Computer network - This is a lot of computers connected by information transfer lines.

The exchange of information through a computer network is called telecommunications.

Types of computer networks

Local

network

Global Internet Network

Regional networks

Corporate networks

The local network is a small computer network operating within one room, one enterprise.

Network topologies

1. Tire topology

All computers are connected to one cable (tire). Terminators are installed at the ends of the cable. A coaxial cable is used as a cable. Disabling any of the connected devices for networking does not affect any influence.

2. Star-shaped topology

Each computer is connected to a separate wire to a separate port of the hub or switch (Switches).

3. Ring Topology

With the "Ring" topology, computers are connected to the cable closed in the ring. In contrast to the passive topology "Tire", here each computer enhances the signals and transmits them with the next computer. Therefore, if one computer fails, the network functioning can break.

Corporate networks are formed to combine computers of certain organizations (military, banking, etc.) who are interested in protecting information from unauthorized access.

The corporate network can combine thousands and tens of thousands of computers placed in various cities and countries.

An example is Microsoft Network Corporation - Microsoft Network (MSN)

Regional networks - combine computers, within one region (city, country, continent).

The needs of the formation of a single world information space led to the creation of a global computer network.

The needs of the formation of a single world information space led to the creation

Global computer network.

Regional Computer Networks, United

in the global Internet

Regional computer networks combined into the global Internet

The reliability of the network functioning is provided by a large number of channel transmission channels with high bandwidths between local, regional and corporate networks.

the Internet – This is a global computer network in which local, regional and corporate networks are interconnected by numerous information transmission channels with high bandwidth.

Currently (January 2008) The basis of the Internet is more than 400 million servers.

Connection and internet

Each local, regional or corporate network has at least one computer (Internet server), which has a permanent Internet connection.

1. Fiber optic communication lines

However, in cases of connecting uncomfortable or remote computer networks, when the cable laying is difficult or impossible, used

2. Wireless communication lines

If the transmitting and receiving antennas are within the limits of direct visibility, then used

3. Radio channels

otherwise the exchange of information is made through

4. Satellite channel using special antennas

Hundreds of millions of users of users can periodically connect to the Internet using Internet providers. This connection can be made both by fiber optic lines and by switching telephone channels. Internet providers have high-speed connections of their Internet servers and therefore can provide Internet access on telephone channels at the same time hundreds and thousands of users.

To connect a computer computer on a telephone channel with an Internet provider server to both computers, modems must be connected. Modems ensure the transmission of digital computer data on analog telephone channels at a speed of up to 56 kbps.

An example of a regular modem

Modern ADSL technologies allow us to use regular telephone channels for high-speed (1 Mbps and above) Internet connection. It is important that at the same time the phone number remains free.

Conventional and ADSL modems are connected to the USB port of the computer and to the telephone socket connector.

an example of ADSL - modem

Portable computers can connect to the Internet using Wi-Fi wireless technology. At stations, airports and other public places, wireless access points connected to the Internet are installed. Within a radius of 100 meters, a laptop computer equipped with a wireless network card automatically gets access to the Internet at a speed of up to 54 Mbps.

PLC is a new telecommunications technology based on the use of power grid for high-speed information exchange (Internet from the outlet). In this technology based on the frequency separation of the signal, the high-speed flow of data is divided into several low speed, each of which is transmitted at a separate frequency, followed by them to combine into one signal.

In this case, Internet devices can "see" and decode information, although the usual electrical devices are incandescent lamps, engines, etc. - even "do not recognize" about the presence of network traffic signals and work as usual.

Addressing in the Internet

IP address

In order for computers in the process of exchanging information, computers can find each other, there is a single addressing system based on the use IP addresses.

According to the formula Hartley N \u003d 2. I. , Where N. - the number of possible information messages, and I. - the amount of information that received the received message is

IP address carries the amount of information i \u003d 32 bits, therefore the total number of possible IP addresses n is equal to:

N \u003d 2. I. = 2 32 = 4 294 967 296

So, IP address of 32 bits long allows you to connect more than 4 billion computers to the Internet

Each computer connected to the Internet has its own unique binary 32-bit IP address.

Example IP Address: 213.171.37.202

For convenience of perception, the binary 32-bit IP address is divided into

4 parts of 8 bits in each and each part can be represented as in binary and in decimal form.

