What is star topology? What is star topology advantages and disadvantages?

 Star Topology :

What is star topology? 

In a star topology:

•  each device has a dedicated point-to-point link only to a central controller, usually called a hub.
• The devices are not directly linked to one another. Unlike a mesh topology.
• a star topology does not allow direct traffic between devices.

How does star topology work?

• The controller acts as an exchange:
•  If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device .

What is the difference between star topology and mesh topology ? 
In the star topology :

• In a star topology, each device has a dedicated point-to-point link only to a central controller  usually called a hub.
• The devices are not directly linked to one another. Unlike a mesh topology.
• a star topology does not allow direct traffic between devices.
• The controller acts as an exchange:
•  If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device .
• A star topology is less expensive than a mesh topology.
•  In a star, each device needs only one link
• and one I/O port to connect it to any number of others.

In a mesh topology :

• every device has a dedicated point-to-point link to every other device.
• The term dedicated means that the link carries traffic only between the two devices it connects.

types of physical topology ? mesh &star & bus & and ring topology ?

What is star topology advantages and disadvantages?
What are the advantages of a Star network ( topology) ?
Advantages of Star topology :

• easy to install and reconfigure.
• Far less cabling needs to be housed, and additions, moves, and deletions involve only one connection:
• between that device and the hub.
• Other advantages include robustness.
• If one link fails, only that link is affected.
•  All other links remain active.
•  This factor also lends itself to easy fault identification and fault isolation.
•  As long as the hub is working, it can be used to monitor link problems and bypass defective links. 

What are the disadvantages of a Star network ( topology) ?

disadvantages of Star topology :

• One big disadvantage of a star topology is the dependency of the whole topology on one single point, the hub.
• If the hub goes down, the whole system is dead.

Although a star requires far less cable than a mesh, each node must be linked to a central hub. 
For this reason, often more cabling is required in a star than in some other topologies (such as ring or bus). 

The star topology is used in local-area networks (LANs).
High-speed LANs often use a star topology with a central hub. 

3_ Bus Topology

What is Bus Topology ? 

•  is multipoint. 
• One long cable acts as a backbone to link all the devices in a network .
• Nodes are connected to the bus cable by drop lines and taps.
• A drop line is a connection running between the device and the main cable.
• A tap is a connector that either splices into the main cable or punctures the sheathing of a cable to create a contact with the metallic core.

 As a signal travels along the backbone, some of its energy is transformed into heat. 
Therefore, it becomes weaker and weaker as it travels farther and farther. 
For this reason there is a limit on the number of taps a bus can support and on the distance between those taps.

What are Bus topology advantages and disadvantages?
What are the advantages of a Bus network ( topology) ?
Advantages of Bus topology :
Advantages of a bus topology include

• ease of installation.
•  Backbone cable can be laid along the most efficient path, then connected to the nodes by drop lines of various lengths.

What is the difference between star topology , mesh topology and bus topology?

• In this way, a bus uses less cabling than mesh or star topologies.
•  In a star, for example, four network devices in the same room require four lengths of cable reaching all the way to the hub.
• In a bus, this redundancy is eliminated. Only the backbone cable stretches through the entire facility.
• Each drop line has to reach only as far as the nearest point on the backbone.

What are the Disadvantages of a Bus network ( topology) ?
Disadvantages of Bus topology :
Disadvantages include :

• difficult reconnection and fault isolation.
• A bus is usually designed to be optimally efficient at installation.
•  It can therefore be difficult to add new devices.
• Signal reflection at the taps can cause degradation in quality.
• This degradation can be controlled by limiting the number and spacing of devices connected to a given length of cable.
• Adding new devices may therefore require modification or replacement of the backbone.
• In addition, a fault or break in the bus cable stops all transmission, even between devices on the same side of the problem.
• The damaged area reflects signals back in the direction of origin, creating noise in both directions.

Note :
Bus topology was the one of the first topologies used in the design of early local area networks. Traditional Ethernet LANs can use a bus topology. 

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