTP Unknown SRTP, ZRTP Unknown Beta 2008-09-04 (Linux 0.9.224), (macOS 0.9.246), (Windows 0.9.206)
  1. ^ It is possible to connect by SIP to the Skype network via additional "Skype Connect" PBX software and alternative (SIP) client software/hardware. Neither the Skype software nor the Skype network supports SIP directly[1]
  2. ^ a b c Viber must be first installed on a mobile phone to function on a desktop operating system[39][40]

Discontinued softphone service[edit]

Mobile phones[edit]

For mobile VoIP clients:

Program Operating systems License Open source Protocols Codecs Encryption Other abilities Latest release
Acrobits Softphone Android v2.2+, iOS v7.0+ Proprietary No SIP G.711, G.722, iLBC, GSM, G.729 TLS, SRTP, ZRTP VOIP over Wi-Fi or 3G iOS only: push notifications, video, number rewriting, address book matching, sms for betamax providers and pennytel Acrobits Softphone: 3.20 (Android), 5.2 (iOS)
CSipSimple Android GPL Yes SIP Opus, AMR-WB, G.722, iSAC, iLBC, Speex, Silk, Codec2, G.726, G711 (PCMA & PCMU), AMR, GSM SRTP, SIP over TLS 1.0 and ZRTP ? 1.02.02
Google Duo iOS, Android Proprietary, freeware No WebRTC ? ? One-to-one voice and video calling.
Android 29.0.187910126.DR29_RC10 / March 5, 2018; 3 months ago (2018-03-05)[48]
iOS 29.0 / March 8, 2018; 3 months ago (2018-03-08)[49]
iCall Mobile iOS v4.3+ Proprietary, freeware No SIP AIM ICQ XMPP, Facebook, Yahoo! Messenger, Windows Live Speex, CELT, WebM TLS, ZRTP VoIP over Wi-Fi or 3G, SMS, voicemail 2.0.1; April 2012; 6 years ago (2012-04)
Jajah Mobile Web Symbian, Windows Mobile (version unknown) Proprietary No ? ? ? web based service, Call back,no download[50] ?
JusTex by Juphoon Android, iOS v5.1+ Proprietary No SIP PCMA, PCMU, G.722, iLBC, iSAC, Opus, H.264, VP8, H.263 TLS, TCP, UDP, SRTP JusTex Softphone over Wi-Fi or 3G, HD voice and video call, Multiparty call, conference. 3.0.1 (iOS); July 13, 2014; 3 years ago (2014-07-13); 3.0 (Android); July 9, 2014; 3 years ago (2014-07-09)
Line Android, iOS Proprietary No ? ? ? ?
Line2 Android, iOS Proprietary, freeware No Proprietary with SIP core ? ? Tri-mode calling (cellular, 3G/4G data, Wi-Fi), SMS over IP, visual voicemail, 20-person conference calls, auto-attendant, call-forwarding 1.0.4 Android, 3.2.1 iOS
Media5-fone iOS, Android Proprietary No SIP PCMA, PCMU, G.722*, iLBC, iSAC*, G.729* TLS*, SRTP* Wi-Fi and 3G/4G data, second call*, conference calls*, HD Voice, Bluetooth* (* Additional fees) ?
Signal by Open Whisper Systems iOS, Android GPLv3 Yes WebRTC[51] Opus[51] TLS, Signal Protocol[51] End-to-end encryption by default for everything. CallKit and location privacy,[52] one-to-one and group messaging, video calling,[52] image/video sharing, timed messages, identity verification, screenshot blocking. Android only: SMS/MMS messaging, doodling,[53] GIF sharing.[54] Android 4.19.3 (May 3, 2018; 51 days ago (2018-05-03)[55]) [±]

