ITIS 1210 Introduction to Web-Based Information Systems

ITIS 1210Introduction 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 www.vonage.com

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 • www.skype.com • 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

ITIS 1210 Introduction to Web-Based Information Systems