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Team 5

A Survey of VoIP: Now and Future

Bo Cao, Liang Shen


This project is to introduce VoIP. Broadband is a faster way for you to gain access to the internet, it offers high-speed internet access. Due to the increase in broadband, many new applications have been created with enormous benefits to users. The most prominent example of how broadband has resulted in innovative new services is the development of VoIP (Voice over Internet Protocol). VoIP, also known as IP telephone, which is real time transmission of voice signals using internet protocol over public internet or a private network. VoIP is a protocol optimized for the transmission of voice through the internet. It allows high quality two-way voice transmission over broadband connections [9].


VoIP has been a subject of interest almost since first computer network. The technology for transmitting voice conversations over the internet has been available to end-users since at least the early 1980s. VoIP basically has two major supporting technologies, voice which refers to telephone, and internet.

VoIP Image 1

Fig 1 [10]

A. Telephone

Since Alexander Gram Bell and Elisha Gray invent telephone in 1870s, a series of evolution occurred including the use of switch to connect one line to any of hundreds of lines by using relays and sliders; the creation of transistor, and etc. The technologies grow geometrically. In 1963, AT&T used Dr. Shannon’s idea created Touch tone dialing which allowed calls to be switched to digital [11].

B. Internet

Meanwhile, internet was first developed by Advanced Research Projects Agency Network. Besides telephone and internet, Transmission Control Protocol / Internet Protocol (TCP/IP) were also a key technology tribute to VoIP, which was invented by Dr. Vint Cerf in 1972 . It defines the form of network data packets and the way they travel from beginning point to destination. Everything needed was ready.

C. Combination of Technologies

The first internet phone software released by a small company called Vocaltec in February 1995 open a new history of technology. The VoIP software called Internet Phone was designed for home PC just like the PC telephone today, which combines the functionality of microphone, sound card, and speaker. It used H.323 protocol instead of SIP protocol which is widely used worldwide today. However, due to the lack of broadband availability at that time and the modems supported the software result in poor quality of voice compare to normal telephone.

VoIP Table

Fig 2 [10]

D. Growth of VoIP

VoIP traffic had grown slowly by 1% of the America’s voice traffic in 1998. Corporations were trying to develop devices that enabled PC to phone and phone to phone communication. Cisco for example introduced a device allow route and switch the VoIP traffic and increased the total voice traffic to 5% by 2000. In 2003, the average consumer probably did not understand the difference of a telephone call over the internet versus a call over traditional methods. In fact, back then, the public switched telephone circuit probably sounded better because it had been around for a long time. The idea of sound moving as tiny packets of data over the Internet was only interesting to the engineers; most people did not really care [12].

A year later, in 2004, mass market VoIP was introduced that utilizes the existing broadband Internet Access of the users. The sells on VoIP industry begin to grow in a phenomenal way from $3 billion in 2005 up till $8.5 billion in 2008 due to the more matured technology which resolve the problem of voice quality that has been addressed by prioritized VoIP traffic over data traffic to ensure reliable, clear and unbreakable phone calls.

E. How to get VoIP service?

It is very convenient to get VoIP services nowadays, VoIP service provider will provide a piece of equipment called Analog Telephone Adaptor (ATA), which does clear conversion of the analog voice to a digital signal internet can read and send that signal on the broadband modem which pass it over the internet. Below is a typical structure of the network.

VoIP Image 2

Fig 3 [12]

It also works if multiple phones or computers are in one home. Cordless phone is usually used for multiple phones. The base station of cordless phone plugs into ATA then the additional handsets can be put anywhere at home. Multiple computers only need to connect a router to ATA instead of the computer in the graph above, so that the computer is connected to the router.

F. Advantage and Disadvantage

People always think twice or more before purchase anything, cost is the first and foremost factor in everything, which makes VoIP very competitive due to its’ low fee. And even better for internet based phone calls no taxes are charged, not to mention those unexplained taxes or regulatory fees often shows on a phone bill. The table below shows an example of services and the price.

VoIP Most Popular Residential Providers

Fig 4 [14]

Another advantage is that VoIP also support long distance and international calls in a much cheaper price.

One minor disadvantage need to be address is that since VoIP relies heavily on broadband connection, power outage could cause the disconnection of the network and the phone goes down as well. However, it is not a problem for those who owns a cell phone.

Subscribers to the services could use to make phone calls over the internet in much the same way that they would over a telephone. This often included cheap rates to international countries, which made it more popular in America, a land of many nations.