In the decimal record, the IP address consists of 4 numbers, separated by dots, each of which lies in the range from 0 to 255.

The IP addressing system takes into account the structure of the Internet, i.e. The fact that the Internet is a network network, and not unite individual computers. The IP address contains the network address and the address of the computer in this network.

Binary

Decimal

To ensure maximum flexibility in the distribution process

IP addresses, depending on the number of network computers, addresses are divided into 3 Class A, B, C. First bits are discharged to identify the class, and the rest are divided into the network address and the address of the computer.

For example, the class A network address has only 7 bits for the network address and 24 bits for the address of the computer, i.e. can exist only N \u003d 2. I. = 2 7 = 128 networks of this class, but in each of which may be N \u003d 2. I. = 2 24 = 16 777 216 Computers

Binary

Decimal

Class A.

Class B.

Network address (7bit)

Class S.

Network address (14bits)

Computer address (24 bits)

Network address (21bits)

Computer address (16 bits)

Computer address (8bit)

Binary

Decimal

Class A.

Class B.

Class S.

Network address (7bit)

Network address (14bits)

Computer address (24 bits)

Network address (21bits)

Computer address (16 bits)

Network address (8bits)

Computer belonging to a network of this or that class is easily determined by the first number of the computer IP address:

• class A addresses from 0 to 127;
• class V address from 128 to 191;
• class C - number from 192 to 223;

Question: Determine what type of network is our IP address?

Domain system names

Computers can easily find each other by a numeric IP address, but a person remember the numerical address is not easy, and for the convenience of Internet users was introduced Domain Name Systems (DNS - Domain Name System).

Domain names and IP addresses are distributed to the International Coordination Center (ICANN).

DNS. Consists of several words, separated by points. The structure of the name reflects the hierarchical structure DNS. . The first to the right is the domains of the first (top level), the left - the second level domains, etc.

Example: Herba.msu.ru.

this address is equipped with a Herba computer, which is registered in the MSU level 2 domain (Moscow State University) in Russia (RU) /

The domain names of the names are conforming to the numeric IP address of the computer a unique domain name.

Computer Name (Host)

Top-level domains are 2 types:

• Geographical (two-letter - each country corresponds to a two-letter code);
• Administrative (three-letter)

Level 2 domains are registered by the level 1 domain administrators. So, Microsoft registered a Microsoft domain 2 in the top-level administrative domain com. (The main server of Microsoft has a name www.microsoft.com)

Administrative

Type of organization

a commercial

Geographic

The country

Education

Government USA

International

Germany

Military USA

Computer network

former USSR

Non-commercial

England / Ireland

When, with business communication, representatives of two firms exchange business cards, then in them (business cards) will necessarily indicate the email address and the name of the company's corporate Web-site. At the same time, you can also hear the interlocutors exchange "Internet addresses" ("email addresses") companies. In all the above cases, one way or another we are talking about the use of domain names.

In the email address formally, the domain name can be considered what is written after the symbol - "@". For example, in [Email Protected] The domain name of the postal node - Corp.ru.

Attention: by the very name of any access to the resource cannot be obtained.

The procedure for using the name is as follows:

1. First, by name in the Hosts file, IP address are found,

2. Then the IP address establishes a connection with a remote information resource.

Thanks to the domain name system, not just every computer, but each file on the Internet has its exact unique address - URL (Universal Resource Locator - "universal resource pointer"). It is built as follows:

protocol: // Domain Name of the computer / Address in the DIRECTION Tree on the computer / file name

The Internet, which represents a network of networks and uniting the huge number of different local, regional and corporate networks and develops through the use of a single principle of routing and transporting data.

Routing and transportation of data on the Internet is made on the basis of

tCP / IP protocol, which is the main "law" of the Internet.

The term TCP / IP includes the name of two data transfer protocols:

• TCP (TRANSMISSION CONTOCOL) - transport protocol;
• IP (Internet Protocol) - Routing Protocol

Internet Protocol (IP) Provides IP packet routing, i.e. Delivery of information from the computer of the sender to the computer-to the trailer.

sender

TRANSMISSION CONTROL PROTOCOL (TCP), those. Transport protocol, ensures the partition of files to IP packets during the transmission process and assembly of files in the process of obtaining

sender. For example: "To: 198.78.213.185", "From whom: 193.124.5.33". The contents of such a "envelope" with information is called Internet Package (IP Package) and is a set of bytes. IP packets, on the way to a computer, the recipient pass through numerous intermediate Internet servers on which the routing operation is passed (defining their further path)

Data routing

In order for the letter to come to the destination, the address of the recipient and the address of the sender is specified on the envelope. Similarly, information is transmitted between network computers. Where as the addresses of the recipient and the sender are written IP addresses of the recipient computers and

sender

Routing Internet packages (IP Packages ) Provides the delivery of information from the sender's computer to the recipient's computer.

