What is a global computing network. Global networks

Tariffs

Global Computing Network (DHW or WAN - World Area Network) - a network connecting computers removed geographically over long distances from each other. It differs from the local network to more extended communications (satellite, cable, etc.). The global network combines local networks.

WAN (World Area Network) is a global network covering large geographic regions, including both local networks and other telecommunication networks, devices. Example WAN - Package Switching Network (Frame Relay), through which various computer networks can "talk".

Today, when the geographical framework of networks are moved to connect users from different cities and states, the LAN is transformed into a global computing network [DHW (WAN)], and the number of computers in the network can already vary from a dozen to several thousand.

Internet - Global computer networkcovering the whole world. Today, the Internet has about 15 million subscribers in more than 150 countries of the world. Monthly network size increases by 7-10%. The Internet forms a core that provides a connection between various information networks belonging to various institutions around the world, one on the other.

If the network was previously used exclusively as file transfer and messaging environment emailToday, more complex tasks of distributed access to resources are solved today. About three years ago, shells were created that support network search and access to distributed information resources, electronic archives.

The Internet, which once served exclusively with research and training groups, whose interests stretched up to access to supercomputers, is becoming increasingly popular in the business world.

Companies are seduced by speed, cheap global communications, convenience for joint work, available programs, unique internet network database. They consider the global network as an addition to their own local networks.

With a low cost of services (often it is only a fixed monthly fee for the lines of lines or telephone), users can access the commercial and non-commercial information services of the United States, Canada, Australia and many European countries. In the Free Access Archives of the Internet, you can find information for almost all spheres of human activity, starting with new scientific discoveries before the weather forecast for tomorrow.

In addition, the Internet provides unique capabilities of cheap, reliable and confidential global communication worldwide. This turns out to be very convenient for firms with its branches worldwide, transnational corporations and management structures. Usually, the use of the Internet infrastructure for international relationship It costs significantly cheaper direct computer communication through a satellite channel or via the phone.

Email - the most common Internet network service. Currently, your email address has approximately 20 million people. Sending email email costs significantly cheaper than the parcels of the usual letter. In addition, the message sent by email will reach the addressee in a few hours, while the usual letter can get to the addressee several days, and then weeks.

Currently, internally all known links from low-speed telephone lines To high-speed digital satellite channels.

In fact, the Internet consists of a variety of local and global networks belonging to various companies and enterprises related to various communication lines. The Internet can be imagined in the form of a mosaic folded from small networks of different quantities, which actively interact with one on the other, send files, messages, etc.

As in every other network in the Internet, there are 7 levels of interaction between computers: physical, logical, network, transport, communication session, representation and applied level. Accordingly, each interaction level corresponds to a set of protocols (i.e. interaction rules).

Protocols physical level Determine the type and characteristics of communication lines between computers. Internnet uses almost all currently known methods of communication from simple wire (twisted pair) to fiber optic communication lines (Vols).

For each type of lines of communication, the appropriate logical level protocol is developed, managing the transfer of information on the channel. The logical level protocols for telephone lines include SLIP (Serial Line Interface Protocol) and PPP (POINT TO POINT PROTOCOL).

To communicate via a local network cable - this is batch drivers for LAN boards.

The network layer protocols are responsible for transmitting data between devices in different networks, that is, they are engaged in the network route. Network level protocols belong to IP ( Internet Protocol) And ARP (Address Resolution Protocol).

Transport level protocols manage data transfer from one program to another. Transmission Control Protocol and UDP (User Datagram Protocol) are belonging to the Transmission Control Protocol (TRANSMISSION CONTROL PROTOCOL).

Communication session protocols are responsible for the installation, maintenance and destruction of the corresponding channels. On the Internet, these are already mentioned TCP and UDP protocols, as well as the UUCP protocol (UNIX TO UNIX Copy Protocol).