Current Status

The success of new technologies in the market depends, in part, on consumers finding the technology offerings relevant to their needs. The new technology of Voice over IP takes advantage of Broadband internet to provide consumers in the telephony market with access at lower costs. Various providers such as Net2phone,, and are applying Voice over IP to the consumer telephony market. With Voice over IP, the voice data is digitized, compressed, packetized, and sent over the Internet to the destination computer. This method is considerably cheap than that of traditional telephones, and was as low as 4 cents a minute for calls in the US back in 2001 [1]. Voice over IP also provides considerable savings when making international calls. In 2001, a phone-to-phone call from US to Mexico costs $2.00 a minute by traditional methods and 16 cents on the internet.

A. Wireless Internet telephony

Wireless Internet telephony, another name for Voice over IP that has become popular in reports, has grown steadily throughout the decade. From a report by the Yankee Group, a market research firm, growth of wireless Internet telephony has been reported. At the end of 2003, only 130,000 subscribers existed in the market. By 2008, 17.5 million subscribers have started to use wireless Internet telephony. Another reason for the transition from traditional methods is that providers are offering users the technology on their phones now. Before this technology became popular, one can only contact other people by computer using Voice over IP. With the advancement of technology, the mobile phone can only make wireless Internet telephony calls through the IEEE 802.11 (WiFi) wireless LAN and 3G cellular technologies. Wireless Internet telephony is less expensive than the regular mobile telephony because it uses an existing infrastructure, the Internet, instead of building a new one to route calls. The government has also not yet imposed regulations and fees regarding wireless Internet telephony, which makes it even more attractive [3].

Internet telephony has several many concerns: power usage, security, and quality of service (QoS). In the traditional sense, wireless Internet telephony is the standard wireline IP telephony adopted over the Internet. However, even though wireless IP telephony works primarily through WiFI, it has alternative routes available to it. Phones that have part of the call that travel over cellular network and the other part traveling over WiFi have already been developed. Wireless Internet telephony users can now communicate with traditional mobile users wherever they have Internet.

B. WiFi

In WiFi telephony, companies equip their mobile handset with an IEEE 802.11 radio. These phones, when in range of a WiFi access point, which are readily available throughout the world, use IEEE 802.11 to connect to the Internet and then transmit their voice traffic over it.

There are several WiFi standards that are available to telephony. The most popular method is still IEEE 802.11b, which has a theoretical maximum data rate of 11 Mbits per second while using the 2.4 GHz frequency band. The 802.11a has a theoretical maximum rate of 54 Mbps using the 5 GHz band.

In 2003, the 802.11g was proposed. 802.11g uses the same 2.4 GHz band as the b, but uses the same OFDM based transmission scheme as 802.11a. 802.11g has a maximum physical layer bit rate of 54 Mbps exclusive of forward error correction codes, and comes out to about 22 Mbps average throughput. The best and worst parts about 802.11g is the same, that it is fully backwards compatible with 802.11b hardware. The good portion of it is that consumers do not need to replace much of the hardware to change to the 802.11g standard, the bad part is that because of the compatibility, it is encumbered with legacy issues that tends to reduces the output of the standard by about 21% when compared to 802.11a.

Data transfer rates has been steadily increasing in the recent years, and the 802.11 standard had to evolve with it. In 2009, the IEEE 802.11n was released. This standard increased the maximum rate data from 54 Mbps to 600 Mps with the use of four spatial streams at a channel width of 40 Mhz. The 802.11n standard adds multiple-input multiple-output(MIMO) antennas to coherently resolve large quantities’ of information.

One of the way MIMO works is by using Spatial Division Multiplexing (SDM). SDM multiplexes several individual data streams that are transferred simultaneously in a single spectral channel of bandwidth. As the number of resolved spatial data streams is increased, the data throughput is increased. Each of the streams requires a separate antenna at both the transmitter and the receiver. Also, MIMO requires a separate radio frequency chain and analog to digital converts for each antenna which does mean higher implementation costs.

The 40 MHz channels used in the 802.11n is also double the channel width from the 20 MHz used previously in the 802.11a-802.11g standards. The doubling of the data rate can be enabled in the 5 GHz mode or in the 2.4 GHz mode if there is no interference from other systems such as the lower 802.11 standards and Bluetooth devices. All of this together allows a greater than 10 times increase in the raw data rate from the 802.11n to previous incarnations of 802.11 [7].

C. Concerns

In addition to the promises that wireless Internet telephony brings, it has raised several important concerns. The relatively new Wi-Fi internet phones are still expensive to consumers. Prices are, however, dropping rapidly
amount of power that the phones use is also a concern. The battery life of a mobile phone versus that of a computer is very small, and the radio transmissions of WiFi phones uses considerable power. This power usage would necessitate a large phone to accommodate the larger battery, when the customer demand is for a smaller phone.