Internet package routes can be completely different, and therefore Internet packages sent first can reach the recipient's computer last.

For instance:

recipient

sender

Information information on the Internet depends not on server remoteness

The speed of information transmission on the Internet depends not on the remoteness of the Internet server, and from the passage route, i.e. From the number of intermediate servers and quality of communication lines (their bandwidth), which is transmitted from the server to the server

Data transportation

Often computers exchange large in volume files. If such a file is sent entirely, it can "clog" this communication channel, i.e. Make it inaccessible to send other messages.

In order for this not happening, the sender's computer must be divided into a large part of the small parts, numb them and transform them in the form of individual Internet packets to the recipient's computer.

On a recipient computer, you must collect the source file from individual parts in the correct order, so the file can be assembled only when all Internet packages come.

Data transportation It is performed by splitting the files to the Internet packets on the sender's computer, individual routing of each package and build files from the packets in the original order on the computer receiver.

For instance:

recipient

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The Internet is a global computer network that unites local, territorial and corporate networks WWW (World Wide Web - World Wide Web) or just Web (Web).

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The global computer network Internet is a global computer network that unites many Lo-solvent, regional and corporate networks and includes tens of millions of computers. The Internet is actually a network database. Hyperlinks bind hundreds of millions of documents into a single set-via database. the Internet

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The word Internet (eng. INTERNET), denoting the global computer network, has arisen as a reduction in InterConnected Networks - combined networks or "Network Network". Unlike local networks, its "elements" is not separate computers, but networks. Information on the Internet is stored on servers connected by high-speed communication lines (fiber optic, satellite). Almost all Internet services are based on the use of the client-server technology: the client program on the user's computer requests information, the server returns the answer.

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World Wide Web Wide Web or "Web" (English and / and / and / \u003d World Wide Web) is a service to access hypertext documents (web pages) stored on servers. Now WWW is the most popular Internet service. Hypertext is a text in which there are active links (hyperlinks) to other documents. Hyperlinks are usually underlined and highlighted by color (by default - blue). If you click on the left mouse button on the hyperlink, the document is loaded into the browser window to which the link indicates. On modern web pages, not only text, but also graphics, sound, video, and each element can be a hyperlink. Such a document is called hypermedia. Website (website) is a group of web pages that are located on one server are combined with a common idea and are associated with hyperlinks. For the site to become available to other computers, a special program must be launched on the server - a web server. The most popular web servers:

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Apache (httpd.apache.org), free web server for various operating systems, including Windows, Linux, Mac OS; IIS (www.iis.net) - a commercial web server for Windows; nginx (sysoev.ru/nginx) is a free web server and mail server for large sites (there are versions for Windows and UNIX-like systems). To view web pages, browser programs are used on the screen (Internet Explorer, Mozilla Firefox, Safari, Chrome, Opera). The browser sends a request to the web server containing the document URL (web pages, pattern, file, etc.), and the server responds to the requested data. Exchange occurs through the HTTP protocol.

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Ways to connect to the provider: The user gets access to the global network through the provider - a firm, the local network of which is directly related to the Internet. using a modem on a regular telephone line; Data exchange rate does not exceed 56 kbps, so this method is almost not used; using the ADSL modem, which also uses the telephone line, but allows you to simultaneously talk on the phone and work on the Internet; The data transfer rate from the Internet to the user can reach 25 Mbps, but an additional equipment must be installed on the telephone station (splitter separating the low-frequency telephone signal from the high-frequency signal transmitting digital data); via the local network provider (if it exists in your home); In this case, the telephone line is not involved; using wireless modems (USB modems) that use cellular operators and work everywhere where Mobile communications are available; Data transfer rate for 3rd generation networks (English 3G \u003d 3RD Generation) reaches 10 Mbps, and in the 4th generation networks (4G) - up to 1 Gbit / s.

