The network hub. Principle of operation

A network hub, otherwise known as a hub,It is a controller that combines several Ethernet devices into one network segment. Devices are connected to the hub via fiber optic or coaxial cable. Used for this and

twisted pair. The principle of the concentrator is simple: it multiplies all the incoming data packets and sends them to all the ports connected to it.

Network concentrator, as well as other typesconcentrators, has its own qualitative characteristics. First, the performance and price of the hub depends on the number of ports. The more Ethernet devices connected to it, the higher the performance and cost of the hub. Typically, the hub is equipped with an even number of connectors, the number of which varies from four to 24, but some types have five outputs. The number of ports can be increased by cascading several hubs. For this connection, a special connector is provided in each hub.

Has a network hub and another important characteristic - the speed of copying and transferring data packets. Some hubs are capable of

Change your speed in the range of ten toone hundred megabits per second. In such devices, it changes in two ways: either automatically, or manually, using a switch. In this case, the installed speed applies to all active ports. Distinguish between hubs and the type of network media. As a rule, this role goes to either a fiber-optic cable or a twisted pair, but there are concentrators that support other types of media. Also there are hubs for mixed types, for example, supporting a "hybrid" of twisted pair with a coaxial cable.

The principle of hubs is very imperfect. A data packet that has come from one channel, the network hub copies to all other connected channels, which greatly reduces the speed of the Internet, since all web devices connect to the network through a common channel. If two packets are copied simultaneously, a collision may occur, i.e., a collision of the same signals, in which some data is lost. Some types of concentrators are protected from too many collisions. As a rule, they are based on a twisted pair. In the event of a failure, this makes it possible to isolate a single

device, whereas a network hub connected via a coaxial cable disconnects the entire segment at once.

The working principle of the hub also affects the securitydata. If the computer enters the local network, the data packets of one system reach all other nodes. Because of this, all personal settings of social networks, passwords for blogs, forums and other private data can become known to all members of this network. For these reasons, the network USB hub is increasingly replaced with a network switch or switch. This device, which received the erroneous title of "smart hub", distinguishes MAC addresses of computers entering the network and sends data only to the user selected port. Packages in this case pass through the buffer, which eliminates collisions, line overload and data leakage. Due to reliability and low price, switches are increasingly used in home systems, while hubs are almost not sold.