Agenda

• Last class: Digitization

• Today: Network Hardware– How do computers talk to each other?– Needs?

• Same hardware• Same rules (protocols) for encoding data

• Typing

Hardware

Network Cable

How to connect

2 computers?

4 computers?

Client-ServerNetwork

One computer is the “server”

- stores important files, data

Other computers are “clients”

- asks the server to use its files

Client-ServerANALOGY

Server is like a waiter

Clients are like customers

- asks the server for food

- not allowed into the kitchen

Peer to PeerNetwork

All computers have equal access to others.

Good for sharing.

Peer to PeerNetwork

Another way to connect the computers

Hello!Hello

!Bye!

Bye!

Peer to PeerNetwork

Router

3 computers1 internet connection

To Internet

Peer to Peer vs Client-ServerPros and Cons

Client-Server

++ Pros?

-- Cons?

Peer to Peer

++ Pros?

-- Cons?

Peer to Peer vs Client-ServerPros and Cons

Client-Server

-- Broken server = Broken network

-- Need a fast server

+ More security

+ Easier to configure many computers

P2P

+ More independent

+ File sharing

+ No wait time for server

-- Low security

-- Share internet connection (slow)

LAN and WAN

LAN = Local Area Network

(eg: home, personal use)

WAN = Wide Area Network

(eg: school, apartment,for internet)

Internet Connection

RouterWIFIBluetooth

ModemCableDSLSatellite

InternetServiceProvider

(ISP)

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

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

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

Other connections

• T1 line– For government, university, big business– $$$$$$$$$$$$$$$$$$$, but very fast

• Satellite– For people living away from the city– $$$ to set up

Internet Connection

Router

Cable – faster, $$, TVSatellite – away from city

InternetServiceProvider

(ISP)

Modem – slow, $, phoneDSL – fast, $$$, phone at same time

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?

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

Internet in China

• Government wants control– If you try to do something bad

• The Firewall will try to stop you first(Block site, delete email / messages)

• Go to Jail• Die

Wednesday

• Quiz about networking