iOS 2.25.3 (June 8, 2018; 15 days ago (2018-06-08)[56]) [±]
Desktop 1.12.1 (June 14, 2018; 9 days ago (2018-06-14)[57]) [±]
Sipdroid Android GPL Yes SIP ? ? Uses Wi-Fi, 3G or EDGE 2.7
Tango by TangoME Inc. iOS, Android, Microsoft Windows, macOS, Windows Phone Proprietary, freeware ? ? ? ? VoIP, Wi-Fi out & in, SMS over IP, call-through & call-back, instant messaging, videoconferencing ?
Truphone Nokia-Symbian, iOS, Android, BlackBerry Proprietary, freeware No SIP ? ? VoIP, Wi-Fi out & in, SMS over IP, call-through & call-back, connection management, provisioning Symbian 4.0, iOS 1.11.1
Vopium Symbian, Java ME, Android, BlackBerry RIM, iOS, Windows Mobile 2003 SE and higher Proprietary, freeware No SIP, MSN, Skype, Yahoo, AOL, ICQ, Google Talk, Facebook & Twitter GSM ? Wi-Fi VoIP, GSM call-through, SMS over IP, least cost routing, synchronising-backup mobile contacts and calendar 2.0
WhatsApp

Android, BlackBerry, iOS, Symbian, Windows Phone

 Proprietary, freeware No ? ? ECDH, SRTP[58] VoIP and instant messaging over Wi-Fi or a data connection.
iOS 2.18.11 / January 11, 2018; 5 months ago (2018-01-11)[59]
Android 2.17.427 / November 29, 2017; 6 months ago (2017-11-29)[60]
Windows Phone 8, Windows 10 Mobile 2.18.52[61]
Symbian 2.16.57[62]
BlackBerry 2.17.2 / June 26, 2016; 23 months ago (2016-06-26)[63]
Windows Mobile 6 Windows Mobile 6 Professional/Standard Proprietary No SIP to publicly and non-publicly routable servers ? ? Wi-Fi Mobile VoIP 6.1
X-PRO for Pocket PC Windows Mobile 2003 (earlier versions support Windows PocketPC 2002) Proprietary, discontinued in April 2007[64] No SIP ? ? 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.[65] 2.2
Yuilop Android, iOS, Windows Phone, BlackBerry OS Proprietary, freeware No XMPP, RTP iLBC TLS VoIP over 3G-4G-LTE and Wi-fi, SMS, group chat, photo sharing, Location sharing, virtual phone numbers iOS 2.4 (November 26, 2014; 3 years ago (2014-11-26)[66]) [±]

Android 2.0.2 (February 12, 2014; 4 years ago (2014-02-12)) [±]
Windows Phone 7.x 1.0.1.7 (September 12, 2013; 4 years ago (2013-09-12)) [±]
Windows Phone 8.x 1.0.0.4 (September 18, 2013; 4 years ago (2013-09-18)) [±]
BlackBerry OS 1.0.1 (May 31, 2013; 5 years ago (2013-05-31)) [±]
Kindle Fire 2.0 (December 19, 2013; 4 years ago (2013-12-19)[67]) [±]

Frameworks and libraries[edit]

Program Operating systems License Protocols, based on, compatible with Encryption Other abilities Key and target markets Latest release
Tapioca Linux GPL Telepathy (software) No 0.3.9; June 12, 2006; 12 years ago (2006-06-12)
Telepathy, Farstream Linux, macOS, Windows LGPL SIP, XMPP (Jingle), ICE (STUN/TURN), UPnP No Multi-user A/V conferencing, IM, collaborative applications Mobile devices (Maemo, Meego), Linux desktop or embedded spec 0.27.2; September 24, 2013; 4 years ago (2013-09-24)
OPAL Windows, Linux (including embedded variants), macOS MPL SIP, H.323, IAX2, CAPI, VXML Unknown Multi-user A/V conferencing, IM, IVR Softphones, softswitches, telephony application servers 3.14.3; October 10, 2014; 3 years ago (2014-10-10)
GNU oSIP Linux, Windows, macOS, Android, iPhone, BlackBerry LGPL SIP, SDP Unknown Multi-user A/V conferencing, IM, IVR Softphones, embedded and mobile devices, telephony application servers 4.1.0; December 18, 2013; 4 years ago (2013-12-18)

Server software[edit]

