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Here Kinds of Network topologies

Here Kinds of Network Topplogies

. Commonly used topologies include:
• Bus
• Star
• Tree (hierarchical)
• Ring
• Mesh

Bus Topology
Bus topology is the simplest way a network can be organized. In bus topology, all computers are linked to the same transmission line by using a cable, usually coaxial. The'word “bus” refers to the physical line that joins all the machines on the network.

This is a computer network that permits the connection of terminals, peripheral devices, and microcomputers along an open ended central cable which is called bus. The term bus is used because people on a bus can get off at any stop along the route. This cable is used as as hared medium. Coaxial cable and BNC(British Naval Connector) is used in this topology. A device wanting to communicate with another device on the network will broadcast message on the network and all the devices can see the message but only that device can receive message whose address is with the message. Here are some advantages and disadvantages'of this kind of topology.

1-The advantages of this topology are that it is easy to implement and functions easily.
2-It is easy to understand.
3-Bus topology is simple and it is easy to connect additional terminals to this kind of network.
4-This is the best topology for connecting the devices, which are close to one another.

1-It is highly vulnerable, since if one of the connections is defective, the whole network is affected.
2-If there is any error in the network, it cannot be easily detected. 3-Chances of data collision are very high due to shared medium of communication.

Star topology
In star topology, the network computers are linked to a piece of hardware called a hub. This is a box which contains a certain number of sockets into which cables coming out of the computers can be plugged. Its role is to ensure communications between those sockets. Unlike networks built with bus topology, networks which use star topology are much less vulnerable, as one of the connections can easily be removed by disconnecting it from the hub, without paralysing the rest of the network. The critical point in this network is the hub, as without it, communication between the computers on the network is no longer possible. However, a star topology network is bulkier than a bus network, as additional hardware is required (the hub).

This is a computer network that involves a centralized host computer connected to a number of smaller computer systems with a central device called hub or switch. The smaller computer systems communicate with one another through this central device and usually share the host computer’s database. Any computer can communicate with any other computer in the network. Twisted Pair cable and RJ-45 connector is used in this topology.
Here are some common advantages and disadvantages of this kind of network topology:

1-The advantage of the star topology is that if one computer on the star topology fails, then only the failed computer is unable to send or receive data. The remainder of the network functions normally.
2-If any terminal becomes defective, it does not affect any other terminal of this network.
3-The central computer controls the flow of the data. 4-There is no chance of data collision in star topology.

1-The disadvantage of using this topology is that because each computer is connected to a central hub or switch, if this device fails, the entire network fails!
2-This type of topology is expensive because each terminal is connected with a separate able. 3-If the central device is shutdown, the whole network will suffer.

Ring topology

In a ring-topology network, computers each take turns communicating, creating a loop of computers in which they each "have their turn to speak" one after another.

In reality, ring topology networks are not linked together in loops. They are actually linked to a distributor (called a MAU, Multistation Access Unit) which manages communication between the computers linked to it, by giving each of them time to "speak

The two main logical topologies which use this physical topology are Token ring and FDDI.
In ring topology every device has exactly two neighbors. All messages travel through a ring in the same direction. A failure in any cable segment or device breaks the loop and can take down the entire network. Token passing scheme is used in this topology. Only one token is available on the network. When a node wants to transmit data it will capture the token and then transmit the data. In this way only one device can transmit data at a time. After successfully transmitting, token is released for other nodes. Thus no collision occurs but data transfer rate is very slow in this scheme. Twisted pair cable and RJ-45 connector is used
in this topology. Here are some common advantages and disadvantages of this kind of network topology:

1-If the central computer fails, any other computer can be made central computer.
2-There are no chances of data collision in this type of topology.

1-If one of the terminals becomes defective, it affects the whole network.
2-It is difficult to troubleshoot the ring topology.

Tree topology
Tree topologies integrate multiple star topologies together onto a bus. In its simplest form,
only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone. A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

1- Point-to-point wiring for individual segments.
2- Supported by several hardware and software venders.

1- Overall length of each segment is limited by the type of cabling used.
2- If the backbone line breaks, the entire segment goes down.
3- More difficult to configure and wire than other topologies.

Mesh topology
In a mesh topology, each computer is connected to every other computer by a separate cable. This configuration provides redundant paths through the new work, so if one computer blows up, you don't lose the network :) On a large scale, you can connect multiple LANs using mesh topology with leased telephone lines, Thicknet coaxial cable or fiber optic cable. Mesh topologies involve the concept of routes. Unlike each of the previous topologies,
messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing. A mesh network in which every device connects to every other is called a full mesh.

gain, the big advantage of this topology is its backup capabilities by providing multiple paths through the network

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