Network and network technology. Network Information Technologies

Today, networks and networking technologies connect people in every corner of the world and provide them with access to the greatest luxury in the world - human communication. People without interference communicate and play with friends who are in other parts of the world.

The events that are happening are becoming known in all countries of the world in a matter of seconds. Everyone is able to connect to the Internet and lay out his portion of information.

Network information technologies: the roots of their origin

In the second half of the last century, two of its major scientific and technical branches - computer and telecommunication technologies - were formed by human civilization . About a quarter of a century, both these industries developed independently, and within their framework, respectively, were created computer and telecommunications networks. However, in the last quarter of the 20th century, as a result of the evolution and interpenetration of these two branches of human knowledge, there emerged what we call the term "network technology", which is a subsection of the more general concept of "information technology".

As a result of their appearance in the world, a new technological revolution took place. Just as several decades before its surface was covered with a network of expressways, at the end of the last century all countries, cities and villages, enterprises and organizations, as well as individual dwellings, proved to be connected "information highways". At the same time, they all became elements of various data transmission networks between computers in which various technologies of information transmission were implemented.

Network technology: concept and content

Network technology is a complete set of rules for the representation and transmission of information, realized in the form of so-called "standard protocols", as well as hardware and software, including network adapters with drivers, cables and fiber-optic links, various connectors ( Connectors).

The "sufficiency" of this set means means its minimization while preserving the possibility of constructing an efficient network. It should have the potential for improvement, for example, by creating subnets that require the use of protocols of various levels, as well as special communicators, usually called "routers". After the improvement, the network becomes more reliable and faster, but at the cost of the appearance of add-ons over the main network technology, which is its basis.

The term "network technology" is most often used in the narrow sense described above, but it is often interpreted as any set of tools and rules for constructing networks of a certain type, for example, "local computer network technology."

The prototype of network technology

The first prototype of a computer network, but not yet the network, became in the 60-80-ies. The last century multi-terminal systems. Representing a combination of a monitor and a keyboard that are located at large distances from large computers and connected to them via telephone modems or through dedicated channels, the terminals left the premises of the ITC and spread out throughout the building.

Moreover, in addition to the operator of the computer on the ITC, all users of the terminals were able to enter their tasks from the keyboard and monitor their execution on the monitor, and carry out some operations for managing tasks. Such systems, implementing both time-sharing and batch-processing algorithms, were called remote task entry systems.

Global networks

Following the multi-terminal systems in the late 60's. XX century. The first type of network was also created - global computer networks (GCS). They linked supercomputers that existed in single copies and stored unique data and software, with large computers that were located at distances of up to many thousands of kilometers, through telephone networks and modems. This network technology was previously tested in multi-terminal systems.

The first SCS in 1969 was ARPANET, which worked in the US Department of Defense and combined various types of computers with different operating systems. They were equipped with dopmodules for the implementation of communication network protocols common to all computers on the network. It was on it that the basics of network technologies were developed, which are still used today.

The first example of the convergence of computer and telecommunications networks

SCS inherited the link from older and more global networks - telephone, since it was very expensive to build new long lines. Therefore, for many years they used analogue telephone channels to transmit at a given time only one conversation. Digital data was transmitted on them with very low speed (tens of Kbps), and the possibilities were limited to the transfer of data files and e-mail.

However, inheriting telephone lines, the GCS did not take their main technology, based on the principle of switching channels, when each pair of subscribers for the entire communication session was allocated a channel at a constant rate. The SCS used new computer network technologies based on the principle of packet switching, in which data in the form of small packets-packages with constant speed are given out to a non-switched network and received by their addressees in the network by address codes embedded in packet headers.

Predecessors of local networks

Appearance in the late 70's. XX century. BIS led to the creation of a mini-computer with low cost and rich functionality. They really competed with large computers.

A mini-computer of the PDP-11 family has become very popular. They began to be installed in all, even very small production units for management of technical processes and separate technological installations, as well as in departments of enterprise departments for performing office tasks.

Arose the concept of distributed computer resources throughout the enterprise, although all mini-computers still operated autonomously.

The emergence of LAN-networks

By the mid-80's. XX century. The technologies of combining minicomputers in a network based on switching data packets were introduced, as in the GCS.

