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Skype is an application That Provides video chat and voice call services. Such users may exchange digital documents or images, text, video and any others, and may Transmi Both text and video messages. Skype Allows the creation of video conference calls. Skype is available for Microsoft Windows, Macintosh, or Linux, as well as Android, Blackberry, Apple and Windows smartphones and tablets.  Skype is based on a freemium model. Much of the service is free, soft Skype Credit or a subscription is required to call a Landline or a mobile phone number. At the end of 2010 There were over 660 million users Worldwide, with over 300 million active Each month estimated as of August 2015.  At one point in February 2012, There were thirty four million users concurrently online on Skype. 
First released in August 2003, Skype Was created by the Swede Niklas Zennström and the Dane Janus Friis, in Cooperation with Ahti Heinle, Priit Kasesalu, and Jaan Tallinn, Estonians WHO Developed the backend That Was Also used in the music-sharing application Kazaa.  In September 2005, eBay Skype Acquired for $ 2.6 billion.  In September 2009  Silver Lake, Andreessen Horowitz and the Canada Pension Plan Investment Board Announced the acquisition of 65% of Skype for $ 1.9 billion from eBay, Which attributed to the enterprise a market value of $ 2.92 billion. Microsoft Bought Skype in May 2011 for $ 8.5 billion. Its Skype division headquarters are in Luxembourg, soft Most of the development team and 44% of all the division’s Employees are still situated in Tallinn and Tartu, Estonia.   
Allows Skype users over the Internet to Communicate by voice using a microphone, video by using a webcam, and by instant messaging. Skype-to-Skype calls to other users are free of charge, the while calls to Landline telephones and mobile phones (over traditional telephone networks) are Charged via a debit-based user account system called Skype Credit. Some network administrators have banned Skype on corporate, government, home, and education networks,  citing Reasons Such as inappropriate usage of resources, excessive bandwidth usage and security Concerns. 
Skype Originally featured a hybrid peer-to-peer and client-server system.  Skype has been powered entirely by Microsoft-operated supernodes SINCE May 2012.  The 2013 mass surveillance Disclosures Microsoft Revealed That hadd Granted unfettered access to intelligence Agencies Skype supernodes and communication content.
Was Skype Founded in 2003 by Niklas Zennstrom, from Sweden, and Janus Friis, from Denmark.  The Skype software Was created by Estonians Ahti Heinle, Priit Kasesalu, and Jaan Tallinn.  The first public beta version was released on 29 August 2003.
In June 2005, Skype entered Into an agreement with the Polish web portal Onet.pl for an Integrated Offering on the Polish market.  On 12 September 2005, eBay Inc. Agreed to acquire Luxembourg-based Skype Technologies SA for approximately US $ 2.5 billion in up-front cash and eBay stock, plus Potential performance-based consideration.
On 1 September 2009 Announced That It Was Was eBay selling 65% of Skype to Silver Lake, Andreessen Horowitz, and the Canada Pension Plan Investment Board for US $ 1.9 billion, valuing Skype at US $ 2.75 billion.
On 10 May 2011 Microsoft Corporation Acquired Skype Communications, S.à r.l for US $ 8.5 billion.  Was The company incorporated as a division of Microsoft, and Microsoft Acquired all of the company’s technologies with the purchase. This Was completed on 13 October 2011.
Its acquisition Shortly after, Microsoft Integrating the Skype service Began With its own products:
Along with taking over development of Existing Skype desktop and mobile apps, the company Developed a dedicated client app, called Skype for Modern Windows, for Its Newly released, touch-Focused Windows 8 and Windows RT operating systems. This became downloadable app from the Windows Store When the new OS Launched on October 26, 2012. The Following year, Skype for Modern Windows became the default messaging app for Windows 8.1, replacing the Windows 8 Messaging app at the time, and became pre- Every device software installed on That came with or upgraded to 8.1.
