Skype


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Skype (Template:Pron-en) 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. The network is operated by Skype Limited, which has its headquarters in Luxembourg and is partly owned by eBay.

Skype
File:Skype logo2.svg

Skype 5.1 running on Windows 7

Developer(s)Skype Limited
Initial releaseAugust 2003
Stable release
Windows, UWP15.129.3202.0 / 1 October 2024; 3 days ago[1][2]
Windows, desktop8.129.0.201 / 27 September 2024; 7 days ago[1]
macOS8.128.0.207 / 23 September 2024; 11 days ago[1]
Linux8.128.0.207 / 23 September 2024; 11 days ago[1]
Android8.129.0.202 / 29 September 2024; 5 days ago[3][4][5]
iOS8.128.0.207 / 17 September 2024; 17 days ago[3][6]
Written inEmbarcadero Delphi / Objective-C (Mac OS X/iPhone) / C++ with Qt4 (Linux)
Operating systemCross-platform
Available inMultilingual
TypeVoice over Internet Protocol / instant messaging / videoconferencing
LicenseFreeware (with some paid features)
WebsiteSkype.com

Unlike other VoIP services, the Skype company does not run servers, but makes use of background processing on computers running Skype software; the original name proposed—Sky peer-to-peer (see below)—reflects this.

Some network administrators have banned Skype on corporate,[7] government, home, and education networks,[8] citing reasons such as inappropriate usage of resources, excessive bandwidth usage,[9] and security concerns.[10]

Features

Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory.[11] 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 (since version 5) and editing of previous messages. The usual features familiar to instant messaging users—user profiles, online status indicators, and so on—are also included.

The Online Number (aka 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, Belgium, 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.[12][13] 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.[14] Version 5 beta 1 for Windows, released May 13, 2010, offers free video conferencing with up to 5 people.[15]

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.[16] Skype audio conferences currently support up to 25 people at a time, including the host.

The Skype 3.0 app released on 30 December 2010 for Apple's iOS platform also introduced video chat for iPhone, iPad and iPod Touch devices, although this is limited to only receiving incoming video calls as the iPad and previous-generation iPod Touch models do not have a video cameras. However, reviewers have noted the poor quality and performance of Skype 3.0 videocalls over both Wi-Fi and 3G mobile phone networks compared to Apple's FaceTime app built into the iPhone 4 and fourth-generation iPod Touch.[17]. A new free software called Vodburner allows users to record and edit their skype calls [18]. It works like a plugin for Skype, and once installed automatically integrates with Skype to make the process as seamless as possible.

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.[19] 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".[20] As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.[21]

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.[22] Other platforms officially supported include:

  • Around 50 mobile phones, as of 2008[23]
  • 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.[24] PSP Go has the ability to use Bluetooth connections with the Skype application, in addition to its built-in microphone.[25]
  • Mobile devices running Windows Mobile;[26] in February 2010, Skype announced its decision to discontinue development Skype for Windows Mobile.[27] In May 2010, Skype announced it would not develop a version of Skype for Windows Phone 7.[28]
  • Symbian; Skype version 5.0 is the latest version for the Symbian platform[29]
  • The X-Series together with mobile operator 3. However this uses a regular mobile phone call and iSkoot[30] to a Skype gateway, rather than mobile Internet. Other companies produce dedicated Skype phones which connect via WiFi
  • iOS, using an official application released on 31 March 2009. As of version 2.x, the iPhone application is capable of placing voice calls over 3G and EDGE networks. Skype originally announced it will charge a monthly fee for this feature at the start of 2011, but that was eventually dropped.[31] On December 29 (PST), Skype updated their iOS app to version 3.0, allowing mobile video calling.
  • A variety of BlackBerry and Android 3G Smartphones, through Verizon Wireless' Skype mobile service. 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 U.S. use minutes from their calling plan when calling U.S. land lines or cell phones.[32]