Program Operating systems License Protocols, based on, compatible with Encryption Other abilities Key and target markets Latest release
3CX Phone System Windows, Linux Proprietary SIP TLS, SRTP Voice and video IP telephony and conferencing, voice mail and instant messaging < 50,000 users 15.5 ; June 7, 2017; 12 months ago (2017-06-07)
AS5300 Linux, Windows Server 2003 Proprietary 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; January 2008; 10 years ago (2008-01)
AskoziaPBX no additional OS required (Linux based) GPL, Open core SIP, H.323, IAX, SCCP No ISDN, analog, Voicemail, Conferencing, MOH, ACD, IVR, Call forwarding, Call recording SMEs up to 50 users 2.2.2; December 2012; 5 years ago (2012-12)
Asterisk PBX Linux, BSD, macOS, Solaris Mixed: GPL, Proprietary[68] SIP, H.323, IAX, MGCP, VOFR, XMPP, Google Talk, TDM 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) 15.4.1 (11 June 2018; 12 days ago (2018-06-11)[69]) [±]

13.21.1 (11 June 2018; 12 days ago (2018-06-11)[70]) [±]
Brekeke SIP Server Linux, Windows Proprietary SIP TLS, SRTP SIP Registrar, SIP Proxy SIP Service Providers, VoIP service providers, Healthcare, Security 3.8.3.4; February 2, 2018; 4 months ago (2018-02-02)
Brekeke PBX Linux, Windows Proprietary SIP TLS, SRTP Voice and Video IP telephony, Voice and Video conferencing, and voice mail Hosted service providers, Mid-large enterprise 3.8.4.4; April 18, 2018; 2 months ago (2018-04-18)
CallMax Softswitch Linux Proprietary SIP, H.323 SSL, TLS, HTTPS Integrated billing, IP PBX Platform, Calling card platform, Callshop module, Customer Web Portal, Retail SMS Platform. SIP Service Providers, Residential & Business VoIP providers, Corporate Clients, Other Class 5 softswitch users 3.6; October 2015; 2 years ago (2015-10)
CommuniGate Pro Linux, BSD, macOS, Windows, Solaris, HPUX, AIX Proprietary SIP, XIMSS Protocol, XMPP, WebRTC SSL, TLS, SRTP SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, many others Carriers, enterprises, MNOs, ISPs, SaaS providers 6.1.11; June 2016; 2 years ago (2016-06)
Dial-Gate Softswitch PBX Linux, Windows Proprietary SIP TLS, SRTP Billing server, real-time account and line monitoring, web-based user interface Softswitch users, service providers 4.3; June 2014; 4 years ago (2014-06)
Dial-Office IP-PBX Linux, Windows Proprietary SIP TLS, SRTP Unified Communications, Conferencing, remote worker support and voice mail Small businesses, Mid-large enterprises 4.1; December 2013; 4 years ago (2013-12)
Elastix Linux GPL SIP, IAX, H323, XMPP TLS, SRTP Unified communication server that also supports chat, mail and fax. Capacity dependent on server design, scalable across multiple servers 2.5.0 (stable), 3.0.0 (stable), 4.0.0 (stable); February 10, 2016; 2 years ago (2016-02-10)
FreeSWITCH Linux, BSD, macOS, Solaris, Windows Mozilla Public License 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 1.6.20 (January 23, 2018; 4 months ago (2018-01-23)) [±]
FreePBX Linux, BSD, Solaris GPL SIP, IAX, H323, XMPP TLS, SRTP Complete PABX Service, based on Asterisk and PHP 5.3; provides a full replacement for a legacy non-VoIP phone system; under current and active development Scales from Raspberry PI (3 users) to multiple parallel clusters (10K+ simultaneous calls) 12.0; October 2014; 3 years ago (2014-10)
GNU Gatekeeper Linux, FreeBSD, macOS, Windows XP-2000-Vista-7 GPL H.323 H.235 H.460.18 firewall traversal, routing, accounting video conferencing, VoIP carriers large and small 3.7; August 15, 2014; 3 years ago (2014-08-15)
