CNET network simulator

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CNET network simulator

• Comp 211 practical

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Omar Baqueiro Espinosa

• Thursday practical session
• Email omar_at_csc.liv.ac.uk
• Office 211 email first
• Web page
• www.csc.liv.ac.uk/omar

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This Lecture

• How to use CNET
• How it works
• Built-in protocols
• What questions to answer

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Part 1 CNET intro

• What is CNET
• What is Jnet

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Simulation

• Finding errors
• Visualizing algorithms
• Estimating performance
• Complements proving and real testing

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Experiments

• Simulations are the CS equivalent of experiments
• Must be repeated!
• Averages and standard deviation
• Use plots and graphs (gnuplot, excel)

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CNET

• Educational simulator
• Everything on one computer
• Simulates application and physical layer
• You (we) supply the in-between

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CNET screenshot
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CNET
Application
Messages
Protocol
Protocol
Frames
Physical Layer
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Jnet

• Java front-end for CNET
• Allows you to choose protocols and options
• Gives statistics

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Protocol Selection
Show CNET interface?
Enable FL in simulation?
Enable FC in simulation?
Set Link delay time
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Protocol Selection
Show CNET interface?
Enable FL in simulation?
Enable FC in simulation?
Set Link delay time
CNET output window (also saved in logfile.txt
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Jnet and CNET
Jnet.class
logfile.txt
Jnet. java
MYPROTOCOL
CNET
Proto col
Proto col
Proto col
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Summary

• Use jnet to start CNET
• Can test different protocols
• See them working
• Collect statistics

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Part 2 Protocols

• 5 different protocols

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Protocol1

• Simplest protocol possible
• Assumes perfect network
• No checksum
• No acknowledgements

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Stop and Wait

• Checksum
• Positive acknowledgements
• One packet at a time

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Adaptive

• Measures round-trip time
• And sets time-outs accordingly
• Good time-out times

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Piggyback

• Sends acknowledgments with data
• More efficient

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Selective Repeat

• Uses sliding window
• Positive and negative acknowledgements
• Repeats only what is needed

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Summary

• Simple to advanced protocols
• Source in C files
• Test them under different circumstances

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Part 3 the practical

• What you are going to do

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Planning

• 28th Sept. Simple questions
• 5th Oct Start on your own question
• 12th, 19th Oct Run simulations, collect data
• 26th Oct Finish simulations, write report

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28th Sept Simple questions

• Get familiar with the Jnet interface
• Run some test simulations and understand the
  results obtained.
• Ask simple questions
• Which protocols cannot deal with frame
  corruption?
• Which ones cannot deal with frame loss?
• Ask me LOTS of questions!!!!!!

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5th Oct Start on your own question

• Think of a research question (hyptothesis) to
  test.
• It must be possible to answer it with information
  given by the simulator
• Ask me more questions
• Is my research question adequate? ?
• Can my question be X with Y and Z? ?
• Can you give me a research question? ?

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12th, 19th Oct Run simulations, collect data

• Run simulations with different parameters to
  collect data for your question.
• Save this data (see my comp211 page)
• Make sure the data does answer your question.
• Oh yeah, ASK.

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26th Oct Finish simulations, write report

• Did something go wrong? Repeat simulations.
• Write your report. Use graphics and tables to
  illustrate your answer.

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Log files

• Write down your experiments
• Life sciences use log books
• Do not delay processing
• Jnet supplies logfile.txt

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Questions (week 1)

• Which protocols cannot deal with frame
  corruption?
• Which ones cannot deal with frame loss?

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More Simple Questions

• Does piggyback use negative acks? (read source)
• Which node sends more messages? (simulate, then
  check topology file)
• How often did/should you repeat the simulation?

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Research sample Question

• Adaptive should get better over time. Can you
  show this in a graph? (you must use a extra
  option)

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Sample question 2

• You can change the propagation delay of a network
  link.
• How does this influence the relative performance
  of each protocol?
• Can you estimate the real delay between Liverpool
  and Manchester

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Summary

• Think of a short question, give a long answer
• Think, guess, inspect, run experiments
• Be creative
• Keep it Simple

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Important urls

• CNET page
• www.csse.uwa.edu.au/pls/cnet/
• By Chris McDonald
• Internet principles page
• www.csc.liv.ac.uk/omar/teaching/comp211.htm
• By Omar Baqueiro
• Warriors of the net video (just 13 minutes
  long)
• www.csc.liv.ac.uk/omar/teaching/warriors-700-VBR.
  mpg
• By Gunilla Elam, Tomas Stephanson, Niklas
  Hanberger
• http//www.warriorsofthe.net/