Executive Level Protocols are engaged in servicing application programs. Executive Level Programs own programs running, for example, on a UNIX server, to provide various services to subscribers. Such programs include: Telnet Server, FTP Server, Gopher Server, NFS Server, NNTP (Simple Mail Transfer Protocol), POP2 and POP3 (Post Office Protocol), etc.

Applied level protocols include network services and programs for their provision.

Under the concept of "global networks" means computer communications that combine LANs and individual computing machines that are at a considerable distance. They are intended for the overall application of world information resources and provide easy access to users to all kinds of data accumulated by humanity. Global networks, like local, open the ability: Applications network software and hardware resources; general access Users to information resources. [...]

Global networks, like local, discover the possibility:

applications of network programs and hardware resources;
shared user access to information resources.

But unlike LAN global networks (in English-speaking abbreviation - WAN, from Wide Area Networks phrases) provide services to a much larger number of people staying on an extensive area - at different points of the settlement, region, states, parts of light or in general planet. We list the types of global networks and briefly describe them.

Types of global networks

The most popular among all existing global networks has gained Internet. It binds a lot of various computer networks and computing machines, the transfer of information between which occurs through the lines of public telecommunications. Servers are used to store information in this network, services are based on client-server connections, and information exchange occurs through high-speed communication channels or highways. Also, the WAN category are less famous networks, including FIDONET, EUNET, EARNET, CREN.

Due to significant territorial coverage, the creation of such networks requires huge investments, so they often organize large telecommunications companies in order to provide subscribers paid services. So the public (public) network appear. Sometimes WANs are organized in the form of private networks of large corporations for their internal needs. So appear private WAN.

There are combinations of the above forms - when the corporate network uses public WAN resources together with its own. For example, territorial networks are often organized on leased communication channels. In addition to computing global networks, there are also other types of communications used for informational exchange. In particular, these are telex, telephone and telegraphic networks.

What are the global networks by the type of leased components?

Compare, what are the varieties of global networks in the category of leased resources. There are networks created:

Using packet switching - WAN technologies are used to create a connection between LAN and computers, Wan: X.25, Frame Relay, ATM, SMDS. There is also the ability to use TCP / IP territorial network services. They are also presented in the Internet version, and as leased by the Wan commercial nature TCP / IP.
Using channel switching. They can perform analog telephone communications or digital networks with the implementation of ISDN services. The first often possess low-quality channels and a long time establish a link. Digital systems are deprived of these shortcomings.
With the use of selected channels - they are rented from companies that own long-distance channels or renting urban or regional channels. Through such lines, it is possible:

create a territorial network by applying leased lines to communicate intermediate packet switches;
do not install transit switches of packages operating using WAN technology, but to connect the dedicated Channels of the LAN or other subscribers.

In terms of traffic, the optimal is the work of WAN on the packet switching method. As a rule, with identical values \u200b\u200bof access speeds, this option is at least twice as low as the public telephone networkoperating on channel switching technology. But often such WAN in a particular city is inaccessible, and there are networks, ready to provide dedicated channels. As a result, in the formation of its network, it is sometimes beneficial to use resources by rented them with the owners of a telephone or primary network.

Access Networks and Main Networks

When describing what global networks are, you can classify them on 2 main categories:

Mains - they are used to create peer-to-peer bonds between large-scale LANs belonging to major enterprise units. Since the highways connect the threads of the set of subnets, from such territorial networks requires a substantial bandwidth and permanent availability of network access.
Access networks are in demand when connected small LAN and individual remote PCs with the central LAN enterprise. They provide prompt access to corporate information from employees who are in different cities or even countries.

»[Informatics Exam] [Ticket number 22]

Local and global computer networks. Addressing in networks.

Computer network is a totality of computers and various devicesproviding information exchange between computers in the network without using any intermediate information carriers.

Creating computer networks is caused by the practical need of users remote from each other computers in the same information. Networks provide users with the opportunity not only to quickly exchange information, but also collaboration on printers and other peripheral devices, and even simultaneous processing of documents.

