CS422

Week 1 (08/25/03 to 08/29/03)


Lecture on
Monday, 08/25/03
 

 

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 Grade Distribution:

• 50% Projects
• 50% Midterm and Final exam
• Late policy: 5% penalty per day, up to 7 days
• You cannot turning later than 7 days after due date
• 1% extra for writing notes – signup sheet will be bought to class next week

Topics that will be cover:

Low level details:

• Signals & Media
• Digital Vs. Analog
• Synchronous vs. Asynchronous communication
• Modulation
• Bandwidth, throughput and noise
• Time & frequency multiplexing

Packet Transmission :

• Frames
• Error detection techniques
• LAN/WAN topologies
• Bus topology, CSMA/CD, CSMA/CA
• Ethernet hubs
• FDDI, ATM, ADSL
• Repeaters, bridges, switches
• Routing algorithm (Distance vector, link state)

Internetworking :

• Protocol layering
• IP Addressing
• APP
• IP Fragmentation & assembly
• TCP, Reliability, flow control, port demultiplexing

Applications :

• Socket API
• Client/Server concurrentcy
• TELNET, FTP, HTTP, CGI
• RPC, CORBA, Java RPC
• NFS, SMB, IPv6

 

Lecture on
Wednesday, 08/27/03
 
History of Internet

• Started in late 1960’s
• Department of defense (DoD) through advance research project agency (ARPA) created a network to link different research centers
• Since computers were expensive, instead of giving a computer to every university, a few computers were shared using a network (ARPA-NET)
• Main use of this network was remote access (TELNET)
• After telnet, the next most popular application that used the network was E-mail
• The research on the internet continues in the 1970’s and 1980’s
• Internet becomes a commercial success in the 1990's
• Internet has been doubling in size every 9-12 months! 

What is a network?

• A group of inter-connected computers
• Uses of a network:
• Remote access to a computer
• Remote file access:
• FTP (File transfer protocol)
• NFS (Network file system – Used on UNIX)
• SMB ("samba", used in Windows)
• HTTP (Hyper text transfer protocol – Used on Internet
• Distributed computing:
• Multiple computers working on the same projects/problem simultaneously.
  
• Eg. (1) Cluster computing: A group of inexpensive machines are connected through a fast network like Ethernet. Google distributes its search query among multiple machines
• Eg. (2) Rendering farms: Render frames in a computer generated picture
• Eg. (3) SETI (Search for extra-terrestrial intelligence) Project: People donate idle CPU cycles to analyze radio telescope data
  

 

Basic tools to test the network:

• Ping:
• Usage in windows: ping <host>
• Tells if the machine is alive or not by sending an ICMP (Internet control Message Protocol)
• In solaris, PING program is located in /usr/sbin/ping
• Tracert
• Usage in windows: tracert <host>
• Lists the intermediate routers needed to reach a destination host
•  Tracert is not perfect, since routes may change. However, this does not happen too often
•  In solaris, this program is located in /usr/etc/traceroute
• IPConfig
• Lists the network interfaces and IP Addresses in your computer
• In solaris, this program is located in /use/sbin/ipconfig –a

 

Lecture 3 on
Friday, 08/29/03
 

Forms of energy used for transmissions:

• Electricity
• Radio
• Light – Laser & Infrared
• Sound

 
Media used for transmission

• Copper wire
• Other metals like gold, platinum, etc are used, but less frequently because they are expensive
• Coaxial cable: Cable is in center with protection around it to prevent noise from entering the cable
• Twisted pair: To reduce electro-magnetic noise. Coaxial cables are more expensive, but have better resistance to noise
• Transmission speed in copper wire is 0.7c (c = speed of light = 3 * 108 m/s)
• Radio waves         
• Also called radio frequency (RF)
• Uses electro-magnetic waves
• Different frequencies used by different channels
• Frequency spectrum of each channel is limited
  

Each channel has a position in the spectrum, and a bandwidth

• Wide bandwidth implies more information is transmitted. For example, to transmit voice, 3hz is enough, but images need more bandwidth
• RF can be used with satellites
• Two types of satellites        
• GEO (Geo-stationary Earth Orbit)       
• Remain at the same point in sky
• They are about 36000Km (~ 20000miles) above Earth and around the equator
• Limited to 40-45 satellites
• Long delay (~ 0.5 seconds)
• LEO (Low Earth orbit)
• Not in the equator
• 200-400 miles above Earth
• Rotates faster than Earth (Takes about 1.5 hours per revolution)
• Need an array of satellites to cover an area
  

•  Microwave: Need a clear path
• Infrared light
• Laser and optical fibres: Expensive, but a lot of data can be sent
  

Important limits of transmission system:

• Propogation delay: Time required for signal to travel across the media. Copper wire takes 0.7c
• Bandwidth: Maximum number of times per second that a signal can change. Bandwidth limits the maximum throughput