home Magazine Internet structure: basic operating principles. Structure and principles of operation of the Internet Structural diagram of the Internet

Internet structure: basic operating principles. Structure and principles of operation of the Internet Structural diagram of the Internet

Internet-- a worldwide system of interconnected computer networks for storing and transmitting information. Often referred to as the World Wide Web and the Global Network. Built on the TCP/IP protocol stack. The World Wide Web (WWW) and many other data transmission systems operate on the basis of the Internet.

Internet addressing system

The Internet independently transfers data. Station addresses are presented special requirements. The address must be in a format that allows it to be processed automatically, and must contain some information about its owner.

For this purpose, two addresses are established for each computer: a digital IP address (IP - Internetwork Protocol) and a domain address.

Both of these addresses can be used equally. The digital address is convenient for processing on a computer, and the domain address is convenient for the user to perceive.

Digital address has a length of 32 bits. For convenience, it is divided into four blocks of 8 bits, which can be written in decimal form. The address contains all the information necessary to identify the computer.

Two blocks define the network address, and the other two define the address of a computer within this network. There is certain rule to establish the boundary between these addresses. Therefore, an IP address includes three components: the network address, the subnet address, and the address of the computer in the subnet.

In binary code, the digital address is written as follows:

10000000001011010000100110001000. In decimal code it looks like: 192.45.9.200. Network address -- 192.45; subnet address is 9, computer address is 200.

Domain address defines an area representing a number of host computers. Unlike a digital address, it is read in reverse order. First comes the name of the computer, then the name of the network on which it is located.

Reference model open system- Open Sistem Interconnect (OSI) - refers to a system that performs all communication functions for exchanging messages in a network, grouped in accordance with the open systems reference model. The model was developed by the International Standard Organization (ISO), and the model itself is abbreviated as EMVOS. The model is constructed in relation to the method of packet message transmission and is implemented by network software located in subscriber computers and specialized network devices.

Moving information between computers of different circuits is an extremely difficult task. At the beginning of the 1980s. The International Organization for Standardization (ISO) and the International Telegraphy and Telephony Consultative Committee (CITT) have recognized the need to create a network model that can help vendors create interoperable network implementations. In close collaboration, the Open Systems Interconnection (OSI) reference model was developed. This model was described in recommendations X.200 (CCITT) and ISO 7498 (ISO). Compliance with EMVOS CCITT and ISO.

EMVOS quickly became the main architectural model for the transmission of computer-to-computer messages. Although other architectural models (mostly proprietary ones) have been developed, most network vendors, when they need to provide training information to users of their products, refer to them as reference model network products. Indeed, this model is the best tool available to those hoping to learn networking technology.

Protocol- these are the rules for interaction of levels of the same name in remote systems.

Protocols are implemented by network software and are divided into:

network dependent

transport

network independent.

To network dependent These include network, link and physical layer protocols. Their characteristics are determined by the transmission medium, coding and modulation methods, and error protection methods.

Transport protocols are located at the transport level and perform intermediate functions related to the transfer of information between interacting systems through all physical connections and communication systems located between them.

Network independent protocols located at the application, presentation and session levels. Their characteristics and structure do not depend on the communications created and used in the network. They are determined only by the information processing tasks assigned to it.

Protocols at all levels must be quasi-independent: this is necessary so that replacing a protocol at one level does not require reworking protocols at other levels.

In addition, it is necessary that the protocol of each level be transparent to protocols of higher levels, that is, it does not distort their work. Among the seven protocol layers, the most important are those located at the application layer.

During administrative control, the protocols of the three lower levels also ensure the interaction of computers in the network. However, the application points for higher-level protocols (4-7) change here. During basic control, these protocols connected pairs of computers. However, during administrative control, these protocols ensure the interaction of a computer specialized for the purposes of administrative management network, with all other systems.

Basic Internet protocols

To transfer information to Internet networks TCP/IP protocol is used.

TCP/IP (Transmission Control Protocol/Internet Protocol) is a protocol (family of protocols) that is a standard for transmitting data between networks, including the Internet.

The TCP (Transmission Control Protocol) breaks information into chunks (packets) and numbers them. The Internet Protocol (IP) then adds service information to each packet with the source and destination addresses and ensures that all packets are delivered.

Thanks to this method of transmitting information to the Internet, there is no need to establish a separate communication channel between two computers. Each computer can simultaneously receive packets from a large number of other computers.

TCP/IP is the main protocol of the Internet, therefore, in order to work on the global network, the operating system installed on the user's computer must provide support for the specified protocol.

Basic Internet resources

Let's consider the main Internet resources (services). The most popular resource is the World Wide Web or WWW, which represents a huge amount (over a billion) of multimedia documents, distinctive feature which is the ability to refer to each other. This means the presence in the current document of a link that implements the transition to any WWW document that can physically be located on another computer on the Internet. Using special WWW document viewing programs, an Internet user can quickly navigate through links from one document to another, traveling across the World Wide Web.

WWW (World Wide Web, World Wide Web)-- a set of interconnected hypermedia documents.

Entire libraries of files are located on the Internet, access to which is provided by the FTP service.

FTP (File Transfer Protocol)) - storage and transfer system for all kinds of files.

As mentioned above, in the beginning, the computer network was heavily used to quickly send text messages. Therefore, the oldest resource on the Internet is E-mail (electronic mail).

E-mail (e-mail)-- email forwarding system.

There is a special service on the Internet that allows you to post messages on interconnected computers for the exchange of opinions. By connecting to one of these computers and selecting a discussion group (teleconference) based on your interests, you can read posted messages, ask a question to the group, or answer someone else's question. Messages are usually quickly replicated to other computers and stored for a short period of time, so this resource called the News Group.

Newsgroups (newsgroups)-- global distributed system for messaging and discussions.

One of the most popular systems of this kind is Usenet newsgroups.

The Telnet service allows you to connect to remote computer and work with its resources.

Telnet-- a service for remote control of computers.

However, most often such computers operate under one or another variant operating system Unix (Unix), so currently this service is used primarily by network administrators.

Finally, the Internet has the IRC (Chat) system, which allows users to communicate in real time by entering text from the keyboard.

