Networking

Currently, local area networks (LAN) have a very broad distribution. This is due to several reasons:

- The union of computers in the network allows saving money by reducing maintenance costs of computers

- Local networks provide users with a mailbox in order to send messages to other computers, where documents are delivered from one computer to another in the shortest period of time;

- Local networks with special software organize better sharing of files.

Among other things, in some areas it is simply impossible work without the LAN. These areas are: banking, warehousing operations of large companies, libraries electronic archives, etc. In these cases every single workstation can not store all the information (mainly due to its large volume). Network allows selected (registered on the file server) users to access the information, and network operator grants that access.

There are three main types of computer networks:

- Local Area Network (LAN);

- Wide Area Network (WAN);

- Global Computer Network (Internet).

In addition, each of these networks can be:

- A single server - the network is served by one file server (FS);

- A multi-server - network served by several FS;

- Distributed - Two or more LANs that are connected by internal or external bridge (bridge or interconnection controls process of exchanging data packets between one cable system and another).

Local Area Network - a group of computers that can communicate with each other, share peripheral equipment (e.g., hard drives, printers, etc.) and contact remote central computer or other local networks. LAN can consist of one or more file servers, workstations and peripherals. Users can share the same files, such as data and programs, send messages directly between workstations and protect files with powerful protection tools. The main types of LANs are Ethernet and ARCNET. Moreover, Ethernet can have multiple types of cables:

- Thin Ethernet cable, also known as "Thinnet", has a number of benefits, such as lower cost of the cable and a usage of equipment that is easier to install;

- Thick Ethernet cable, also known as "Thicknet", has received its name due to the use of standard, or a thick Ethernet cable. Thick cable allows connecting greater number of computers in the system and increasing the distance between them. However, this cable is more expensive and its installation is more complicated comparing to a thin Ethernet cable;

- Ethernet over twisted pair. It is cheaper than aforementioned cables and easier to install.

Ways of organizing (topology) of Computer Networks is the physical layout of network components (cables, stations, gateways, splitters, etc.). 

There are three main topologies: star, ring and bus.

In the networks with “Star” topology workstations are connected directly to the file server, but not connected with each other.

In the networks with the "Ring" topology file server and workstations are connected by cable and create a shape of the ring; Packets from one workstation can go through several other workstations before they reach the file server.

In the network with “Bus” topology all workstations and file server are connected to a central cable, called the bus.

Hardware connectivity devices, such as hubs, switches or routers, are the center of data transmission.

The simplest type of such devices is a network hub which works on the physical level of Open Systems Interconnection (OSI) model and simply repeats the data from input port and sends it to output ports.

The next type of devices is network switches which are now widespread. Operating at the data link layer of network protocols, they copy MAC-addresses of connected computers, IDs of the network cards and then forward the packet only to that computer, which MAC-address is written in the packet. Switch can have a dedicated port, so-called UpLink, designed to send packets that haven’t found a recipient in the local area network. 

Let’s take a look at the routers.  They work at the network level of OSI model. A router typically has two IP-addresses – one for the outside world and one for the local network. In a local network router can distribute IP-address via Dynamic Host Configuration Protocol (DHCP) and control valid IP-addresses. Typically, in this case the router is a gateway for computers in a local network. Router’s external address is configured by analogy with a computer, and can be both static and dynamic.