TOPOLOGY: PHYSICAL TOPOLOGY

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TOPOLOGY

It defines the shape of network (logical /physical).

Physical topology defines the physical connection used.

Logical  topology defines how communication occurs in the network.

Physical Topology


Bus Topology

Specifications:

Speed: 10 mbps

Number of computers: 30/100

Cables: ThinNet / ThickNet (coaxial cable)

Connectors: BNC /AUI

In this network all computers are directly connected to the central cable bus.

This bus is the shared communication media for all network devices.

Advantage:

It is cheap and affordable. 


 Disadvantage:

Speed is very low.

Number of computer is low.

In case of the cable failure entire network will fail.

Difficult to pin point area of failure.


Ring Topology

Specification:

Speed: 10 mbs

Computer: 30/ 100

Cable: ThinNet/ ThickNet 

Connector: BNC/AUI

In thus network the first computer is connected to second, then second and third, and final computer is connected back to first forming a ring shape.


Types of Ring Topology:

Single Ring : Data is sent in one direction at a time.( Clockwise or counter clockwise)

Dual Ring: Data is sent in both direction at once 


Advantage:

It doesnot require terminators.

It is fault tolerant.


 Disadvantage:

Low speed, less computer.

In case of cable break difficult to find area of problem.

Cable break will either slow down the network or entire network will fail.

Difficult to physically setup.


 Star Topology:

Specifications:

Speed: 10/100/1000

Number of computers:1024 per HUB

Cables: UTP/ STP

Connectors:RJ-45

In this network the central cable has been replaced by a central device (HUB)

This device is responsible for sending / receiving messages of all network devices 


Advantage:

Higher speed are available.

More computers can be connected.

In case of errors the area of failure can be easily identified.

An intelligent device auto manages the network.

In case of cable failure only the particular computer will be affected.


 Disadvantage:

Lot of cabling is required (expansive).

If central device fails entire network will fail.

 

Mesh Topology

In this network there is no  central device or cable.

All computers are directly connected to every other computer in the network.It is highly fault tolerant.

Advantage:

The message being sent will surely reach its destination using any of the available route. 


 Disadvantage:

Much expensive as more cable and devices are required.

Difficult to physically setup.

Each connection has to be separately managed.

In the case of cable damage diffcult to find the damage.


Wireless Topology

In this network  a central device called WAP is used.

It is according to the WAP that the range of the network is decided.

All computers within the range can communicate with each other.

The WAP is responsible for passing all network message to network device.

Advantage:

No physical connection is required.

This makes it easy to setup a new network and also to rearrange a existing network.


 Disadvantage:

Currently wireless devices are costly.

Security is low.

The speed is never constant.

Currently this technology is very expensive.



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