T324: Keeping ahead in ICTs
Tutor-Marked Assignment, Fall 2013 2014
Cut-Off Date: Week 11, Dec. 11 Total Marks: 100
Q1. Investigating socio-technical system
You have studied in block three of the course materials the
socio-technical system approach for investigating system failures. To
demonstrate your understanding of this part of the course, answer to the
following questions:
1. Select a socio-technical system that you use in your
daily life.
2. Draw the system map that you think representative for the
selected system.
3. Present briefly two processes of the selected system.
4. Discuss the major criteria of failure of such system.
5. From your point of view, what is the major reason(s) that
may lead such system to failure?
6. Based on your answer in the previous part, which system
questions can be regarded as counterparts to these?
7. Explain briefly how investigating the system questions of
the previous part could help in avoiding failure or identifying its reasons.
Q2. Innovation in IEEE 802.11
IEEE 802.11ac is the fifth generation of WiFi which is
faster and more scalable version of 802.11n. IEEE 802.11ac couples the freedom
of wireless with the capabilities of Gigabit Ethernet. Using the AOU e-library
and Internet resources, you are asked to write an essay presenting an overview
on the standard IEEE 802.11ac while providing its major physical layer
specifications (e.g., throughput, RF bandwidth, channel bonding, number of MIMO
spatial streams, modulation technique). Your essay should contain at least 500
words and the list of references. It should not include unapproved websites as
Wikipedia or like citation. Marks will be deducted in case of essay lacking
reliable references or containing errors in syntax, structure, and style.
Q3. Sniffing wireless traffic using Wireshark
Wireshark is the world’s most popular network protocol
analyzer. It is used for troubleshooting, analysis, development and education.
The software and its user guide could be downloaded from its home page (i.e.,
http://www.wireshark.org/). In this question, you will investigate the 802.11
wireless network protocol using this passive measurement tool. For more
information on 802.11 management frame types, you can find many references as
for example “Understanding 802.11 Frame Types” by Jim Geier (i.e.,
http://www.wi-fiplanet.com/tutorials/article.php/1447501).
Unfortunately, most of the device drivers for wireless
802.11 NICs (particularly for Windows operating systems) don’t provide the
hooks to capture/copy received 802.11 frames for use in Wireshark. Therefore,
we will provide you in this question a trace of captured 802.11 frames to
analyze; assume in the following questions that you are using this trace. If
you are able to capture 802.11 frames using your hardware settings, we
encourage you to train on this software using your proper tests. An alternative
solution for packet capture that you can use in your upcoming projects is to
use a small USB device, AirPcap, (i.e., http://www.cacetech.com) that captures
802.11 frames and provides integrated support for Wireshark under Windows.
To start the experiment, open in Wireshark the trace
Wireshark_802_11.pcap which is attached to the TMA files. You can load the
trace into Wireshark using the File pull down menu, choosing Open, and then
selecting the Wireshark_802_11.pcap trace file. The resulting display should
look just like Figure 1.
Figure 1: Wireshark window, after opening the
Wireshark_802_11.pcap file
For answering the following questions, you should look at
the details of the IEEE 802.11 frame and subfields in the middle Wireshark
window.
To deal with the plagiarized answers in this question, the
student must make an oral demo of the software for his/her tutor showing
him/her how he/she has opened the trace and manipulated the packets to find the
answers provided in the submitted TMA. Then, tutor can decide to deduct (or
not) part or whole of the marks awarded based on the quality of the demo.
1. Given that beacon frames are used by an 802.11 AP to
advertise its existence. What are the SSIDs of the two access points that are
issuing most of the beacon frames in this trace?
2. What are the intervals of time between the transmission
of the beacon frames from the
linksys_ses_24086 access point? From the 30 Munroe St. access point? (Hint: this
interval of time is contained in the beacon frame itself).
3. What (in hexadecimal notation) is the source MAC address
on the beacon frame from 30 Munroe
St ?
4. What (in hexadecimal notation) is the destination MAC
address on the beacon frame from 30
Munroe St ?
5. What is the BSS ID of 30 Munroe St?
6. The beacon frames from the 30 Munroe St access point advertise that
the access point can support four data rates and eight additional “extended
supported rates.” What are these rates?
7. What is the Channel number used for WiFi communication?
8. Consider the first PROBE REQUEST and the soonest
subsequent PROBE RESPONSE PAIR occurs after t = 2.0 seconds in the trace. When
these frames sent and what are the sender, receiver and BSS ID MAC addresses
for these frames? What is the purpose of these two types of frames?
