About transmission media ?

What is network topology?

A network topology refers to the layout of the computers and devices in a communications network.

it refers to both the physical and logical layout of a network.

PHYSICAL TOPOLOGY

• The arrangement of a cabling is the physical topology

LOGICAL TOPOLOGY

• The path that data travels between computers on a network is the logical topology

                                                                   STAR NETWORK

       BUS NETWORK

              RING NETWORK

STAR TOPOLOGY

Hub/Switch

• The device that provides a common central connection point for other devices on a network.
• All data that transfers from one device to another passes through the hub or switch.
• The hub/switch takes a signal that comes from any device and passes it along to all the other devices in the network.

Advantages:~

1.If one device fails, only that device is affected.

2.Devices can be added to or removed from network with little or no disruption.

3.Easy to troubleshoot and isolate problem.

Disadvantages:~

1.If the hub or switch fails, the entire network will be inoperable.

2.Requires more cable than most of the other topologies.

3.More expensive because cost of the hub/switch.

BUS TOPOLOGY

• The bus is the physical cable that connects the computers and other devices.
• The bus in a bus network transmit data, instructions, and information as a seruies of signal.
• Those signals are sent as electrical pulses that travel along the length of the cable in all directions.
• Each devices is connected to the single bhus cable through T-Connector.
• A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable.
• When a sending device transmit data, the address of the receiving device is included with the transmission.
• If the device address does not match the intended address for the data, the device ignores the data.
• If the data does match the device address, the data is accepted.
• All devices receive the data but only the receiving device accept them.

Advantages:~

1.Bus networks are inexpensive and easy to install.

2.Computers and other devices can be attached and detached at any point on the bus without disturbing the rest of the network.

3.Failure of one device usually does not affect the rest of the bus network.

Disadvantages:~

1.There might be disruption when compute or other devices are added or removed.

2.Because all systems on the network connect to a single cable or backbone, a break in the cable will prevent all systems from accessing the network.

3.It is difficult to identify the problem if the entire network shut down.

RING TOPOLOGY

• Data transmitted on a ring network travels from device to device around the entire ring, in one direction (clockwise or counterclockwise).
• Token passing is one method for sending data around a ring.
• Each device takes a turn sending and receiving information through the use of a token.
• The token along with any data is sent from the first device to the second device which extracts the data addressed to it and adds any data it wishes to send.
• Then second device passes the token and data to the third device until it comes back around to the first device again.
• Only the device with the token is allowed to send data.
• All other devices must wait for the token to come to them.

Advantages:~

1.The transmission of data is relatively simple as packets travel in one direction only.

2.Cable faults are easily located, making troubleshooting easier.

3.The uses of token passing enables all devices in a ring topology to share the network resources fairly.

Disadvantages:~
1.A failure in any cable or device breaks the loop and can take down the entire network.
2.Data packets must pass through every computer therefore, this makes it slower.
3.A ring network can span a larger distance than a bus network, but it is more difficult to install.