Some devices are made to work with Skype by talking to a desktop Skype client or by embedding Skype software into the device. 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.[citation needed]

The Skype Wi-Fi Phone is a wireless mobile phone that allows users to make Skype calls, using a 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 and so can not access hotspots, which require web-based login or authentication.[33]

Third-party developers, such as Truphone, Nimbuzz and Fring, have allowed Skype to run in parallel with several other competing VoIP/IM networks (Truphone and Nimbuzz provide truphoneOut and NimbuzzOut as a competing paid service) in any Symbian or Java environment. Nimbuzz has made Skype available to BlackBerry users. In July 2010, however, Fring disabled users from accessing Skype despite claiming that Skype themselves disabled the access;[34] Fring had provided mobile video calling over Skype as well as support for the Android platform. Nimbuzz discontinued support on request of Skype in October 2010.[35]

Until November 2010, only certain Samsung and Panasonic TVs offered Skype video service.[36]

History

Skype was founded in 2003 by the Swedish entrepreneur Niklas Zennström and Dane Janus Friis.[37] The Skype software was developed by Estonian developers Ahti Heinla, Priit Kasesalu and Jaan Tallinn, the same individuals who together with Niklas and Janus were also originally behind the peer-to-peer file sharing software Kazaa.[38] In April 2003, Skype.com and Skype.net domain names were registered. In August 2003, the first public beta version was released.

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.[39] Dropping the final "r" left the current title "Skype", for which domain names were available.[40]

In September 2005, SkypeOut was banned in South China.[41] In October of the same year, eBay purchased Skype[42] and in fall of 2009 sold a majority stake to an investor group.[43] In December 2005, videotelephony was introduced.[44]

In April 2006, the number of registered users reached 100 million. In October, Skype 2.0 for Mac was released, the first full release of Skype with video for Macintosh, and in December, Skype announced a new pricing structure, with connection fees for all SkypeOut calls.[45] Skype 3.0 for Windows was released.[46]

In 2006, a now-discontinued feature called "Skypecasting" was introduced. It allowed recordings of Skype voice over IP voice calls and teleconferences to be used as podcasts. Skypecasts 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. Skypecasts was discontinued as of September 1, 2008.[47]

Throughout 2007 updates (3.1, 3.2 and 3.5) added new features including Skype Find, Skype Prime, Send Money (which allowed users to send money via PayPal from one Skype user to another), video in mood, inclusion of video content in chat, call transfer to another person or a group, and auto-redial. 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 in the call window. During several days in August, Skype users were unable to connect to full Skype network in many countries[48] because of a Skype system-wide crash which was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").[49] And in November, there was controversy when it was announced that users having London (020) 7 numbers would lose them.[50]

In 2008, Skype released various updates including versions for the Sony PSP hand-held gaming system, version 2.0 for Linux with support for video-conferencing, and version 4 for Windows (with both a full screen[51] and a compact[52] mode). Skype also discontinued its SkypeCast service without explanation and added internal monthly and daily usage caps on their SkypeOut subscriptions, which had been advertised as "Unlimited". Many users and observers had commented on the high rate of dropped calls and the difficulty reconnecting dropped calls. Skype was used in the seventh season of the U.S. syndicated game show Who Wants To Be a Millionaire in a new Ask the Expert video chat lifeline. In October, analysis revealed TOM-skype—the Chinese version of Skype run by TOM Online—sends content of text messages and encryption keys to monitoring servers.[53]

In 2009, Skype 4 was released,[54] the Linux client was updated, and Skype for SIP, a service aimed at business users, was launched. At that time around 35% of Skype's users were business users.[55] In April 2009, eBay announced plans to spin off Skype through an initial public offering in 2010.[56] In August, Joltid filed 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 have caused a shutdown of Skype in its current form.[57] In September, eBay announced the sale of 65% of Skype to a consortium of Index Ventures and Silver Lake Partners. Early in September, Skype had shut down the Extras developer program.[58] In November, eBay completed the sale of 70% of Skype to a consortium comprising Silver Lake Partners, CPPIB, Andreessen Horowitz, and the original founders valuing the business at USD2.75 billion.[43]