All variety of computer networks can be classified by group of features:

Territorial prevalence;
Departmental affiliation;
Information transfer rate;
Type of transmission medium;

On the territorial distribution of the network can be local, global, and regional.

According to the accessories vary departmental and government networks. The departmental belongs to one organization and are located on its territory.

In terms of information transfer, computer networks are divided into low-, medium and high-speed.

The type of transmission medium is divided into coaxial networks, on a twisted pair, fiber optic, with transmission of information on radio channels, in the infrared range.

Local computer networks.

The local network combines computers installed in the same room (for example, a school computer class, consisting of 8-12 computers) or in one building (for example, in the school building, several dozen computers installed in various subject rooms can be combined into a local network.

In small local networks, all computers are usually equal, i.e. users independently decide which resources of their computer (discs, directories, files) are publicly available over the network. Such networks are called peer-to-peer.

If more than ten computers are connected to the local network, the peer-to-peer network may not be quite productive. To increase productivity, as well as in order to ensure greater reliability when storing information on the network, some computers are specifically allocated for storing files or application programs. Such computers are called servers, and the local network - Network based on servers.
Each computer connected to the local network must have a special fee (network adapter). Among themselves computers ( network adapters) Connect with cables.

Topology network.

The general scheme for connecting computers to local networks is called the network topology. Network topology may be different.

Ethernet networks can have a "tire" and "star" topology. In the first case, all computers are connected to one general cable (tire), in the second - there is a special central device (hub), from which the "rays" go to each computer, i.e. Each computer is connected to your cable.

The structure of the "tire" type is easier and more economical, as it is not required for it additional device And less cable is consumed. But it is very sensitive to the malfunctions of the cable system. If the cable is damaged at least in one place, problems arise for the entire network. Fault location is difficult to detect.

In this sense, the "star" is more stable. A damaged cable is a problem for one particular computer, on the operation of the network as a whole does not affect. No effort to localize malfunction is required.

In a network with a "ring" structure, the information is transmitted between the stations along the rings with a rift in each network controller. Culture is performed through buffer drives performed on the basis of operational storage devices, so when you exit, the structure of one network controller May break the work of the entire rings.
The dignity of the ring structure is the simplicity of the implementation of the devices, and the disadvantage is low reliability.

Regional computer networks.

Local networks do not allow to provide joint access to information to users, for example, in various parts of the city. Regional networks come to the rescue, uniting computers within one region (city, country, continent).

Corporate computer networks.

Many organizations interested in protecting information from unauthorized access (for example, military, banking, etc.) create their own, so-called corporate networks. The corporate network can combine thousands and tens of thousands of computers posted in various countries and cities (as an example, a network of Microsoft, MSN Corporation).

Global computer network.

In 1969, an ARPAnet computer network was created in the United States, uniting computer centers of the Ministry of Defense and a number of academic organizations. This network was intended for a narrow target: mainly to explore how to maintain communication in the event of a nuclear attack and to help researchers in the exchange of information. As this network grows, many other networks have been created and developed. Even before the era of personal computers, Arpanet's creators have begun to develop the InternetTING PROJECT program ("Networking Project"). The success of this project led to the following results. First, the largest Internet Internet network was created (from the lowercase letter I). Secondly, various options for the interaction of this network with a number of other US networks were tested. It created prerequisites for the successful integration of many networks into a single world network. Such a "network of networks" is now everywhere called the Internet (Russian-speaking writing - Internet is widely used in domestic publications).

Currently, tens of millions of computers connected to the Internet are stored a huge amount of information (hundreds of millions of files, documents, etc.) and hundreds of millions of people enjoy the information services of the global network.

The Internet is a global computer network that unites many local, regional and corporate networks and includes tens of millions of computers.

In each local or corporate network usually there is at least one computer that has a permanent connection to the Internet using a high link throughput (Internet server).

The reliability of the global network is ensured by redundancy of communication lines: as a rule, servers have more than two lines of communication connecting them with the Internet.