IRC (Internet Relay Chat, conversation over the Internet)-- a service for communication between Internet users in real time by entering text from the keyboard.

The Internet can be used in various areas:

- professional activity;
- commercial activity;
- receiving educational services;
- recreation and entertainment.

Email-- technology and the services it provides for sending and receiving electronic messages (called "letters" or " emails") over a distributed (including global) computer network.

In terms of the composition of its elements and operating principle, e-mail practically replicates the system of regular (paper) mail, borrowing both terms (mail, letter, envelope, attachment, box, delivery, etc.) characteristics-- ease of use, message transmission delays, sufficient reliability and at the same time no guarantee of delivery.

The advantages of e-mail are: easy-to-understand and remember addresses of the form user_name@domain_name (for example, This e-mail address is being protected from spambots. To view it, you must have Java-Script enabled); the ability to transfer both plain text and formatted, as well as arbitrary files; independence of servers (in general, they access each other directly); sufficiently high reliability of message delivery; ease of use by humans and programs.

Disadvantages of e-mail: the presence of such a phenomenon as spam (mass advertising and viral mailings); the theoretical impossibility of guaranteed delivery of a specific letter; possible delays in message delivery (up to several days); restrictions on the size of one message and on the total size of messages in a mailbox (personal for users). Currently, any novice user can create their own free email account; just register on one of the Internet portals.

Target: become familiar with the structure and basic operating principles worldwide network Internet, with basic Internet protocols and addressing system.

Architecture and operating principles of the Internet

Global networks, reaching millions of people, have completely changed the process of dissemination and perception of information.

Wide Area Network (WAN)– these are networks designed to connect individual computers and local networks located at a considerable distance (hundreds and thousands of kilometers) from each other. Global networks connect users located around the world using a wide variety of communication channels.

Modern Internet- a very complex and high-tech system that allows the user to communicate with people located anywhere in the world, quickly and comfortably find any necessary information, publish for public information the data that he would like to communicate to the whole world.

In reality, the Internet is not just a network, it is a structure that unites ordinary networks. The Internet is a “network of networks.”

To describe today's Internet, it is useful to use a strict definition.

In his book « TheMatrix:ComputerNetworksandConferencingSystemsWorldwide » John Quarterman describes the Internet as “a metanetwork consisting of many networks that operate according to the TCP/IP family of protocols, connected through gateways and using a single address space and name space”.

There is no single point of subscription or registration on the Internet; instead, you contact a service provider who gives you access to the network through a local computer. The consequences of such decentralization in terms of the availability of network resources are also quite significant. The data transmission environment on the Internet cannot be considered only as a web of wires or fiber optic lines. Digitized data is sent via routers , which connect networks and, using complex algorithms, select the best routes for information flows (Fig. 1).

Unlike local networks, which have their own high-speed information transmission channels, global (as well as regional and, as a rule, corporate ) the network includes a communication subnetwork (otherwise: a territorial communication network, an information transmission system) to which they connect local networks, individual components and terminals (means for entering and displaying information) (Fig. 2).

A communication subnetwork consists of information transmission channels and communication nodes, which are designed to transmit data over the network, select optimal route transmission of information, packet switching and implementation of a number of other functions using a computer (one or more) and the corresponding software available in the communication node. The computers on which client users work are called workstations , and computers that are sources of network resources provided to users are called servers . This network structure is called nodal .

Fig.1 Scheme of interaction on the Internet

Internet is a global information system that:

· logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP);

· capable of supporting communications using the Transmission Control Protocol family - TCP/IP or its subsequent extensions/successors and/or other IP-compatible protocols;

· provides, uses, or makes available, on a public or private basis, high-level services built on top of the communications and other related infrastructure described herein.

Internet infrastructure(Fig.2):

1.backbone level (system of connected high-speed telecommunication servers).

2.level of networks and access points (large telecommunications networks) connected to the backbone.

3.level of regional and other networks.

4.ISP – Internet providers.

5.users.

To technical resources on the Internet include computer nodes, routers, gateways, communication channels, etc.

Fig.2 Internet infrastructure

The network architecture is based on multi-level message transmission principle . The message is generated usingthe highest level of the model ISO/OSI .. Then (when transmitting) it is afterThe message consistently passes through all levels of the system down to the lowest level, where it is transmitted via a communication channel to the recipient. As each one passesfrom the levels of the system the message is transformed, divided into relatively short parts that are equipped with additionalwith headers that provide similar levels of informationnor on the destination node. At this node, the message passes from the lower level to the upper level, stripping itself of headers. As a result, the recipient receives the message in its original form.

In territorial networks data exchange management realizedcovered by protocols top level models ISO/OSI . Regardless internal design of each specific top protocollevel, they are characterized by the presence of common functions: initialization of communication, transmission and reception of data, completion of exchange. Every protothe count has the means to identify any workstation on the networkby name, network address, or both. Activization of information exchange between interacting nodesis found after the destination node has been identified by the initiating nodedata exchange. The originating station installs one of the Methods for organizing data exchange: datagram method or method communication sessions. The protocol provides a means to receive/transmitchi messages by addressee and source. In this case, usually overlayingThere are restrictions on the length of messages.

TCP/IP- internetworking technology

The most common exchange control protocoldata is the TCP/IP protocol. The main difference between the network Internet from other networks lies precisely in its TCP/IP protocols, coveringcontaining a whole family of protocols for interaction between computersterami network. TCP/IP is an internetworking technology Internet technology. Therefore r a global network that connects manyvariety of networks with technologyTCP/IP, called Internet.

TCP/IP protocol is a family of software-implementedhigher-level protocols that do not work with hardware devicesjerking. Technically, the TCP/IP protocol consists of two parts - IP and TCP.

Protocol IP ( Internet Protocol - internetwork protocol) is the main protocol of the family, it implements the distribution of information formations in IP -network and is executed at the third (network) level of the mode whether ISO/OSI. IP protocol provides datagram delivery to the packageComrade, its main task is packet routing. He is not responsible for the reliability of information delivery, for its integrity, for the preservationchanging the order of the packet flow. Networks that use the protocol IP, called IP -networks. They work mainly analogue channels (i.e., to connect a computer to the network you need IP-mo dem) and are packet switched networks. The package is called hereyes datagram.

