Skype

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Skype

Skype 3.6 Beta running in Windows Vista
Developer Skype Limited
Stable release 3.6.0.244 (Windows),
2.6.0.151 (Mac OS X),
1.4.0.118 (Linux),
2.2.0.36 (Windows Mobile)
  (December 13, 2007 (Windows),
July 18, 2007 (Mac OS X)
October 4, 2007 (Linux)) [+/-]
Preview release 2.7.0.195 (Mac OS X),
2.0.0.27 (Linux)
  (November 29, 2007 (Mac OS X),
December 2007 (Linux)) [+/-]
OS Cross-platform
Genre P2P/VoIP/instant messaging/
video call/videophone
License Freeware (with some paid features)
Website www.skype.com

Skype (IPA: [skaɪp], rhymes with type) is a software program created by the entrepreneurs Niklas Zennström and Janus Friis. Skype allows users to make telephone calls from their computer to other Skype users free of charge, or to landlines and cell phones for a fee. Additional features include instant messaging, file transfer, short message service, video conferencing and its ability to circumvent firewalls.

The Skype Group, acquired by eBay in September 2005, has headquarters in Luxembourg, with offices in London, Tallinn, Tartu, Prague[1] and San Jose, California. Skype experienced rapid growth in both popular usage and software development since the launch, both of its free and its paid services.

Contents

Main article: Features of Skype

SkypeOut allows Skype users to call traditional telephone numbers, including mobile telephones, for a fee. This fee is as low as US$0.021 per minute for most developed countries, and as high as US$2.142 per minute for calls to the dependency of Diego Garcia. Beginning January 2007, Skype also charges an equivalent of €0.039 for each SkypeOut call, in addition to the ordinary rate.[2] After 180 days of not making a SkypeOut call the Skype balance expires. As of January 30, 2007, SkypeOut calls to Canada and the United States are no longer free.

SkypeOut calls to most toll free numbers in France (+33 800, +33 805, +33 809), Poland: (+48 800), UK: (+44 500, +44 800, +44 808) and the United States and Canada: (+1 800, +1 866, +1 877, +1 888 ) are free for all Skype users, even if they do not have the SkypeOut service.[3][4] However, for many other countries SkypeOut doesn't support calling toll-free and premium rate numbers, and SkypeOut doesn't support calling emergency numbers (such as 112 the Universal Emergency number for GSM mobile phones, 911 in Canada and the USA, 000 in Australia and 999 In the UK).

SkypeIn allows Skype users to receive calls on their computers dialed by regular phone subscribers to a local Skype phone number. It permits users to subscribe to numbers in Australia, Brazil, Chile,[5] Denmark, the Dominican Republic, Estonia, Finland, France, Hong Kong, Ireland, Japan, Mexico, New Zealand,[5] Poland, Romania, Sweden, Switzerland, UK, and the United States.

For example, a user in San Francisco could create a local telephone number in Helsinki. Callers from Helsinki would pay only local rates to call that number. Some jurisdictions such as France and Norway, however, forbid the registration of their local telephone numbers to anyone without a physical presence or citizenship in the country.

First introduced in January 2006, Skype provides videoconferencing for Windows, Mac OS X and Linux (Skype 2.0 or above required). With version 3.6.0.216 for Windows, Skype now supports “High Quality Video" with quality and features (eg. full-screen and screen-in-screen modes) similar to those found in middle-range video-conferencing systems.[6]

2002 - 2005
2006 - 2007
  • 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.[10] Skype 3.0 for Windows is released.[11]
  • 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.[12][13] Skype reports the system-wide crash was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").[14]
  • November 2007: Skype users are set to lose their 020 7 numbers after 20 December 2007.[15]

A typical early version of Skype 1.0, running on a Windows XP desktop
A typical early version of Skype 1.0, running on a Windows XP desktop
Date Total user accounts
(in millions)		 Skype to Skype minutes
(in billions)		 Skype Out minutes
(in billions)		 Net revenue USD
(in millions)
Q1 2006 95 6.9 0.7 35
Q2 2006 113.1 7.1 0.8 44
Q3 2006 135.9 6.6 1.1 50
Q4 2006 171.2 7.6 1.5 66
Q1 2007 195.5 7.7 1.3 79
Q2 2007 219.6 7.1 1.3 90
Q3 2007 245.7 6.1 1.4 98

As of September 30, 2007, Skype had a cumulative number of unique user accounts of 246 million. Users may register more than once, and as a result, may have more than one account.

