Network topology
Networks can get from hundreds and thousands of computers to a couple of hosts in a single network. If there is more than two computers than it can be called a LAN (Local Area Network) and there are a few topology that describe how the computers are connected and how they transfer data in the network.
The network topology is describes the logical connection between the computers and not the physical way that they are set up. The charts in the following examples are describe how the traffic between the computers is managed for this specific topology. In realty their physical set up is completely different than what is shown in the chart.
Physical topology: the physical topology is describes and defines the way the computers (hosts), printers and network devices (router, switch, hub…) are connected to each other physically. The physical chart also shows where the wires goes and in which wires they use. The chart also shows where the hosts and the other devices are located.
Logical topology: describes and maps the logical set up of a network, which way the hosts and the other devices are connected. The logical topology chart shows the groups that the hosts belong to and the topology that they are using to communicate, regardless of their physical location. The logical also combines the names of the hosts, the addresses and the group’s information.
Point-to-point: this topology is the simplest one. It connects two endpoint.
Bus topology: in this type of topology all the hosts are connected to the main cable, and therefore is called the “bus”. Every sent message goes through all the hosts with destination address. If the address of the host that received the message is identical to the destination address it will “open” the message. If it’s not identical to the destination address it won’t open the message and will ignore it. In the endpoints of the cable there is a component that get the data but “swallows” it to avoid duplication. It doesn't continue to transferring the data and returning the message it has received. It’s called “terminator”, since it’s used for preventing unnecessary data in the cable network. Since the bus topology uses only one cable it is less expensive from other topology. The disadvantage is that there is no device that manages the traffic so it won’t get cross messages or send unnecessary messages to hosts. Moreover, the whole network can be in trouble if there is failure in the main cable, but in case of device failure it won’t damage the network. This topology is suitable for small networks.
Ring topology: this topology is similar to the bus topology, but here the hosts connect in a circle form or a closed ring. Every host connects only to the two hosts next to him (on the logical level). The way that the data\messages between the hosts flow is in one direction, clockwise or counter-clockwise. The message that is sent from the source hosts travel between the hosts until it gets to the destination host. When a host receives the message it checks if the destination address matches his destination. If not, and here it’s different from the bus topology, it will just ignore the message, and will send the message to the next host. The message is “packed” to a frame called “Token”. It creates a very neat network but every failure or problem in one computer affects all the others and damages the ring.
Star topology: This is a more modern topology compared to the others mentioned above. The star topology includes network devices like switch that functions as the main device that arranges the traffic in the LAN (Local Area Network). All the hosts are connect to the main component, the switch for example, and they send to him the frames with the messages, and the switch is handles the delivery. In this topology it’s simple to add a new device to the LAN but all the hosts are depend on one device.
Mesh topology: The mesh topology is the best way to communicate between the computers, but at the same time it is also the most complicated one to connect. In this topology all the hosts are connected to each other with straight cables from one to another. Because of that it is expensive and very hard to arrange and set up this type of network, especially if there are many devices. On the other hand, the network won’t be affected by a damaged cable or a problem in a device. The mesh topology has 2 types:
1) partially mesh - not all the hosts have point-to-point connections to the others.
2) fully mesh - all the hosts are fully connected point-to-point.