High level protocol TCP ( Transmission Control Protocol- transmission control protocol) works at the transport layer andpartially - at the session level. This is a protocol with the establishment of lological connection between sender and recipient. He is promisedprints a session connection between two nodes with guaranteed delivery of information, monitors the integrity of the transmission information received, preserves the order of the packet flow.

For computers, the TCP/IP protocol is the same as the rulestalk for people. It is accepted as an official standard on the web Internet , i.e. TCP/IP network technology has become the de facto technologygy of the World Wide Web.

A key part of the protocol is a packet routing scheme based on unique network addresses. Internet. Each work tea station, part of a local or global network, hasThere is a unique address that includes two parts identifyingnetwork address and station address within the network. This scheme allows give messages both within this network and to external networks.

ADDRESSING ON THE INTERNET

Basic Internet protocols

The operation of the Internet is based on the use of families of communication protocols TCP/IP (TransmissionControlProtocol/ InternetProtocol). TCP/IP is used for data transmission both on the Internet and on many local networks.

The name TCP/IP defines a family of network data transfer protocols. Protocol is a set of rules that all companies must adhere to to ensure the compatibility of the hardware and software they produce. These rules ensure that the hardware and software produced are compatible. In addition, TCP / IP is a guarantee that your personal computer will be able to communicate via the Internet with any computer in the world that also works with TCP / IP. As long as certain standards are met for the operation of the entire system, it does not matter who the software or hardware manufacturer is. The open systems ideology involves the use of standard hardware and software. TCP/IP is an open protocol and all specific information is published and can be freely used.

The various services included in TCP/IP and the functions of this protocol family can be classified according to the type of tasks they perform. We will only mention the main protocols, since their total number amounts to more than a dozen:

· transport protocols- manage data transfer between two machines :

· TCP/ IP(Transmission Control Protocol),

· UDP(User Datagram Protocol);

· routing protocols- process data addressing, ensure the actual transfer of data and determine the best path for the packet to travel :

· IP(Internet Protocol),

· ICMP(Internet Control Message Protocol),

· R.I.P.(Routing Information Protocol)

· and others;

· network address support protocols- process data addressing, provide machine identification with a unique number and name :

· DNS(Domain Name System),

· ARP(Address Resolution Protocol)

· and others;

· application service protocols are programs that a user (or computer) uses to access various services :

· FTP(File Transfer Protocol),

· TELNET,

· HTTP(HyperText Transfer Protocol)

· NNTP(NetNewsTransfer Protocol)

·and others

This includes transferring files between computers, remote terminal access to the system, transfer of hypermedia information, etc.;

· gateway protocols help transmit routing messages and network status information over the network, as well as process data for local networks :

· E.G.P.(Exterior Gateway Protocol),

· GGP(Gateway-to-Gateway Protocol),

· IGP(Interior Gateway Protocol);

· other protocols– used to transmit email messages, when working with directories and files on a remote computer, and so on :

· SMTP(Simple Mail Transfer Protocol),

· NFS(Network File System).

IP-addressing

Now let's take a closer look at the concept of IP address.

Every computer on the Internet (including any PC when it establishes a session connection with an ISP over a telephone line) has a unique address called IP-address.

An IP address is 32 bits long and consists of four 8-bit parts, named according to network terminology octets (octets) . This means that each part of the IP address can have a value between 0 and 255. The four parts are combined into a notation in which each eight-bit value is separated by a period. When we talk about a network address, we usually mean an IP address.

If all 32 bits of an IP address were used, there would be over four billion possible addresses - more than enough for the future expansion of the Internet. However, some bit combinations are reserved for special purposes, which reduces the number of potential addresses. In addition, the 8-bit quads are grouped in special ways depending on the type of network, so that the actual number of addresses is even smaller.

With the concept IP addresses are a closely related concept hosta (host) . Some simply equate the concept of a host with the concept of a computer connected to the Internet. In principle, this is true, but in general under host refers to any device that uses the TCP/IP protocol to communicate with other equipment. That is, in addition to computers, these can be special network devices - routers, hubs and others. These devices also have their own unique I P addresses, just like the computers of users’ network nodes.

Any IP-the address consists of two parts: network addresses(network identifier, Network ID) and host addresses(host identifier, Host ID) on this network. Thanks to this structure, the IP addresses of computers on different networks can have the same numbers. But since the network addresses are different, these computers are uniquely identified and cannot be confused with each other.

IP addresses are allocated depending on the size of the organization and the type of its activities. If this is a small organization, then most likely there are few computers (and, therefore, IP addresses) on its network. In contrast, a large corporation may have thousands (or even more) of computers organized into many interconnected local networks. For maximum flexibility IP-addresses are divided into classes: A, B and C. There are also classes D And E, but they are used for specific service purposes.

So, three classes of IP addresses allow them to be distributed depending on the size of the organization's network. Since 32 bits is the legal full size of an IP address, the classes break the four 8-bit parts of the address into a network address and a host address depending on the class.

Class network addressA determined by the first octet of the IP address (counted from left to right). The value of the first octet, which is in the range 1-126, is reserved for giant multinational corporations and the largest providers. Thus, in Class A there may be only 126 large companies in the world, each of which may contain almost 17 million computers.

ClassBuses The first 2 octets as the network address, the value of the first octet can range from 128-191. Each Class B network can have about 65 thousand computers, and the largest universities and other large organizations have such networks.

Respectively, in classC The first three octets are already allocated for the network address, and the value of the first octet can be in the range 192-223. These are the most common networks, their number can exceed more than two million, and the number of computers (hosts) in each network can be up to 254. It should be noted that “gaps” in the permissible values of the first octet between classes of networks appear due to the fact that one or several bits are reserved at the beginning of the IP address to identify the class.

If any An IP address is symbolically designated as a set of octets w .x .y .z, then the structure for networks of various classes can be presented in Table 1.

