2. Introduction:
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. Niklas Zennström Janus Friis
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.

3. 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.

4. 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 codecs
VP7 is used for versions prior to Skype 5.5
As 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.
Client
Clients 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

5. The Benefit of Using Skype
Free Computer-to-Computer calls
-using a computer or via mobile application

6. 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.

7. Skype Online number and Voice Mail
The Benefit of Using Skype
-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

8. 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.

9. 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.

10. Video : The example of skype user.
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