HERO Hosted PBX Linux, Windows Proprietary SIP TLS, SRTP Unified Communications, billing server, cloud-based management and web interface Mid-large enterprises, VoIP carriers and service providers, telecom operators 4.3; December 2013; 4 years ago (2013-12)
Kerio Operator Linux, VM Proprietary SIP SSL, TLS, SRTP integrated firewall, Auto attendant, Call queues, Conference calling, Call forwarding, pickup, parking, recording, Click to Call, Video calling, Fax support, Paging, Salesforce.com and CRM integration, Voicemail to email, complementary desktop Softphone app SME 2.5.2; November 15, 2016; 18 months ago (2016-11-15)
MediaCore SBC Linux Proprietary H.323, SIP, SMPP SSL, TLS, HTTPS Dynamic routing mechanism including LCR, Jurisdictional routing support, A-number based routing for EU-based providers), integrated billing, SIP-H.323 protocol converter, Transcoding - codec converter module, Guardian - revenue assurance module, SBC functionality, full and media proxy, Carrier SMS support Transit VoIP services providers, VoIP wholesale carriers, VoIP termination providers, SMS carriers 4.6.1; May 2017; 1 year ago (2017-05)
Murmur Linux, BSD, macOS, Windows BSD, GPL CELT, Speex, Opus 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) 1.2.17; September 24, 2016; 20 months ago (2016-09-24)
Mysipswitch Linux BSD SIP, Ajax SSL SIP proxy server which allows the use of multiple SIP accounts with a single SIP login Individuals August 2007; 10 years ago (2007-08)
Objectworld UC Server Windows XP-2003-2008 Proprietary SIP No 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; 9 years ago (2009-05)
Kamailio, OpenSIPS (formerly named OpenSER) Linux, BSD, Solaris GPL SIP, XMPP TLS, SRTP SIP registrar-proxy, authentication, Diameter, RADIUS, ENUM, least-cost-routing, many others SIP Service Providers 4.0.1 (25 April 2013; 5 years ago (2013-04-25)) [±]
Pbxnsip Linux, BSD, macOS, Windows 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; 9 years ago (2009-04)
SIP Express Router (SER) Linux, BSD, Solaris GPL SIP No SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, many others SIP Service Providers 2.0.0 Ottendorf
sipXecs IP PBX Linux AGPL Native SIP call control, XMPP TLS, SRTP Full redundancy (HA), instant messaging, voicemail, user portal, admin GUI, plug & play management including phones and gateways, fully featured Enterprises between 10 and 10,000 users, multi-site 14.04.2; July 2014; 3 years ago (2014-07)
vzRoom Windows Proprietary SIP SSL, TLS, AES Instant messaging-chat, VoIP, video, sharing (desktop, video, file), whiteboard, scheduler, recording Individual to small and medium enterprise (2-1,000 users) 0.8.8.735; November 2010; 7 years ago (2010-11)
Yate BSD, Linux, macOS, Windows GPL SIP, IAX, H.323, ISDN, XMPP (Jabber), Jingle (Google Talk), MGCP, SS7 over IP, Cisco SLT (Signalling Link Transport) (SS7 MTP2 backhaul over IP), SCTP, SCCP, TCAP, MAP CAMEL SSL, TLS, SRTP Voice, video, file transfer, data, H323 to SIP signalling proxy, instant messaging, IVR, PC2Phone and Phone2PC gateway, SCCP — GTT routing between networks, Secure Unified Communications, SIP registrar-proxy, SIP SBC (session border controller), USSD, voicemail, VoIP, VoIP to PSTN gateway, conference server (max 200 voice channels per conference), call centre server, prepaid and postpaid cards Deployed on home servers and large networks with millions of users 5.5; May 2015; 3 years ago (2015-05)

Secure VoIP software[edit]

VoIP software with client-to-client encryption[edit]

The following table is an overview of those VoIP clients which provide end-to-end encryption.

