Network devices

Network devices.

Any device that is able to access the network is called a network device.

There are two groups of devices:

User devices are those devices with which the user directly interacts. Try to give an example of such devices yourself.

Network - these are those who are responsible for the network infrastructure. These devices will be discussed in this synopsis.

In order to make it easier to navigate the devices, they can be considered grouped by levels of the OSI model, because such devices solve the tasks of these levels.

Physical layer devices

Network card

A network card is a device that allows you to receive network signals and send them.

We can say that this is the interface of interaction with the network. Since most devices are modular (they consist of several modules, such as a computer or a phone), network cards are connected to slots on the motherboard. To work on the network, each host must be equipped with a Network Interface Card (Network Interface Card — NIC), also called a network adapter. As a rule, such devices can function without a computer network. Each NIC adapter has a unique code called a MAC address.

WIFI Adapter

A WIFI adapter is a device (similar in function to a network card) that a host needs to access a wireless network.

Repeater

A repeater is a device that is capable of amplifying and re-shaping the shape of the incoming analog signal of the network at a distance of another segment (i.e. repeat). This is especially useful for long communication lines, since the signal tends to fade during transmission. When the signals leave the transmitting station, they are clear and easily recognizable. However, the longer the cable length, the weaker and less distinguishable the signal becomes as it passes through the network transmission medium. The purpose of using a repeater is to regenerate and resynchronize network signals at the bit level, which allows them to be transmitted over a longer distance through the medium.

Hub

A hub is a central device of a cable system or a network of the physical topology "zvezda", which, when receiving a packet to one of its ports, forwards it to all the others. The result is a network with a logical structure of a common bus. There are active and passive hubs. Active hubs amplify the received signals and transmit them. Passive hubs transmit a signal through themselves without amplifying or restoring it.

It simply receives electronic signals from one port and reproduces (or retransmits) the same message for all other ports. Hubs and repeaters have similar characteristics, so hubs are often called multiport repeaters (multiport repeater).

Terminator

Terminators are 50 ohm resistors that produce signal attenuation at the ends of a network segment. It is most often used for "bus" type topologies.

Channel-level devices

Network Bridge

A network bridge is a device used to connect network segments. Most often, it connects to the "main" device of the network segment (i.e. the one that switches all the devices of the network segment).

When receiving a frame (packet) from the network, the bridge checks the MAC address in its header and, if it belongs to this subnet, transmits (broadcasts) the frame further to the segment to which this frame was intended. If the frame does not belong to this subnet, the bridge does nothing.

Bridges "study" the nature of the location of network segments by constructing address tables of the form "Interface: MAC address", which contain the addresses of all network devices and segments necessary to gain access to this device. If the destination port is currently busy, the bridge can temporarily save the frame until the port is released.

Switchboard

A switch is a device designed to connect multiple network devices. It has several ports (from 1 to more than 100), each of them is mapped to a specific device. Unlike a hub, a switch is able to transmit a message to a specific node. When a node sends a message to another node through the switch, it receives and decodes the frames and reads the physical (MAC) address of the message. In order to transmit frames, switches use a MAC address table, in which the port number is mapped to the MAC address.