Skype

Skype
Skype logo2.svg

Skype 4 in Compact View running on Windows 7
Developer(s) Skype Limited
Initial release August 2003 (2003-08)
Written in CodeGear Delphi / Objective-C (Mac OS X/iPhone) / C++ with Qt4 (Linux)
Operating system Cross-platform
Available in Multilingual
Type Voice over Internet Protocol / instant messaging / videoconferencing
License Freeware (with some paid features)
Website www.skype.com
Part of a series on
Skype
Skype Limited
Features of Skype
Skype protocol
Skype security

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. The network is operated by a company called Skype Limited, headquartered in Luxembourg and partly owned by eBay.

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.

Contents

Features

Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory.[1] 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—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.[2][3] 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.[4] Version 5 beta 1 for Windows, released 13 May 2010, offers free video conferencing with up to 5 people.[5]

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.[6] 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.[7] 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.[8] 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".[9] As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.[10]

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.[11] Other platforms officially supported include:

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 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.[22]

Third-party developers, such as Nimbuzz and Fring, have allowed Skype to run in parallel with several other competing VoIP/IM networks (Nimbuzz provides 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;[23] Fring had provided mobile video calling over Skype as well as support for the Android platform.

History

Skype was founded in 2003 by the Swedish entrepeneur Niklas Zennström and the Dane Janus Friis[24]. 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.[25] 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[26]. Dropping the final "r" left the current title "Skype", for which domain names were available.[27]

eBay acquired Skype Limited in September 2005 and in fall of 2009 sold a majority stake to an investor group.[28]

In September 2005, SkypeOut was banned in South China.[29] In October of the same year, eBay purchased Skype.[30] In December, videotelephony was introduced.[31]

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 announces a new pricing structure, with connection fees for all SkypeOut calls.[32] Skype 3.0 for Windows was released.[33]

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. In August, Skype users unable to connect to full Skype network in many countries[34] because of a Skype system-wide crash which was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").[35] And in November, there was controversy when it was announced that users having London (020) 7 numbers would lose them.[36]

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, version 4 for Windows (with both a full screen[37] and a compact[38] mode), but also discontinued its SkypeCast service, without explanation and added internal monthly and daily usage caps on their SkypeOut subscriptions advertised as "Unlimited". Many users and observers had commented on the high rate of dropped calls, and the difficulty of reconnecting dropped calls. Skype was also used in the seventh season of the U.S. syndicated game show Who Wants To Be a Millionaire, for a new Ask the Expert lifeline for video chat. In October, analysis revealed TOM-skype in China sends content of text messages and encryption keys to monitoring servers.[39]

In 2009, Skype 4 was released[40], their Linux client was updated, and also launched Skype for SIP, a service aimed at business users. At the time of launch around 35% of Skype's users were business users.[41] In April, 2009, eBay announced plans to spin off Skype through an initial public offering in 2010.[42] 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.[43] 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.[44] 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. [45]

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.[46] In May, Skype 5.0 beta 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[20]. On August 9, 2010, Skype filed with the SEC to raise up to $100 million in an initial public offering.[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; 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.[55]

Year International call market share
2005 2.9%[56]
2006 4.4%[56]
2008 8%[55]
2010 13%[46]

System and software

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[57]), 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.

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.[58]. 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[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]

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.[61]
Skype 2.1, running on a Linux desktop  
Skype 2.7, running on Mac OS X Leopard  
Skype 1.0.2 running on iPhone  
Skype 2.2, running on a Windows Mobile 6 device  
Skype 4 in Default View running on Windows Vista  
Skype 4 in Default View running on Windows XP  

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.[62] 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.[63]

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.[64]

In an interview with Kurt Sauer, Chief Security Officer Skype, he said, "We provide a safe communication option. I will not tell you whether we can listen or not."[65] 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.[66] 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.[67] Several media sources have reported that at a meeting about the "Lawful interception of IP based services" held on 25 June 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".[68][69] Skype declined to comment on the reports.[70]

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.[71] According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution;[72] more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect.[73][74]

On 20 February 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"[75]

Service in People's Republic of China

Since September 2007, users in China trying to download the Skype software 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.[76] 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.[77][78] 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."[79] 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.[78][80][81]

Customer service

There have been complaints about Skype's poor customer support.[82][83] 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.

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 [84] A settlement of up to US$4 was paid to persons who opted in to the action.