Client name Development status Open source client End-to-end authentication[a] Encryption protocols Forward secrecy Multiple encryption Encrypted group calling Proxy, Tor
ZRTP ECDH DTLS SRTP
FaceTime Active No[71] No[71] ? ? ? ? Yes[71] ? No No
Google Duo Active No No ? ? ? ? ? ? No No
Jitsi[b] Active Yes Yes[71] Yes No Yes Yes Yes[71] Yes Yes ?
Line[72][73] Active No ? ? ? ? ? ? ? No[72] No
Linphone[b] Active Yes Yes Yes ? Yes Yes Yes Yes ? No
PGPfone Abandonware Viewable source[74] Yes ? ? ? ? ? ? ? ?
Signal Active Yes Yes[71] No Yes No Yes Yes[71] Yes No Depends[75]
Silent Phone Active Viewable source[76] Yes[71] Yes ? ? Yes Yes[71] Yes Yes No
Telegram Active Yes Yes[77] No No No No Yes ? No No
Threema Active Partially[c][78] Yes[79] No Yes[79] Yes[79] Yes[79] Partially[d][79] Yes No No
Viber[41] Active No ? ? ? ? ? ? ? ? No
WhatsApp Active Partially[c][80] Yes[80] No Yes[80] No Yes[80] Yes[80] Yes[80] No No
Wire Active Yes Yes[81] No ? Yes[46] Yes[46] ? Yes Yes No
Zfone Abandonware Viewable source[82] Yes Yes Optional[83] ? Yes[84] Yes Yes ? ?

VoIP software with client-to-server encryption[edit]

The following table is an overview of those VoIP clients which provide client-to-server encryption.

Client name Encryption protocols
Google Hangouts[71] SRTP[85]
Skype[71] A custom protocol
Notes
  1. ^ End-to-end authentication protects communications from man-in-the-middle attacks by the service provider.
  2. ^ a b Only if the user has registered with a compatible SIP provider. Some SIP providers do not support certain encryption protocols.
  3. ^ a b Only the encryption related source code is open.
  4. ^ Only on the network connection, not on the end-to-end layer.

See also[edit]

References[edit]

