Internet Technologies and Applications (ITS 413)

Assignment 1

Group project, 3 students per group
15% of course score
15 December 2010, 10:40am (start of lecture)
Late assignments:
-10 marks per hour

Overview and Requirements

This assignment has two (somewhat independent) tasks about IEEE 802.11 wireless LANs:

  1. Map the wireless LAN coverage in Bangkadi campus.
  2. Measure the throughput performance of a wireless LAN link.

Both tasks require the use of your own (laptop) computers with IEEE 802.11 wireless LAN capabilities. When you form your group, you should make sure that at least two laptops will be available to the group throughout the assignment. If this is a problem, then please let me know.

Task 1: Bangkadi Wireless LAN Coverage Map

Each group is assigned an area on the Bangkadi campus (see below). Using their laptops and commonly available software (e.g. applications that come with your wireless card or operating system; or specialist applications like Netstumbler or InSSIDer for Windows and Kismet for Linux), each group must record the signal strength of available access points, and map that data. The goal is to combine the data/maps from all groups to produce a coverage map for the entire Bangkadi campus.

The objectives of this task are for students to learn about the information available from access points (e.g. signal strength, data rates, SSIDs) and familiarise students with common techniques for detecting wireless LANs.

Bangkadi campus is divided into the following seven areas. Each area will be assigned to a group:

  1. Sirindhralai Building: Ground floor
  2. Sirindhralai Building: 2nd floor
  3. Sirindhralai Building: 5th floor
  4. Sirindhralai Building: Library and 6th floor
  5. IT/MT Building: Ground floor and 2nd floor
  6. IT/MT Building: 3rd and 4th floor
  7. IT/MT Building: 5th and 6th floor

Some guidelines about what to measure:

Where to measure?
Locate points where the wireless LAN maybe used, separated by about 5 to 10 metres. Take measurements at those points (you don't need to take measurements as you are moving between points). For example, in a hallway in Sirindhralai Building there may be 6 to 8 points along the hallway. In a small/medium classroom, maybe 3 points (front, middle, back). In larger areas (large lecture rooms, outside) you may separate the points by larger distances.
How many measurements?
At each point, monitor the signal strength and record a single value when it is stable. You may consider taking measurements from multiple laptops at the same points, e.g. two people with laptops stand next to each other and monitor the data, while the third student records the measured location and data.
When to measure?
Although it may not be possible, preferably when there are few people around. But make sure it is during normal hours (8am to 5pm).
What to measure and record?
Signal strength and other data that is useful (e.g. SSID of AP, what type of security is needed for the AP, data rate). And of course the location where the measurement is made. You should have an approximate map of your area drawn up before starting the measurements.
How to record the measurements?
While taking the measurements it maybe quickest to write them on a paper (with a map). Or you could enter them directly into a spreadsheet.

Some safety and security guidelines for collecting data:

Task 2: Wireless LAN Throughput Performance

Each group will measure the throughput of a wireless LAN link (e.g. laptop to access point) under various conditions. iperf (or its Java-version, jperf) will be used to send packets from laptop to a computer attached to the wired interface of an access point. Measurements for different sending rates will be used to determine the maximum throughput of the wireless LAN link.

The objectives of this task are for students to learn about the factors that impact on wireless LAN performance and to familiarise students with techniques for testing network performance.

For the measurements you should use one of the Linksys WRT54GL wireless routers provided. Alternatively you could use your own wireless router, but check that it is capable of doing everything needed.

Some guidelines on performing the throughput tests:

What transport protocol to use?
UDP only (the -u option in iperf). TCP should not be used, as TCP itself may impact on performance, whereas with UDP the performance is mainly influenced by the wireless LAN.
What network topology?
One or more (source) laptops associate with a single AP; the AP connected via an Ethernet cable to another (destination) computer.
What default (fixed) parameters should be used?
You should fix the test scenario for all tests. For example, choose a channel that is not used by other nearby nodes. Place the source laptop(s) close to the AP (e.g. less than 1 metre). Do not move nodes. Use the default wireless LAN parameters of the AP.
What different conditions to measure for?
You must consider the impact of using IEEE 802.11b only, IEEE 802.11g only, and a mixture. Also you must consider the impact of using 1 source versus 2 sources (and possibly 3 sources if a 3rd laptop is available).
How does iperf/jperf work?
On the destination computer you run iperf in server mode. On the source laptop you run iperf in client mode. When you start the iperf client, it sends UDP packets at the rate specified by you (using the -b bandwidth option) to the server for 10 seconds. At the end of the test, both the client and server report the data received at the server, i.e. the throughput.
How long should each test run?
The default 10 seconds is sufficient.
What sending rates should be used?
You want to determine the maximum throughput available under certain conditions. Therefore you should run tests for increasing values of sending rate (in iperf, this is called bandwidth). For example, first try bandwidths of 5, 10, 15, 20, 25Mb/s. If you find the measured throughputs are 5, 10, 12, 11, 12Mb/s, respectively, then you may guess that the maximum is about 12Mb/s. Now you should confirm that guess by running more tests, e.g. with bandwidth of 10, 11, 12, 13, 14Mb/s.
How many tests?
As stated above, you should run tests for different bandwidths to discover the maximum throughput. In some cases you need only a single test (e.g. sending rate 5Mb/s, throughput 5Mb/s). But as you get closer to the maximum, run multiple tests to confirm you've found the maximum. Remember that in a wireless network, different factors may impact performance, such as others transmitting and different obstacles.
How accurate should the results be?
Round to the nearest megabit/second (Mb/s).
What plots should be produced?
You should at least show plots of sending rate versus throughput for multiple conditions. You may also show maximum throughput versus different conditions (such as number of laptops).
How do I used iperf/jperf?
See instructions from last year to get started. With this, once you've installed the software you should be able to explore the options via running some simple tests. Make sure you understand how it works and the options to use before you start running your real tests.

Deliverables and Marking Scheme

For Task 1 each group must deliver two items:

  1. Spreadsheet containing the measured data. You must provide a nice layout and presentation such that I can understand what the data is. This will be worth 15 marks.
  2. Map showing the important summary data for your area. This should be easy to read and obtain the important information from. You may have multiple maps of the same area (e.g. one showing signal strength, another showing security levels). This will be worth 25 marks.

For Task 2 each group must deliver two items:

  1. Spreadsheet containing measured data. You must provide a nice layout and presentation such that I can understand what the data is. This will be worth 15 marks.
  2. Report summarising: the test setup (e.g. overview of how you performed your tests and what devices/software you used); test results (plots); and explanation of results (e.g. why the results are as they are, what conclusions can you draw from the results). This will be worth 45 marks.

The assignment is group work. Each member of the group should contribute equally to the work. This includes providing intellectual input (e.g. thinking about the tests and measurements, understanding the results), editing input (e.g. writing the text, formatting the figures) and performing data collection.

Sharing information (with other groups) on how to use the software (as well as general understanding of WLANs) is allowed and encouraged. Using other peoples data and conclusions is NOT allowed. Copying text, results, figures etc. from other groups or external sources (e.g. web sites) is NOT allowed unless properly acknowledged.

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