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Assignment 1

The document is an assignment from the Department of Computer Science and Engineering at Motilal Nehru National Institute of Technology, Allahabad, focusing on wireless and mobile networks. It includes questions on wireless topologies, packet transfer processes in different scenarios, mobile IP, differences in backoff mechanisms between 802.3 and 802.11, and events affecting the contention window in IEEE 802.11. The assignment requires detailed explanations and sketches related to network protocols and packet flows.

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19 views2 pages

Assignment 1

The document is an assignment from the Department of Computer Science and Engineering at Motilal Nehru National Institute of Technology, Allahabad, focusing on wireless and mobile networks. It includes questions on wireless topologies, packet transfer processes in different scenarios, mobile IP, differences in backoff mechanisms between 802.3 and 802.11, and events affecting the contention window in IEEE 802.11. The assignment requires detailed explanations and sketches related to network protocols and packet flows.

Uploaded by

prafullika
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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MOTILAL NEHRU NATIONAL INSTITUTE OF TECHNOLOGY, ALLAHABAD

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING


Wireless and Mobile Networks
ASSIGNMENT-1

1. Consider the wireless topologies of 5 nodes given in figure below, circle around each node
illustrate their transmission range. Assume that the transmissions of two nodes collide if and
only if transmit at the same time in overlapping transmission areas. Further, assume that
losses occur only due to collisions.

a. When node A transmits to node B, list the potential hidden and exposed terminals.
b. What about when node B transmits to node C.
c. Taking help from above cases, explain how RTS/CTS control packets can solve the
problem both hidden as well as exposed terminal problems.

2. Consider the scenario given in Figure below. Node A and B are in transmission range of
AP1 whereas node C is in range of AP2. All three APs and Router R are connected via a
layer-2 switch supporting IEEE 802.3. Assume that ARP caches at all the devices (Node
A, B, C, APs, and router R) are flushed. In this question, you have to explain the packet
transfer process in different cases asked. Special attention should be given to the values of
ToDS and FromDS fields and discovery of address1, address2, address3 and address4 in
all the cases.

a. Packet transfer from node A to B


b. Packet transfer from node C to B
c. Packet transfer from node A to B when node B has moved from range of AP1 to range
of AP3.

3. [Mobile IP]
a. Suppose the correspondent is a mobile nodes in the following figure. Sketch the
additional network-layer infrastructure that would be needed to route the datagram
from the original mobile user to the (now mobile) correspondent. Show the
structure of the datagram(s) between the original mobile user and the (now mobile)
correspondent.

b. Show the delivery of an IP packet to a mobile node (MN) from a corresponding


node (CN). Assume MN is in foreign network currently duly registered. Consider
different IP addresses as follows:
CN- 128.119.40.180/24, HA- 128.120.40.181/24, FA-79.129.13.2/24, Old MN-
128.120.40.182/24, COA- 79.129.13.2/24. Further, the hardware address of FA=H-
FA and of MN=H-MN. You are also required to show routing table entries made at
HA and at FA during the registration process when MN moved from the home
network to foreign network.
c. Explain the packet flow if the two mobile nodes communicate and both are in
foreign networks. What additional routes do packet take if reverse tunnelling is
required?
4. What is the most important difference between backoff mechanism of 802.3 and 802.11.
Explain the reasons of these differences.
5. List and explain the events which trigger the increase and decrease of contention window
(CW) of IEEE 802.11.

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