Skype

An Internet telephone and video calling service from Skype Limited, Luxembourg www.skype.com). Being software based, calls from Skype subscribers originate from their computers, and all computer-to-computer calls between subscribers are free, including video calls. Access to regular telephones is also available. With "SkypeOut," users dial a regular telephone for a low per-minute charge. "SkypeIn" lets people worldwide call a Skype subscriber from a regular telephone by dialing a local Skype phone number. See softphone.

Explosive Growth

Introduced in July 2004, within a year, more than a hundred million people downloaded the software. In the fall of 2005, Skype claimed 40 million active users and was acquired by eBay for $2.6 billion. By late 2008, an average of 10 million users were using Skype simultaneously. In 2009, Skype was acquired by private investors with eBay retaining a major equity position.

Supernodes

Rather than using standard voice over IP (VoIP) protocols such as SIP and H.323, Skype uses proprietary protocols that incorporate a peer-to-peer architecture. If Skype cannot make a direct connection from one user to the other, it may elicit one of its users who has the Skype application loaded to become a "supernode" and relay the call. Only a fraction of the millions of Skype users become supernodes at any given time. See supernode.

Portable Skype Phones

Similar to a cordless phone, a Skype telephone is portable and frees subscribers from being tethered to their PCs. It transmits wireless to a base station that plugs into the PC via USB or into a free port on a network router. In addition, there are adapters that let existing desk and portable phones make regular phone calls and Skype calls. The user's phone plugs into the adapter, which plugs into both the PC and the telephone jack on the wall.

Skype (pronounced /ˈskaɪp/) is a software application that allows users to make voice calls over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system. Skype has also become popular for its additional features which include instant messaging, file transfer, and video conferencing.

Skype was developed by Estonian developers Ahti Heinla, Priit Kasesalu and Jaan Tallinn, who had also originally developed the peer-to-peer file sharing software Kazaa.^[1]

Skype Limited, the company that operates Skype, was founded in 2003 by Niklas Zennström and Janus Friis with headquarters in Luxembourg.

eBay acquired Skype Limited in September 2005 and in April 2009 announced plans to spin it off in a 2010 IPO.^[2][3]

Contents [hide] 1 Features 2 Client applications and devices 3 Origin of the name 4 History 5 Usage and traffic 6 System and software 7 Privacy 7.1 Service in People's Republic of China 8 Customer service 9 See also 10 References 11 External links

Features

Main article: Features of Skype

Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory.^[4] Skype allows these registered users to communicate through both instant messaging and voice chat. Voice chat allows calls between pairs of users and conference calling, and uses a proprietary audio codec. Skype's text chat client allows group chats, emoticons, storing chat history, offline messaging and (in recent versions) editing of previous messages. The usual features familiar to instant messaging users — such as user profiles, online status indicators, and so on — are also included.

The SkypeIn service allows Skype users to receive calls on their computers dialed by regular phone subscribers to a local Skype phone number; local numbers are available for Australia, Brazil, Chile, Colombia, Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Italy, Japan, Mexico, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, the Netherlands, the United Kingdom, and the United States.^[5][6] A Skype user can have local numbers in any of these countries, with calls to the number charged at the same rate as calls to fixed lines in the country.

Video conferencing between two users was introduced in January 2006 for the Windows and Mac OS X platform clients. Skype 2.0 for Linux, released on March 13, 2008, also features support for video conferencing.^[7] Version 5 beta 1 for Windows, released 13 May 2010, offers free video conferencing with up to 5 people.^[8]

Skype for Windows, starting with version 3.6.0.216, supports "High Quality Video" with quality and features, e.g., full-screen and screen-in-screen modes, similar to those of mid-range videoconferencing systems.^[9] Skype audio conferences currently support up to 25 people at a time, including the host.

A discontinued feature called "Skypecasting" allowed recordings of Skype voice over IP voice calls and teleconferences to be used as podcasts, which allow audio or video content to be syndicated over the Internet. Skype launched its "Skypecasts Beta" service in 2006. It remained in beta until its end. Skypecasts hosted public conference calls, up to 100 people at a time. Unlike ordinary Skype p2p conference calls, Skypecasts supported moderation features suitable for panel discussions, lectures, and town hall forums. Skype operated a directory of public Skypecasts.

