The topology of a computer network refers to a way to connect its components (computers, servers, printers, etc.). There are three basic topologies:
- a star topology;
- ring topologies;
- shared bus topologies.
When using topologies star between the client network is transmitted through a single central site. As the central node can be a server or a special device - Hub (Hub).
The advantages of this topology are:
- High speed network, since the overall performance of the network depends on the performance of the unit.
- The absence of a collision of transmitted data, because the data between the workstation and the server are transmitted on a separate channel without affecting other computers.
However, apart from the merits of this topology, there are drawbacks:
- Low reliability, because the reliability of the network is determined by the central node reliability. If the central computer fails, the entire network will stop.
- The high costs of connecting the PC, as to each new subscriber must enter a separate line.
When topologies ring all the computers are connected to the line, closed in a ring. The signals are transmitted around the ring in one direction and pass through each computer.
Transmission of information in the network is as follows. Marker (a special tone) sequentially from one computer to another is transmitted as long as it does not get the one you want to transfer data. After receiving the token, the computer creates a so-called “package”, which puts the address and data, and then sends the packet to the ring. Data passes through each computer until they are from someone whose address matches the address of the recipient.
After that, the receiving computer sends information source confirmation of the receipt of the data. After receiving confirmation, the transmitting computer creates a new token and returns it to the network.
The advantages of such a ring topology as follows:
- Message forwarding is very effective, because You can send multiple messages to each other around the ring. Ie computer, sending the first message, can send him the following message, without waiting for the first to reach the destination.
- The length of the network can be significant. Ie computers can connect to each other over long distances without the use of signal amplifier.
The disadvantages of this topology are:
- Low reliability of the network, as the failure of any computer entails rejection of the system.
- To add a new client, you must disable the network.
- With a large number of clients in the network speed slows down, as all the information passes through each computer, and their options are limited.
- Overall network performance defined performance ¬ sequence of the slowest computer.
When topologies common bus all the clients are connected to a common data channel. However, they can directly get in touch with any computer on the network.
Transmission of information in the network is as follows. The data in the form of electrical signals are sent to all computers on the network. However, the information takes only the computer whose address matches the address of the recipient. And at any given time only one computer can maintain the data transfer.
The advantages of shared bus topology:
- All the information is online and available to every computer.
- The workstations can be connected independently. Ie when a new subscriber does not need to stop the transmission of information in the network.
- Building networks based on shared bus topology is less expensive because there is no cost for the laying of additional lines when a new client.
- The network is highly reliable, as that the network is not dependent on the performance of individual computers.
The disadvantages of such a common bus topology include:
- Low data rate, because All information is circulating on the same channel (bus).
- Network performance depends on the number of connected computers. The more computers connected to a network, the slower the transmission of information from one computer to another.
- For networks that are based on this topology, characterized by low security because information on each computer can be accessed from any other computer.
The most common type of network topology shared bus is the standard Ethernet network with a transmission speed of information 10 – 100 Mbit / s.
We covered the basic topology LAN. However, in practice when creating a corporate LAN can be used simultaneously by a combination of several topologies. For example, computers in one department can be connected in star, and another department under the scheme shared bus, and between these departments laid line of communication.