See also

Part of a series on
Skype
Skype Limited
Features of Skype
Skype protocol
Skype security


References

  1. ↑ "Usernames, aliases and nicknames – your Skype passport". http://www.skype.com/allfeatures/skypename/. Retrieved August 27, 2009.  (official site)
  2. ↑ Villu Arak. "Four new SkypeIn countries". Skype Blogs. http://share.skype.com/sites/en/2007/06/four_new_skypein_countries.html. Retrieved 2007-08-13.  (official site)
  3. ↑ Skype.com
  4. ↑ "Skype 2.0 Beta for Linux, the Great Revolution". November 7, 2007. http://share.skype.com/sites/garage/2007/11/skype_20_beta_for_linux_the_great_revolution.html. Retrieved 2008-02-19. 
  5. ↑ Skype 5.0 beta 1 for Windows, May 2010 (vendor blog)
  6. ↑ Skype User Guide "Using Skype for Desk-top Video-Conferences". http://www.HL7.com.au/Skype-Video-Conferencing.htm.  (official site)
  7. ↑ "Goodnight Skypecasts — Skype Blogs". Share.skype.com. August 2008. http://share.skype.com/sites/en/2008/08/goodnight_skypecasts.html. Retrieved 2009-03-31. 
  8. ↑ "Skype and Emergency Services". http://www.skype.com/allfeatures/no911/. 
  9. ↑ "Draft Report from TEITAC Task Force on 255/508 differences, with proposals for TEITAC discussion". http://www.access-board.gov/sec508/refresh/teitac8th/tf-report.htm. Retrieved 2010-07-13. 
  10. ↑ "Frequently Asked Questions". 911VoIP.org. http://www.911voip.org/faqs.htm. Retrieved 2009-03-31. 
  11. ↑ Skype: 3 Skypephone Delivers Free Skype to Skype Mobile Calls and Instant Messages at the Touch of a Button, October 29, 2007
  12. ↑ Skype: Skype Tests Software for Mass-Market Mobile Phones, April 24, 2008
  13. ↑ Skype: Skype Expands Mobile Strategy at 2008 International CES, January 7, 2008
  14. ↑ Playstationlifestyle.net
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  16. ↑ "Skype Discontinued for Windows Mobile?". treocentral.com. Retrieved 2010-3-29
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  21. ↑ Verizon's Skype Mobile webpage
  22. ↑ NETGEAR Skype WiFi Phone voipyeah.com
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  32. ↑ Skype to Announce Disruptive Pricing Strategy for SkypeOut Retrieved, December 19, 2006
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  44. ↑ Skype.com
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  47. ↑ Internet communications provider Skype files for upcoming IPO
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  55. ↑ 55.0 55.1 "Skype is largest international voice carrier, says study". http://www.networkworld.com/news/2009/032509-skype-is-largest-international-voice.html?tc=vc=html. 
  56. ↑ 56.0 56.1 "International carriers' traffic grows despite Skype popularity". TeleGeography Report and Database. http://www.telegeography.com/cu/article.php?article_id=15656&email=html. Retrieved 2006-12-07. 
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  59. ↑ Hjelmvik, Erik; John, Wolfgang (2010-07-27). "Breaking and Improving Protocol Obfuscation". http://www.iis.se/docs/hjelmvik_breaking.pdf. 
  60. ↑ "Skype's new super wideband codec". Wirevolution.com. http://www.wirevolution.com/2009/01/13/skypes-new-super-wideband-codec/. Retrieved 2009-03-31. 
  61. ↑ "Skype for TV". Skype. http://www.skype.com/intl/en-us/get-skype/on-your-tv/. Retrieved 2010-05-28. 
  62. ↑ "Skype Privacy FAQ". Skype. http://www.skype.com/intl/en/legal/privacy/general/. Retrieved 2006-12-05. 
  63. ↑ Philippe Biondi and Fabrice Desclaux. "Silver Needle in the Skype" (PDF). blackhat. http://www.blackhat.com/presentations/bh-europe-06/bh-eu-06-biondi/bh-eu-06-biondi-up.pdf. Retrieved 2006-03-02. 
  64. ↑ George Mason University
  65. ↑ ZDNet.de. "Telefonieren übers Internet: Wie sicher ist Skype wirklich? – Telekommunikation | Mobile Business". ZDNet.de. http://www.zdnet.de/mobiles_internet_drahtloses_arbeiten_telefonieren_uebers_internet_wie_sicher_ist_skype_wirklich_story-39001620-39151472-1.htm. Retrieved 2009-03-31. 
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