The Technology behind Skype

Skype is a revolutionary system of making free phone calls to other Skype users and very cheap calls to everyone else in the world. It is easy to install and has many functions, including sending instant messages, making video calls, conference calls, transferring files, and switching easily between voice and text communications. Its basic technology is based on the Kazaa file-sharing program and it is a type of peer-to-peer VOIP client. Its voice quality is better than MSN or Yahoo Messenger and it can encrypt calls end-to-end.

Super Nodes
Skype network uses two types of machines – Super Node (SN) and ordinary host (Skype Client). The computer of an ordinary host has to link up with the network and to Super Nodes, which are the ends of the ordinary hosts. If a computer has a public IP, it can become an SN. For a proper login, an ordinary host needs to register with Skype login server, after connecting to a super node. The Skype login server maintains a record of your name, password, e-mail address, and user name. All Super Nodes have to connect to this server in order to verify the above data.
Super Nodes are very useful, because they improve search performance, accelerate file transfers and scalability of the network, help the mutual connectivity of ordinary hosts, and steer the encrypted network traffic properly. Super Nodes also help in looking for other users in the network, by the process of 'Global Indexing'.

Functioning Of Skype
The login process is an important step of the functioning of the Skype. The SC has to connect to a SN, so that the username and password can be authenticated. When Skype is able to establish a TCP connection to the HC IP address, the user name and the password will have to be verified with the Skype login server. Thereafter, the media transfer process starts, in which the Skype video/voice communication is established via the UDP. The media traffic will flow, without any difficulty, if both Skype clients are on real IPs. If, however, one client or both the clients are not on public IP, then the voice traffic will flow on UDP or TCP. Even when there is silence between both the clients, voice packets keep flowing between the two ends so that the connection is kept alive.

Success of Skype
Skype has been very successful, mainly because of the following reasons: it is easy to install and use; its voice quality is superior to that of other systems; no problems are encountered while using it on computers with firewall; and, it ensures privacy as the communication is encrypted. Adware or Spyware is not included in the Skype application but third parties can add these functionalities. All these advantages have increased the popularity of Skype considerably.

Skype and the Skype logo are trademarks of Skype Technologies S.A. U3

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