Performance Analysis of Bus and Hub Based CSMA/CD Networks

ELEC3500 Surname
Monash University
Faculty of Engineering
ELEC3500 Telecommunications Networks
Performance Analysis of Bus and Hub Based CSMA/CD Networks
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ELEC3500 Surname
2. Summary
Carrier sense multiple access with collision detection (CSMA/CD) networks are mostly used to
control access in Ethernets for local area networks (LAN). It immediately terminates the
transmission of any data or information upon detection of any collision. In this lab experiment,
the performance of bus and hub configurations based CSMA/CD networks are analyzed using
OMNET++ simulation models that were developed previously.
The models are run in either hub or bus network configurations. Four simulations are conducted
based on the given parameters to obtain the desired results for analysis. From the results
obtained, a plot of load versus delay, the number of collisions are generated and analyzed.
The simulation results show more similarities in the performance of both bus and hub
configurations. With the inclusion of the CSMA/CD, both the performance of the bus and hub
configurations improve significantly.
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Table of Contents
2. Summary......................................................................................................................................ii
3. Introduction..................................................................................................................................1
4. Methodology................................................................................................................................2
4.1 Objectives...............................................................................................................................2
4.2 Model description..................................................................................................................2
4.2 Procedure...............................................................................................................................3
5. Results and discussion.................................................................................................................3
6. Questions.....................................................................................................................................6
6. Conclusion...................................................................................................................................7
7. References....................................................................................................................................8
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ELEC3500 Surname
3. Introduction
CSMA/CD detects collisions in the transmitting station through the carrier sensing that enables
the transmitting station to detect transmissions from other stations [2]. Upon detection of the
collision, the transmission process is stopped and the station waits for a random interval of time
before resending the frame again [7]. Generally, CSMA/CD is a medication to improve the
efficiency of the original CSMA by shortening the required time to resend a frame after collision
detection.
The objective of this simulation experiment is to analyse the performance of bus and hub based
CSMA/CD network protocols in OMNET++ simulation models. When several devices in a
communication line share the same physical connection, the type of network is referred to us bus
topology. Figure 1 show the bus topology in a communication network [5]. If one stations
transmit on the bus, the other stations are alerted and if more than one station transmits
simultaneously, a collision occurs [1]. Therefore, CSMA/CD technique allows more than one
station to transmit on the bus without collision.
For hub network configuration however, several devices are connected to one central point.
Some devices use a switch or a router instead of a hub [8]. Figure 2 show hub network topology
[6]. When a packet is received it the hub, it is broadcasted to all other devices connected to the
hub thus all of them receive the package at the same time with the possibility of collision [3][4].
However, CSMA/CD prevents occurrence of any collision.
In this lab, four simulations are conducted using the bus and hub network configurations. From
the given parameters, simulation results are obtained and analyzed. The total load was divided by
the number of hosts to determine the inter-arrival time of the packets.
Figure 1: Bus network topology
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