Many people are interested in the question of what are hubs and what they are used for. Now we will understand this issue. In general, a hub is a node of a network. This term has different meanings in different industries.
Using the hub in various industries
For example, in transport, hubs are hubs for transfer or transshipment, hub airports. In the energy industry, this is a special center in which one route is divided into several. On SUVs, this word refers to a freewheel mounted on the front axle. Various Internet networks also use hubs. What is this in the Fidonet network? Here the hub is the node that serves to send mail. Direct Connect is the name of a network server on a file sharing network.
But the concept is most widely used in computer technology and the Internet. A specific set of network equipment is based on the tasks that are set for the designed network and the cost of implementing a specific solution. An important element of such tasks is the choice of devices, among which the main role is played by routers, switches and hubs. What is it, we will try to figure it out.
Hubs in computer networks
Technologies for building
computer networks are constantly evolving. The devices that underlie them and are used to organize communication between computers are called differently: hub, switch, and router. What is this, we will consider in more detail.
Each of the listed devices performs its role in organizing communication between computers on a network. Outwardly, they can look the same: small metal boxes with a number of ports or connectors where an Ethernet cable is connected. As for concepts such as a switch, hub, hub, router, they are often used as synonyms, but this is a mistake. These are all different devices.
Hub
One of the first network devices are hubs. What are these devices? The term is of English origin. The word hub means the center of activity. A hub, or
network hub, is designed to combine computers into a simple ad hoc network. The device has a certain number of ports to which you can connect all personal computers on the network. Most often, twisted pair is used for this purpose, which is crimped in a special way.
The principle of the hub
Consider the principle of operation of a network hub. When one of the computers in the network of the network equipped with the hub tries to access another PC, the first device sends a special block of information called a packet to the address of the network hub.
Let's try to figure out an example of a scheme with three computers. Suppose PC1, PC2, and PC3 are connected to the device. The role of the hub is to multiply the data packet from PC1 by transmitting it to other devices connected to the local network, that is, PC2 and PC3. When the signal arrives at PC3, for which it was intended, the latter sends the response packet to the hub. The network hub again sends this packet to all network computers until the response from PC3 returns to the sending computer PC1.
This is an example interface diagram of computers connected to a local network with a hub. The main disadvantage of such networks is that too much information is sent. The network hub continuously sends data packets to all devices on the computer network, even if the destination is one specific PC. At the same time, computers receive blocks of information that they often absolutely do not need. Technology turns out to be very costly. That's why network hubs are almost out of use now. Instead, more intelligent devices were developed - network switches, which are commonly called switches.
Switch
The term
“switch” is of an English nature and means a switch, or network switch. Like a hub, a switch is required to connect computers on the same local network. The scheme for connecting it to computers does not differ from the scheme with a network hub. Just instead of the hub, PCs are connected to the switch.
Being outwardly very similar to a network hub, the switch has fundamental differences from it, consisting in the method by which information is transmitted between computers on the local network.
After receiving a packet of information from a computer, the network switch, unlike a hub, does not forward it to all the PCs participating in the network, but organizes the direction of the packet to the address of the computer for which the package is intended. For example, when PK1 sends an information packet to PK3, the switch organizes the transfer to him, bypassing PK2. The network switch also returns the response packet from PK3 only to the sender of the information packet - PK1.
The switch has the ability to remember the addresses of all computers that are connected to its ports, and due to this it can work as a traffic controller, transferring information only to the destination PC and ignoring others.
The network switch was based on a table of special MAC addresses of users' network equipment in the external and internal network. As a result, a packet of information falling on each of the ports is compared with the routing table and is forwarded to the port address where the corresponding equipment is located.
Router
The name "router" spawned the English router. This is a router capable of organizing the transfer of information between two or more different local networks. In addition, the router provides the ports that are required to connect some other devices to it using a cable.
The principle of the router
Like a network switch that stores a table of registered MAC addresses, the router stores a table of IP addresses as a routing table. The main task of the router is to store this data and to ensure that other routers are aware of changes in the network configuration. It is solved by applying
routing protocols to coordinate with other routers. When packets arrive at the router, the latter uses different protocols and criteria to determine the best way to forward the packet of information to the addressee.
The router can be programmed to include multi-level rules, which are determined by the content of the packets of information that come to it. The router is programmed to activate the network equipment protection system, translate network NAT addresses and represent DHCP network services.
With smart hardware, routers are among the most sophisticated network devices. In addition to the ability to redirect information packet traffic, routers can be used to control traffic on the network. In addition, they have the ability to respond to changes in the network, dynamically detecting them, protect it with packet filtering, calculating packets for blocking or skipping.
USB hub
In addition to Ethernet network hubs, the term “hub” is used for USB technology. The development of new equipment has increased requirements for the level of development of user interfaces of computer technology. A lot of various computer peripherals that are connected via a USB connection need a special device that makes it possible to connect several devices simultaneously via USB. It is called a USB hub. What is the principle of its work?
A USB hub (USB hub) is a small device with multiple ports. Connect it through a computer jack. It allows you to connect multiple USB devices to the same USB port on a PC.
USB hub device
The design and construction of the hubs are not very complex. They are designed to switch signals and provide power voltage. In addition, they monitor the status of peripherals connected to them, notifying the host of changes.
The hub consists of two modules - a controller and a repeater. A repeater is a managed key that connects the input and output ports. It has the ability to reset and pause signal transmission. Registers are included in the controller, allowing interaction with the host. Registers are controlled through special commands that allow you to configure the hub, monitor the status and change the parameters of the downstream ports. It is possible to use the hub of the contract when the devices are connected in series.
Types of USB Hubs
One of these types is the internal card on the system bus. It serves to connect USB devices to the motherboard. This is done using a USB PCI card, which is installed on the free space of the PCI bus located directly on the motherboard. This type of USB hub is best used by those who are familiar with a computer device. Those who have no experience, it is better to dwell on another form.
Another view is an external USB hub without power. Such a device is simple and relatively inexpensive. This kind of USB hub connects to your computer’s USB port. Such a device is great for laptop owners. The use of such a USB hub is also possible for home computer users, however, it should be borne in mind that a number of devices connected to a computer require power supplied through a USB port. This type of hub is not able to power several such devices at once. In this situation, it is best to use powered hubs. What are these devices and how do they differ from devices without power?
A powered USB hub has exactly the same operating principle as a powered hub. The difference is that it can be plugged into an outlet. This allows you to provide adequate power to all devices that connect via USB. The largest USB hubs are seven-port.
Another type of such device is a USB computer board. This device is suitable for laptop users. It connects to a special USB port located on the laptop case and makes it possible to use two ports instead of one.