A local network topology is a logical diagram of the connection of computers or network nodes with communication channels. Topology is the geometric representation of relationships on a network. There are a large number of different topologies. The main ones are the "bus", "star", "ring", in addition, there are additional ones - "tree", "count", "lattice" and others.
A star network topology is a type of network when all computers are connected through a central site. The role of the central node is usually played by the server or the hub. This topology has its advantages and disadvantages. The advantages include high performance, since the performance of the entire network directly depends only on the maximum performance of the central device. A plus is the lack of the possibility of collision of data transmitted over the network, due to the fact that the data exchange between the station and the server is carried out on a separate channel and does not affect other computers.
The central node is the most vulnerable place of the topology, the reliability of the network is determined precisely by the reliability of the central element. If for some reason the central node stops working, the network will stop functioning. The minus “stars” is also called the high cost of connection, because for each new network subscriber you need to maintain a separate line.
The topology of the “ring” networks is based on the fact that all workstations are connected to a line closed in a ring, from which the name appeared. The signals in the "ring" are transmitted in only one direction and pass sequentially through all computers. The essence of information transfer is that a special marker is transmitted from computer to computer until it is received by the workstation to which data is to be transmitted. Having received a token, the computer creates a packet containing the recipient’s address and data, and then sends the packet in a ring. Information passes through each station until it is at the one whose address is identical to the address of the recipient. After that, the receiving party sends the source a confirmation of the receipt of data. The advantages of this topology are that message forwarding is quite effective, since you can send several messages one after another. The length of such a network can reach considerable dimensions without the use of any signal amplifiers. A huge drawback is the low reliability of the network with such a topology, because the failure of any one computer will lead to the collapse of the entire system. To connect a new client, you will have to disconnect the entire network, and if there are a large number of subscribers, the speed of work will significantly slow down. Total network performance is determined by the performance of the slowest computer.
The topology of the "bus" networks is that all subscribers are connected to one common information transmission channel. In this case, customers can make contact with any computer on the network. Data is sent to all computers, but only the station whose address matches the recipient's address can receive information. This network topology has several important advantages. Firstly, all the data is in the network and accessible to each workstation, secondly, computers can be connected independently, thirdly, such networks are cheaper because there is no need to spend money on laying additional lines connecting a new subscriber. Such a network has high reliability. Unfortunately, the transmission speed is quite low, since all data circulates on the same bus, and the speed depends on the number of connected clients. The larger this number, the slower the information is transmitted. Security in such a network is low, because the data on each workstation can be accessed from another computer.
The considered topologies of local networks are quite effective, but in practice often use the simultaneous combination of several topologies.