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Internet
 
is a global computer “super-network” interconnecting smaller networks using a set of IP protocols.

Its name comes from the English word “network”, thanks to it the traditional names of American computer networks ended with “-net” and international (formerly latin) prefix inter- that expresses that the Internet has interconnected and assimilated various older, partial, specialized, proprietary or local networks. Internet is used for transferring information and providing many services as the electronic mail, chat, web pages, file sharing, online gaming, searching, catalogues, etc.

Computer identification

Each computer connected to the internet has its own IP address. IP address is a 32bit number which is written as 4 decimal numbers between 0 and 255 divided by a dot – e.g. 192.168.1.1. Each of them is a result of conversion of the eight address bits. The overall amount of different IP addresses is 232 = 4 294 967 296.

 

TCP/IP (Transmission Control Protocol/Internet Protocol)

The protocol (rules of communication) used for transferring data over the internet. Domains – the sources on the internet are not designated by IP addresses. Instead, names are set for them that are easier to remember (these are, in fact, being translated to IP addresses anyway).

Domains (DNS)

Top Level Domain (TLD)
is the internet domain of the highest level of the domain names tree. In the tree the domain of the highest level is the one at the end (e.g. as for en.wikipedia.org, the top level domain is org). The TLD describes the basic group of domain names, e.g. all domain names within a given country. They are set by the internet standardization organization IANA. There are three types of TLDs:

Country-Code TLDs (ccTLDs) are the domains covering the domains within one country. Their name consist of two letters and with some exceptions it corresponds to the country code according to ISO 3166-1, e.g.cz for the Czech Republic

Generic TLDs (gTLDs) cover the other, common domains (e.g. org for non-profit organizations) that are not connected with one particular country (except the mil and gov TLD that are – for historical reasons – dedicated to military and government computer networks in the USA).

Infrastructural TLD used for inner mechanisms of the Internet. Right now there is only one such TLD: arpa.

Hypertext

Structured electronic text containing links to other texts, images, sounds, animations or video. It is used both on the internet and locally (encyclopedias, helps, etc.)

WWW (World Wide Web)

information system for working with hypertext documents where links to internet sources are introduced in the form of an address. The most common service in the present internet. A certain flaw lies in archiving of the published documents – they may be modified arbitrarily and it is therefore impossible to ensure that no one will attempt to fake history. You also cannot be sure that a document that has been published earlier will always be available on the internet. These flaws can partly be solved by services such as www.archive.org that are trying to archive at the contents of at least parts of the web..

Examples of hyperlinks:

http://www.nic.cz

http://www.euro-face.cz

Browser

This term stands for "internet browser". It is a program that can display web pages. The most commonly used browsers are the Internet Explorer, Mozilla Firefox, Opera, Netscape Navigator and Safari.

Basic services (protocols)

  • SMTP - Simple Mail Transfer Protocol, electronic mail
  • FTP - File Transfer Protocol, service for file transferring
  • Telnet - Virtual terminal, remote access
  • NFS - Network File System, sharing remote files
  • DHCP - Dynamic Host Configuration Protocol, dynamic configuration of network station
  • SNMP - Simple Network Management Protocol, simple protocol for network administration
  • HTTP - Hypertext Transfer Protocol, World Wide Web protocol for transfer of hypertext; basic protocol for service WWW.
  • DNS - Domain Name System, translation of domains names
  • ICQ, chat, IRC, Jabber, skype - online communication

Means of connecting a computer to the internet

Via a phone line

Classic analog connection – the dial-up (modem, telephone plug). Speed: max. 56 kb/s.

ISDN

Digital telephone line, you can call and work on the internet at the same time. Speed: 64kb/s (128 kb/s).

ADSL

High speed internet over the telephone lines. The speed of the data transfer is different for uplink (to the internet) and downlink (from the internet). Speed: theoretically in Mb/s. ADSL modem and the possibility of its connection is required as it is not automatically possible for each telephone line.

Telephone
Via a mobile phone

A slow but nowadays popular connection (used especially in case of notebooks). Speed: Theoretically 171 kb/s, in the Czech Republic around 50 kb/s maximum (but more often 10-20 kb/s) – it is largely dependent on the quality and equipment of the operator’s network. The most common technologies are GPRS and EDGE. Recently a new type of connection has been introduced in the form of CDMA (O2, cca 800kb/s), UMTS (O2, 384kb/s so far – designated as 3G) a Internet 4G (T-Mobile, 3G technology). These ways of connection are acceptable as for the connection speed. Compared to ADSL they are just characterized by a several times longer response time.
Mobile phone
Cable TV

Quick and high-quality connection, very budget-priced, dependent on the availability of the cable television. Network interface controller and cable modem are required.
Cable TV

Wireless connection

Usually used for connection of local networks to the internet or for the realization of wireless local networks.

Wi-Fi (Wireless Fidelity)

The best-known standard for wireless networks (IEEE 802.11a, b or g). Uses microwaves to transfer information. Suitable for short to middle ranges. Speed 11Mb/s (b), 54Mb/s (g,a).

Works on the following frequencies:

2,4 GHz
3,5 GHz (licensed band)
5 GHz
10 GHz
The most common is the technology based on 2,4 GHz frequency.

Especially in the Czech Republic this technology is widely used for internet connection. The providers build networks of transmitters (access points). The necessary condition is direct visibility to the AP. The participant is required to have an antenna that communicates with the AP, provides the transfer of the signal and is connected to a device called the client. This may be a wireless card in the PC or a separate device. The most commonly used antennas are connected via a coaxial cable with this client. Depending on the length and quality of the cables, losses occur. That is why this cable should be as short as possible.

WiFi
Optical systems

High speed (155 Mb/s (B-ISDN), 622 Mb/s, 10Gb/s up to 40 and more Gb/s (wave multiplex WDM)). Uses light to transfer information. High costs on cable placement predetermine this technology for backbone networks.
Fibre cable

The History of Internet