ISO-8859-1__Network Topologies

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Classification of Network

TopologiesPhysical Topologies

� The mapping of the nodes of a network and the physicalconnections between them ± i.e., the layout of wiring, cables,the locations of nodes, and the interconnections between the

nodes and the cabling or wiring system

Logical Topology

� The mapping of the apparent connections between the nodes of a network, as evidenced by the path that data appears to takewhen traveling between the nodes

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Main Types of Topologies

The five most common network topologies(physical) -

� Bus

� Ring

� Star

� Mesh

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Bus Topology

Commonly referred toas a linear bus, all thedevices on a bus

topology are connectedby one single cable.

Introduction to Computer Networks



Bus Topology h Hardware required

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Bus Topology h

Merits and Demerits

� Merits of a Bus Topology

� Easy to connect a computer or peripher al to a linear bus

� Requires less cable length than a star topology

� Demerits of a Bus Topology

� Entire network shuts down if there is a break in the maincable

� Terminator s are required at both ends of the backbonecable

� Difficult to identif y the problem / location of the problemas the entire network shuts down

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Ring Topology


A frame travels around the ring,stopping at each node. If a nodewants to transmit data, it adds thedata as well as the destination

address to the frame.

The frame then continues aroundthe ring until it finds thedestination node, which takes the

data out of the frame.Single ring ± All the devices onthe network share a single cable

Dual ring ± The dual ring topology

allows data to be sent in bothdirections.



Ring Topology h

Merits and Demerits� Merits of a Ring Topology

� Point-to-point wiring for individual segments

� Supported by several hardware and software venders

� Demerits of a Ring Topology

� Overall length of each segment is limited by the type of cabling used

� If the backbone line breaks, the entire segment goes down

� More difficult to configure and wire than other topologies

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Star & Tree Topology


The star topology is the mostcommonly used architecture inEthernet LANs.

When installed, the star

topology resembles spokes ina bicycle wheel.

Larger networks use theextended star topology alsocalled tree topology. When

used with network devices thatfilter frames or packets, likebridges, switches, and routers,this topology significantlyreduces the traffic on the wiresby sending packets only to thewires of the destination host.



Star Topology h

Merits and Demerits� Merits of a Star Topology

� Easy to install and wire

� No disruptions to the network while connecting or removingdevices

� Easy to detect faults and to remove nodes (except the centralone)

� Demerits of a Star Topology

� Requires more cable length than a bus topology

� If the hub or concentrator fails, nodes attached are disabled

� More expensive than bus topologies because of the cost of theconcentrators

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Tree Topology h

M

erits and Demerits� Merits of a Tree Topology

� Individual segments can be linked to increase theoverall length of the network

� Easy to segregate each zone from the other

� Demerits of a Tree Topology

� Difficult to provide different services to each node inthe same sub-tree

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Mes Topology The mesh topologyconnects all devices (nodes)to each other for

redundancy and faulttolerance.

It is used in WANs tointerconnect LANs and for mission critical networks

like those used by banksand financial institutions.

Implementing the meshtopology is expensive anddifficult.A

n example of aM

eshN

etwork is theMobile Adhoc Network or MANet




Mes Topology

Merits and Demerits

� Merits of a Mesh Topology

� Fault-tolerance is very high

� Reliability is very high

� Demerits of a Mesh Topology

� Uses a lot of cable

� Every node needs to connected to every other node in the

network

� Adding or removing nodes is very difficult

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Topologies ± Revised

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