Monday - August 21, 2000

Web page - http://www.cs.purdue.,edu/homes/cs422

To Subscribe to Mailing List - (from CS account) type:

> mailer add me to cs422 l? (1 or PSO division 1, 2 for PSO division 2, etc.)

Grading

    5% - Quizzes

    5% - HW/Problems

    50% - Projects

    40% - Final/Midterm

** For this class the textbook is important. **

Wednesday - August 23, 2000

ifconfig - gives IP adfdress of a computer

loopback network - implemented by software not a cable

IP Addresses

lab network - 128.10....

private network - 10.0.0....

What is a network?

- A group of interconnected computers

Why a network?

- Resource sharing

    files, information, databases, devices (printers), processing power ( ** why internet started ** )

- Communication between users and applications

- Personal Computers started as autonomous units.  Now the connections to the internet has become an important part of the computer.

"The Network is the computer." © Sun

History of the Internet

- In the late 1960s the department of defense advanced research project agency (ARPA) created a network nationwide to give computer access to different research centers.

- The alternation was to give a computer to each center, which was too expensive.

- Research in the internet evolved in the '70s and '80s. ( TCP/IP, FTP, telnet )

- The internet becomes a commercial success in the '90s.

- The internet has been doubling in size ( number of computers connected ) every 9 - 12 months

Transmission Media

Forms of energy used for transmission:

- electricity

- light *

- microwaves *

- sound

- infrared light *

* examples of Radio Frequencies

Radio Frequencies are succeptible to interruptions by sun, thunderstorms, etc.

Media Used for Transmission

Copper wire is used for electricity

- coaxial cable ( used for television cable ): more bandwidth, less noise and faster

- twisted pair ( used for telephone ): noise in both cables cancels each other

Friday - August 25, 2000

Media Used for Transmission

Copper Wire

- Coaxial Cable (less noisy than twisted pair)

-  Twisted Pair

- Transmission speed is .7c ( c = 3 x 10^{8 m}/_s)

- Not good for long distances because

    * noise is added

    * signal decreases due to resistance of cable

Fiber Optic

 - less succeptible to noise

- good for long distances

- expensive

- not easy to fix a break (easy to break)

- difficult to connect ends of optic fiber

- high bandwidth - high throughput

Radio (Radio Frequency - RF)

- Wireless Networks

- RF are electromagnectic waves

- Frequency Spectrum is limited:

- Because RF is good for short distances, two users in different geographic areas can have the same frequency

Microwaves

- Also used to link two points

- A clear path between the two points is needed

Satellite

- Good for long distances

- bandwidth is comparable to DSL & Cable

- expensive

- two types of Satellite:

    * GEO ( geostationarly earth orbit) - remain at same point in sky relative to the earth: about 36,000 km (20,000 miles) above the earth; long delay