skype
Skype is a program for Internet telephony( VoIP) that is available for free. The concept of this anarchic network is a peer-to-peer( P2P) network, in which every computer is directly connected to every other and can use the resources and services of the other computers.
Skype was programmed by the developers of Kazaa and uses super-peer technology to connect to other Skype users and establishes voice communication over it.
VoIP has been implementedin Skype, through which telephone connections can be made to other computers, to softphones, but also to telephones. Skype supports Internet telephony through some features such as conference calls, video transmission, high voice quality according to Full- HD-Voice or file transfer and also shows which contacts are currently available. In addition to telephony and conferencing, Skype supports video telephony and web conferencing.
VoIP has been implemented in Skype, through which telephone connections can be made to other computers, to softphones but also to telephones. Skype supports Internet telephony through some features such as conference calling, video transmission, high voice quality according to Full-HD-Voice or file transfer and also shows which contacts are currently reachable. In addition to telephony and conferencing, Skype supports video telephony and web conferences with 50 or more participants.
http://www.skype.com