Network topology
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Network Topology. Introduction. Physical and Logical Topologies Topologies Bus Ring Star Extended Star Mesh Hybrid. Physical vs. Logical Topology. The actual layout of a network and its media is its Physical Topology

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Network Topology

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Network topology

Network Topology


Introduction

Introduction

  • Physical and Logical Topologies

  • Topologies

    • Bus

    • Ring

    • Star

    • Extended Star

    • Mesh

    • Hybrid


Physical vs logical topology

Physical vs. Logical Topology

  • The actual layout of a network and its media is its Physical Topology

  • The way in which the data access the medium and transmits packets is the Logical Topology

  • A glance at a network is not always revealing. Cables emerging from a Hub does not make it necessarily a Star Topology – it may actually be a bus or a ring


Bus topology

Bus Topology


Bus topology 5

Bus Topology (5)

Disadvantages

  • No longer recommended

  • Backbone breaks, whole network down

  • Limited no of devices can be attached

  • Difficult to isolate problems

  • Sharing same cable slows response rates

Advantages

  • Inexpensive to install

  • Easy to add stations

  • Use less cable than other topologies

  • Works well for small networks


Ring topology

Ring Topology


Ring topology 3

Ring Topology (3)

Advantages

  • Data packets travel at great speed

  • No collisions

  • Easier to fault find

  • No terminators required

Disadvantages

  • Requires more cable than a bus

  • A break in the ring will bring it down

  • Not as common as the bus – less devices available


Star topology

Star Topology


Star topology 3

Star Topology (3)

  • Advantages

  • Easy to add devices as the network expands

  • One cable failure does not bring down the entire network (resilience)

  • Hub provides centralised management

  • Easy to find device and cable problems

  • Can be upgraded to faster speeds

  • Lots of support as it is the most used

  • Disadvantages

  • A star network requires more cable than a ring or bus network

  • Failure of the central hub can bring down the entire network

  • Costs are higher (installation and equipment) than for most bus networks


Extended star topology

Extended Star Topology

A Star Network which has been expanded to include an additional hub or hubs.


Mesh topology web

Mesh Topology (Web)


Mesh topology 2

Mesh Topology (2)

  • Not common on LANs

  • Most often used in WANs to interconnect LANS

  • Each node is connected to every other node

  • Allows communication to continue in the event of a break in any one connection

  • It is “Fault Tolerant”


Mesh topology 3

Mesh Topology (3)

Disadvantages

  • Expensive

  • Difficult to install

  • Difficult to manage

  • Difficult to troubleshoot

Advantages

  • Improves Fault Tolerance

CP2073 Networking


Hybrid topology

Hybrid Topology


Logical bus

Logical Bus

  • Modern Ethernet networks are Star Topologies (physically)

  • The Hub is at the centre, and defines a Star Topology

  • The Hub itself uses a Logical Bus Topology internally, to transmit data to all segments


Logical bus1

Logical Bus

Advantages

  • A single node failure does not bring the network down

  • Most widely implemented topology

  • Network can be added to or changed without affecting other stations

Disadvantages

  • Collisions can occur easily

  • Only one device can access the network media at a time


Logical ring

Logical Ring

  • Data in a Star Topology can transmit data in a Ring

  • The MAU (Multistation Access Unit) looks like an ordinary Hub, but data is passed internally using a logical ring

  • It is superior to a Logical Bus Hub – see later slide


Logical ring 2

Logical Ring (2)


Logical ring 3

Logical Ring (3)

Advantages

  • The amount of data that can be carried in a single message is greater than on a logical bus

  • There are no collisions

Disadvantages

  • A broken ring will stop all transmissions

  • A device must wait for an empty token to be able to transmit


Summary

Summary

  • Bus Topology

  • Ring Topology

  • Star Topology

  • Other Topologies

  • Logical Topologies

  • Questions and Answers


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