Computer Network Topology
Computer Network Topology
Virtual Shape or Structure of the Network
The layout pattern of the interconnections between computers in a network is referred to as network topology. Think of topology as the virtual shape or structure of the network or the physical layout of computers, cables, and other components on the network. The network topology is also referred to as 'network architecture.'
When you are creating a new network the first most important thing to think of is the type of network topology to use. Devices on the network are referred to as 'nodes.' The most common nodes are computers and peripheral devices.
We have a number of network topologies that can be implemented on a network:
The Bus Topology
Bus Topology has a Common Central Cable
In the bus topology computers and other devices are linked to one another by tapping into a common central cable. This kind of a network topology shares a common single cable. It is often referred to as a linear bus because the computers are connected in a straight line. Both ends of the network cable are terminated using a terminator to prevent signals from bouncing back. If signals bounce back, they will cause interference within the network.
In the bus topology, data packets (a piece of message sent through a network) are sent to all computers on the trunk. Each computer examines every packet on the wire to determine who the packet is for and accepts only messages addressed to them. Usually, bus topology makes use of thinnet or thicknet media type. The devices connected to the bus are referred to as nodes.
One of the disadvantages of using Bus Topology is that if the main cable breaks, the entire network goes down. This type of network is also difficult to troubleshoot. For these reasons, this type of topology is not used for large networks, such as those covering an entire building.
The Star Topology
Centralized Multiple Port Device
In the star topology, all systems are connected to a centralized multiple port device called a hub (obsolete) or a switch. Data packets or signals are transmitted from the sending computer through the switch to the respective computer on the network. The switch is an intelligent device that controls the flow of data within the network.
The star topology is widely used nowadays. It offers Centralized monitoring management and it is easy to modify and add new computers. If one computer fails it will not affect the rest of the network, but if the switch fails the whole network segment will be down.
- Star topology is very popular because the startup costs are low.
- It is also easy to add new nodes to the network.
- The network is robust in the sense that if one connection between a computer and the hub fails, the other connections remain intact.
- If the central hub fails, however, the entire network goes down.
- It also requires more cable than bus topology.
Ring or Loop Topology
Ring Topology Uses Token Passing
In a ring or loop topology, as the name suggests, the computers are wired on a single circle of cable, such that they are organized into a ring or a loop. Each station acts as a repeater and keeps the signal strong by repeating it or regenerating it.
The ring topology makes use of token passing access method. A token can be seen as an envelope or a bag where data is placed for transmission around the token ring network. Only the computer with the token is allowed to transmit. On receiving the data, the computer receiving it checks the source and destination address of the data packets to determine where the data is coming from and its destination. If it does not belong to it, it will be passed to the next computer.
- If there's a problem in the network, it is easy to pinpoint which connection is defective.
- It is also good for handling high-volume traffic over long distances since every computer can act as a booster of the signal.
- On the downside, adding computers to this type of network is more cumbersome.
- If one single computer fails, the entire network goes down.
In a mesh topology, each computer is connected to every other computer by separate cabling. That means every computer has multiple possible connection paths to the other computers on the network, so a single cable break will not stop network communications between any two computers.
This kind of configuration used in mesh topology provides redundant paths throughout the network so that if one cable fails, another will take over the traffic. Nodes that are not directly connected make use of intermediate nodes. A mesh topology network offers superior redundancy and reliability.
- This type of topology requires a lot of cables and is, therefore, expensive.
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© 2011 Patrick Kamau