On August 26, 2008, Skype announced that Skypecasts would be discontinued beginning September 1, 2008.^[10] Skypecasts were shut down without any concrete explanation on 1 September 2008 at 12:00 UTC. In late 2009 the company Skype for Power Gamers announced that in Q2 2010 it would be releasing both a client and server Skype Add-on that will enable Skype end-users to host their own "Skypecast-like" auto-conference rooms.

Skype does not provide the ability to call emergency numbers such as 911 in the United States and Canada, 111 in New Zealand, 000 in Australia, 112 in Europe, or 999 in the UK.^[11] The U.S. Federal Communications Commission (FCC) has ruled that, for the purposes of section 255 of the Telecommunications Act, Skype is not an "interconnected VoIP provider".^[12] As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.^[13]

Client applications and devices

Skype runs on a number of platforms, and on October 29, 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.^[14] Other platforms officially supported include:

• Around 50 mobile phones, as of 2008^[15]
• The Nokia N800, N810 and N900 Internet Tablets, which use the Maemo environment
• Both the Sony mylo COM-1 and COM-2 models
• The PlayStation Portable Slim and Lite series, though the user needs to purchase a specially-designed microphone peripheral. The PSP-3000 has a built in microphone which allows communication without the Skype peripheral.^[16] PSP Go has the ability to use Bluetooth connections with the Skype application, in addition to its built-in microphone.^[17]
• Mobile devices running Windows Mobile;^[18] in February 2010, Skype announced its decision to discontinue development Skype for Windows Mobile.^[19]In May 2010, Skype announced it would not develop a version of Skype for Windows Phone 7.^[20]
• Symbian; a limited beta was announced on December 10, 2009, and was available for several different Nokia phones^[21]
• The X-Series together with mobile operator 3. However this uses a regular mobile phone call and iSkoot^[22] to a Skype gateway, rather than mobile Internet. Other companies produce dedicated Skype phones which connect via WiFi
• iPhone OS, using an official application released on March 31, 2009.^[23] Skype also claims to have a 3G version of the application ready to enter the App Store approval process.^[24] However, some network operators do not allow Skype calls to be made over their 3G network, restricting it to WiFi use only^[25]
• A variety of Verizon Wireless BlackBerry® and Android™ 3G Smartphones, through Verizon's Skype mobile™ service. Skype is ‘always on’, meaning customers can receive Skype calls, instant messages and see friends’ presence any time the phone is on. Skype usage isn't charged against customers’ monthly Verizon Wireless minute allowance when calling another Skype account (Skype-to-Skype). Customers in the US use minutes from their calling plan when calling US land lines or cell phones.^[26]

Recently a number of manufactures have launched hardware devices compatible with Skype. These are usually either tethered to a PC, or have a built-in Wi-Fi client to allow calling from Wi-Fi hotspots like the Netgear SPH101 Skype Wi-Fi Phone, the SMC WSKP100 Skype Wi-Fi Phone, the Belkin F1PP000GN-SK Wi-Fi Skype Phone, the Panasonic KX-WP1050 Wi-Fi Phone for Skype Executive Travel Set, the IPEVO So-20 Wi-Fi Phone for Skype and the Linksys CIT200 Wi-Fi Phone. There are also embedded cordless Skype phones based on DECT, which do not need a PC either, like the DUALphone 3088 from RTX. Netgear and SMC's Wi-Fi phones are considered the two major competitors in the market, with reviews of the Wi-Fi phones giving them equal coverage.

The Skype Wi-Fi Phone is a wireless mobile phone that allows users to make free Internet calls to anyone who has Skype, anytime there is a Wi-Fi wireless Internet connection. The Skype Wi-Fi Phone has an on-screen menu that lets Skype users see who is online and available to talk, similar to what is seen on a PC. It can also be used to talk with non-Skype users. SkypeOut minutes can be used to call any phone for a low price and no monthly fee. The Skype Wi-Fi phone does not contain a web browser therefore can not access hotspots, which require web-based login or authentication.^[27]

Third party developers, such as Nimbuzz and Fring, have allowed Skype to run in parallel with several other competing VoIP/IM networks (Nimbuzz has even NimbuzzOut as competing paid service) in any Symbian or Java environment. Nimbuzz has made Skype available to BlackBerry users.

