CS 422

Week 1

08/25/03 to 08/29/03

Notes written by: Mihir Gandhi

 

Download printable format (PDF) of this page here

Lecture 1: 08/25/03 (on Course policies and topics)

 

Instructor: Gustavo

Office: CS 116

Email: grr@cs.purdue.edu

Web: http://www.cs.purdue.edu/homes/cs422/

 

Add yourself to mailing list:

-         Login to lore.cs.purdue.edu using your CS account

-         Type “mailer add me to cs422-pso<#>”

-         # = Your PSO Section number

-         Eg. mailer add me to cs422-pso2

 

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 we will cover:

  1. Low level details

-         Signals & Media

-         Digital Vs. Analog

-         Synchronous vs. Asynchronous communication

-         Modulation

-         Bandwidth, throughput and noise

-         Time & frequency multiplexing

 

  1. 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)

 

  1. Internetworking

-         Protocol layering

-         IP Addressing

-         APP

-         IP Fragmentation & assembly

-         TCP, Reliability, flow control, port demultiplexing

 

  1. Applications

-         Socket API

-         Client/Server concurrency

-         TELNET, FTP, HTTP, CGI

-         RPC, CORBA, Java RPC

-         NFS, SMB, IPv6

 

 

Lecture 2: 08/27/03 (on Introduction to Network)

 

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

o       FTP (File transfer protocol)

o       NFS (Network file system – Used on UNIX)

o       SMB (pronounced ‘samba’) (Super message block – Used in Windows)

o       HTTP (Hyper text transfer protocol – Used on Internet)

·        Distributed Computing

o       Multiple machines work on the same problem/program simultaneously

o       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

o       Eg. (2) Rendering farms: Render frames in a computer generated picture

o       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: 08/29/03 (on Transmission Media)

 

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)

o       Remain at the same point in sky

o       They are about 36000Km (~ 20000miles) above Earth and around the equator

o       Limited to 40-45 satellites

o       Long delay (~ 0.5 seconds)

·        LEO (Low Earth orbit)

o       Not in the equator

o       200-400 miles above Earth

o       Rotates faster than Earth (Takes about 1.5 hours per revolution)

o       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