D. Security

As with any technology, Internet telephony raises concerns about security. An example of this is the authentication approach that determines whether the person accessing the system is who they say they are. These authentications are currently not very standardized, and competing technologies from vendors causes multiple system incompatibilities.

In the mean time, wireless security itself is still plagued with problems. The Wired Equivalent Privacy Protocol (WEP), used in early WiFi applications, is not nearly strong enough to perform the task. The industry has then included both WiFi Protected Access (WPA) and WPA2, based on the IEEE 802.11i wireless security standards, and uses the new Advanced Encryption Standard. However, wireless Internet telephony security requires the exchange of additional information between the sender and receiver and this will slow the data transmission rate, which will definitely affect the voice quality.

E. Quality of Service

Quality of Service (QoS) is an important issue for Internet telephony. The traditional telephony network has been around for over a century and its quality has been superb. To compete with it, wireless Internet telephony must also have good quality. Unlike other data traffic on the Internet, voice data must be transmitted in real time, and therefore must be prioritized. If the voice data is not prioritized, then the quality of the voice significantly degrades and latency becomes a huge issue.

Currently, several proprietary approaches have been proposed for the QoS of Internet telephony. The standard that was under consideration would prioritize packets based on traffic type, enabling access points to schedule resources based on transmission rates and latencies, improving bandwidth efficiency.

F. Throttling

Throttling, sometimes known as bandwidth throttling, is one of the reactive ways used in communication networks to regulate traffic and minimize bandwidth congestion.

Throttling can occur on various levels in the network. In the local area network (LAN), a web administrator may employ throttling to limit network congestion and prevent server crashes. On a wider note, the Internet Service Provider (ISP) can enable throttling to reduce a user’s bandwidth that is supplied to the network. This can be used to actively limit how much a user downloads/uploads and how fast they can do it using such programs as BitTorrent and other file sharing applications [6].

ISPs these days have resorted to the throttling because the file sharing in the developed world is out of control. Throttling is not without its share of problems however, as lawsuits over throttling has been occurring. In 2007, the Free Press and Public Knowedge, along with the Federal Communications Commission, filed a complaint against Comcast’s Internet Service. Several of Comcast’s subscribers claimed that the ISP was interfering with their use of peer-to-peer applications and was therefore violating their rights. The Commission claimed it has jurisdiction over Comcast’s networks management practices and that negotiation rather than rulemaking was preferred. In 2010, the courts decided that because the Commission had “failed to tie its assertion of ancillary authority over Comcast’s Internet service to any ‘statutorily mandated responsibility,” Comcast would be granted a review for its petition [4].

G. Disadvantages

As with all reports, VoIP has some disadvantages to it. The current disadvantages compared to regular services include:
VoIP phones depend on wall power. Whether you are using a computer with software installed or a dedicated VoIP phone, you are both relying on a wall jack while the traditional phone uses a separate line from the central office. This is why when the power goes out your phone is still available.

Many other services in your home are still integrated with regular phones only. These services include: digital video recorders, subscription TV, home security systems. As of now, most of these services cannot be integrated with VoIP systems.

Calling 911 with VoIP may cause problems. Since an ordinary phone is easily tracked by location, the police can quickly locate the caller and respond. The IP address used by a VoIP phone does not provide location and the central 911 offices do not know where to route your call or where to send the nearest emergency stations. This issue is currently under development by VoIP providers, but the solution may deprive VoIP of other benefits.

VoIP uses your internet connection and therefore all problems regarding your internet will affect it as well. Latency issues, jitter, packet loss, and disconnections may affect your VoIP experience.

As with any other information stored on a computer with an internet connection, VoIP protocols are susceptible to viruses and hackers.

VoIP depends heavily on the performance of your computer, if you run more than one program at the same time as it, your experience may be deteriorated.

All of these problems are currently being looked upon and solutions are attempted to be found by the developers of VoIP.


There is currently a large amount of software available to VoIP users. For residential markets, VoIP phone services is cheaper than the traditional public switched telephone service and can be used to remove geographic restrictions on telephone numbers, e.g. a user can have a New York number while in Tokyo. For businesses, VoIP separates data and voice and channels them through an IP network while giving the user a wide range of advanced capabilities.

Softphones are devices for making and receiving voice and video calls over the IP network with basically the same functionalities as the standard PSTN and will allow integration with IP and USB phones instead of using a computer’s headset/microphone and speak. Many softphone clients run on the open Session Initiation Protocol (SIP) that supports various codecs. Skype itself runs on a closed proprietary network through the network, but also supports SIP clients.