When Office 2013 Introduced the company on February 27, 2013, Announced That It Was 60 Skype world minutes per month WOULD BE consumer Included in Office 365 Plans (Home and Personal, and University).
In a month-long transition period from April 8 to 30, 2013, it Phased out Its long-standing Windows Live Messenger instant messaging service in favor of Skype, Messenger Continued although in mainland China. On 11 November 2014, Microsoft Lync Announced That in 2015 WOULD BE Replaced by Skype for Business. The latest version of the communication software combines features of Lync and Skype software the consumer. There are two user interfaces – Organizations Can Their switch from the default users Skype for Business interface to the Skype for Business (Lync) interface.
Registered users of Skype are Identified by a unique Skype Name and may be listed in the Skype directory. These Allows Skype registered users Both to Communicate through instant messaging and voice chat. Voice chat Allows telephone 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, and editing of previous messages. Offline messages Were Implemented in a soft beta of version 5 after a few weeks removed without notification. The usual features familiar to instant messaging users-user profiles, online status Indicators, and so on-are Also Included.
The Online Number, a.k.a. SkypeIn, service Allows users to Receive Skype calls on Their computers Subscribers dialed by conventional phone 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, India, Ireland, Japan, Mexico, Nepal, New Zealand, Poland, Romania , South Africa, South Korea, Sweden, Switzerland, Turkey, the Netherlands, the United Kingdom, and the United States. 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. The Growing Countries on this list are Referred to collectively as the SkypeIn Countries.
Skype supports conference calls, video chats, and screen sharing between 25 people at a time for free.
Skype does not Provide the Ability to call emergency numbers, Such as 112 in Europe, 911 in North America, or 100 in India and Nepal.  Howevera, as of December 2012, there is limited support for emergency calls in the United Kingdom, Australia, Denmark, and Finland. 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”. As a Result, the U.S. National Emergency Number Association Recommends That all VoIP users have an analog line available as a backup.
On July 14, 2011, Skype partnered with Comcast to Bring Its video chat service to Comcast via Their Subscribers HDTV sets.
On 17 June 2013, Skype released a free video messaging service, Which Can Be operated on Windows, Mac OS, iOS, Android and BlackBerry.
On 12 August 2013, Skype released the 4:10 update to the app for Apple iPhone and iPad That Allows HD quality video for iPhone 5 and fourth-generation iPads.
On 20 November 2014, Microsoft Office’s team Announced That a new chat powered by Skype is going to swear Implemented in developer’s software, giving tools to swear Able to chat with co-workers in the Same document.
On 15 September 2015, Skype Announced the release of Mojis, “a brand new way to express yourself on Skype.” Mojis are short clips / gifs featuring characters from films and TV shows to swear entered Into the Same conversations with ease as emoticons. They are working with Universal Studios, Disney Muppets, BBC and other studios to add to the collection of Mojis available.
On 21 December 2015, Gurdeep Singh Pall, Corporate Vice President of Skype, Microsoft Announced That the technology Acquired from Talco, “maker of an innovative mobile app for on-the-go business communications (…) Together, the new technology and Will talent help us deliver great new features and capabilities in Both Skype and Skype for Business. ”
In January 2016 Skype Announced It would roll out free group video calling to users on mobile devices, Including iOS and Android. In February 2016 Microsoft Announced That it hadd Started to Introduce group calling on smartphones and tablets in North America and Western Europe.
In July 2016, an early Skype Alpha Introduced a new version of Skype for Linux client, built with WebRTC technology, after petitions Several Asked hadd Microsoft to continue development for Linux.
On September 30, 2016 Their Skype iOS app updated with new features, Including an option to call Skype contacts on voice commands through Siri.