  1. ^ a b "Skype Connect..." skype.com. Microsoft Corporation Inc. Archived from the original on 2014-11-11. Retrieved 15 November 2014. 
  2. ^ "Download Blink". Blink Project's Website. Retrieved 22 June 2016. 
  3. ^ "Release Notes for Cisco IP Communicator 8.6.6". Cisco. Retrieved 2018-04-03. 
  4. ^ "Cisco IP Communicator 8.6". Cisco. Retrieved 2018-04-03. 
  5. ^ "Discord on Twitter". Twitter. Retrieved 2016-12-29. 
  6. ^ "Ekiga 4.0.1 [STABLE] available". www.ekiga.org. 21 February 2013. Retrieved 2014-05-09. 
  7. ^ "Telepathy Q&A from the Boston GNOME Summit". Retrieved 4 February 2014. 
  8. ^ "ANNOUNCE: Empathy 3.12.12". 13 May 2016. Retrieved 17 August 2016. 
  9. ^ Eyeball Chat 3.2 Features. EyeballlChat.com.
  10. ^ "Chrome Web Store Hangouts". Retrieved July 11, 2013. 
  11. ^ "Telephony with Lotus Sametime software". IBM.com. Retrieved 2010-02-16
  12. ^ "Jitsi (SIP Communicator) Android — Nightly Builds Index". Jitsi.org. Retrieved 2014-11-15. 
  13. ^ Interview with Emil Ivov, Deploy360 blog
  14. ^ "[#JITSI-1166] P2P IPv6 calls still do not work with explicit IPv6 addresses, no matter if brackets are used — Java.net JIRA". Java.net. Retrieved 2014-02-13. 
  15. ^ "Kiax open source project."
  16. ^ "Kiax - an IAX Softphone"
  17. ^ Release history on Phoner download page
  18. ^ Changelog on PhonerLite download page
  19. ^ "Supported Codecs". qutecom.org. Retrieved 19 December 2014. 
  20. ^ "Announcement: QuteCom 2.2.1". Archived from the original on 2 April 2013. 
  21. ^ http://opensourceforu.com/2017/06/microsoft-retire-skype-linux-app-july-1/
  22. ^ "What's new in Skype for Windows 10?". Skype Support. 
  23. ^ a b "Download Skype". Skype. Microsoft. Retrieved 20 May 2018. 
  24. ^ a b c "Release Notes for Skype for Desktop, Mac and Linux". Skype Support. 
  25. ^ "skypeforlinux package". Microsoft. Retrieved 29 April 2018. 
  26. ^ "Skype". APKMirror. Retrieved 29 April 2018. 
  27. ^ a b "Release Notes for Skype on Mobile". Skype Support. 
  28. ^ "Skype for iOS". iTunes. Apple Inc. Retrieved 29 April 2018. 
  29. ^ "New TeamSpeak3 Client and Server released today". TeamSpeak Systems GmbH. Retrieved 2015-08-04. 
  30. ^ "TeamViewer overview". GetApp. 
  31. ^ "TeamViewer". Softpedia. SoftNews. 4 April 2018. 
  32. ^ "TeamViewer for Mac". Softpedia. SoftNews. 21 March 2018. 
  33. ^ "TeamViewer". Softpedia. SoftNews. 24 February 2017. 
  34. ^ "TeamViewer". GooglePlay. Google. Retrieved 24 February 2018. 
  35. ^ "TeamViewer: Remote Control". App Store. Apple. Retrieved 18 December 2017. 
  36. ^ "TeamViewer: Remote Control". Windows Store. Microsoft. Retrieved 18 December 2017. 
  37. ^ "TeamViewer: Remote Control". BlackBerry World. BlackBerry Limited. Retrieved 18 December 2017. 
  38. ^ "TeamViewer". Chrome Web Store. Google. Retrieved 18 December 2017. 
  39. ^ Brad Chacos, Brad. "Hands on with Viber's new desktop app: It's no Skype". www.pcworld.com. IDG Consumer & SMB. Archived from the original on 2014-07-25. Retrieved 15 November 2014. If you don’t have Viber on your phone and try to install the service on your PC, the app will redirect you to its website and ask you to install Viber on your phone first. 
  40. ^ Viber Unveils Desktop App
  41. ^ a b Lunden, Ingrid (19 April 2016). "Viber adds end-to-end encryption and hidden chats as the messaging app privacy wave grows". TechCrunch. AOL Inc. Retrieved 12 July 2016. 
  42. ^ Viber Media S.à r.l. (13 June 2017). "Viber - Android Apps on Google Play". Google Play. Google. Retrieved 19 June 2017. 
  43. ^ Viber Media, Inc (13 June 2017). "Viber On the App Store on iTunes". App Store. Apple. Retrieved 19 June 2017. 
  44. ^ Viber Media (2018-04-26). "Viber". Windows Phone Marketplace. Retrieved 2018-04-26. 
  45. ^ Viber Media (23 April 2014). "Viber 10 - BlackBerry World". BlackBerry App World. Research In Motion (RIM). Retrieved 20 April 2016. 
  46. ^ a b c "Wire Security Whitepaper". Wire Swiss GmbH. Retrieved 13 April 2016. 
  47. ^ "Wire on Twitter". Twitter. Retrieved 2017-02-28. 