It was reported that 10,140,836 concurrent Skype users were online as of October 30, 2007.[16]

Date Users [17] Days
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 -

Although the volume of international traffic routed via Skype is significant, the quantity is still small when compared to the cumulated global switched and VoIP traffic. Computer-to-computer traffic between Skype users in 2005 was equivalent to 2.9% of international carrier traffic in 2005 and approximately 4.4% of total international traffic base of 264 billion minutes in 2006.[18]

Skype incorporates some features which obfuscate its traffic, but it is not specifically designed to thwart traffic analysis and therefore does not provide anonymous communication. Some researchers have also been able to watermark the traffic so that it is identifiable even after passing it through an anonymizing network [1].

Skype 1.4, running on a Linux desktop, over 7,630,000 people online
Skype 1.4, running on a Linux desktop, over 7,630,000 people online

Versions now exist for Microsoft Windows (2000, XP, Vista and Windows Mobile), Mac OS X and Linux 32-bit only. Under Windows, Skype can also be run from a USB stick without requiring to be installed on the target computer.[19] The Linux version runs on FreeBSD through its Linux binary compatibility layer. Skype can also run in Solaris branded zones.

Skype offers its own mobile phone under the brand name Skypephone, which runs a BREW OS. Skype is also available on mobile devices running Windows Mobile [20] The official Symbian version is currently under development[21]. Skype is also available on Symbian and Java as part of X-Series. Moreover, thanks to a third party developer, it is also possible to run Skype in a Symbian environment using Fring, which also offers other services.

Main article: Skype Protocol

The main difference between Skype and VoIP clients is that Skype operates on a peer-to-peer model, rather than the more traditional server-client model. The Skype user directory is entirely decentralized and distributed among the nodes in the network, which means the network can scale very easily to large sizes (currently about 240 million users)[22] without a complex and costly centralized infrastructure.

Skype running on a Windows Mobile 6 Professional device.
Skype running on a Windows Mobile 6 Professional device.

Skype accesses the hard disk several times each minute. This can be verified by observing the HDD's activity LED, or by using a file access monitor such as FileMon.[23] With regard to internet bandwidth, certain users are selected by software to act as "supernodes"[24]. Under certain conditions, Skype is reportedly willing to accept thousands of connections, but is stated to limit itself to 40 kb/s upload and download.[25][26][27]

Main article: Skype security

Secure communication is a feature of Skype. The encryption cannot be turned on or off. The user is not involved in the encryption process and therefore does not have to deal with the issues of public key infrastructure. Skype reportedly uses non-proprietary, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations.[28]

Skype provides an uncontrolled registration system for users: registration requires no proof of identity. This works two ways: you can use the system safely without revealing your real-life identity to other users of the system, but on the other hand you have no guarantees that the person you communicate with is the one they say they are in real life. The downside of this is that it is easy to use the personal name (but not identity) of a trusted person as a Skype nickname and trick a naive user into revealing information or executing a program sent to them.

 It has been suggested that some of the information in this article's "Criticism" or "Controversy" section(s) be merged into other sections to achieve a more neutral presentation. (Discuss)

Due to the design of the protocol, if given access to an unrestricted network connection, Skype clients can become supernodes. These supernodes hold together the peer-to-peer network and provide data routing for other clients behind more restrictive firewalls, which can generate a significant amount of bandwidth usage. For this reason, some network providers, such as universities, have banned the use of Skype.[30] The French ministry of research strongly discourages the use of Skype in all French public universities and laboratories, especially those with sensitive research, leading to an outright ban in many laboratories.[31]

A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006.[32] It analyzed Skype and made these observations:

  • Heavy use of anti debugging techniques (used to deter development of alternative clients, hacking tools)
  • Significant use of obfuscated code (slows reverse engineering, less description of what program code does internal to the executable file)
  • Keeps chatting on the network, even when idle (even for non-supernodes. May be used for NAT traversal)
  • Blind trust in anything else speaking Skype
  • Ability to build a parallel Skype network
  • Lack of privacy (Skype has the keys to decrypt calls or sessions)
  • Heap overflow in Skype
  • Skype makes it hard to enforce a (corporate) security policy
  • "No way to know if there is/will be a backdoor"

SkypeOut rates are "per minute" based, contrary to the trend in charges for calls from conventional telephones[citation needed]. In some countries, many calls are charged at a specified fixed amount per call. In this method, SkypeOut is more expensive for longer calls, whereas it is cheaper for relatively short calls.

