iLab Solution II

1. Running Head: MIXED 11B/11G WLAN PERFORMANCE 1
Week 5/6 iLab Report
Group Leader: Vizcaino, Maximo
DeVry University
MIS589: Networking Concepts and Applications
MIXED 11B/11G WLAN PERFORMANCE
Submitted to:
Professor: Sunil, Samanta
Date: December 7, 2014
Members:
Ahmed, Muntazir
Choudhury, Sajid
Raham, Md
Tariq, Ufuq
Yin, Ting

2. Week 5/6 iLab: Mixed 11b/11g WLAN Performance 2
Mixed 11b/11g WLAN Performance
Specific questions from iLab
Guidelines
 Answer each of the following questions using the sequence and data from the iLab
instructions. Answer all questions in full graduate-level sentences.
1. In your opinion, what is the purpose of our dropping the transmit power to such a low level?
The purpose of dropping the transmit power to such a low level is to get reduce interference
and extra capacity.
2. What do access point connectivity statistics collected for the roaming station show?
For the roaming station, the access point connectivity statistics collected indicates that the
connectivity state change every 10 seconds.
3. What do you think the Wireless LAN control traffic received by the roaming 11b node when
it is in the engineering building is composed of?
The roaming 11b node is passed through with the wireless LAN control traffic. The wireless
LAN control traffic is composed of the WLAN 11b and 11g.
4. How much did our roaming node reduce the total throughput in our heavily loaded WLAN?
In the heavily loaded WLAN, the roaming node reduces the total throughput of 15* 106
bits/second.
5. What caused this reduction in “goodput” on the 11g WLAN?
WLAN load control is the cause of reduction.

3. Week 5/6 iLab: Mixed 11b/11g WLAN Performance 3
General questions concerning mixing 11b and 11g clients
Guidelines
 Answer each of the following questions using knowledge gained from the iLab,
readings from the textbook, and individual research on the Web. Answer all questions
in full graduate-level sentences and paragraphs.
6. Supposedly, 802.11b is “backwards compatible” with 802.11g, yet this lab demonstrates
there are significant problems with allowing the two to coexist. What is the primary
“incompatibility” between b and g?
The 11b runs at 11Mbps, and the 11g runs at 54Mbps. The primary reason of compatibility is
between b and g is the speed.
7. There is another mechanism besides RTS/CTS that helps the incompatibility. Explain briefly
the difference between RTS/CTS and CTS-to-self and when each is used.
DCP protocol is another mechanism beside RTS/CTS. DCP protocol uses carrier sensing
along with a 4-way handshake for maximizing the throughput at the same time preventing
packet collisions.
The RTS/CTS mechanism avoids network congestions that are resulted from frequent packet
collisions.
The following phenomenon is known as CTS-TO-SELF mechanism. The mechanism happen
when a node wants to distribute NAV information. The node may first transmit a cts frame
with the RA = (equal) to its own mac address and with a duration that elicit the pending
transition.
8. What is the “protection” scheme talked about in the standard? In short, how do 11g nodes
know that an 11b node is associating and how is CCK involved?
The protection scheme that is talked about in the standard is known as the Intrusion Detection
System (IDS). IDS is a protection scheme that collect, analyze, and audit data for the entire
network.
802.11 WLAN use CSMA/CA. CSMA/CA use a 4-way handshake to gain access to airwaves to
avoid collision. It also know about hidden nodes from different standard.

4. Week 5/6 iLab: Mixed 11b/11g WLAN Performance 4
9. In addition to the added overhead of the RTS/CTS scheme, what else causes the drop in
throughput you see? Are there other factors that can affect the throughput?
The roaming legacy node could cause the drop in throughput. Yes, the interference could
cause of the throughput drop.
10. In situations where 802.11g and 802.11b are coexisting, what steps might you take to
minimize the impact of the presence of the legacy nodes?
To minimize the impact of the presence of the legacy node people have to make sure that the
frequencies are not overlapping in situation when 802.11b and 801.11g are coexistent.
Conclusion
Guidelines
Minimum of two paragraphs that describe the following:
 What you accomplished in the assignment or iLab
 What you learned from performing it
 How it relates to course material
 How you feel it will benefit you in your academic and professional career
What I accomplished in this lab is figuring out the knowledge of hidden nodes and their uses.
What I learned from performing this lab is the purpose of our dropping the transmit power to
such a low level, and what does access point connectivity does in the lab. I also learned how
roaming nodes reduce the total throughout in heavily loaded WLAN. Supposedly, 802.11b is
“backwards compatible” with 802.11g yet this lab demonstrates there are significant problems
with allowing the two to coexist. This will benefit me from my professional career if I want to
connect certain devices in a Wireless LAN wirelessly.

5. Week 5/6 iLab: Mixed 11b/11g WLAN Performance 5
References
Guidelines
 Include all references used to complete this iLab. This must be in APA format.

6. MIXED 11B/11G WLAN PERFORMANCE 1
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