CS422 Class Notes
August 25, 2003 (Monday) to August 29, 2003 (Friday)
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Grading:
- 50% Projects
- 50% Midterm and Final exam
- Late policy: 5% penalty
per day after the deadline up to a week
Topics:
1. Low level details
- Signals & Media
- Digital Vs. Analog
- Synchronous vs. Asynchronous communication
- Modulation
- Bandwidth, throughput and noise
- Time & frequency multiplexing
2. 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)
3. Internetworking
- Protocol layering
- IP Addressing
- APP
- IP Fragmentation & assembly
- TCP, Reliability, flow control, port demultiplexing
4. Applications
- Socket API
- Client/Server concurrency
- TELNET, FTP, HTTP, CGI
- RPC, CORBA, Java RPC
- NFS, SMB, IPv6
History of the Internet
- It started in late 1960’s.
- The 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 this network (ARPANET).
- The main use of the network was
remote access (telnet).
- After telnet, the next most popular
application that uses the net was e-mail.
- The research on the internet continues
in the 70’s and 80’s.
- The internet becomes a commercial
success in the 90’s.
- The 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).
- FS (Network File System) ( in UNIX)
- HTTP (Hyper Text Transfer Protocol) (Internet)
- Distributed Computing
- Multiple machines work on the
same problem/program simultaneously
- Cluster computing: A group of inexpensive machines are connected
through a fast network like Ethernet. Google distributes its search query
among multiple machines
- Rendering farms: Render frames in a computer generated picture
- 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 command:
/usr/sbin/ping
- Tracert
- Usage in windows: tracert <host>
- Lists the intermediate routers
needed to reach a destination host
- 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
Transmission Media
Forms of Energy used for transmission:
- Electricity
- Radio Waves
- Light – Laser or infrared
- Sound
Media used for transmission:
- Copper Wire
- Twisted Pair
- Better version of the telephone cableà Four cables which
are twisted on the ends if there is an electromagnetic voice, if they are
twisted, so it will be added in one and subtracted from the other so will
in turn become zero
- Twisted pair is a better way now. The transmission speed
in copper wire is .7c where c is the speed of light.
- C = 3 * 10^8 m/s.
- Also called Radio Frequency (RF).
- It uses electromagnetic waves.
- Different frequencies are used by
different channels.
- Different spectrum of each element
is limited.
- Each channel has a position in the
spectrum and a bandwidth.
- Higher the wavelength the straight
line they try to go into.
- Wider the bandwidth, the more info
you can send.
- RF can be used with satellites:
- GEO (Geostationary Earth Orbit)
- They remain at the same
point in the sky as compare to the same point on the earth.
- They are about 36000 km (20000
miles) above the earth, around the equator.
- Limited to 40-45 satellites.
- 200-400 miles above earth.
- Rotate faster than earth
(1.3 /hrs/revolution).
- You need an array of satellites to
cover an area.
- Microwave
- Infrared Light
- Laser and optical fibers.
Important limits of a transmission system:
- Propagation Delay: Time required for a signal to travel across media.
- Light, c = 3 *10^8 m/s.
- Electricity in copper = 0.7 c.
Bandwidth:
- Maximum number of times/sec that a signal can change. The bandwidth
limits the maximum throughput
Type of Encoding
- Analog
- Change signal propotional to the value sent
- Digital
- Encode value in 0's and 1's and send the 0's and 1's.
- A 0 and 1 has t be easier to distinguish than propotional change
to the signal
- Digital signals are more tolerant to noise bu use a higher bandwidth