Whenever a message is sent to any host on the Internet, the IP address is used to indicate the sender and recipient addresses. Of course, users do not have to remember all IP addresses themselves, since there is a special service TCP/IP, called Domain Name System

Table 1. Structure of IP addresses in networks of various classes

Network class	First octet value (W)	Network number octets	Host number octets	Number of possible networks	Number of hosts in such networks
	1-126		x.y.z	128(2 7)	16777214(2 24)
	128-191	w.x	y.z	16384(2 14)	65536(2 16)
	192-223	w.x.y		2097151(2 21)	254(2 8)

The concept of a subnet mask

To separate the network ID from the host ID, a special 32-bit number called a subnet mask is used. Purely outwardly, a subnet mask is exactly the same set of four octets, separated by dots, like any IP address. Table 2 shows the default subnet mask values for class A, B, C networks.

Table 2. Subnet mask value (default)

Network class	Mask value in bits (binary representation)	Mask value in decimal form
	11111111 00000000 00000000 00000000	255.0.0.0
	11111111 11111111 00000000 00000000	255.255.0,0
	11111111 11111111 1111111100000000	255,255.255.0

The mask is also used to logically divide large IP networks into a number of smaller subnets. Let's imagine, for example, that at the Siberian Federal University, which has a class B network, there are 10 faculties and 200 computers (hosts) are installed in each of them. By using a subnet mask of 255.255.0.0, this network can be divided into 254 separate subnets with up to 254 hosts each.

The default subnet mask values are not the only possible ones. For example, a system administrator on a particular IP network might use a different subnet mask value to highlight just some of the bits in the host ID octet.

How to registerIP-the network of your organization?

In fact, end users are not involved in this task, which falls on the shoulders of the system administrator of a given organization. In turn, he is assisted in this by Internet providers, usually taking upon themselves all registration procedures in the relevant international organization called InterNIC (NetworkInformationCenter). For example, Siberian Federal University wants to receive an Internet email address containing the string sfu -kras .ru. This identifier, which includes the company name, allows the sender of the email to identify the recipient's company.

To obtain one of these unique identifiers, called a domain name, a company or ISP sends a request to the authority that controls Internet connections - InterNIC. If InterNIC (or the body authorized by it for such registration in a given country) approves the company name, then it is added to the Internet database. Domain names must be unique to prevent errors. The concept of a domain and its role in addressing messages sent over the Internet will be discussed below. Additional information You can learn about the work of InterNIC by visiting the Internet page http://rs.internic.ru.

DOMAIN NAME SYSTEM

Domain names

In addition to IP addresses, the so-called Domain host name . Just like an IP address, it is a name is unique for each computer (host) connected to the Internet - only here words are used instead of digital address values.

In this case, the concept domain means a collection of Internet hosts united according to some characteristic (for example, by territorial, when we are talking about the domain of the state).

Of course, the use of a domain host name was introduced only to make it easier for users to remember the names of the computers they need. The computers themselves, for obvious reasons, do not need such a service and make do with IP addresses. But just imagine that instead of such sonorous names as, www. microsoft. com or www. ibm. com you would have to remember the sets of numbers - 207.46.19.190 or 129.42.60.216 respectively.

If we talk about the rules for composing domain names, then there are no such strict restrictions on the number of components of the name and their meanings as in the case of IP addresses. For example, if in KhTI - Branch of Siberian Federal University there is a host with the name khti, included in the domain of the Republic of Khakassia khakassia, and that, in turn, is part of the Russian domain ru, then the domain name of such a computer will be khti. khakassia. ru. In general, the number of components of a domain name can be different and contain one or more parts, for example, rage. mp3. apple. sda. org or www. ru .

Most often, a company’s domain name consists of three components, the first part is the host name, the second is the company’s domain name, and the last is the country’s domain name or the name of one of seven special domains indicating the affiliation of the host with an organization of a certain activity profile (see Table 1 ). So, if your company is called "KomLinc", then most often the company's Web server will be named www.komlinc.ru (if it is a Russian company), or, for example, www.komlinc.com, if you asked the provider to register you mainly international domain of commercial organizations.

The last part of the domain name is called the top-level domain identifier (for example, . ru or . com). There are seven top-level domains established by InterNIC.

Table1. International top level domains

domain name	Domain host ownership
ARPA	Great-great... grandmother of the Internet, ARPANet network (obsolete)
COM	Commercial organizations (firms, companies, banks, etc.)
GOV	Government agencies and organizations
EDU	Educational institutions
MIL	Military institutions
NET	"Network" organizations that manage the Internet or are part of its structure
ORG	Organizations that do not belong to any of the listed categories

Historically, these seven default top-level domains denote the fact that a host (belonging to them) is geographically located in the United States. Therefore, the international committee InterNIC, along with the above top-level domains, allows the use of domains (special combinations of characters) to identify other countries in which the organization that owns this host is located.

So, top level domains are divided into organizational(see table 1) and territorial. There are two-letter designations for all countries of the world: . ru- for Russia (the domain is still in use . su, uniting hosts on the territory of the republics former USSR), .sa- for Canada, . uk- for Great Britain, etc. They are usually used in place of one of the seven identifiers listed in Table 1 above.

Territorial top level domains:

. ru (Russia) - Russia;

Su (Soviet Union ) - countries of the former USSR, now a number of CIS countries;

UK (United Kingdom ) - Great Britain;

Ua (Ukraine) - Ukraine;

Bg (Bulgaria) - Bulgaria;

Hu (Hungary) - Hungary;

De (Dutchland ) - Germany, etc.

A complete list of all domain names of states can be found on various servers on the Internet.

Not all companies outside the US have country IDs. To some extent, whether you use a country identifier or one of the seven US identifiers depends on when the company's domain name was registered. Thus, companies that connected to the Internet quite a long time ago (when the number of registered organizations was relatively small) were given a three-letter identifier. Some corporations operating outside the United States but registering a domain name through American company, choose whether to use the host country identifier. Today in Russia you can get a domain identifier . com, for which you should discuss this issue with your Internet provider.

HowworkserversDNS

Now let's talk about how domain names are converted into computer-readable IP addresses.

Is doing this DomainNameSystem(DNS, Domain Name System) a service provided by TCP/IP that helps in addressing messages. Thanks to DNS work You don't have to remember the IP address, but use a much simpler domain address. The DNS system translates a computer's symbolic domain name into an IP address by finding an entry in a distributed database (stored on thousands of computers) that matches it domain name. It is also worth noting that DNS servers in Russian-language computer literature are often called "name servers".

