Today, networks and networking technologies connect people all over the world and provide them with access to the greatest luxury in the world - human communication. People communicate and play without interference with friends in other parts of the world.
Occurring events become known in all countries of the world in a matter of seconds. Everyone is able to connect to the Internet and post their portion of information.
Network information technology: the roots of their occurrence
In the second half of the last century, human civilization formed two of its most important scientific and technical sectors - computer and telecommunication technologies. About a quarter of a century, both of these industries developed independently, and computer and telecommunication networks, respectively, were created within their framework. However, in the last quarter of the twentieth century, as a result of the evolution and interpenetration of these two branches of human knowledge, what emerged is 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 it, the land 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, were connected by “information highways”. At the same time, they all became elements of various data transfer networks between computers in which certain information transfer technologies were implemented.
Network technology: concept and content
Network technology is a complete set of rules for the presentation and transmission of information that are implemented 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 complex of means means its minimization while maintaining the possibility of building a workable network. It should have the potential for improvement, for example, by creating subnets in it that require the use of protocols of various levels, as well as special communicators, usually referred to as “routers”. After improvement, the network becomes more reliable and faster, but at the cost of the appearance of add-ons over the main network technology, which forms its basis.
The term "network technology" is most often used in the narrow sense described above, but it is often interpreted extensively as any set of tools and rules for building networks of a certain type, for example, "technology of local computer networks."
The prototype of network technology
The first prototype of a computer network, but not the network itself, began in the 60-80s. last century multi-terminal systems. Representing a combination of a monitor and keyboard located at large distances from large computers and connected to them by means of telephone modems or through dedicated channels, the terminals exited the IVC premises and dispersed throughout the building.
At the same time, in addition to the operator of the computer itself at the ITC, all terminal users were given the opportunity to enter their tasks from the keyboard and monitor their progress on the monitor, performing some task management operations. Such systems implementing both time-sharing and batch processing algorithms were called remote task input systems.
Global networks
Following the multi-terminal systems in the late 60s. XX century the first type of networks was created - global computer networks (GCS). They connected the supercomputers that existed in single copies and stored unique data and software with large computers located from them at distances up to many thousands of kilometers through telephone networks and modems. This networking technology has been previously tested in multi-terminal systems.
The first SCS in 1969 was ARPANET, which worked in the US Department of Defense and combined different types of computers with various operating systems. They were equipped with additional modules for the implementation of communication network protocols common to all computers included in the network. It was on it that the foundations of network technologies were developed, which are currently used.
The first example of convergence of computer and telecommunication networks
GKS inherited communication lines from older and more global networks - telephone networks, since it was very expensive to lay new long lines. Therefore, for many years they used analog telephone channels to transmit only one conversation at a given time. Digital data was transmitted over them at a very low speed (tens of kbit / s), and the possibilities were limited to the transfer of data files and e-mail.
However, having inherited telephone communication lines, the GCS did not take their basic technology, based on the principle of switching channels, when a channel with a constant speed was allocated to each pair of subscribers for the entire duration of the communication session. The SCS used new computer network technologies based on the principle of packet switching, in which data in the form of small portions of packets is transmitted at a constant speed to a non-switched network and received by their addresses on the network using address codes embedded in the packet headers.
LAN predecessors
Appearance in the late 70's. XX century LSI has led to the creation of mini-computers with low cost and rich functionality. They began to really compete with large computers.
Widespread popularity mini-computers of the PDP-11 family. They began to be installed in all, even very small production units for the management of technological processes and individual technological units, as well as in departments of enterprise management for office tasks.
The concept of computer resources distributed throughout the enterprise arose, although all minicomputers still worked autonomously.
The advent of LANs
By the mid-80s. XX century technologies for combining minicomputers into networks based on switching data packets, as in the GCS, were introduced.
They turned the construction of the network of one enterprise, called the local (LAN - network), into an almost trivial task. To create it, you only need to buy network adapters for the selected LAN technology, for example, Ethernet, a standard cable system, install connectors (sockets) on its cables, and connect the adapters to the mini-computer and to each other through these cables. Next, one of the operating systems designed for organizing a LAN network was installed on the computer server. After that, she began to work, and the subsequent connection of each new minicomputer did not cause any problems.
The inevitability of the advent of the Internet
If the advent of mini-computers made it possible to distribute computer resources evenly across the territories of enterprises, then the emergence in the early 90s. PC caused their gradual appearance first at every workplace of any mental worker, and then in individual human dwellings.
The relative cheapness and high reliability of the PC at 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 has covered all countries of the world today.
The size of the Internet is growing by 7-10% every month. It is the core linking various local and global networks of enterprises and institutions around the world with each other.
If at the first stage data files and e-mail messages were mainly 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 almost all areas of human knowledge and activity - from new directions in science to weather forecasts.
Basic network technology LAN-networks
Among them, basic technologies are distinguished, on which the basis of any particular network can be built. An example is the well-known LAN-technologies such as Ethernet (1980), Token Ring (1985) and FDDI (end of the 80s).
In the late 90's. Ethernet technology has become the leader in LAN network technology, combining its classic version with data transfer speeds of up to 10 Mbps, as well as Fast Ethernet (up to 100 Mbps) and Gigabit Ethernet (up to 1000 Mbps). All Ethernet technologies have similar operating principles that simplify their maintenance and integration of LAN networks built on their basis.
In the same period, their developers began to integrate network functions into the kernels of almost all computer OSs that implement the above network information technologies. There are even specialized communications OSs like Cisco Systems' iOS.
How GKS-technologies developed
Due to the high level of distortion, GCS technologies on analog telephone channels were distinguished by sophisticated control and data recovery algorithms. An example of this is the X.25 technology of the development of the early 70s. XX century More modern network technologies are frame relay, ISDN, ATM.
ISDN stands for Digital Integrated Services Network, which allows remote video conferencing. Remote access is provided by installing ISDN adapters in the PC, which are many times faster than any modems. There is also special software that allows popular OS and browsers to work with ISDN. But the high cost of equipment and the need to lay special communication lines impedes the development of this technology.
WAN technologies have progressed along with telephone networks. After the advent of digital telephony, the Plesiochronous Digital Hierarchy (PDH) special technology was developed, supporting speeds up to 140 Mbps and used to create their own networks by enterprises.
New Synchronous Digital Hierarchy (SDH) technology in the late 80s. XX century expanded the bandwidth of digital telephone channels to 10 Gb / s, and Dense Wave Division Multiplexing (DWDM) technology to hundreds of Gb / s and even several Tbit / s.
Internet technology
Internet networking technologies are based on the use of the hypertext language (or HTML-language) - a special language for marking up electronic documents, which is an ordered set of attributes (tags) that are preliminarily implemented by website developers on each page. Of course, in this case we are not talking about text or graphic documents (photographs, pictures) that have already been "downloaded" by the user from the Internet, are in the memory of his PC and are viewed through text or graphic editors. We are talking about the so-called web pages viewed through browser programs.
Website developers create them in HTML (many tools and technologies have been created for this work, collectively referred to as "site layout") as a set of web pages, and website owners put them on Internet servers on a rental basis from the owners of their memory server (the so-called "hosting"). They work around the clock on the Internet, serving the requests of its users to view the downloaded web pages.
Browsers of user PCs, having received access to a specific server through the server of their Internet provider, the address of which is contained in the name of the requested Internet site, get access to this site. Further, analyzing the HTML tags of each page viewed, browsers form its image on the monitor screen in the form that was intended by the site developer - with all the headers, font and background colors, various inserts in the form of photos, diagrams, pictures, etc. .