Origin of the name

One of the initial names for the project was "Sky peer-to-peer", which was then abbreviated to "Skyper". However, some of the domain names associated with "Skyper" were already taken. Dropping the final "r" left the current title "Skype", for which domain names were available.^[28]

History

This section may need to be wikified to meet Wikipedia's quality standards. Please help by adding relevant internal links, or by improving the section's layout. (April 2010)

• September 2002 — investment from Draper Investment Company and at that time, original name was Skyper.^[29]
• April 2003 — Skype.com and Skype.net domain names registered.
• August 2003 — First public beta version released.
• September 2005 — SkypeOut banned in South China.^[30]
• October 2005 — eBay purchased Skype (Oct 14).^[31]
• December 2005 — videotelephony introduced.^[32] In April 2006, Number of registered users reaches 100 million.
• October 2006 — Skype 2.0 for Mac is released, the first full release of Skype with video for Macintosh.
• December 2006: Skype announces a new pricing structure as of January 18, 2007, with connection fees for all SkypeOut calls.^[33] Skype 3.0 for Windows is released.^[34]
• In March 2007 — Skype 3.1 is released, adding some new features, including Skype Find and Skype Prime. Skype also released a 3.2 beta with a new feature called Send Money which allows users to send money via PayPal from one Skype user to another.
• August 2007 — Skype 3.5 for Windows released with additions such as video in mood, inclusion of video content in chat, call transfer to another person or a group, auto-redial.
• August 15, 2007 — Skype 2.7.0.49 (beta) for Mac OS X released adding availability of contacts in the Mac Address Book to the Skype contact list, auto redial, contact groups, public chat creation, and an in-window volume slider to the call window.
• August 16 / August 17, 2007 — Skype users unable to connect to full Skype network in many countries.^[35] Skype reports the system-wide crash was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").^[36]
• November 2007 — the controversial move was announced that Skype users having London (020) 7 numbers would lose them after December 20, 2007.^[37]
• January 30, 2008 — Skype released for the Sony PSP hand-held gaming system.
• March 13, 2008 — Skype 2.0 for Linux released with support for videoconferencing.
• July 9, 2008 — Skype 4.0 Beta is released, changing Skype into a full-screen application.^[38]
• September 1, 2008 — Skype discontinues its SkypeCast service, without explanation.
• September 8, 2008 — The seventh season of the U.S. syndicated game show Who Wants To Be a Millionaire premieres, with a new Ask the Expert lifeline that uses Skype for video chat.
• September 30, 2008 — Skype 4.0 Beta 2 released, introducing 'Compact mode', after user criticism of the new default full-screen mode.^[39]
• October 2, 2008 — Analysis reveals TOM-skype sends content of text messages and encryption keys to monitoring servers.^[40]
• November 2008 — Skype added internal monthly and daily usage caps on their SkypeOut subscriptions advertised as "Unlimited". Many users and observers have commented on the high rate of dropped calls, and the difficulty of reconnecting dropped calls. These are most common for video calls and free (PC to PC) calls.^[41]
• February 6, 2009 — Skype 4.0 is released.^[42]
• March 2009 — Skype launched Skype for SIP, a service aimed at business users. At the time of launch around 35% of Skype's users were business users.^[43]
• April 14, 2009 — eBay announced plans to spin off of Skype through an initial public offering in 2010.^[44]
• August 1, 2009 — Joltid files a motion with the U.S. Securities and Exchange Commission, seeking to terminate a licensing agreement with eBay which allows eBay (and therefore Skype) to use the peer-to-peer communications technology on which Skype is based. If successful, this may cause a shutdown of Skype in its current form.^[45]
• August 27, 2009 — Skype releases an update to their more than one year old Linux-client.
• September 1, 2009 — eBay announces sale of 65% of Skype to a consortium of Index Ventures and Silver Lake Partners.
• Early September 2009 — Skype shuts down the Extras developer program.^[46]
• Late November 2009 — eBay completes sale of 70% of Skype to a consortium comprising Silver Lake Partners, CPPIB, Andreessen Horowitz, and the original founders.
• In 2010, a report by TeleGeography Research Skype-to-Skype calls accounted for 13% of all international call minutes in 2009. Out of the 406 billion international call minutes a total of 54 billion were used by Skype calls.^[47]

