Skype is a proprietary voice-over-Internet Protocol service and software application originally created by Niklas Zennström and Janus Friis in 2003, and owned by Microsoft since 2011. The service allows users to communicate with peers by voice, video, and instant messaging over the Internet. Phone calls may be placed to recipients on the traditional telephone networks. Calls to other users within the Skype service are free of charge, while calls to landline telephones and mobile phones are charged via a debit-based user account system. Skype has also become popular for its additional features, including file transfer, and videoconferencing. Competitors include SIP and H.323-based services, such as Empathy, Linphone, Ekiga as well as theGoogle Talk service.

Introduction:

Niklas Zennström Janus Friis

Security & Privacy:

Skype is claimed to be a secure communication; encryption cannot be disabled, and is invisible to the user. Skype reportedly uses publicly-documented, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations. The company's Policy includes:

1. Usernames are unique.2. Callers must present a username and

password or other authentication credential.3. Each caller provides the other with proof of

identity and privileges whenever a session is established. Each verifies the other’s proof before the session is allowed to carry messages.

4. Messages transmitted are encrypted from caller to caller. No intermediate node (router) has access to the meaning of these messages.

System & 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, rather than the more usual client–server model.

Audio codecs: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".

Video codecsVP7 is used for versions prior to Skype 5.5As of version 5.7 VP8 is used for both group and one on one standard definition video chat and H264 is used for 720p and 1080p high definition group and one on one video chat.

ClientClients are available for Microsoft Windows (2000, XP, Vista, 7, Mobile), iOS (iPad, iPhone, iPod Touch), Mac OS X (Intel, PPC), Symbian S60, Sony PlayStation Portable (PSP), Linux (includes Android, Maemo), and for 2010 TV models from LG, Panasonic, and Samsung, but these TVs need a special webcam

The Benefit of Using Skype

Free Computer-to-Computer calls-using a computer or via mobile application

Calling and Texting Phones-This comes especially in handy if you're traveling without a working cell phone: simply find a Wi-Fi connection, connect your phone to it, launch the Skype application and make calls.

The Benefit of Using Skype

Skype Online number and Voice Mail

-you can purchase a number which allows friends and family to call you at local rates as if you were using a phone, only you'll answer with Skype. Skype also offers a voice mail service

Group Calling video-Catch up face-to-face with more people at the same time on a group video call with Skype. Whether you’re kicking off a project or showing off the latest addition to the family, it’s the next best thing to being there.

Skype Internet Access-allows you to use Skype credit to pay for access to Boingo Internet hotspots, which you can find in coffee shops, bookstores and even airports around the world.

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Video : The example of skype user.