Skype (IPA: [skaɪp]) is a software application that allows users to make telephone calls over the Internet. Calls to other users of the service, and in some countries to free-of-charge numbers are free, while calls to other landlines and mobile phones can be made for a fee. Additional features include instant messaging, file transfer and video conferencing.

Skype was written by Estonia-based developers Ahti Heinla, Priit Kasesalu and Jaan Tallinn, who had also originally developed Kazaa.^[1] The Skype Group, founded by Swedish-born entrepreneur Niklas Zennström and the Dane Janus Friis, has its headquarters in Luxembourg, with offices in London, Tallinn, Tartu, Stockholm, Prague,^[2] and San Jose.

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.^[3]

Skype has experienced rapid growth in popular usage since the launch of its services. The company was acquired by eBay in September 2005 for $2.6 billion.^[4] EBay has written Skype down to $1.7 billion on its books and announced a public stock offering for 2010 to spin Skype off as a separate company.^[5]

Features

SkypeIn 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, Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Italy, Japan, Mexico, New Zealand, Poland, Romania, South Korea, Sweden, Switzerland, the Netherlands, the United Kingdom, and the United States.^[6][7] 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. Some jurisdictions, including France and Germany, forbid the registration of their telephone numbers to anyone without a physical presence or residency in the country^{[citation needed]}.

Video conferencing was introduced in January 2006 for the Windows and Mac OS X platform clients. Skype 2.0 for Linux, which was released on March 13, 2008, also features support for video conferencing.^[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 that of mid-range videoconferencing systems.^[9] Skype conferences currently support up to 25 people at a time, including the host.

The word 'Skypecasting' is a portmanteau of 'Skype' and 'broadcasting'. Its original usage referred to recording Skype voice over IP voice calls and teleconferences. The recordings would be used as podcasts, which allow audio or video content to be syndicated over the Internet. Skype launched a "Skypecasts Beta" service in 2006 where it remained in beta until its end in September 2008. Skypecasts hosted public conference calls, up to 100 people at a time. Unlike ordinary Skype p2p conference calls, Skypecasts support 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] 1 September 2008 at 12:00 GMT, Skypecasts were shutdown without any concrete explanation.

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

Skype Clients

• On April 24, 2008, Skype announced that they offer Skype on around 50 mobile phones.^[14]
• On October 29, 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.^[15]
• Skype is available for the N800 and N810 Internet Tablets, which use the Linux Maemo environment.
• Skype is available on both the Sony Mylo COM-1 and newer COM-2 models.
• Skype is available for the PSP (PlayStation Portable) Slim and Lite with firmware version 3.90 or higher, but the user needs to purchase one of three microphone input peripherals.
• The new PSP-3000 has a built in microphone which allows communication without the Skype peripheral^[16]
• Skype is available on mobile devices running Windows Mobile.^[17]
• The official Symbian version was under development in 2006, but was not released.^[18]
• Official Skype support is available as part of X-Series together with mobile operator 3. However this uses a regular mobile phone call and iskoot^[19]WiFi. to a Skype gateway, rather than mobile internet. Other companies produce dedicated Skype phones which connect via
• Third party developers, such as Nimbuzz and Fring, have allowed Skype to run in parallel with several other competing VoIP/IM networks in any Symbian or Java environment. Nimbuzz has made Skype available to BlackBerry users.
• An official free Skype application for the iPhone OS was released in the iTunes store on March 31 2009.^[20] However, some network operators do not allow Skype calls to be made from their 3G, so if users want to use Skype on iPhone they need to connect it to a wifi network first.^[21]

History

• September 2002, investment from Draper Investment Company and at that time, original name was Skyper.^{[citation needed]}
• April 2003, Skype.com and Skype.net domain names registered.
• August 2003, First public beta version released.
• September 2005, SkypeOut banned in South China.^[22]
• October 2005, eBay purchased Skype (Oct 14).^[23]
• December 2005, videotelephony introduced.^[24] 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.^[25] Skype 3.0 for Windows is released.^[26]
• 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.^[27] Skype reports the system-wide crash was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").^[28]
• November 2007, Skype users are set to lose their 020 7 numbers after December 20, 2007.^[29]
• 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.^[30]
• September 1, 2008, Skype discontinues its SkypeCast service, citing difficulties in moderating chat rooms.
• September 8, 2008, The seventh season of Who Wants To Be a Millionaire premieres—the new Ask the Expert lifeline 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.^[31]
• October 2, 2008: Analysis reveals TOM-skype sends content of text messages and encryption keys to monitoring servers.^[32]
• 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.^[33]
• Feb 6, 2009, Skype 4.0 is released.^[34]
• 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 (rather than personal).^[35]
• April 14, 2009, eBay announced plans to spinoff of Skype through an initial public offering in 2010. ^[5]