The basis, the "frame" of the Internet makes more than one hundred million servers constantly connected to the network.

Internet servers can be connected using local networks or commutable telephone lines of hundreds of millions of network users.

Addressing online

In order to contact some computer on the Internet, you need to know his unique Internet address. There are two equivalent addresses formats that differ only in their form: IP address and DNS address.

IP address

IP address consists of four digits blocks separated by points. It may have this kind:
84.42.63.1

Each block may contain a number from 0 to 255. Thanks to such an organization, it is possible to obtain over four billion possible addresses. But since some addresses are reserved for special purposes, and blocks are configured depending on the type of network, the actual number of possible addresses is slightly smaller. And nevertheless, it is more than enough for the future Internet expansion.

The concept of "host" is closely connected with the concept of IP addresses. The host is understood to be any device using the TCP / IP protocol to communicate with other equipment. It may be not only a computer, but also a router, a hub, and the like. All these devices connected to the network are required to have their own unique IP address.

DNS - address

The IP address has a numeric look, as computers are used in its work. But it is quite complicated for memorization, so it was developed domain system Names: DNS. The DNS address includes more convenient letter-cuts, which are also separated by points to separate information blocks (domains). For example:

If you enter the DNS address, then it is first sent to the so-called name server that converts it to a 32-bit IP address for machine reading.

Domain names

DNS - the address usually has three components (although they can be as much as possible).

The domain name system has a hierarchical structure: top-level domains - second-level domains and so on. Top-level domains are two types: geographical (two-letter - each country has its own code) and administrative (three-letter).

Russia belongs a geographic domain ru.

The Klyax @ .NET portal has registered the second level of Klyaksa in the top-level administrative domain NET.

Computer names that are Internet servers include a full domain name and the name of the computer. So the full address of the portal of Klyaks @ .NET has the view www.set

gOV - Governmental institution or organization
MIL - Military Institution
COM - Commercial Organization
NET - network organization
ORG is an organization that does not apply to one of the above listed

Among the frequently used domains - the identifiers of countries can be allocated as follows:

aT - Austria
Au - Australia
CA - Canada
CH - Switzerland
DE - Germany
DK - Denmark
ES - Spain
Fi - Finland
FR - France
IT - Italy
JP - Japan
NL - Netherlands
NO - Norway
NZ - New Zealand
RU - Russia
SE - Sweden
UK - Ukraine
ZA - South Africa

E-mail address

Using IP addresses or DNS addresses, you can contact any desired computer. If you want to send a message by e-mail, the instructions of only these addresses will not be enough, since the message should get not only in required computerBut also to a specific system user.

SMPT Special Mail Protocol (Simple Mail Transport Protocol) is intended for delivery and prime email messages. A computer through which email messages are transmitted to the Internet are called the SMPT server. E-mail messages are delivered to the computer specified in the address, which is responsible for further delivery. Therefore, such data as the username and the name of the corresponding SMPT server are divided by the "@" sign. This sign is called "AT Commercial" (on a jargon - a dog, a dog). Thus, you add your message to a specific user of a particular computer. For example:
[Email Protected]site Here Ivanov is a user who is intended to be a message, and the SMPT site is the server on which its email box is located. IN mailbox Messages that came to a specific address are stored.

URL (Uniform Resource Locator, Unified Resource Determined) is the address of some information on the Internet. It has the following format:
Resource Type: // Node Address / Other Information
The most common are the following types of resources:

FTP: // FTP server
GoPher: // Gopher Menu
http: // address in www
MailTo: // Email Address
NEWS: // Usnet news group
Telnet: // Computer in which you can register using Telnet

The resource part of the URL always ends with a colon and two or three inclined features. Next follows the specific address of the node you want to visit. Behind him, as a limiter washes an oblique trait. In principle, this is quite enough. But if you want to view a specific document on this node and you know exactly its location, you can enable its address in the URL. Below are several URLs and decrypt their values:

Http: //www..php Home Information and Educational Portal Klyax @ .net

ftp://ftp.microsoft.com/dirmap.txt file named dirmap.txt on FTP - Microsoft server

So, the following types of addresses are available on the Internet.

