CS422 Lecture Notes 8/25-8/29

 
Instructor: Professor Gustavo Rivera-Rodriguez
Email: grr@cs.purdue.edu
Website: http://www.cs.purdue.edu/homes/cs422/  
 
Mailing list

•  Login to lore.cs.purdue.edu using your CS account
•  Type “mailer add me to cs422-pso<#>”
•  where # is your PSO section

 
Grade Distribution

• 50% Projects
• 50% Midterm and Final exam
• Late policy: 5% penalty per day, for 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 covered this semester:

Low level details

• Signals and 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 and assembly
• TCP, Reliability, flow control, port demultiplexing

Applications

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

 

 
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 email
• The research on the internet continues in the 1970's and 1980's
• Internet becomes a commercial success in the 1990's (Internet Revolution)
• 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 in 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

 
Forms of energy used for transmissions:

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

 
Media used for transmission

• Copper wire
• Coaxial cable
• Twisted pair - four cables twised on thes ends, reduces electomagnetic noise
• Transmission speed in copper wire is 0.7c where c = 3 * 108 m/s)
• Radio         
• 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 you can send

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 (about 20000 miles) above Earth and around the equator
• Limited to 40-45 satellites
• Long delay (about 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