## Topologies

Topology is a Greek word; it shows the physical & logical structure/layout of a network.

Categories of Topologies

The Star Topology

In this topology each of the devices and computers on a network connection to a central hub/switch. A major disadvantage of this type of network topology is that if the central hub fails, all computers connected to that hub would be disconnected. All information on a star network first passes through hub or switch before continuing to its destination. It also acts as a repeater for data flow. Mostly we use twisted pair cable to connect all computers with the central device but we can also use coaxial or fiber optical cable.

• It is easy to modify and can add a new computer or remove it without disturbing the rest of the network.
• Single computer backbones do not necessary backbone the whole Network.
• Several cable type can be used in the same network with a hub
• Easy to install and wire
• Easy to detect faults and remove parts

• Requires more cable length than a linear topology
• If the hub or connector fails, nodes attach are disturbed.
• More expensive than linear bus topology because of the cast of the concentration.

Ring Topology

In-ring topology, all devices or computers are connected to each other in a circular shape. All the data which will be sent move around the ring until it reaches its final destination.

• As every computer is given is equal access to the token. No one computer can normalize the Network.
• If a terminal becomes effective, it can be bypass without affecting the Network.
• If a terminal working as the central computer. Any other node can be made by the central computer and the network keep on  working

• Failure of the one computer of the ring can be an effective whole Network.
• It is difficult to troubleshoot a ring network.
• Adding and removing computer disturb the network

Token-Ring

In a token ring topology, all the computers are organized in a ring topology. Data passes sequentially between nodes on the network until it returns to the source station. To prevent traffic and collision, a token is used to ensure that only one computer on the line is used at a time. A token ring LAN is physically wired as a star topology but configured as a ring topology.

The Bus Topology

In this topology, all the computers and devices are connected to a single cable. This is typically used in small networks and take advantage of using less cable. Their main disadvantage is that if any segment of the network fails, all transmissions do as well.

• The bus is simple, reliable in a very small network, easy to use and easy to understand
•  The bus requires the last amount of cable to connect the computer together and therefore less expensive than another cabling arrangement
• It is easy to extend the bus. The cable can be joint into one longer cable allowing more computers to attach

• Heavy network traffic can slow the bus considerably.
• It is difficult to be easy to troubleshoot the bus. If there is an error in the system it cannot be easy to detect.
• The entire network shuts down if there is a break with the main cable.

Tree Topology

In tree topology, more than two HUBs are connected to each other this topology is a collection of linear bus and star topology. each star network is a local area network with a central computer or server and all the node direct ally link to this server and central computers or server of the star networks are connected to a main cable called the bus.

• Point to point wiring for individual segments.
• Supported by several hardware and software vendors.

• The overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks the entire segment goes down.
• More difficult to configure and wire than other topologies