Transcript Chapter 15 - Personal Web Pages

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 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