Root zone name servers

Although there are thousands of name servers in the world, at the top of the entire DNS system are nine servers called root zone servers ( root zone servers ) . Root zone servers are named a. root_ server. net, b. root_ server. net and so on until i. root_ server. net. The first one is a. root_ server. net- acts as the primary Internet name server, controlled from the InterNIC information center, which registers all domains included in several domains top level. The remaining name servers are secondary to it, but they all store copies of the same files. Thanks to this, any of the root zone servers can replace and back up the others.

These computers contain information about the host computers of the name servers serving seven top-level domains: .com, .edu, .mil, .gov, .net, .org and special.arpa (Fig. 1). Any of these nine servers carries the same top-level file as .uk (UK), .de (Germany), .jp (Japan) and so on.

Rice. 1. Hierarchical structure of Internet domain names

The root zone files contain all host names and IP -name server addresses for each subdomain included in the top-level domain. In other words, each root server has information about all top-level domains, and also knows the name of the host computer and IP -the address of at least one name server serving each of the secondary domains included in any top-level domain. For domains of foreign countries, the database stores information on name servers for each country. For example, in a certain domaincompany. comroot zone files for a domain contain nameserver information for any address ending incompany. com.

In addition to the root zone nameservers, there are local name servers installed in domains over low level. The local name server caches a list of host computers that it has recently searched for. This eliminates the need to constantly access the system DNS with queries about frequently used host computers. Additionally, local name servers are iterative, and the root zone servers are recursive. This means that the local name server will repeat the process of requesting information about other name servers until it receives a response.

Root servers Internet , located at the top of the structure DNS , on the contrary, only provide pointers to the next level domains. Get to the end of the chain and get the required IP -address is the task of the local name server. To solve it, he must go down the hierarchical structure, sequentially asking local name servers for pointers to its lower levels.

A computer network consists of several computers connected to each other to process data together. Computer networks are divided into local and global. Local networks unite computers located in the same room or building, and wide area networks unite local networks or individual computers located at a distance of more than 1 km. The Internet is a worldwide computer network consisting of a variety of computer networks united by standard agreements on how to exchange information and unified system addressing. The unit of the Internet is a local area network, the totality of which is united by some regional (global) network (departmental or commercial). At the highest level, regional networks are connected to one of the so-called Internet backbone networks. (In fact, regional networks can be interconnected without access to the core network.) Wire lines, fiber optics, radio communications, satellite communications, etc. are used as connecting lines on the Internet. Generalized structure of the Internet There is a certain analogy between the diagram of transport highways and the topology of the Internet, reminiscent of a map of automobile, railways and air transportation scheme. Internet protocols comply with cargo transportation regulations; addressing system - traditional postal addresses; transport highways - communication channels between networks on the Internet.

The World Wide Web is the Internet.

It is also called a network.

A browser is a program on your computer with which you access the Internet, view information there, and navigate it. It processes data on the World Wide Web and allows browsing. In fact, this is a program with which you can surf the Internet. Very often the browser icon is located on the Desktop of your computer. When you click on it, you go to the Internet. The standard browser that most people know is Internet Explorer.

The Internet can work differently in different browsers: what one browser cannot do, another can do. If you are unable to view, listen to information, or do anything on the Internet, try accessing the Internet through a different browser. You may be able to do this in another browser. The most popular browsers are Google Chrome, Opera, Mozilla Firefox. They can be found through an Internet search and installed on your computer.

A site (website) is an Internet resource that contains information (texts, pictures or videos), can perform certain functions (for example, receiving and sending letters), has its own address, its own name, its own owner and consists of separate pages. A page on a website is called a web page.

The address (name) of a site is a set of characters that consists of three parts: it begins with “http://” or “www.”, then the name of the site, at the end of which a specific zone (domain zone) is a short designation of the country or type of organization : .com, .ru, .net, .biz, .org, .kz, .ua, etc. For example, let’s look at the address http://website-income.ru/. First – http://, then the name – website-income.ru, at the end – .ru. As a rule, when you see the name of a site on any page on the Internet and click on it, you go to that site.

Email is a system through which you can send and receive letters on the Internet. In fact, this is a website or program that is used to send letters. Email is also the name given to the personal email address of a specific person or organization. In this case, they usually say whose email it is.

The distinctive sign of email is the @ symbol (pronounced "dog" or "doggy"). To type it in text, on your computer keyboard you need to press the Shift key and the number 2 in Russian font mode.

Differences between website and email (i.e. email address): in the name of the site there are http:// or www symbols at the very beginning, and in the name of the email there is an @ sign in the middle. For example, http://website-income.ru/- this is a website, and [email protected] - this is email.

The browser bar is the top line on the Internet page where you enter the address of the site you want to visit. It is on any page of any website. Computers may have different settings: on some computers, to go to a site, you only need to enter its address in the browser; and on other computers, you still need to press the “Enter” key on the keyboard.

A search engine is a system that allows you to find the necessary information on the Internet. In fact, it is a site that provides search capabilities. When you go online, a certain search system. For example, Google. If you want to use another search engine, then you enter its name in the browser line and go to its website.

The search bar is a blank line in a search engine, usually located in the middle of the page, in which you write the words you want to find on the Internet. Next to this line there is a button labeled “Search”, “Find”, “Go”, etc. Once you enter words into the search bar and click on this button, the search process begins.

Services: Telnet- a network program that allows remote access to computers via the command line. Requires knowledge of a special command language. FTP File Transfer Protocol - file transfer protocol is a protocol of the TCP/IP family. There are many FTP applications that have an accessible graphical interface and allow you to find and copy files from FTP servers. Email Email is one of the most popular Internet services. Allows people with email addresses to exchange email messages. You can attach files in any format to text email messages. Gopher Although FTP is great for transferring files, it doesn't have a good way to deal with files scattered across multiple computers. In this regard, an improved file transfer system was developed. It is called Gopher.

