HW#2 --- last modified February 17 2019 19:25:18..

Solution set.

Due date: Mar 9

Files to be submitted:
  Hw2.zip

Purpose: To use the ns2 simulator to learn about direct linked networks, in particular, Ethernet and the Sliding Window Protocol.

Related Course Outcomes:

The main course outcomes covered by this assignment are:

LO1 -- Understand layered architectures.

LO3 -- Analyze the performance metrics of networks, including bandwidth, delay, and error rate.

LO4 -- Describe local area network protocols including Ethernet, Token Ring, and Wireless LAN, and their major schemes such as Spanning Tree Protocol (STP) in IEEE 802.1D.

LO5 -- Develop a software simulator for local area network protocols.

Specification: Within your zip file I would like a file Hw2.pdf with a write-up of the following book problems: Ch 2: 2, 9, 20, 23, 28, 41. Then I would like you to download and install ns2. I want you to create two files sliding-experiment.tcl and ethernet.tcl in which you put code for some sliding window experiments and ethernet experiments respectively. In addition you should have a file Experiments.pdf with a write-up of the discussion of your experiments as well as a few screenshots proving that you actually got these experiments running under ns2.

For the sliding window experiment I want you to create a network of ten pairs of nodes s1,r1,s2,r2 ...s10,r10. Node sn and rn for 1 ≤ n ≤ 10 should be connected by a duplex-link with a line rate of n Mbps, a drop tail queue and 10ms latency. Between sn and rn I want you to set a constant bit rate traffic with a packet size of 500 and an interval between packets of 0.05. In sliding-experiment.tcl I want you to have this set up and set up the sender window to be 5 frames for each sn and the receiver window to be 1. You can use tcp agent to do this. I want you to simulate for 10 seconds. Have the line between pairs go down at 4 and 6 seconds for a quarter second before coming back up. Your write-up should try to come up with an explanation for what you see when you visualize this in nam. Include some screenshots.

For ethernet.tcl, I want you to create a four node newLan with -macType Mac/Csma/Ca. Nodes should be arrange in the order 1,2,3,4. I want you to send traffic between node 1 and 4 and node 2 and 3. I want you to play with the settings of the traffic to try to get as many collisions as possible. i.e., try to get the exponential back-off to kick in as much as possible. Your ethernet.tcl script should be your final network of doom. Your write-up should have a discussion on your experiments in doom creation. The syntax for creating a new lan is something like:
set mylan [$ns newLan $nodelist $bandwidth $delay -llType LL -ifqtype Queue/DropTail -macType mac/Csma/CA -chanType channel]

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