Computer network is nothing but to combine multiple computers with each other, allowing them to exchange data. The global networks are called when they cover users from around the world. Note that the first civilian networks appeared in the United States. But few people know that the principle of this technology was first used in the USSR, and thanks to this, the first system was once created for a long time ago.

Today there is a fairly wide classification of networks. By territorial prevalence, global, local and regional computer networks are distinguished. Global computer networks are nominated by networks located in the territory of the state or several states, for example, worldwide internet. Covered the territory within up to several tens of square meters, and regional is the networks that are located in the area or city.

However, the two main terms in the classification of networks are: WAN and LAN.

To connect to such networks, modems were used, which worked under specialized telecommunication programs, by type Comit, ProCom, Bitcom, Mitez, etc. Controlled MS-DOS OS, they exchanged information with the computer to which the connection was established.

It is not quite difficult to build a global network. The global network consists of cells that are local networks. In the same place, local networks consist of smaller networks and individual computers. This is such a multi-level hierarchy and provides network construction. In addition, each device in the network must have its own IP address or unique identifier.

Nowadays, single computers included in global computer networks are increasing. Basically, it is home PC. For the most part, subscribers of networks are those computers that are included in local consequences, most often specialists are being developed by options, as it is better to interact at once several local computer networks. Need to provide for remote computer Availability with any computer included in the remote local network, or vice versa. The last option is very relevant with increasing the number of home and personal computers.

Now the switching centers are used for network centers that are X.25 specialized devices of Telenet, Ericsson, Siemens, Alcatel, etc., and for networks with TCP / IP, DECNIS and Cisco routers apply. However, technology does not stand still, and it is likely that in the future we will see an even more efficient organization of the global network, which today has a huge impact on the lives of almost every person.

Covering large territories and including big number computers.

GKS serve to combine disparate networks so that users and computers, wherever they be, can interact with all the other participants in the global network.

Some GKS are built exclusively for private organizations, others are a means of communicating corporate LAN with the Internet network or through the Internet with remote networks that are part of corporate. Most often, the GCS relies on the dedicated lines, at one end of which the router is connected to the LAN, and on the other, the switch is associated with the rest of the GKS. The main used protocols are TCP / IP, SONET / SDH, MPLS, ATM and Frame Relay. Earlier, the X.25 protocol was widely widespread, which can be considered the progenitor Frame Relay.

Description

Binds computers dispersed at a distance of hundreds and thousands of kilometers. Frequently used already existing not very high quality lines. Lower than in local networks, data transfer rates (tens of kilobit per second) limit the set of file transfer services, mostly not in operational, but in background modeusing email. For the discrete data rack, more complex methods and equipment are used than in local networks.

The difference between the global network from local

Global networks differ from local making on the unlimited number of subscribers and used, as a rule, not too high-quality communication channels and a relatively low transmission rate, and the exchange control mechanism, in principle cannot be guaranteed soon.

In global networks, no quality of communication is much more important, and the very fact of its existence. True, B. currently Already it is impossible to conduct a clear and unambiguous limit between local and global networks. Most local networks have access to the global network, but the nature of the transmitted information, the principles of the exchange of exchange, the modes of access to resources inside the local network, as a rule, are very different from those adopted in the global network. And although all the LAN computers in this case are also included in the global network, the specifics of the local network does not cancel. The ability to go to the global network remains only one of the resources, divided users of the local network.

The largest GKS.

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Watch what is a "global computer network" in other dictionaries:

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Informatics course lectures, Fedotova E., Fedotov A .. The course of lecture on computer science includes consideration of the following topics: informatics and information Technology (general provisions); PC device; software; Windows OS; Applied ...