Using a menu system, Gopher not only allows you to browse lists of resources, but also sends the material you need without knowing where it is located. Gopher is one of the most comprehensive browsing systems available, integrated with other programs such as FTP or Telnet. It is widespread on the Internet.

Gopher computers are linked - through distributed indexes - into a single search engine called Gopherspace. Access to Gopher spaces is carried out through the menus they offer, and search is carried out using several types of search engines. The most famous among them are the Veronica system and the index search system of the global information server (wAIS - wide Area Information Server).

WAIS Wide Area Information Servers is a system for storing and retrieving documents in thematic databases. For fast work, an index search is used. WWW The World Wide Web is the most popular Internet service. It is a collection of tens of millions of Web servers scattered around the world and containing a huge amount of information. Web documents, called Web pages, are magazine-style documents containing multimedia elements (graphics, audio, video, etc.), as well as hyperlinks that, when clicked, move users from one document to another.

Teleconferences

The teleconferencing system emerged as a means for groups of people with similar interests to communicate. Since its inception, it has spread widely, becoming one of the most popular Internet services.

This type of service is similar to Internet mailing lists, except that messages are not sent to all subscribers of a given newsgroup, but are placed on special computers called newsgroup servers or news servers. Subscribers to the teleconference can then read the incoming message and, if desired, respond to it.

A teleconference is like a bulletin board where everyone can post their own announcement and read the announcements posted by others. To make it easier to work with this system, all teleconferences are divided into topics, the names of which are reflected in their names. On this moment there are about 10,000 different newsgroups discussing everything you can imagine.

To work with the teleconferencing system, you need special software with which you can establish a connection to the news server and gain access to the teleconference articles stored on it. Since the news server stores articles from a very large number of newsgroups, users usually select those that are of interest to them (or, in other words, subscribe to them) and then work only with them.

After subscribing to the selected newsgroups, you will have to establish a connection to the news server to view incoming messages. The difference is that you can configure the newsgroup reader to only track the status of the newsgroups you've signed up for, rather than forcing you to view the entire list.

Thus, teleconferences are virtual communication clubs. Each teleconference has its own address and is accessible from almost any other part of the Internet. Teleconferences usually have a more or less constant circle of participants.

Principles of information retrieval.

The basic principles of information retrieval were formulated back in the first half of this century. Between 1939 and 1945, W. E. Batten developed a system for finding patents. Each patent was classified according to the concepts to which it related. An 800-position punch card was created for each concept used in the system. When registering a new patent in the system, there were cards corresponding to the concepts covered in it, and the patent numbers were punched into the position. To find a patent that covered several concepts simultaneously, it was necessary to combine the cards corresponding to these concepts. The number of the required patent was determined from the position of the lumen. The basic principles of information retrieval have not changed since then. Using this IPS as an example, you can see how the search process occurs. First, an array of pointers to information resources must be created. A pointer (index) contains a certain property of a document and links to documents that have this property. Pointers can be various types. For example, the author's index is widespread. Such an index allows us to obtain links to the works of the author of interest to us. Indexes can also be compiled based on other document attributes. The Batten system used a subject index, that is, documents were classified according to the concepts (subjects) that they addressed. The process of creating pointers to documents is called indexing, and the terms used for indexing are called indexing terms. In the case of an author's index, the role of indexing terms will be played by the names of the authors of the works stored in the collection. The collection of indexing terms used is called a dictionary. The array of pointers obtained after indexing information resources is called an index (Index database). Once an index is created, it is accessed through queries. Since the search process involves matching a user's query with available data, the resulting query must also be translated into an indexing language. The index searches for documents that match the request, and the user is given a list of links to suitable resources. To increase the speed of indexing and searching, the dictionary and index must be organized according to a system that best suits the search tasks in a given subject area.

Question 77 is not necessary

Indexing and search engine.

Content

Introduction…………………………………………………………….... ...….3
1. History of the development of the Internet……………………….......4
2. Structure and basic principles of construction
Internet…………………………………………………………………….…. …8
3. Problems and prospects for the development of the Internet……..11
Conclusion………………………………………….. ……14
List of used literature…………………………16

Introduction

Computer science is a new information industry associated with the use of personal computers and the Internet.
In the new millennium, most of the information related to human activities will be stored in computer memory.
Computers - electronic computing machines- one of the most important inventions of the 20th century. Abroad, and later in our country, computers were called computers. Computers are used as universal devices for processing, transmitting and storing a wide variety of information.
The basis of the modern information industry is the Internet computer network.
The Internet is an international computer network that connects computers in all countries and continents, stores gigantic amounts of information and gives quick access to this information to almost all people.
The Internet has become an inseparable part of modern civilization. Rapidly breaking into the spheres of education, trade, communications, services, it gives rise to new forms of communication and learning, commerce and entertainment. The “Network Generation” is a real socio-cultural phenomenon of our days. For its representatives, the Internet has long become a familiar and convenient life partner. Humanity is entering a new – informational – stage of its development, and network technologies play a huge role in it.

History of the development of the Internet.