They turned the construction of a network of one enterprise, called local (LAN - network), into an almost trivial task. To create it, you only need to buy network adapters for the chosen LAN technology, for example, Ethernet, a standard cable system, install connectors on its cables and connect the adapters to the mini-computer and each other through these cables. Then one of the operating systems was installed on the computer server, designed for the organization of the LAN network. After that, it began to work, and the subsequent joining of each new mini-computer did not cause any problems.

The inevitability of the appearance of the Internet

If the emergence of a mini-computer allowed to distribute computer resources evenly across the territories of enterprises, then the appearance in the early 90's. PC caused their gradual appearance first in every workplace of any worker of intellectual work, and then in individual human dwellings.

Relative cheapness and high reliability of PC work first gave a powerful impetus to the development of LAN-networks, and then led to the emergence of a global computer network - the Internet, which now covers all countries of the world.

The size of the Internet every month grows by 7-10%. It is the core that connects various local and global networks of enterprises and institutions around the world with each other.

If in the first stage, mainly data files and e-mails were transmitted via the Internet, today it provides mainly remote access to distributed information resources and electronic archives, to commercial and non-commercial information services of many countries. Its free access archives contain information on virtually all areas of human knowledge and activity - from new directions in science to weather forecasts.

The main network technologies of LAN-networks

Among them, there are basic technologies, on which the basis of any particular network can be built. Examples include well-known LAN technologies such as Ethernet (1980), Token Ring (1985) and FDDI (late 80's).

In the late 90's. Ethernet technology has become the leaders of LAN-network technology, combining its classical version with data transmission speed up to 10 mbit / s, as well as Fast Ethernet (up to 100 Mbit / s) and Gigabit Ethernet (up to 1000 Mbit / s). All Ethernet technologies have similar operating principles, simplifying their maintenance and combining the LAN networks built on their basis.

In the same period, in the nucleus of almost all computer OS, their developers began to integrate network functions that implement the above-mentioned network information technologies. There were even specialized communication OS like IOS of Cisco Systems.

How did GCS technology evolve?

Technologies of SCS on analogue telephone channels because of the high level of distortion in them were distinguished by complex algorithms of control and data recovery. An example of them is the X.25 technology of the early 70's. XX century. More modern network technologies are frame relay, ISDN, ATM.

ISDN - the abbreviation, meaning "digital network with integration of services", allows carrying out remote videoconferences. Remote access is provided by installing in the PC adapters ISDN, working many times faster than any modem. There is also a special software that allows popular OS and browsers to work with ISDN. But the high cost of equipment and the need to build special communication lines hampers the development of this technology.

Global network technologies have progressed along with telephone networks. After the advent of digital telephony, the special technology Plesiochronous Digital Hierarchy (PDH) was developed, supporting speeds up to 140 Mbit / s and used to create enterprises of their own networks.

New technology Synchronous Digital Hierarchy (SDH) in the late 80's. XX century. Has expanded the capacity of digital telephone channels to 10 Gb / s, and Dense Wave Division Multiplexing (DWDM) technology - up to hundreds of Gbit / s and even up to several Tb / s.

Internet technologies

Network technologies of the Internet are based on the use of the hypertext language (or HTML-language) - a special language for marking electronic documents, which is an ordered set of attributes (tags) introduced by developers of Internet sites in each page. Of course, speech in this case is not about text or graphic documents (photos, pictures) that are already "downloaded" by the user from the Internet, are in the memory of his PC and are viewed through text or graphic editors. It's about the so-called web pages viewed through browser programs.

Developers of Internet sites create them in HTML-language (now many tools and technologies of this work, collectively called "website layout") are created in the form of a set of web pages, and site owners are placed on Internet servers on lease terms from the owners of their memory servers (The so-called "hosting"). They work around the clock on the Internet, serving the requests of its users to view downloaded web pages.

Browsers of the user PCs, having received through the server of their Internet provider access to a specific server, whose address is contained in the name of the requested Internet site, access this site. Further, analyzing the HTML tags of each page viewed, the browsers form its image on the monitor screen in the form, as it was conceived by the developer of the site - with all the titles, font and background colors, various inserts in the form of photos, diagrams, pictures, etc. .