Skype has changed Many Times on Windows. It has a desktop-only Offered SINCE 2003. Later app, a mobile version Was created for Windows Phones. In 2012 Introduced a new version of Skype for Windows 8 Similar to the Windows Phone version That ran in the Metro interface.  On July 7, 2015 Skype modified the Windows app to direct users to download the desktop version of the app, But It Was set to continue working on Windows RT Until October 2016.  In November 2015, Skype Introduced three new apps, called Messaging, Skype Video, and Phone, intended to Provide an Integrated Skype experience in Windows 10.   On March 24, 2016 Announced the Integrated Skype apps Most did not satisfy users’ needs and Announced That They Would app and the desktop eu Eventually UWP Replaced with a new app.
Currently, Skype offers a Win32 desktop-only app and Skype Preview That is the default app Skype Mobile app in Windows 10 and Included as an option in the latest update to Windows 10.
On 29 October 2007 Launched Its own Skype mobile phone under the brand name 3 Skypephone, Which runs a BREW OS.
Also offers a Skype Skype Wi-Fi Phone, Which 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 eu used to talk with non-Skype users. Can Be used SkypeOut minutes to call any phone for a low price and no monthly fee. The Skype Wi-Fi phone does not Contain a web browser and access hotspots so can’t That requir web-based login or authentication. 
The Nokia N800, N810, and N900 Internet tablets, qual run Maemo
The Nokia N9, Which runs MeeGo, comes with Skype voice calling and text messaging Integrated; howevera, it lacks video-calling.
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.  The PSP Go has the Ability to use Bluetooth connections with the Skype application, in addition to Its built-in microphone.  Skype for PlayStation Vita May Be downloaded via the PlayStation Network in the U.S. It Includes the capability to Receive incoming calls with the application running in the background.
Samsung Smart TV has a Skype app, Which Can Be downloaded for free.  It uses the built-in camera and microphone for the newer models. Alternatively, a Skype Separate mountable camera with built-in speakers and microphones is available to purchase for older models.  This functionality has now been disabled.
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 WSKP100 SMC 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.
Third party Licensing
Third-party developers, Such as Truphone, Nimbuzz, and Fring, Previously 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 made Skype available to BlackBerry users and mobile Provided Fring video calling over Skype as well as support for the Android platform. Skype Fring disabled users from Accessing Skype in July 2010.  Nimbuzz discontinued support on request of Skype in October 2010.
Before and During the Microsoft acquisition, Skype Licensing withdrew from Third Parties Several Producing software and hardware compatible with Skype. The Skype for Asterisk from Digium Was withdrawn product as “no longer available for sale”.  The Senao SN358 + long-range (10-15 km) cordless phone Was discontinued due to loss of license to participate in the Skype network as Peers. In combination, These two products made it Possible to create roaming cordless mesh networks with a robust handoff.
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 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 ), Rather than the more usual client-server model (note That the very popular Session Initiation Protocol (SIP) VoIP is Also a model of peer-to-peer, soft Generally Implementation Requires registration with a server, as does Skype).
On June 20, 2014, Microsoft Announced the deprecation of the old Skype protocol. Within Several months from this date, in order to continue using Skype services, Skype users Will have to update to Skype applications released in 2014. The new protocol Skype-Microsoft Notification Protocol 24. The deprecation became Effective in the second week of August 2014. Transferred files are now saved on central servers.
As far as support is Concerned networking stack, Skype only supports the IPv4 protocol. It lacks support for the next-generation Internet protocol, IPv6.
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 These companies are used by private Often, Pearson’s chi-squared test and Naive Bayes classification are two approaches That Were published in 2008.  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.
G.729 and SVOPC. Skype added a Skype-created codec called SILK to Skype 4.0 for Windows and other Skype Clients. SILK is intended to be “lightweight and embeddable”.  Additionally, Skype has released Opus as an open-source codec, Which Integrates the SILK codec for voice transmission Principles Celta codec with the Principles for higher-quality audio Transmissions, Such as live music performance. Opus Was Submitted to the Internet Engineering Task Force (IETF) in September 2010.  Since crack, it has been standardized as RFC 6716
VP7 is used for versions Prior to Skype 5.5.
As of version 7.0, H.264 is used for Both standard definition and 720p and 1080p high-definition group and one-on-one video chat.