ITIS 1210 Introduction to Web-Based Information Systems Chapter 15 How VoIP and Skype Work

Introduction  Internet pioneered many new forms of communication  Enabled old forms as well  Telephone calls  Voice converted to digital  Digital packaged in packets  Sent to destination over Internet using TCP/IP

Introduction  Don’t even need a phone  Call directly from computer to computer  Microphone & speakers on each end  Might even be a USB connection  Must be using the same software though  Sometimes built into popular IM programs  Yahoo Messenger  AOL IM

Introduction  Big advantage for businesses is cost  Separate telephone and data networks not required  Calls inside the network are free

Vonage  VoIP also implemented without a computer at all  Vonage uses special hardware  Connects directly to a network connection  Cable modem, home router, corporate network  Still uses TCP/IP over local network  Then over Internet  Then to regular telephone network at end

Vonage  In order to use Vonage service you need  A high speed Internet connection such as Cable or DSL  A US or Puerto Rico billing and shipping address  A Vonage Phone Adapter  Any touch-tone phone, corded or cordless

Vonage  Call anywhere, any time for less  Doesn’t affect using your computer  Surf & call at same time  Find out more at

Skype  Co-creators of KaZaA  Skype sold to eBay in 2005 for $2.6 billion

Skype  Skype permits calling from computer to  Landlines  Mobile phones  Enters normal telephone network only at end  Pay for these calls but not much

Skype  Download Skype for free   Skype-to-Skype is free  Add a Webcam and Skype video calls are possible  Also free to other Skype users  Cannot be used for emergency calling

Skype  Skype is peer-to-peer technology  There is no central server  You first log in using your PC  Skype connects you to a “supernode”  Typically an ordinary PC running Skype  Perhaps even your PC without your knowledge  Supernode sends you “host cache” information  IP address & port number for other supernodes

Skype  Having this information lets Skype connect you to these other supernodes  To locate another Skype user you can search for them  Search information sent to a supernode  If it has that person’s information it returns it to you  If not, it contacts other supernodes

Skype  To make a call you select a Skype user you know  Your PC sends packets to the destination  Can also call to normal telephones  Skype connects to PSTN or mobile network at end

Joost  System for distributing recorded TV shows and other forms of video over the Web using peer-to-peer  P2P TV technology differs from streaming in the sense that the servers serve only a handful of clients  Each of the clients in turn propagate the stream to more downstream clients and so on  This moves the distribution costs from the channel owner to the user