  48. ^ "Google Duo". APKMirror. Android Police. March 11, 2018. Retrieved March 11, 2018. 
  49. ^ "Google Duo - Video Calling". App Store. Apple Inc. March 11, 2018. Retrieved March 11, 2018. 
  50. ^ "JAJAH.Mobile Web" Archived 2009-06-29 at the Wayback Machine.. Jajah.com.
  51. ^ a b c Marlinspike, Moxie (14 February 2017). "Video calls for Signal now in public beta". Open Whisper Systems. Retrieved 22 March 2017. 
  52. ^ a b Marlinspike, Moxie (13 March 2017). "Video calls for Signal out of beta". Open Whisper Systems. Retrieved 22 March 2017. 
  53. ^ Marlinspike, Moxie (21 December 2016). "Doodles, stickers, and censorship circumvention for Signal Android". Open Whisper Systems. Retrieved 22 March 2017. 
  54. ^ Marlinspike, Moxie (1 November 2016). "Signal and GIPHY". Open Whisper Systems. Retrieved 22 March 2017. 
  55. ^ Open Whisper Systems (3 May 2018). "Signal – Private Messenger". Google Play. Google. Retrieved 12 May 2018. 
  56. ^ Open Whisper Systems (8 June 2018). "Signal - Private Messenger". App Store. Apple. Retrieved 15 June 2018. 
  57. ^ Open Whisper Systems (14 June 2018). "Releases - WhisperSystems/Signal-Desktop". GitHub. Retrieved 15 June 2018. 
  58. ^ "WhatsApp Encryption Overview – Technical white paper" (PDF). WhatsApp Inc. 4 April 2016. Retrieved 9 April 2016. 
  59. ^ WhatsApp Inc. (2017). "WhatsApp Messenger". App Store. Apple. Retrieved 19 January 2018. 
  60. ^ WhatsApp Inc. (4 August 2017). "WhatsApp Messenger". APKMirror. Android Police. Retrieved 27 October 2017. 
  61. ^ WhatsApp Inc. "WhatsApp Messenger". Windows Store. Microsoft. Retrieved 7 April 2018. 
  62. ^ WhatsApp Inc. "WhatsApp for Nokia S60". whatsapp.com. WhatsApp Inc. Retrieved 4 April 2017. 
  63. ^ WhatsApp Inc. (26 June 2017). "WhatsApp Messenger". BlackBerry World. BlackBerry. Retrieved 7 August 2017. 
  64. ^ "Pocket PC SIP Softphone". Counterpath.com.
  65. ^ "Recommended Pocket PCs". Counterpath.com.
  66. ^ http://www.mod-gadget.com/upptalk-app-updated-ipad/
  67. ^ "yuilop - Free texts and SMS". Amazon. Retrieved 10 March 2014. 
  68. ^ "Asterisk Commercial Licensing". Digium. Retrieved 12 October 2013
  69. ^ "ChangeLog-15-current". Retrieved 12 June 2018. 
  70. ^ "ChangeLog-13-current". Retrieved 12 June 2018. 
  71. ^ a b c d e f g h i j k "Secure Messaging Scorecard. Which apps and tools actually keep your messages safe?". Electronic Frontier Foundation. 4 November 2014. Retrieved 11 July 2016. 
  72. ^ a b ""Letter Sealing" End-to-End Encryption Indicator Icon Introduced to LINE Messaging App". Line Corporation. 10 August 2016. Retrieved 29 September 2016. 
  73. ^ Shin, Ki Bin (11 August 2016). "The next step for even safer messaging: Letter Sealing". Line Corporation. Retrieved 30 September 2016. 
  74. ^ "PGPfone". pgpi.org. n.d. Retrieved 26 August 2016. 
  75. ^ Marlinspike, Moxie (13 March 2017). "Video calls for Signal out of beta". Open Whisper Systems. Retrieved 30 March 2017. 
  76. ^ "Is Silent Phone open source?". silentcircle.com. Silent Circle. n.d. Retrieved 26 August 2016. 
  77. ^ "Voice Calls: Secure, Crystal-Clear, AI-Powered". Telegram. 30 March 2017. Retrieved 30 March 2017. 
  78. ^ "Where can I find Threema's source code?". threema.ch. Threema. n.d. Retrieved 30 October 2017. 
  79. ^ a b c d e "Threema cryptography whitepaper" (PDF). threema.ch. Threema. n.d. Retrieved 30 October 2017. 
  80. ^ a b c d e f "WhatsApp Encryption Overview – Technical white paper" (PDF). WhatsApp Inc. 4 April 2016. Retrieved 5 April 2016. 
  81. ^ "A major upgrade to calling". Medium. Wire Swiss GmbH. 14 March 2017. Retrieved 14 March 2017. 
  82. ^ "Is Zfone open source?". zfoneproject.com. Zfone. 2006. Retrieved 26 August 2016. 
  83. ^ "Do you support Elliptic Curve Diffie-Hellman?". zfoneproject.com. Zfone. 2006. Retrieved 26 August 2016. 
  84. ^ "Why do we need ZRTP if we already have SRTP? Isn't SRTP good enough?". zfoneproject.com. Zfone. 2006. Retrieved 26 August 2016. 
  85. ^ https://support.google.com/hangouts/answer/6046115

 

goava Low Cost VoIP Calls