Other VoIP software includes conference servers, intercom systems, virtual FXOs, and adapted telephony software that support both VoIP and PSTN [8].

These are tables of available VoIP Software:

General Softphone Clients

Program Operating systems License Open Source? Protocols/based upon/compatible with Encryption Max conference peers
AOL Instant Messenger Linux, Mac OS, Windows Freeware / Closed Proprietary NO SIP (Windows ver. only), RTP Unknown Unknown
Avaya Application Server 5300 Soft Client Windows Proprietary No SIP, RTP SRTP, TLS Unkown
Blink Linux, Mac OS, Windows GPL / Free software Yes ICE, SIP, MSRP, RFB (VNC) SRTP, TLS Unlimited
Bria by CounterPath Corporationk Windows, Mac OS, Linux (Voice calling only) Proprietary No SIP, XMPP, STUN, ICE SRTP, TLS 6 party audio; 3 party video
Brosix Windows, Mac OS, Linux Freeware / Closed Proprietary No   Yes Unknown
Cisco IP Communicator Windows Closed Proprietary No   Yes Unknown
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
Empathy Linux GPL / Free software Yes SIP, XMPP (Jingle), ICE (STUN/TURN), Zeroconf No Unknown
Eyeball Chat Windows Freeware / Closed Proprietary No SIP, STUN, ICE, XMPP Yes Unknown
eyeBeam by CounterPath Corporation Windows Proprietary No SIP TLS, SRTP 6 party audio; 3 party video
Gizmo5 Linux, Mac OS X, Windows, Windows Mobile Phone, Blackberry, Nokia, PDA Java Freeware / Closed Proprietary No SIP, XMPP SRTP Unknown
Gizmo5 Linux, Mac OS X, Windows, Windows Mobile Phone, Blackberry, Nokia, PDA Java Freeware / Closed Proprietary No SIP, XXMP SRTP Unknown
Google Talk Windows Closed Proprietary (using libjingle) No XMPP ZRTP Unknown
iChat Mac OS X Closed Proprietary No SIP AIM ICQ XMPP H263 H264 Unknown Unknown
iChat Mac OS X Closed Proprietary No SIP AIM ICQ XMPP H263 H264 Unknown Unknown
Jitsi Linux, Mac OS, Windows XP/2000 (all java supported) LGPL / Free software Yes SIP/SIMPLE, XMPP Voice encryption (SRTP and negotiation with zRTP), Signaling encryption (TLS) Unknown
Jitsi Linux, Mac OS, Windows XP/2000 (all java supported) LGPL / Free software Yes SIP/SIMPLE, XMPP Voice encryption (SRTP and negotiation with zRTP), Signaling encryption (TLS) Unknown
KPhone Linux (KDE) GPL / Free software Yes SIP, STUN, NAPTR/SRV SRTP Unknown
Linphone Linux, Windows, Android GPL / Free software Yes SIP No Unknown
Lotus Sametime Linux, Mac OS X, Windows, mobile Closed Proprietary No SIP, SIMPLE, T.120 and H.323 TLSo Unknown
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 DSLR-SRTP Unknown
Mumble Linux, Mac OS X, Windows, Android BSD Yes CELT / Speex TLS and OCB-AES128 No max (limited only by server bandwidth and memory)
OctroTalk Symbian, Windows Mobile, Windows Shareware / Closed Proprietary No SIP, (XMPP, STUN, ICE, Libjingle and RTP (media) TLS and SASL Unknown
PhonerLite Windows Freeware / Closed Proprietary No SIP TLS, SRTP, ZRTP 8
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
Revation Communicator Windows 2000/XP/Vista/7 Closed Proprietary No SIP/SIMPLE TLS and SRTP No max (limited by server mixing services)
SFLphone Linux GPL3 / Free software Yes SIP, RTP, IAX2, STUN per account, SRV Voice encryption (SRTP), Signaling encryption (TLS), Multiple realms authentification mechanism Unknown
SightSpeed Mac OS X, Windows Freeware / Closed Proprietary No SIP, RTP,Proprietary P2P protocol Unknown Unknown
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[1] Yes 25 starting with version 10 with 2.x
Spikko Windows 2000/XP/Vista/7/Mobile , iPhone, Freeware / Closed Proprietary No SIP Yes 8
TeamSpeak Linux, Windows, Mac OS X Freeware Closed / Proprietary No   Yes (Optional) Unknown
Telephone Mac OS X 10.5 BSD / Free Software Yes SIP, STUN, ICE No Unknown
Tokbox Mac OS X, Windows XP/2000/Vista Freeware / Closed Proprietary No Unknown Unknown Unknown
Toktumi Unlimited / Line2 Pro Windows XP/Vista/7, Mac OS X, iOS, Android Freeware / Closed Proprietary No Proprietary with SIP core Unknown 20
Tpad Windows 2000/XP/Vista Freeware / Closed Proprietary No SIP, STUN Unknown Unknown
Tru App Windows 2000/XP/Vista/7, Mac OS X, LinuxiOS, Android, Symbian, BlackBerry OS Freeware / Closed Proprietary No SIP, XMPP Unknown Unknown
Twinkle Linux GPL / Free software Yes SIP SRTP, ZRTP Unknown
Vbuzzer Windows 2000/XP/Vista Freeware / Closed Proprietary No SIP TLS Unknown
Ventrilo Mac OS X, Windows/td> Freeware / Closed Proprietary No   No Unknown
Voice Operator Panel Windows 2000/XP/Vista Closed Proprietary No SIP, RTP Unknown Unknown
X-Lite Mac OS, Windows, (Linux) Freeware/ Closed Proprietary No SIP, STUN, ICE No Unknown
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
Zfone Linux, Mac OS X, Windows Freeware / Viewable source Proprietary (includes time bomb provision) No SIP, RTP SRTP, ZRTP Unknown

