ITIS 1210ITIS 1210Introduction to Web-Based Introduction to Web-Based

Information SystemsInformation Systems

Chapter 15Chapter 15How VoIP and Skype WorkHow VoIP and Skype Work

IntroductionIntroduction

Internet pioneered many new forms of Internet pioneered many new forms of communicationcommunication

Enabled old forms as wellEnabled old forms as well Telephone callsTelephone calls Voice converted to digitalVoice converted to digital Digital packaged in packetsDigital packaged in packets Sent to destination over Internet using TCP/IPSent to destination over Internet using TCP/IP

IntroductionIntroduction

Don’t even need a phoneDon’t even need a phone Call directly from computer to computerCall directly from computer to computer Microphone & speakers on each endMicrophone & speakers on each end

Might even be a USB connectionMight even be a USB connection

Must be using the same software thoughMust be using the same software though Sometimes built into popular IM programsSometimes built into popular IM programs

Yahoo MessengerYahoo Messenger AOL IMAOL IM

IntroductionIntroduction

Big advantage for businesses is costBig advantage for businesses is cost Separate telephone and data networks not Separate telephone and data networks not

requiredrequired Calls inside the network are freeCalls inside the network are free

VonageVonage

VoIP also implemented without a VoIP also implemented without a computer at allcomputer at all

Vonage uses special hardwareVonage uses special hardware Connects directly to a network connectionConnects directly to a network connection

Cable modem, home router, corporate networkCable modem, home router, corporate network

Still uses TCP/IP over local networkStill uses TCP/IP over local network Then over InternetThen over Internet Then to regular telephone network at endThen to regular telephone network at end

VonageVonage

In order to use Vonage service you needIn order to use Vonage service you need A high speed Internet connection such as A high speed Internet connection such as

Cable or DSL Cable or DSL A US or Puerto Rico billing and shipping A US or Puerto Rico billing and shipping

address address A Vonage Phone Adapter A Vonage Phone Adapter Any touch-tone phone, corded or cordless Any touch-tone phone, corded or cordless

VonageVonage

Call anywhere, any time for lessCall anywhere, any time for less Doesn’t affect using your computerDoesn’t affect using your computer

Surf & call at same timeSurf & call at same time

Find out more at Find out more at www.vonage.com

SkypeSkype

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

SkypeSkype

Skype permits calling from computer toSkype permits calling from computer to LandlinesLandlines Mobile phonesMobile phones

Enters normal telephone network only at Enters normal telephone network only at endend

Pay for these calls but not muchPay for these calls but not much

SkypeSkype

Download Skype for freeDownload Skype for free www.skype.com

Skype-to-Skype is freeSkype-to-Skype is free Add a Webcam and Skype video calls are Add a Webcam and Skype video calls are

possiblepossible Also free to other Skype usersAlso free to other Skype users

Cannot be used for emergency callingCannot be used for emergency calling

SkypeSkype

Skype is peer-to-peer technologySkype is peer-to-peer technology There is no central serverThere is no central server

You first log in using your PCYou first log in using your PC Skype connects you to a “supernode”Skype connects you to a “supernode”

Typically an ordinary PC running SkypeTypically an ordinary PC running Skype Perhaps even your PC without your knowledgePerhaps even your PC without your knowledge

Supernode sends you “host cache” Supernode sends you “host cache” informationinformation IP address & port number for other supernodesIP address & port number for other supernodes

SkypeSkype

Having this information lets Skype connect Having this information lets Skype connect you to these other supernodesyou to these other supernodes

To locate another Skype user you can To locate another Skype user you can search for themsearch for them Search information sent to a supernodeSearch information sent to a supernode If it has that person’s information it returns it If it has that person’s information it returns it

to youto you If not, it contacts other supernodesIf not, it contacts other supernodes

SkypeSkype

To make a call you select a Skype user To make a call you select a Skype user you knowyou know

Your PC sends packets to the destinationYour PC sends packets to the destination Can also call to normal telephonesCan also call to normal telephones

Skype connects to PSTN or mobile network at Skype connects to PSTN or mobile network at endend

JoostJoost

System for distributing recorded TV shows System for distributing recorded TV shows and other forms of video over the Web and other forms of video over the Web using peer-to-peerusing peer-to-peer

P2P TV technology differs from streaming P2P TV technology differs from streaming in the sense that the servers serve only a in the sense that the servers serve only a handful of clientshandful of clients Each of the clients in turn propagate the Each of the clients in turn propagate the

stream to more downstream clients and so onstream to more downstream clients and so on This moves the distribution costs from the This moves the distribution costs from the

channel owner to the userchannel owner to the user