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CS558 - Homework 7

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• Experimentation with Deficit Round Round
  • This project lets you experiment with the DRR technique that allows different flows to share an output link fairly.

  • You will use a new type of transport agent - called UDP - that does not respond to packet losses. You should see how the DRR schedule can force fair sharing even when the flow does not respond.

  • We will use the classic dumb-bell network in this experiment:

• Network Parameters
  • Link A-X: BW = 1 Mbps, Delay = 10 msec, Buffer Size = default, always DropTail
  • Link B-X: BW = 1 Mbps, Delay = 10 msec, Buffer Size = default, always DropTail

  • Link Y-C: BW = 1 Mbps, Delay = 10 msec, Buffer Size = default, always DropTail
  • Link Y-D: BW = 1 Mbps, Delay = 10 msec, Buffer Size = default, always DropTail

  • Link X-Y: BW = 0.4 Mbps, Delay = 100 msec, Buffer Size = 20, uses different queueing methods

  • Simulation length = 300 sec

• Traffic flows
  • FTP/TCP source 1 at A sending to TCP sink at C
    • Advertized window size = 100,000
    • Packet size = 552 bytes
    • Start time: 0 sec

  • CBR/UDP source 1 at B sending to TCP sink at D
    • Data rate = 0.39 mbps
    • Packet size = 1000 bytes
    • Start time: 0 sec

• Simulating UDP flow in NS
  • UDP flow is a unreliable data rate flow and will not react to packet losses.

  • The way to create a UDP flow in NS is very similar to a TCP flow.

  • The agent entity that simulate an unreliable UDP flow in NS is Agent/UDP and it is created using this OTcl command:

    set VariableName [new Agent/UDP] E.g.: set udp1 [new Agent/UDP]

  • The sink agent entity that receives the unreliable packets is Agent/Null (this entity will receive the packet and discard it - this is necessary, otherwise, NS will run out of memory) The "null agent" is created using this OTcl command:

    set VariableName [new Agent/Null] E.g.: set sink1 [new Agent/Null]

  • Just like TCP, you need to connect the source and the sink using the connect command in NS:

    $ns connect SOURCE DESTINATION E.g.: $ns connect $udp1 $sink1

  • A commonly used traffic generator for an UDP connection is the constant bit rate traffic generator. The name of this class is Application/Traffic/CBR and you can set the transmission rate using the following parameters:

    rate_ = transmission data rate packet_size_ = packet size of each packet sent random_: set to false if packet transmission interval is constant, and set to true otherwise.

  • Example:

    Create a constant bit rate traffic generator that transmits data at a rate of 0.39 Mbps and uses packet size of 1000 bytes. The source sends packets at regular intervals.

    set cbr1 [new Application/Traffic/CBR] ;# create CBR application $cbr1 set rate_ 0.39mbps $cbr1 set packet_size_ 1000 $cbr1 set random_ false

  • Just like the FTP application, you need to attach the CBR traffic generator to a UDP source agent using the attach-agent command:

    $CBR-Object attach-agent $UDP-Agent E.g.: $cbr1 attach-agent $udp1

  • And don't forget to start the CBR application:

    $CBR-Object start E.g.: $ns at 0.0 "$cbr1 start"

    You do not need to start the UDP agent - it will send any packet that it receives from the CBR Object to the corresponding destination.

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• Experiment 1
  • Use:
    • Link X-Y: BW = 0.4 Mbps, Delay = 100 msec, DropTail

  • Plot the throughput of the TCP flow

  • Output GIF file name: DropTail.gif

• Experiment 2
  • Use:
    • Link X-Y: BW = 0.4 Mbps, Delay = 100 msec, RED

    • RED Parameters:
      • min_threshold = 2, 3 or 4
      • max_threshold = 3 * min_threshold
      • max_p = 0.1
      • w_q = 0.002

  • Plot the throughput of the TCP flow

  • Output GIF file names:
    • RED2.gif when min_threshold = 2
    • RED3.gif when min_threshold = 3
    • RED4.gif when min_threshold = 4

• Experiment 3
  • Use:
    • Link X-Y: BW = 0.4 Mbps, Delay = 100 msec, DRR

  • Plot the throughput of the TCP flow

  • Output GIF file name: DRR.gif

• Experiment 4
  • Use:
    • Link X-Y: BW = 0.2 Mbps, Delay = 100 msec, DropTail
    • Do NOT activate the UDP flow (so the TCP flow is the ONLY flow but the bottle neck bandwidth is HALF of the original value)

  • Plot the throughput of the TCP flow

  • Output GIF file name: Half.gif

• Experiment 5
  • Use:
    • Link X-Y: BW = 0.4 Mbps, Delay = 100 msec, DropTail
    • Do NOT activate the UDP flow (so the TCP flow is the ONLY flow but the bottle neck bandwidth is HALF of the original value)

  • Plot the throughput of the TCP flow

  • Output GIF file name: Full.gif

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• Answer Page
  • To help you organize (and to help me grade) the project, here is the answer webpage: Right Click and Save

  • Please save the file as: ~/cs558/hw7/hw7-ans.html

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• Program
  • Your program should be run as follows:

    ns hw7.tcl Queue XY-BandWidth [UDP or noUDP] The following commands are used to run the 4 different experimenmts: 1. ns hw7.tcl DropTail 0.4mbps UDP 2a. ns hw7.tcl RED2 0.4mbps UDP 2b. ns hw7.tcl RED3 0.4mbps UDP 2c. ns hw7.tcl RED4 0.4mbps UDP 3. ns hw7.tcl DRR 0.4mbps UDP 4. ns hw7.tcl DropTail 0.2mbps noUDP 5. ns hw7.tcl DropTail 0.4mbps noUDP

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• Turnin

  /home/cs558000/turnin hw7.tcl hw7