Protocols

Most standards-based solutions use either the H.323 or Session Initiation Protocol (SIP) protocols. A number of proprietary designs also exist.

Signaling protocols:

Session Initiation Protocol (SIP) 

defined by the IETF, newer than H.323

H.323 

defined by the ITU-T

Megaco (a.k.a. H.248) and MGCP 

both media gateway control protocols

Skinny Client Control Protocol 

proprietary protocol from Cisco

MiNET 

proprietary protocol from Mitel

CorNet-IP 

proprietary protocol from Siemens

IAX 

the Inter-Asterisk eXchange protocol used by the Asterisk open source PBX server and associated client software

Skype 

a proprietary peer-to-peer protocol used in the Skype application

Jajah 

a proprietary peer-to-peer protocol used in the Jajah SIP and IAX compatible webphone

Several different speech codecs can be used for stream audio compression. Commonly used codecs for VoIP traffic include G.711, G.723.1 and G.729, all ITU-T-specified.

See also

Networks: Full Phone Service

• AOL TotalTalk : A U.S. and Canadian VoIP phone service provider.
• Bandwidth.com : A U.S.-based Business VoIP carrier.
• BroadVoice : A U.S.-based VoIP network.
• Cliconnect Internet Telephony : A Canadian-Brazilian based Voip Service Provider.
• Congruent IP Communications : A Canadian-based hosted VoIP services provider.
• Internode NodePhone : An Australian-based VoIP service provider.
• IXP Voice : A U.S.-based VoIP phone service provider.
• Lingo : U.S. VoIP offering of Primus Telecommunications.
• OpenWengo : A France-based VoIP Provider.
• MetroTel : A U.S.-based VoIP Provider.
• MyWebCalls : A UK-based VoIP phone service.
• Packet8 : A U.S.-based VoIP network.
• sipgate: German SIP based provider also operating in Austria and the UK
• SIPphone : A SIP-based VoIP network.
• SunRocket : A U.S.-based VoIP phone service provider.
• TheGlobe : A U.S.-based Voice over Internet Protocol communications company.
• TeleCable Services : A U.S.-based VoIP phone service provider.
• Telio : A Norwegian-based VoIP phone service provider
• TexVoIP : Italian VoIP phone service provider
• VoicePulse : A U.S.-based VoIP phone service provider
• Vonage : A U.S.-based VoIP phone service provider
• Verizon VoiceWing : Verizon's version of VoIP
• VoIP User : A UK based free SIP based network with a community funded PSTN gateway
• Voxbone : A EU based provider of worldwide VoIP virtual numbers

Networks: Software Service

• Camfrog : Camfrog Video Chat uses a proprietary system with instant messaging to do multi-user audio and video.
• FWD (formerly Free World Dialup) : A free SIP-based VoIP network.
• Gizmo_Project : Gizmo Project uses your internet connection (broadband or dial-up) to make calls to other computers, phones and mobiles.
• Paltalk : A proprietary freeware VoIP system which uses a messenger-like client for video, voice and text chat. Also offers interoperable #REDIRECT Instant Messenger (IM) with #REDIRECT AOL/AIM, #REDIRECT Yahoo Messenger, #REDIRECT MSN Messenger and #REDIRECT ICQ using the Paltalk client.
• PeerMe : A proprietary freeware VoIP system which uses a messenger-like client.
• Skype : A proprietary freeware VoIP system which uses a messenger-like client.
• SIP Broker : One of the biggest free VoIP peering and ENUM services.
• Teleo : A VoIP network using a P2P model
• TelSIP : A European-based VoIP using SIP.
• TheGlobe : A proprietary freeware VoIP plugin which adds a messenger-like client to your browser.
• Vbuzzer : A SIP-based VoIP service with low cost access to conventional PSTN network.
• Chattercube : The worlds first Peer-to-Peer VoIP network.

Hardware: Wi-Fi Phone

• UTStarcom F1000: a wi-fi SIP handset

Software

• Asterisk PBX : The popular Linux-based open source software PBX switch. It is known to compile and run on GNU/Linux for PPC along with OpenBSD, FreeBSD, and Mac OS X Jaguar.
• GameComm, Roger Wilco, Teamspeak, and Ventrilo : Voice communication programs popular in online gaming.
• Gizmo : A freeware VoIP client using SIP with Jabber protocol support.
• Google Talk : A free VoIP system from Google.
• Ekiga : The popular Linux-based open source softphone which supports a wide variety of video and audio codecs. Version 1 supported only H.323, while version 2 supports H.323 and SIP.
• KCall is an open source Linux softphone using Qt toolkit libraries.
• MSN Messenger
• IP Multimedia Subsystem : architectural model (with several SIP extensions), used by the traditional telecommunications industry to develop systems to replace the current circuit switched network with a NGN network.
• Jajah : A freeware VoIP client with free videotelephony, chat, text messaging, voicemailbox and is compatible to SIP, Skype, Gizmo and IAX/H.323
• OpenH323 : An implementation of the H.323 protocol released under the MPL license. It is used as the basis of several other VoIP applications including Ekiga and GnuGK. A new version of OpenH323 called OPAL is available that supports both H.323 and SIP
• OpenWengo : Voip-application published under GNU GPL license
• PhoneGaim : A free VoIP system based on Gaim and SIP.
• PeerMe : A proprietary freeware VoIP system which uses a messenger-like client.
• ReSIProcate : A robust and feature-rich open source SIP stack.
• SIP Express Router (SER) : Fast, scalable, free SIP server.
• SIMPLE : An instant messaging and presence protocol based on SIP.
• sipX : The popular open source SIP PBX, native SIP call control, many features, Web management, and fully standards-compliant
• SJphone : SJphone is a popular free SIP/H.323 softphone that many services use.
• Skype : Skype is a free VoIP client that offers in and outbound PSTN facilities. It is closed source and is based on a closed protocol.
• *starShop-OSS : Open Source professional and powerful billing and management system based on Asterisk PBX for Calling Shops and Internet cafes.
• Tivi : A SIP VoIP client softphone.
• TERAVoice Server - TERAVoice VoIP Gateway
• Vbuzzer : Vbuzzer Softphone is a proprietary freeware to be used in conjunction with Vbuzzer Internet telephone service.
• Yahoo! Messenger
• YATE : A GPL (free) software VoIP telephony engine (VoIP server and client for H.323,IAX,SIP) for Windows and Linux

VoIP Testing

TestYourVoIP 

A free VoIP quality test website (requires a Java-enabled Web browser).

VOIP Test Equipment Vendors

• Agilent
• Empirix
• Shenick Network Systems
• Spirent

Related concepts

• Computer conferencing
• Differentiated services
• Integrated services
• Predictive dialers

External links and research sources

• FCC VoIP Information from the FCC
• DMOZ listing of VoIP web sites
• Sicker, Lookabaugh and Ryan's law-review article discussing various technical and policy issues related to VoIP

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• Multichannel Merchant

Jupiter Research [1] The Kelsey Group [2] Google [3] Forrester Research [4] 1 to 1 Media [5]