About 20 years ago, the US Department of Defense created a network that was the forerunner of the Internet - it was called ARPAnet. ARPAnet was an experimental network - it was created to support scientific research in the military-industrial sphere, - in particular, to study methods for constructing networks that were resistant to partial damage received, for example, from air bombing and could continue to function normally under such conditions. This requirement provides the key to understanding the principles of construction and structure of the Internet. In the ARPAnet model, there was always communication between the source computer and the destination computer (destination station). The network was supposed to be unreliable: any part of the network could disappear at any moment.
The communicating computers—not just the network itself—also have the responsibility of establishing and maintaining communications. The basic principle was that any computer could communicate peer-to-peer with any other computer.
Data transmission on the network was organized based on the IP protocol. The IP protocol is the rules and description of how a network operates. This set includes rules for establishing and maintaining communications in the network, rules for handling and processing IP packets, descriptions of network packets of the IP family (their structure, etc.). The network was conceived and designed so that users were not required to have any information about the specific structure of the network. In order to send a message over the network, the computer must place data in a certain “envelope” called, for example, IP, indicate on this “envelope” a specific network address and transmit the resulting packets to the network.
These decisions may seem strange, as does the assumption of an "untrusted" network, but experience has shown that most of these decisions are quite reasonable and correct. So far, the International Organization for Standardization (Organization for Standardization) International Standardization– ISO) spent years creating the final standard for computer networks, users did not want to wait. Internet activists began installing IP software on every type of computer possible. This soon became the only acceptable way to connect disparate computers. This scheme appealed to the government and universities, which have a policy of purchasing computers from various manufacturers. Everyone bought the computer that he liked and had the right to expect that it would be able to work on a network together with other computers.
About 10 years after the advent of ARPAnet, Local Area Networks (LANs) appeared, for example, such as Ethernet, etc. At the same time, computers appeared, which began to be called workstations. Most workstations had the UNIX operating system installed. This OS had the ability to work on a network with the Internet Protocol (IP). In connection with the emergence of fundamentally new problems and methods for solving them, a new need arose: organizations wanted to connect to ARPAnet with their local network. Around the same time, other organizations emerged and began creating their own networks using IP-like communication protocols. It became clear that everyone would benefit if these networks could all communicate together, because then users on one network could communicate with users on another network.
One of the most important of these new networks was NSFNET, developed as an initiative of the National Science Foundation (NSF). In the late 1980s, NSF created five supercomputing centers, making them available for use in any scientific institution. Only five centers were created because they are very expensive even for rich America. That is why they should have been used cooperatively. A communication problem arose: a way was needed to connect these centers and provide access to them to different users. An attempt was first made to use ARPAnet communications, but this solution failed when faced with defense industry bureaucracy and staffing problems.
NSF then decided to build its own network based on ARPAnet IP technology. The centers were connected by special telephone lines with a throughput of 56 KBPS (7 KB/s). However, it was obvious that it was not worth even trying to connect all universities and research organizations directly with the centers, because laying such a quantity of cable is not only very expensive, but practically impossible. Therefore, it was decided to create networks on a regional basis. In every part of the country the institutions concerned were to connect with their nearest neighbours. The resulting chains were connected to the supercomputer at one of their points, thus the supercomputer centers were connected together. In such a topology, any computer could communicate with any other by passing messages through its neighbors.
This decision was successful, but the time came when the network could no longer cope with the increased needs. Sharing supercomputers allowed connected communities to use many other things outside of supercomputers. Suddenly, universities, schools and other organizations realized that they had a sea of data and a world of users at their fingertips. The flow of messages on the network (traffic) grew faster and faster until, in the end, it overloaded the computers managing the network and the telephone lines connecting them. In 1987, the contract to manage and develop the network was awarded to Merit Network Inc., which operated the Michigan Educational Network in partnership with IBM and MCI. The old physical network was replaced by faster (about 20 times faster) telephone lines. They were replaced by faster and more networked control machines.
The process of improving the network is ongoing. However, most of these changes occur unnoticed by users. When you turn on your computer, you will not see an advertisement stating that the Internet will not be available for the next six months due to modernization. Perhaps even more importantly, network congestion and improvements have created a mature and practical technology. Problems were solved, and development ideas were tested in practice.

Structure and basic principles of building the Internet.

The Internet is a worldwide information computer network, which is a union of many regional computer networks and computers that exchange information with each other via public telecommunications channels (dedicated analog and digital telephone lines, optical communication channels and radio channels, including satellite communication lines).
Information on the Internet is stored on servers. Servers have their own addresses and are controlled by specialized programs. They allow you to forward mail and files, search databases, and perform other tasks.
Information exchange between network servers is carried out via high-speed communication channels (dedicated telephone lines, fiber optic and satellite communication channels). Individual users' access to Internet information resources is usually carried out through a provider or corporate network.
Provider - network service provider - a person or organization providing connection services to computer networks. The provider is an organization that has a modem pool for connecting to clients and accessing the World Wide Web.
The main cells of the global network are local area networks. If a local network is directly connected to a global network, then every workstation on this network can be connected to it.
There are also computers that are directly connected to the global network. They are called host computers (host - master).
A host is any computer that is a permanent part of the Internet, i.e. connected via the Internet protocol to another host, which in turn is connected to another, and so on.
To connect communication lines to computers, special electronic devices are used, which are called network cards, network adapters, modems, etc.
Almost all Internet services are built on the client-server principle. All information on the Internet is stored on servers. Information exchange between servers is carried out via high-speed communication channels or highways. Servers connected by high-speed highways make up the basic part of the Internet.
Individual users connect to the network through the computers of local Internet service providers, Internet Service Providers (ISPs), which have a permanent connection to the Internet. A regional provider connects to a larger national provider that has nodes in various cities of the country. Networks of national providers are combined into networks of transnational providers or first-tier providers. United networks of first-tier providers make up the global Internet.
The transfer of information to the Internet is ensured by the fact that each computer on the network has a unique address (IP address), and network protocols ensure the interaction of different types of computers running different operating systems.
The Internet primarily uses the TCP/IP family of network protocols (stack). At the data link and physical layers, the TCP/IP stack supports Ethernet, FDDI, and other technologies. The basis of the TCP/IP protocol family is the network layer, represented by the IP protocol, as well as various routing protocols. This layer facilitates the movement of packets across the network and controls their routing. The packet size, transmission parameters, and integrity control are carried out at the TCP transport layer.
The application layer integrates all the services that the system provides to the user. The main application protocols include: telnet remote access protocol, FTP file transfer protocol, HTTP hypertext transfer protocol, email protocols: SMTP, POP, IMAP, MIME.

Problems and prospects for the development of the Internet.

Today, the speed of development of the Internet has reached unprecedented levels. Due to its convenience and inexpensive price, this method of exchanging information is becoming more and more popular among people around the world.
Billions of websites and information resources are attracting an increasing number of visitors. On the Internet, since its inception, more and more new communities have already been formed and continue to form, which have their own traditions, ethics, common tasks and goals.
We only need to plunge once into the vast expanses of www, quickly and easily access necessary information- and we immediately understand that we have at our disposal the greatest invention of mankind, which has already made the planet a large common home (a village or a metropolis, as is more convenient for us). Every time we connect to the network, we realize that on the other side of the monitor there are people and opportunities waiting for us, the existence of which we did not even know yesterday. It is these features of www that explain its rapid development.
Today, according to Internet World Stats (http://www., etc.........