In 2010, a report by TeleGeography Research stated that 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.[59] In May, Skype 5.0 beta was released, with support of group video calls with up to four participants. Also in May, Skype released an updated client for the Apple iPhone which allowed Skype calls to be made over a 3G network. Originally, a 3G call subscription plan was to be instituted in 2011, but the plan was eventually dropped by Skype.[31]

On August 9, 2010, Skype filed with the SEC to raise up to $100 million in an initial public offering.[60][61] In October 2010, Skype announced it had named Tony Bates as their CEO; Bates has been a senior VP at Cisco and responsible for its multi-billion-dollar enterprise, commercial and small business division.[62]

On October 14, 2010, Skype 5.0 for Windows was released with a number of improvements and feature additions, including a Facebook tab to allow users to SMS, chat with, or call their Facebook friends via Skype from the News Feed.[63]

Usage and traffic

This article needs to be updated. Please help update this article to reflect recent events or newly available information. (July 2010)

Date Total user accounts
(in millions)[64][65][66][67][68][69] 		Active users — daily presence
(in millions)[70] 		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 16.0 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; it is not possible to count actual users, just accounts.

The volume of international traffic routed via Skype is significant. It has become the largest international voice carrier.[71]

Year International call market share
2005 2.9%[72]
2006 4.4%[72]
2008 8%[71]
2010 13%[59]

System and software

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 Ltd. 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[73]), rather than the more usual client–server model (note that the very popular SIP model of VoIP is also peer to peer, but implementation generally requires registration with a server, as does Skype).

Protocol Detection and Control

Many networking and security companies 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 Naive Bayes classification are two approaches that were published in 2007.[74] Combining statistical measurements of payload properties (such as byte frequencies and initial byte sequences) as well as flow properties (like packet sizes and packet directions) has also shown to be an effective method for identifying Skype's TCP- and UDP-based protocols.[75]

User Directory

The Skype user directory is sometimes claimed to be entirely decentralized and distributed among the nodes.

Audio codecs

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".[76]

Video codecs

Unknown.

Clients

There are versions for Linux (though none of them have x86-64 native support, hence requiring additional 32-bit libraries installed), Linux-based Maemo, Symbian S60, Mac OS X (Intel and PPC), iOS (iPhone and iPod Touch), Android, Microsoft Windows (2000, XP, Vista, 7, Mobile), Sony PSP and also in 2010 TV models from Panasonic, Samsung and LG, but requires a special webcam built for those TVs.[77]

Security and privacy

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.[78] 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.[79]

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.[80]

In an interview Kurt Sauer, the Chief Security Officer of Skype, he said, "We provide a safe communication option. I will not tell you whether we can listen or not."[81] Skype's client uses an undocumented and proprietary protocol. The Free Software Foundation (FSF) is concerned by user privacy issues arising from using proprietary software and protocols and has made replacement for Skype one of their high priority projects.[82] Security researchers Biondi and Desclaux have speculated that Skype may have a back door, since Skype sends traffic even when it is turned off and because Skype has taken extreme measures to obfuscate their traffic and functioning of their program.[83] Several media sources have reported that at a meeting about the "Lawful interception of IP based services" held on June 25, 2008, high-ranking but not named officials at the Austrian interior ministry said that they could listen in on Skype conversations without problem. Austrian public broadcasting service ORF, citing minutes from the meeting, have reported that "the Austrian police are able to listen in on Skype connections".[84][85] Skype declined to comment on the reports.[86]

The United States Federal Communications Commission (FCC) has interpreted the Communications Assistance for Law Enforcement Act (CALEA) as requiring digital phone networks to allow wiretapping if authorized by an FBI warrant, in the same way as other phone services. In February 2009 Skype said that, not being a telephone company owning phone lines, it is exempt from CALEA and similar laws which regulate US phone companies, and in fact it is not clear whether Skype could support wiretapping even if it wanted to.[87] According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution;[88] more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect.[89][90]