Mobile phones

Program Operating systems License Protocols/based upon/compatible with Encryption Other Capabalities Latest Release
Bria Android Edition by CounterPath Corporation Android v2.1 or later Proprietary SIP TLS, SRTP VoIP over Wi-Fi or 3G with data plan; Audio codecs G.711, G.722, iLBC and GSM, option to purchase G.729; Call display and voicemail indicator; Speakerphone, mute and hold; Three-way audio conference; Ringtones and contact avatars 1.1 (May 5, 2011)
Bria Android Edition by CounterPath Corporation AiPhone 3GS or 4 running iOS v4.0+, iPod touch 3rd Generation+, iPad compatible Proprietary SIP TLS, SRTP VoIP over Wi-Fi or 3G with data plan; Audio codecs G.711, G.722 iLBC and GSM, option to purchase G.729; Call display and voicemail indicator; Call history; Speakerphone, mute and hold; Three-way audio conference; Ringtones and contact avatars 1.2.8 (May 2011)
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 Unknown   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)
Jajah Mobile Web Symbian OS, Windows Mobile (version unknown) web based service, no download[3]   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 wifi3G or EDGE  
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[4]   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.[5] 2.2
CSipSimple Android GPL SIP SRTP / ZRTP / SIP over TLS (using special builds)    

Frameworks and libraries

Program Operating systems License Protocols/based upon/compatible with Encryption Other Capabalities Key and Target Markets Latest Release
Tapioca Linux GPL / Free software Telepathy (software) Unknown     0.3.9 (June 12, 2006)
Telepathy/Farsight Linux, Mac OS X, Windows LGPL / Free software SIP, XMPP (Jingle), ICE (STUN/TURN), UPnP Not 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 Capabalities Latest Release
3CX Phone System Microsoft Windows Closed SIP SRTP, TLS Voice and Video IP telephony, Voice and Video conferencing, voice mail and instant messaging 25,000 – 50,000 users
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
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), 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)
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
Cisco Unified Communications Manager Linux Proprietary SIP, SCCP, MGCP, H.323 SSL, TLS, SRTP SIP Registrar/Proxy, Authentication Enterprise users
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
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
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
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
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
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
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)
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
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)
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
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)
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
SIP Express Router (SER) Linux/BSD, Solaris GPL / Free software SIP   SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others… SIP Service Providers
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
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)
vzRoom Windows Closed Proprietary SIP SSL, TLS, AES Instant Messaging/Chat, VoIP, Video, Desktop Sharing, Video Sharing, whiteboard, File Sharing, scheduler, recording

These tables include the general software used in VoIP and their metrics, including: operating system, license, open source (Y/N), protocols/based upon/compatible with, encryption methods, max number of conferencing peers, key and target markets, latest released, and other capabilities.

As is shown, VoIP has a large variety of software that differs from each other greatly that is available to the end user.


VoIP is a growing tremendously and will eventually take its rightful place along normal PSTN and mobile users. It is still a relatively young technology that has a lot of potential. With the number of business that uses Voice over IP as a conferencing tool over traditional methods, its future success is certain. Regulatory issues have been raised about VoIP. The biggest challenge in VoIP is the issue of the legacy equipment. Concerns about VoIP relates to convergence.


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