Today the Internet will not surprise anyone. A huge number of users access this network every day. According to 2015 data, the number of connected users exceeded 3.3 billion. True, not everyone knows what the structure of the Internet is in technical terms. Most people don't really need this. However, you still need to know the fundamentals laid down in the principles of operation of the World Wide Web, at least at an initial level.

What is the Internet in a modern interpretation

In general, when we're talking about O modern Internet, quite often the concept of the World Wide Web or Network is used instead, into which computers from all over the world are united.

In general, this is true, but one clarification should be made here. As you know, not a single computer connects directly to the Internet, only through a service provider, to which God knows how many other terminals or mobile devices are connected. It turns out that they are all united into one network. And in this sense, the Internet is called a “network of networks.”

Indeed, the structure of the Internet is based on combining, so to speak, subnets and has a high-tech hierarchy. In addition, accessing a particular resource is impossible to imagine without a router that is able to choose the optimal path for accelerated access to a given resource.

And here's what's interesting. The Internet as such has no owner, and the network itself is rather a virtual space, which affects people more and more every day, sometimes even replacing reality. Whether this is good or bad is not for us to judge. But let’s dwell on the main aspects of the construction and functioning of the World Wide Web.

Structure of the global Internet: history of emergence and development

The Internet was not always the way we know it today. If you dig into history, it should be noted that the first attempts to create a single information network, which could not only transmit data, but also serve in some way as a “translator” of many programming languages for perceiving information, were undertaken back in 1962, at the height of “ cold war"between the USA and the USSR. Then a program based on packet switching theory appeared for Leonard Kleinrock, led by Joseph Licklider. The main focus was not only but also its “indestructibility”.

Based on these developments, the first network emerged in 1969, called ARPANet, which became the progenitor of the Internet, or World Wide Web. In 1971, the first program for sending and receiving e-mail was developed, by 1973, when the Euro-Atlantic cable was continued, the network became international, in 1983 it switched to the unified TCP/IP protocol, in 1984 IRC technology appeared, which made it possible to chat . And only by 1989, the idea of creating a global web, which is now commonly called the Internet, matured at CERN. Of course, it was far from the model used now, however, some basic principles that include the structure of the Internet have still remained unchanged.

World Wide Web Infrastructure

Now let's see how we managed to combine individual computer terminals and networks based on them into a single whole. The key principle was the use of packet data transmission using routing based on a universal protocol that could be understood by any machine. That is, information is not represented in the form of individual bits, bytes or characters, but is transmitted in the form of a formatted block (packet), which can contain quite long combinations of various sequences.

However, the transfer itself does not happen haphazardly. At the same time, Internet resources have several main levels:

Backbone (a system of high-speed servers connected to each other).
Large networks and access points connected to the main backbone.
Regional networks rank lower.
Internet service providers (ISPs).
End users.

The Internet is such that the terminals on which it is stored are called servers, and the user machines (reading or receiving it, as well as sending feedback and streams) are called workstations. The transmission of the information itself, as mentioned above, is carried out on the basis of routers. But this diagram is presented solely for ease of understanding the issue. In reality, everything is much more complicated.

Basic protocols

Now we come to one of key concepts, without which it is impossible to imagine what the structure of the Internet is. These are universal protocols. Today there are quite a lot of them, but the main one for the Internet is TCP/IP.

In this case, it is necessary to clearly distinguish between the two terms. The Internet Protocol (IP) is one of the means of routing, that is, it is solely responsible for the delivery of data packets, but is in no way responsible for the integrity and security of the transmitted information. The TCP protocol, on the contrary, is a means of providing session communication between the sender and the recipient based on a logical connection between two points with the so-called guaranteed delivery of packets, and absolutely intact.

Today, TCP/IP is the de facto Internet standard, although there are many other protocols, such as UDP (transport), ICMP and RIP (routers), DNS and ARP (network address identification), FTP, HTTP, NNTP and TELNET (application applications). ), IGP, GGP and EGP (gateway), SMTP, POP3 and NFS (mail and file access protocols on remote terminals), etc.

Domain Name System

Separately, it should be noted the universal approach to accessing resources. It is clear that writing a page address like 127.11.92.785 in order to get to the desired resource is not so convenient (let alone remembering all these combinations). Therefore, at one time, a unique domain name system was developed that made it possible to enter the address as we see it today (in English).

But even here there is its own hierarchy. It also has several levels. For example, international top-level domains include resources independent of the country identifier (GOV - government, COM - commercial, EDU - educational, NET - network, MIL - military, ORG - general organizational, not related to any of the above types) .

The following are resources that explicitly indicate the country identifier. For example, US - USA, RU - Russia, UA - Ukraine, DE - Germany, UK - Great Britain, etc. In addition, such domains have their own sublevels like COM.UA, ORG.DE, etc. In their own turn, and here you can find a clearer link at lower levels (KIEV.UA, KIEV.COM.UA, etc.). In other words, when looking at the address, you can immediately determine not only the country, but also the territorial affiliation of the resource within it.

Basic Internet services

As for the services that can be found on the Internet today, in their categories they are divided into email, news and newsletters, file-exchange networks, electronic payment systems, Internet radio and television, web forums, blogs, social networks, online stores and auctions, educational projects“Wiki”, video and audio hostings, etc. Since social networks have recently become the most popular, let’s dwell on their structure.

Structure of Internet social networks

A common feature of such an online community is its independence from territorial location or citizenship. Each user creates his own profile (image, place of residence on the Internet, whatever you want to call it), and communication is carried out using an instant messaging system, but not through chat, but in private mode. The only thing comparable to chat is the comment system. In addition, any registered resident of such a community can leave so-called posts, share with the public some materials or links to other publications, etc.

The structure of the Internet is such that when certain protocols are used, such as TCP/IP and IRC, all this is done quite simply. The main condition is registration (creating a login and password to log in), as well as indicating at least minimal information about yourself.

It is not surprising that personal websites and chat rooms are slowly but surely disappearing into oblivion. Even the once popular “dialers” like ICQ or QIP cannot withstand any competition, because social networks have much more opportunities.