1. Agenda Last class: Digitization Today: Network Hardware Typing
How do computers talk to each other?
Needs?
Same hardware
Same rules (protocols) for encoding data
Typing

2. Network Cable How to connect 2 computers? 4 computers?
Hardware
Network Cable How to connect 2 computers? 4 computers?

3. Client-Server Network
One computer is the “server” - stores important files, data Other computers are “clients” - asks the server to use its files

4. Client-Server ANALOGY
Server is like a waiter Clients are like customers - asks the server for food - not allowed into the kitchen

5. Peer to Peer Network
All computers have equal access to others. Good for sharing.

6. Peer to Peer Network
Another way to connect the computers

7. Hub or Repeater Just repeat signals to all computers
Peer to Peer Network
Hub or Repeater Just repeat signals to all computers
Hello!
Hello!
Hello!
Hello!

8. Bridge or Switch Send signal to whom you want
Peer to Peer Network
Bridge or Switch Send signal to whom you want
Hello!
Hello!
Bye!
Bye!

9. Router 3 computers 1 internet connection
Peer to Peer Network
Router 3 computers 1 internet connection
Hello!
Hello!
Bye!
To Internet
Bye!

10. Peer to Peer vs Client-Server Pros and Cons
Client-Server ++ Pros? -- Cons?

11. Peer to Peer vs Client-Server Pros and Cons
P2P
+ More independent
+ File sharing
+ No wait time for server
-- Low security
-- Share internet connection (slow)
Client-Server -- Broken server = Broken network -- Need a fast server + More security + Easier to configure many computers

12. LAN and WAN
LAN = Local Area Network (eg: home, personal use) WAN = Wide Area Network (eg: school, apartment, for internet)

13. Internet Connection Router WIFI Internet Bluetooth Service Provider
(ISP)
Modem
Cable
DSL
Satellite

14. Modem use phone line to send Slow: 56 kbps (56 kilo bits per second)
“Bandwidth”
Cheap
Dial for connection
Can’t use phone at the same time

15. Digital Subscriber Line
DSL = Digital Subscriber Line
Faster 10 Mbps
Expensive ~900 rmb per month
Uses phone lines too, but always online
Can talk on phone at the same time
Problem: need to be near the phone company

16. Cable Cable Faster! 50 Mbps Cheaper than DSL
Use cable TV connection, always on
Can be far from the cable company
Problems:
shared connection – slow during peak hours
Low security

17. Other connections T1 line Satellite
For government, university, big business
$$$$$$$$$$$$$$$$$$$, but very fast
Satellite
For people living away from the city
$$$ to set up

18. Internet Connection Modem – slow, $, phone
DSL – fast, $$$, phone at same time
Router
Internet
Service
Provider
(ISP)
Cable – faster, $$, TV
Satellite – away from city

19. Network History
1973: U of California and Stanford wanted to connect their networks. Made TCP/IP
Military and Research use only
1989: Connect to the world.
China connected in 1994 – why so slow?

20. Internet in China Government wants control Growth – not too fast
Only give Internet to “good” people. Need license.
Information – don’t let bad info spread
Censorship
Block websites (“Great Firewall of China”)
News, politics, foreign sites. Some good, some bad.
Internet police – delete messages of activism, criticism, controversy
Money – government wants it, and they know Internet is good for business… so
“Good” companies get the best opportunities

21. Internet in China Government wants control
If you try to do something bad
The Firewall will try to stop you first (Block site, delete / messages)
Go to Jail
Die

22. Wednesday
Quiz about networking