Usage and traffic

Date	Total user accounts (in millions)[48][49][50][51][52][53]	Active users — daily presence (in millions)[54]	Skype to Skype minutes (in billions)	SkypeOut minutes (in billions)	Revenue USD (in millions)
Q4 2005	74.7	10.8	N/A	N/A	N/A
Q1 2006	94.6	15.2	6.9	0.7	35
Q2 2006	113.1	16.6	7.1	0.8	44
Q3 2006	135.9	18.7	6.6	1.1	50
Q4 2006	171.2	21.2	7.6	1.5	66
Q1 2007	195.5	23.2	7.7	1.3	79
Q2 2007	219.6	23.9	7.1	1.3	90
Q3 2007	245.7	24.2	6.1	1.4	98
Q4 2007	276.3	27.0	11.9	1.6	115
Q1 2008	309.3	31.3	14.2	1.7	126
Q2 2008	338.2	32.0	14.8	1.9	136
Q3 2008	370	33.7	16	2.2	143
Q4 2008	405	36.5	20.5	2.6	145
Q1 2009	443	42.2	23.6	2.9	153
Q2 2009	483	–	25.5	3.0	170
Q3 2009	521	–	27.7	3.1	185

Users may have more than one account, and it is not possible to identify users with multiple accounts.

The volume of international traffic routed via Skype is significant. It has become the largest international voice carrier.^[55] Computer-to-computer traffic between Skype users in 2005 was 2.9% of international carrier traffic in 2005 and about 4.4% of the total international traffic of 264 billion minutes in 2006.^[56] In 2008, about 8% of cross-border calls were carried by Skype.^[55] Skype incorporates some features which tend to hide its traffic, but it is not specifically designed to thwart traffic analysis and therefore does not provide anonymous communication. Some researchers have been able to watermark the traffic so that it is identifiable even after passing through an anonymizing network.^[57]

SkypeNOW! is a service that Skype offers in South Africa to customers with Vodafone mobile service, which can enable Vodafone users to engage in Skype international voice calls wirelessly.

System and software

Main article: Skype protocol

Skype uses a proprietary Internet telephony (VoIP) network, called the Skype protocol. The protocol has not been made publicly available by Skype and official applications using the protocol are closed-source. Part of the Skype technology relies on the Global Index P2P protocol, belonging to the Joltid corporation. The main difference between Skype and standard VoIP clients is that Skype operates on a peer-to-peer model (originally based on the Kazaa software^[58]), rather than the more usual client–server model.

The Skype user directory is sometimes claimed to be entirely decentralized and distributed among the nodes, although this is disputed and does not appear to be technically possible.

Skype offers no interoperability with SIP-based VoIP networks.^{[citation needed]}

Many networking and security companies^[who?] claim to detect and control Skype's protocol for enterprise and carrier applications. While the specific detection methods used by these companies are often private, Pearson's Chi-Square Test and stochastic characterization with Naïve Bayesian Classifiers are two approaches that were published in 2007.^[59]

Skype uses an array of different audio compression methods including G.729 and SVOPC. Skype added a Skype-created codec called SILK to Skype for Windows 4 and other Skype clients. SILK is intended to be "lightweight and embeddable".^[60]

Skype is a secure communication; encryption cannot be disabled, and is invisible to the user. Skype reportedly uses non-proprietary, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations.^[61] Skype provides an uncontrolled registration system for users with no proof of identity. Instead, a free choice of nicknames permits users to use the system without revealing their identity to other users. It is trivial to set up an account using any name; the displayed caller's name is no guarantee of authenticity. A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006. It analyzed Skype and found a number of security issues with the current security model.^[62]

See also: Skype security

Versions exist for Linux, Linux-based Maemo, Symbian S60, Mac OS X (Intel and PPC), iPhone OS (iPhone and iPod Touch), Android, Microsoft Windows (2000, XP, Vista, 7, Mobile), and even Sony's PSP.^[63]