On February 20, 2009 the European Union's Eurojust agency announced that the Italian Desk at Eurojust would "play a key role in the coordination and cooperation of the investigations on the use of internet telephony systems (VoIP), such as 'Skype'. ... The purpose of Eurojust’s coordination role is to overcome the technical and judicial obstacles to the interception of internet telephony systems, taking into account the various data protection rules and civil rights"[91]

Service in People's Republic of China

Since September 2007, users in China trying to download the Skype software client have been redirected to the site of TOM, a joint venture between a Chinese wireless operator and Skype, from which a modified Chinese version can be downloaded.[92] The TOM client participates in China's system of Internet censorship, monitoring text messages between Skype users in China as well as messages exchanged with users outside the country.[93][94] Niklas Zennström, then chief executive of Skype, told reporters that TOM "had implemented a text filter, which is what everyone else in that market is doing. Those are the regulations." He also stated: "One thing that’s certain is that those things are in no way jeopardising the privacy or the security of any of the users."[95] In October 2008, it was reported that TOM had been saving the full message contents of some Skype text conversations on its servers, apparently focusing on conversations containing political issues such as Tibet, Falun Gong, Taiwan independence, and Chinese Communist Party. The saved messages contain personally identifiable information about the messages' senders and recipients, including IP addresses, usernames, land line phone numbers, and the entire content of the text messages, including the time and date of each message. Information about Skype users outside China who were communicating with a TOM-Skype user was also saved. A server misconfiguration made these log files accessible to the public for a time.[94][96][97]

Customer service

There have been complaints about Skype's poor customer support.[98][99] As of May 2010, Skype does not provide any official means to contact customer support, apart from indirect assistance through its web portal only and contact email addresses.

There is no e-mail or phone number for complaints about billing errors. It is not clear, in case a dispute occurs, which country would be the jurisdiction for conflict resolution.[citation needed]

In January 2010 Skype rescinded their policy of seizing funds in Skype accounts that have been inactive (no paid call) for 180 days. This was in settlement to a class action lawsuit.[100] A settlement of up to US$4 was paid to persons who opted in to the action.

Outages and downtime

On Thursday 16 August 2007 and for about two days, Skype became unavailable to a majority of its users. Millions of users at the same time were requesting to log-in following a routine Windows update and this flooded the peer-to-peer system.[101]

On Wednesday 22 December 2010 it was reported that Skype experienced an outage estimated to represent 8 million foregone calls.[102] Skype administrators placed on their Twitter page the following message "Some of you may have problems signing in to Skype -- we're investigating, and we're sorry for the disruption to your conversations...engineers and site operations are working non-stop to get things back to normal."[103][104] The problem came down to the limited availability of "supernodes", affecting some versions of Skype.[105][106]

Later in the day, Skype's CEO, Tony Bates, issued an apology. He said that the matter was being taken very seriously and was being thoroughly investigated. He had said that malicious attack was not being ruled out as a problem cause and he put his estimate of the foregone calls at about 10 million.[107]

On 23 December 2010, Skype's blog with Tony Bates had issued a YouTube apology for the Skype outage.[108]

The problem was persistent across the USA, Latin America, Europe and Asia. It had started to subside by 8:30 pm UTC however users were warned it may take several hours for the program to be fully operative again.[109] It was reported at 9:27 am 23 December UTC that most users were able to log in again although some still could not.[110] On the other hand into Thursday only about a third of the expected traffic was actually using Skype, relative to the time-period.[111]

On 23 December 2010, Skype said on its blog that the system had stabilized, and a detailed explanation of the incident was published six days later.[112]

Bates offered all Pay As You Go and Pre-Pay customers a free call to any landline as compensation.[113]

See also

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