Today, networks and networking technologies connect people in all parts of the world and provide them with access to the greatest luxury in the world - human communication. People communicate and play seamlessly with friends in other parts of the world.
Ongoing 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 technologies: their roots
In the second half of the last century, human civilization formed its two most important scientific and technical branches - computer and telecommunication technologies. For about a quarter of a century, both of these industries developed independently, and within their framework, computer and telecommunication networks were created, respectively. 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 we call the term networktechnology”, which is a subsection of the more general concept of “information technology”.
As a result of their appearance, a new technological revolution took place in the world. Just as a few decades before the surface of the earth was covered with a network of high-speed highways, 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 an integral set of rules for the representation and transmission of information, implemented in the form of so-called "standard protocols", as well as hardware and software, including network adapters with drivers, cables and FOCL, various connectors (connectors).
"Sufficiency" of this set of tools 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". Once upgraded, the network becomes more reliable and faster, but at the cost of building on top of the core network technology that forms its basis.
Term"network technology" is most often used in the narrow sense described above, but it is often broadly interpreted as any set of tools and rules for building 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 itself, was in the 60-80s. last century multi-terminal systems. Representing a combination of a monitor and keyboard, located at great distances from large computers and connected to them via telephone modems or dedicated channels, the terminals left the premises of the ITC and were dispersed throughout the building.
At the same time, in addition to the operator of the computer itself at the ITC, all terminal users got the opportunity to enter their tasks from the keyboard and monitor their execution on the monitor, also performing some task management operations. Such systems, implementing both time-sharing algorithms and batch processing, were called remote job entry systems.
Global networks
Following multi-terminal systems in the late 60s. 20th century was created and the first type of networks - global computer networks (GCN). They connected supercomputers, which existed in single copies and stored unique data and software, with large computers located at distances up to many thousands of kilometers from them, using telephone networks and modems. This network technology was previouslytested in multi-terminal systems.
The first GKS in 1969 was ARPANET, which worked in the US Department of Defense and combined different types of computers with different 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 still used today.
First example of convergence of computer and telecommunications networks
GKS inherited communication lines from older and more global telephone networks, since it was very expensive to lay new long-distance lines. Therefore, for many years they used analog telephone channels to transmit only one conversation at a time. Digital data was transmitted over them at a very low speed (tens of kbps), and the possibilities were limited to the transfer of data files and e-mail.
However, having inherited telephone communication lines, GKS did not take their main technology based on the principle of circuit switching, when each pair of subscribers was allocated a channel with a constant speed for the entire duration of the communication session. The GKS used new computer network technologies based on the principle of packet switching, in which data in the form of small portions of packets are issued at a constant rate to an unswitched network and received by their addressees in the network using address codes embedded in the packet headers.
Predecessors of LANs
Appearance in the late 70s. 20th century LSI has led to the creation of minicomputers with low cost and rich functionality. They began to really compete with mainframe computers.
Minicomputers of the PDP-11 family have gained wide popularity. They began to be installed in everything, even very small production units for managing technical processes and individual technological installations, as well as in departments of enterprise management to perform office tasks.
The concept of enterprise-wide computing resources was born, although all minicomputers still operated autonomously.
The advent of LAN networks
By the mid-80s. 20th century technologies for combining mini-computers in networks based on data packet switching were introduced, as in the GCS.
They have made building a single enterprise network, called a LAN, 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 (connectors) on its cables and connect the adapters to the mini-computer and to each other using these cables. Next, one of the operating systems was installed on the computer server, designed to organize a LAN - network. After that, it started working, and the subsequent connection of each new mini-computer did not cause any problems.
Internet is inevitable
If the advent of minicomputers made it possible to distribute computer resources evenly across the territories of enterprises, then the appearance at the beginning90s PC led to their gradual appearance, first at every workplace of any knowledge worker, and then in individual human dwellings.
The relative cheapness and high reliability of PCs 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 today covered all countries of the world.
The size of the Internet grows by 7-10% every month. It is the core linking various local and global networks of businesses and institutions around the world to each other.
If at the first stage, data files and e-mail messages were mainly transmitted via the Internet, today it mainly provides 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 knowledge and human activity - from new directions in science to weather forecasts.
Basic LAN network technologies
Among them are the 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 80s).
In the late 90s. Ethernet technology has become the leader in LAN-network technology, combining its classic version with data transfer rates up to 10 Mbps, as well as Fast Ethernet (up to 100 Mbps) and Gigabit Ethernet (up to 1000 Mbps). AllEthernet technologies have similar principles of operation, which simplify their maintenance and the integration of LAN networks built on their basis.
At the same time, developers began to integrate network functions into the kernels of almost all computer operating systems that implement the above network information technologies. There are even specialized communication operating systems like Cisco Systems' IOS.
How GCS technologies evolved
GKS technologies on analog telephone channels, due to the high level of distortion in them, were distinguished by complex algorithms for monitoring and recovering data. An example of them is the X.25 technology developed in the early 70s. 20th century More modern network technologies are frame relay, ISDN, ATM.
ISDN is an acronym that stands for Integrated Services Digital Network and enables remote video conferencing. Remote access is provided by installing ISDN adapters in the PC, which work many times faster than any modems. There is also special software that allows popular operating systems and browsers to work with ISDN. But the high cost of equipment and the need to lay special communication lines hinder the development of this technology.
WAN technologies have progressed along with telephone networks. After the advent of digital telephony, Plesiochronous Digital Hierarchy (PDH) was developed, supporting speeds up to 140 Mbps and used by enterprises to create their own networks.
New Synchronous Digital Hierarchy (SDH) technology in the late 80s. 20th century expanded the bandwidth of digit altelephone channels up to 10 Gbps, and Dense Wave Division Multiplexing (DWDM) technology - up to hundreds of Gbps and even up to several Tbps.
Internet Technologies
Internet network technologies are based on the use of hypertext language (or HTML-language) - a special markup language for electronic documents, which is an ordered set of attributes (tags) that are pre-embedded by website developers into each of their pages. Of course, in this case we are not talking about text or graphic documents (photos, 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 (now there are many tools and technologies for this work, collectively called "website layout") in the form of a set of web pages, and site owners place them on Internet servers on a lease basis 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 web pages uploaded to them.
Browsers of user PCs, having obtained 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 viewed page, browsers form its image on the monitor screen in the form as it was intended by the site developer.– with all headings, font and background colors, various inserts in the form of photos, diagrams, pictures, etc.