There have been complaints about Skype's poor customer support.[33] As of June 2007, Skype still does not provide a direct way of contacting its customer support, relying solely on its web portal for all related issues. There have also been criticisms of Skype blocking and disabling customer accounts from using the SkypeOut service.[34]

When Skype 2.0 was released, AMD filed a lawsuit claiming the software offers 10-way conference calls on dual core Intel processors, while other chips, including all AMD chips, will only offer 5-way conference calls.[35]

While available for Windows, Mac OS X and Linux (i386 platform) operating systems, there is no Skype version for the Palm OS, used in mobile devices like the Treo 700p smartphone nor for the Linux versions for different architectures.

Skype has been criticized in the Linux community for bugs and delays in the Linux version.[36]

The Mac OS X version lacks some of the advanced features included in Skype for Windows.[citation needed]

Users of Skype on Mac OS X report poor audio quality when connecting to Mac/Mobile clients, with newer audio engines showing more and more problems. Audio quality when connecting from Mac to Windows seem to be acceptable.

Skype was also found to access BIOS data[37] to identify individual computers and provide DRM protection for plug-ins.[38][39]

It can not be assured that Skype calls are not interceptable. Skype provides end to end encryption for connections between users however in an interview at cnet.com Skype chief security officer Kurt Sauer would not eliminate this possibility.[40]

Skype cannot be used with VOIP analogue telephone adapters (ATAs), which use SIP, H323, and other protocols. Consequently, Skype users are limited to either using software phones or expensive Skype only hardware. However, there are applications that enable users to make free calls from Skype to SIP providers [41] , or vice versa.

Main article: Skype Limited

On October 14, 2005, eBay acquired the company for €1.9 billion in cash and stock, plus an additional €1.5 billion in rewards (earn out) if goals are met by 2008.[42][43]

Skype Limited faces challenges from two main directions. Firstly it faces legal challenges to its intellectual property and secondly it faces political pressures by governments wishing to control the telecommunications systems of their respective countries.

In May 2006, the FCC successfully applied the Communications Assistance for Law Enforcement Act to allow wiretapping on digital phone networks. Skype is not yet compliant to the Act, and has so far stated that it does not plan to comply.[44]

On June 1, 2006, Net2Phone (the Internet telephone unit of IDT Corp.) filed a lawsuit against eBay and Skype accusing the unit of infringing U.S. Patent 6,108,704 , which was granted in 2000.[45]

Skype is one of many companies (others include AOL, Google, Microsoft, Yahoo, Cisco) which have cooperated with the Chinese government in implementing a system of Internet censorship in the People's Republic of China. Niklas Zennström, chief executive to Skype, told reporters that its joint venture partner in China is operating in compliance with domestic law. "TOM Online had implemented a text filter, which is what everyone else in that market is doing," said Zennström. "Those are the regulations," he said. "I may like or not like the laws and regulations to operate businesses in the UK or Germany or the US, but if I do business there I choose to comply with those laws and regulations. I can try to lobby to change them, but I need to comply with them. China in that way is not different."[46]

Since late September, users in China trying to download the Skype software are redirected to the TOM site from which a modified Chinese version can be downloaded. Activists in China are warning about the possibility that TOM's versions have or will have more trojan capability.[47]

These same companies, however, also cooperate with police authorities in the United States by reporting pornography that visually depicts those who appear to be under eighteen years of age.

