Topologies Presentation

7/28/2019 Topologies Presentation

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Topology is the configuration of a communication network. Thedesign or style determines the type of hardware you are going touse.

Topologies

Topology is the way a network is laid out



Computer networks consist of two or more machines connected to each otherthrough network media such as network interface cards, network cabling,routers and bridges.

The manner in which the devices are physically connected to the next device onthe network is determined by the chosen topology for that network.

The selection of a specific topology for a given network is based on practicality,cost, security and ease of management.

Network topology involves cabling, client computers, routers and hubs.



Types of TopologiesBasic network topologies are.

1. Star Topology

2. Bus Topology

3. Ring Topology

4. Mesh Topology

5. Tree Topology

6. Hybrid Topology



Star TopologyStar topology has each machine connecting to a central network device such

as a hub or a router, with all network traffic passing through the central

device.

Systems/nodes

hub

The network does not necessarily have to resemble a star to be classified as a

star network, but all of the nodes on the network must be connected to one

central device.



Advantages :

• Star topology isolates each machine so that if the cable on one

is broken, the others are unaffected.

• The star topology is considered the easiest topology to design

and implement

• the star topology is the simplicity of adding additional nodes.

Disadvantages :

• The primary disadvantage of the star topology is that the hub

represents a single point of failure, if the central hub or router fails, then the entire network will go dark.



In bus network, all stations are attached to a single cable.

• When a device sends a message, it is broadcast down on the cable

in both directions. Terminators at the end of the cable prevent the

signal from reflecting back to the sender.

• All devices on the cable constantly monitor for messages meant to

them. When a device detects a message meant for it, it reads themessage from the cable and the other stations will ignore it.

• Since all devices are sharing the same cable, some form of control

is needed to make sure which device will transmit when,otherwise

there will be a collision.

Bus Topology



Advantages :

• Easy to wire, quick response, less expensive, and if one station dies, it

has no effect on the total network.

• It requires less cable than other topologies.

• It is a simple design and easy to put into operation

Disadvantage :

• However bad connection to the cable can short it and bring down the

entire network.

• Bus topology is subject to failure of large portions of the network if

there is a break in the network cable.

• Terminators are required at both ends of the backbone cable.



A ring topology is a network topology where each node (device on the

network) connects to two other nodes. This forms a continuous path for

the signal through each device.

Ring Topology

Each device incorporates a receiver for the incoming signal and a transmitter

to send the data on to the next device in the ring.



Advantages :

• The ring topology is a very organized network topology, and it performswell under a hefty network load. It can also be used to create a larger

Token Ring network.

• The network is dependent on the ability of the signal to travel around the

ring

• A ring topology is ideal for small businesses that need to share data

across offices. While it is limited in certain ways, it can greatly cut a

company's networking costs.

Disadvantages :

• One bad port, or even a bad node, can disrupt the entire network. Merely

moving a node, adding to or changing the network can also affect the

network.

• Failure of one device shuts down the entire network. This is an old

topology that is rarely used today.



A network setup where each computer and network device is

interconnected with one another, allowing for most transmissions to be

distributed, even if one of the connections go down

Mesh Topology

Its variation of the bus topology . Instead of a central backbone cable, each

device on the network is connected to every other device and each device

can serve as a router to route information to its destination device.



Advantages :

• The network can be expanded without disruption to current users.• Provides multiple paths between devices.

• Even if one of the components fails there is always an alternative

present. So data transfer doesn’t get affected.

Disadvantages :

• The physical fully connected mesh topology is generally too costly and

complex for practical networks.

• Set-up and maintenance of this topology is very difficult. Even

administration of the network is tough.• There are high chances of redundancy(duplication of data) in many of the

network connections.



Tree Topology integrates the characteristics of Star and Bus Topology.

Tree Topology

It consists of multiple star networks connected together by a single

backbone bus. The hub of each star network is connected to the central

backbone.



Advantages :

• It is scalable . Secondary nodes allow more devices to be connected to a

central node.

• Network expansion and alteration is easier.

• Having different levels of the network makes it more manageable hence

easier fault identification and isolation.

Disadvantages :

• If the central backbone fails, the individual star networks continue to

function.

• Maintenance of the network may be an issue when the network spans a

great area.

•Eg : cable tv network



As networks grew beyond single offices, the need for topologies that

could support larger numbers of machine became apparent. Large

networks use one or more of the main topologies to create a hybrid

topology. While each office may be a star topology, the servers may be

wired in a ring or linear bus topology.

Hybrid Topology



Advantages :

• Reliable : Unlike other networks, fault detection and troubleshooting is

easy in this type of topology. The part in which fault is detected can be

isolated from the rest of network and required corrective measures can be

taken, WITHOUT affecting the functioning of rest of the network.

• Scalable: Its easy to increase the size of network by adding newcomponents, without disturbing existing architecture.

• Flexible: Hybrid Network can be designed according to the requirements

of the organization and by optimizing the available resources. Special care

can be given to nodes where traffic is high as well as where chances of

fault are high.

• Effective: Hybrid topology is the combination of two or more topologies,so we can design it in such a way that strengths of constituent topologies

are maximized while there weaknesses are neutralized. For example we

saw Ring Topology has good data reliability and Star topology has high

tolerance capability (as each node is not directly connected to other but

through central device), so these two can be used effectively in hybrid star-

ring topology.



Disadvantages

• Complexity of Design: One of the biggest drawback of hybrid

topology is its design. Its not easy to design this type of architecture

and its a tough job for designers. Configuration and installation

process needs to be very efficient.• Costly Hub: The hubs used to connect two distinct networks, are

very expensive. These hubs are different from usual hubs as they

need to be intelligent enough to work with different architectures and

should be function even if a part of network is down.

• Costly Infrastructure: As hybrid architectures are usually larger in

scale, they require a lot of cables, cooling systems, sophisticate

network devices, etc.



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Topologies Presentation