Basics of networking

One of the key tasks of the network layer is addressing.  >In a computer network, hosts can communicate with each other in three ways:

> use single transmission;

> via multi-mission;

> via transmission.

Unicast broadcast is the most common and is used for a typical connection between two hosts. For example, when a client sends a request to a server, it uses a single broadcast transport to do so.

Using multicast transmission can significantly reduce the bandwidth consumption of a network, as a single packet is not sent to multiple hosts like a unicast transmission, but a single packet is sent that can reach multiple recipients simultaneously.

Routers can use multicast to exchange routing information. Multicast uses a special pool of addresses, called group addresses, and in the IPv4 protocol this is the range shown below:

from 224.0.0.0 to 239.255.255.255

Broadcast, on the other hand, sends a packet to all hosts on a given network. This uses a special address, the broadcast address, so that the addresses of all hosts on the network are not stored in the IP packets. It is technically impossible, then, to use one and two broadcasts, for example, when the address of a particular device is unknown. This type of transport is most often used in local networks, and broadcasting is rarely used to communicate with hosts outside a given local network.

Throughout the IPv4 address pool, there are various groups of addresses known as special purpose addresses. These are addresses that are not used for WAN communication. Among these special addresses are the so-called loopback addresses. A loopback address is nothing more than an address of its own.In addition to the valid IP address used for communication, each computer on the network is also assigned its own address, most commonly 127.0.0.1. In addition, each address in the pool is used to verify the IPv4 configuration on the host.

Another special type of address is the local link address. These address types are used when a host should get an IP address from a DHCP server, but for some reason the address is not available. The host will then receive an address from the local link address pool. Data transfers using such addresses can only take place on the local network where the host data is running. There is also a final set of special addresses, TEST-NET addresses. As with locally-connected addresses, these are only used for communication on the local network, for educational purposes. They can be used in documentation or examples, such as online courses. However, they should not be used permanently. The special address ranges are shown in the table below: