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.)
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
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
Forms of energy used for transmission:
- light *
- microwaves *
- 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
- Coaxial Cable (less noisy than twisted pair)
- Twisted Pair
- Transmission speed is .7c ( c = 3 x 108 m/s)
- Not good for long distances because
* noise is added
* signal decreases due to resistance of cable
- less succeptible to noise
- good for long distances
- 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
- Also used to link two points
- A clear path between the two points is needed
- Good for long distances
- bandwidth is comparable to DSL & Cable
- 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