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