Usage and traffic

http://www.slideshare.net/earningreport/presentation-on-q1-2009-earning-report-of-ebay-inc

Date	Total user accounts (in millions)[36][37][38][39][40][41]	Active users - daily presence (in millions)[42]	Skype to Skype minutes (in billions)	SkypeOut minutes (in billions)	Net 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

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

It was reported that 17,443,598 concurrent Skype users were online as of May 11, 2009.^[43]

As of January 2009, Skype is available for Android and over 100 Java enabled mobile phones. As of January 2009, Skype is adding about 30 million subscribers a quarter.^{[citation needed]}

Date	Users[44]	Days
2009-03-23	17,000,000	49
2009-02-02	16,000,000	21
2009-01-12	15,000,000	84
2008-10-20	14,000,000	35
2008-09-15	13,000,000	209
2008-02-18	12,000,000	42
2008-01-07	11,000,000	84
2007-10-15	10,000,000	259
2007-01-29	9,000,000	82
2006-11-08	8,000,000	71
2006-08-29	7,000,000	155
2006-03-27	6,000,000	66
2006-01-20	5,000,000	92
2005-10-20	4,000,000	155
2005-05-18	3,000,000	93
2005-02-14	2,000,000	117
2004-10-20	1,000,000	418
2003-08-29	0	-

The volume of international traffic routed via Skype is significant, it has become the largest international voice carrier.^[45] . 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.^[46] In 2008, about 8% of cross-border calls were carried by Skype.^[47]

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.^[48]

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

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 proprietary and closed-source. 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^[49]) rather than the more usual client-server model. The Skype user directory is entirely decentralized and distributed among the nodes of the network—i.e., users' computers—which allows the network to scale very easily to large sizes (currently about 240 million users)^[50] without a complex centralized infrastructure costly to the Skype Group. The disadvantage of this approach is that Skype offers no interoperability with SIP-based VOIP networks.

Many networking and security companies claim to detect and control Skype's protocol for enterprise and carrier applications^[who?]. 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.^[51]

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".^[52]

Skype security 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.^[53] Skype provides an uncontrolled registration system for users with absolutely no proof of identity. This permits users to use the system without revealing their identity to other users. It is trivial, of course, for anybody 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.^[54]

Versions exist for Linux, Linux-based Maemo, Mac OS X (Intel and PPC), iPhone OS (iPhone and iPod Touch), Microsoft Windows (2000, XP, Vista, Windows Mobile), and even Sony's PSP^[55]

Skype 1.4, running on a Linux desktop.   Skype 2.7, running on Mac OS X.   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.   Skype 1.0.2 running on iPhone.

Privacy

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 listen or not."^[56] 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.^[57] Security researchers Biondi and Desclaux have speculated that Skype may have a backdoor 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.^[58] Several media sources have reported that at a meeting about the "Lawful interception of IP based services" held on 25 June 2008, officials^[who?] at the Austrian interior ministry said "it is not a problem for them to listen in on Skype conversations". Austrian broadcaster ORF citing minutes from the meeting have reported that "the Austrian police are able to listen in on Skype connections".^[59][60] Skype declined to comment on the reports.^[61]

In the United States, the FCC has interpreted the Communications Assistance for Law Enforcement Act as requiring digital phone networks to allow wiretapping in the presence of an FBI warrant, in the same way as traditional phone service. Skype is not yet compliant with the act and has, so far, stated that it does not plan to comply.^[62] According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution;^[63] more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect.^[64][65] A number of individuals involved in publicly disclosing this information have been placed under investigation.^[65]

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.^[66] 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.^[67][68] 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."^[69] 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, the Chinese Communist Party, milk powder, the 2008 Sichuan earthquake, and democracy. 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. This information was also saved for Skype users outside China who were communicating with a TOM-Skype user. Due to a server misconfiguration, these log files were for a time accessible to the public.^[68][70][71]

On February 2009 Eurojust started working on lawful interception of Skype and VoIP.^{[citation needed]}

[edit] Customer service

There have been a multitude of complaints about Skype's poor customer support.^[72][73] As of April 2009, Skype does not provide a way to contact customer support, offering indirect assistance through its web portal only.

Comparison of VoIP software

• This page was last modified on 1 June 2009 at 21:42.
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