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RAJESH KATRAGADDA BHARATH NADELLA SHIVANANDAN GOUD KOMMURI SRIDHARA PRUDHVI DUTH POTLURI

COMPUTER NETWORKS LAB 3: HUBS AND SWITCHES

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INTRODUCTION

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A switch is a multi-input, multi-output device which transfers packets from an input to one or more outputs.

Switch is basically a star topology having features like

a.Large networks can be built by interconnecting a number of switches

b.Adding new host to network by connecting it to a switch does not necessarily reduce the performance of the network for other hosts already connected.

SWITCHES:

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Switch makes use of header of the packet for an identifier to trace the destination.

Basically three approaches used area.Datagram or connectionless (data transfer

only)b.Virtual circuit or connection-oriented

(connection setup and data transfer)c. Source routing

APPROACH:

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A hub joins multiple computers (or other network devices) together to form a single network segment. On this network segment, all computers can communicate directly with each other.

Hubs do not read any of the data passing through them and are not aware of their source or destination. It just broadcasts the packets out to all devices on the network - including the one that originally sent the packet.

HUBS:

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Three different types of hubs exista.Passive : do not amplify the electrical signal

of incoming packets before broadcasting them out to the network.

b.Active : amplify the electrical signal of incoming packets before broadcasting them out to the network.

c. Intelligent : add extra features to an active hub that are of particular importance to businesses.

TYPES OF HUBS:

LAB EXPERIMENT:

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AIM:

This lab demonstrates the implementation of switched local area networks.

The simulation in this lab will help us to examine the performance of different implementations of local area networks connected by switches and hubs.

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Only HUB Scenario:

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Choosing Results:

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Hub and Switch Scenario:

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Manage Scenarios:

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Compare Results:

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Graph for TRAFFIC SENT:

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Graphs for PACKETS RECEIVED:

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Graph for DELAY:

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Graph for COLLISION COUNT:

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DEMO

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Explain why adding a switch makes the network perform better in terms of throughput and delay

ANS: Unlike hubs, Switches Buffer the frames reaching it. So Switches share the bandwidth equally among all the nodes and maintains address tables to forward frames. Hence it leads to better performance in terms of throughput and delay.

POSSIBLE QUESTIONS:

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We analyzed the collision counts of the hubs. Can you analyze the collision count of the switch?

ANS: As hubs don’t look at the destination address of the frames reaching it and just forwards them to all other nodes, there is collision count for Hubs. But in case of Switches, it look at the destination address and buffer the frames and send them according to the address table. So Switches have no Collisions, so no Collision Count.

POSSIBLE QUESTIONS:

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NETWORK CONTANING ONLY SWITCHES

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Only SWITCHES Scenario:

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Graph for DELAY:

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Graph for TRAFFIC RECEIVED:

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Graph for TRAFFIC SENT:

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CONCLUSION: From above Graph for DELAY, its clear that

delay for Only Hub Scenario (Blue) is pretty high and for Hub and Switch Scenario (Red) it is significantly low compared with Only Hub Scenario. But the Delay for Hub and Switch Scenario and Only Switches Scenario (Green) is not that significantly different, as in the earlier case.

More over as Switches cost more than hubs, Its better to use a Hub and Switch combination in the network than only Switch or only Hub combination.

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THANK YOU