  1. ^ Jaanus Kase. Skype is expanding engineering to Prague. Skype Blogs. Retrieved on 2006-12-05.
  2. ^ Connection Fee for SkypeOut Calls. skype.com. Retrieved on 2007-01-19.
  3. ^ Free calls to toll-free phone numbers global beta
  4. ^ Skype Help: Skype tells me the number I am trying to call is forbidden, why is that?.
  5. ^ a b Villu Arak. Four new SkypeIn countries. Skype Blogs. Retrieved on 2007-08-13.
  6. ^ Skype User Guide Using Skype for Desk-top Video-Conferences.
  7. ^ Jack McCarthy. China bans Skype. InfoWorld. Retrieved on 2006-06-17.
  8. ^ eBay Completes Acquisition of Skype. eBay. Retrieved on 2006-06-17.
  9. ^ Skype Launches Next Generation Free Internet and Video Calling for Everyone. Skype. Retrieved on 2006-06-17.
  10. ^ Skype to Announce Disruptive Pricing Strategy for SkypeOut Retrieved: December 19, 2006
  11. ^ What is Skype?
  12. ^ http://www.chron.com/disp/story.mpl/ap/fn/5059323.html
  13. ^ Error in Skype’s Software Shuts Down Phone Service. NY Times. Retrieved on 2007-08-17.
  14. ^ "Skype blames outage on user reboot". 
  15. ^ "Skype Bombshell: 0207 SkypeIn Numbers Must Change", 2007-11-21. Retrieved on 2007-11-29. 
  16. ^ Ten million online.
  17. ^ 8 million onliners. skypenumerology. Retrieved on 2006-11-08.
  18. ^ International carriers' traffic grows despite Skype popularity. TeleGeography Report and Database. Retrieved on 2006-12-07.
  19. ^ Skype VoIP User Guide, FAQ, Hints and Resources How to run Skype from a USB stick.
  20. ^ Skype on your mobile device
  21. ^ Skype for Symbian Coming
  22. ^ 1 million Joost users prepare for year-end launch
  23. ^ FileMon for Windows. Sysinternals. Retrieved on 2006-06-17.
  24. ^ Skype FAQ How to disable Skype "SuperNodes".
  25. ^ Bruno Giussani. Swiss magazine digs deeper in social blog. Lunch over IP. Retrieved on 2006-06-17.
  26. ^ Fear of a Skype Planet. Paul Kedrosky. Retrieved on 2006-06-17.
  27. ^ Skype supernodes sap bandwidth. Computerworld. IDG. Retrieved on 2006-06-17.
  28. ^ Skype Privacy FAQ. Skype. Retrieved on 2006-12-05.
  29. ^ Is Skype's own codec good? - Skype Forums. Retrieved on 2007-08-20.
  30. ^ Ryan Paul. More universities banning Skype. Ars Technica. Retrieved on 2007-01-12.
  31. ^ Alert for the defense security officer of CNRS
  32. ^ Philippe BIONDI and Fabrice DESCLAUX. Silver Needle in the Skype. blackhat. Retrieved on 2006-03-02.
  33. ^ Ben Charny. Skype callers: 'Customer service, please?'.
  34. ^ SKYPE Account Blocked - Skype Forums
  35. ^ Tom Krazit. AMD's lawyers call on Skype.
  36. ^ Skype Forums: Linux Users are fed up.
  37. ^ pagetable.com » Blog Archive » Skype Reads Your BIOS and Motherboard Serial Number
  38. ^ Skype Security Blog - Skype Extras plug-in manager
  39. ^ The Register » Skype snoop agent reads mobo serial numbers
  40. ^ Interview at CNet
  41. ^ Uplink Skype to SIP Adapter Software - Connect SIP to the Skype Network
  42. ^ eBay Completes Acquisition of Skype. Skype. Retrieved on 2006-06-12.
  43. ^ "eBay to buy Skype in $2.6bn deal", BBC, September 12, 2005. 
  44. ^ Can Skype Keep Its Secrets?
  45. ^ Pallavi Gogoi. "Skype Under Attack", Business Week, McGraw Hill, June 6, 2006. 
  46. ^ "Skype says texts are censored by China", FT.com, Financial Times, April 18, 2006. 
  47. ^ Dynamic Internet Technology Inc. Alleges Skype Redirects Users in China to Censorware Version - Ten Days After Users Are Able To Download Freegate Software Through Skype, TMCnet, September 24, 2007

Retrieved from "http://en.wikipedia.org/wiki/Skype"
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