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New generations of mobile communications began to be developed almost every ten years since the transition from the development of the first generation of analog cellular networks in the 1970s (1G) to networks with digital transmission (2G) in the 1980s. From the beginning of developments to actual implementation, a sufficient amount of time was held (for example, 1G network was introduced in 1984, 2G networks in 1991). In the 1990s, the standard 3G began to be developed. 4G generation networks based on the IP protocol began to be developed in 2000 and began to be implemented in many countries since 2010. 4G - generation of mobile communications with increased requirements. By the fourth generation, it is customary to include promising technologies that allow data transmission at a rate greater than 100 Mbps -c.Viga and 1 Gbps - stationary subscribers. LTE Advanced (LTE-A) and WiMAX 2 (WMAN-Advanced, IEEE 802.16m) were officially recognized by the 4G (IMT-Advanced) of the International Telecommunication Union at the Geneva Conference in 2012. The speed of 100 Mbps should be provided to high-alignment subscribers (for example, trains and cars), and subscribers with small mobility (for example, pedestrians and fixed subscribers) should be provided with a speed of 1 Gbit / s.

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Work sketch of the first global network of ARPA Network's global network. The first network consisted of 4 computers.

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A brief history in the 1960s in the US Department of Defense began the development of a computer data transmission system, which was named Arpanet (English Network, Network of the Agency for Advanced Research). The following ideas were based on this project: the network combines computers having different hardware and software;

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when connecting the new network, it is not necessary to remake the existing part; There is no single center (such a network is called distributed), it provides vitality in case of failure of any node; Package data transfer: Transmitted data are divided into small packages, one communication line is used to simultaneously transmit multiple data blocks.

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In 1969, the first network exchange was held between computers installed in the University of California and the Stanford Research Center. In 1971, a program was created to work with e-mail, which immediately became very popular. Starting from 1973, universities and colleges are connected to the new network, but also in Europe. In 1983, the network is divided into two parts: Milnet military network and a public network that has been named Internet. The history of the Russian Internet begins since 1990, when the "Relcom" postal network was organized - the first provider in the Soviet Union. In 1991, British scientist Tim Bernes-Lee developed a data exchange system in the form of a hypertext - text with active references to other documents. Now it is called worldwide web (eng. Www \u003d World Wide Web) and is the most powerful Internet service. Many mistakenly believe that the Internet and the World Wide Web are the same. In fact, this is not the case, because there are other services on the Internet - email, file sharing, chats, forums, etc.

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Graphic image of connections between internet networks. Depicted only connections between servers

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The Internet operates and develops through the use of a single TCP / IP data transmission protocol. TCP / IP Internet Protokol Data Transmission Protocol - Routing Protocol - Provides IP Package Marging, i.e. Delivery of information from the computer-from the ruler to the recipient's computer. TRANSMISSION CONTROL PROTOCOL (TCP) - Transport protocol - ensures the partition of transmitted files to IP packets during the processing and assembly of files during the preparation process.

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In order to take into account millions of PCs on the network use unique codes, TCP / IP network protocols. This number consists of 4 sections, each from 0 to 255 198.168.10.65 Provider - person or organization, Internet service provider Each computer connected to the Internet has its own unique 32-bit IP address (Internet Protokol). Perhaps 232 \u003d 4 294 967 296 IP addresses recorded in the form of four decimal numbers from 0 to 255, divided by the point: 123.45.67.89. Addressing on the Internet

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Protocols You already know that in order to transmit information, the source and receiver must use the same protocol - a set of rules and agreements that determine the procedure for exchanging data on the network. On the Internet, the TCP / IP protocol was adopted as a standard developed in 1974. Generally speaking, this is not one protocol, but a whole family, the name of which comes from the two most important protocols - TCP (English Transfer Control Protocol - Transfer Management Protocol) and IP (English Internet Protocol - Firewall Protocol). Let's try to figure out why you need to use several protocols to work on the Internet. Suppose that the browser on the computer A requests a web page from the server, which is located on the computer B. "Conversation" between the browser and the server comes using the HTTP protocol (HyperText Transfer Protocol - Hypertext Transmission Protocol). The browser and the web server cannot directly contact. To send a request to the server, the browser transmits the server address and the text of the operating system request, which causes the TCP protocol driver.

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TACP driver task - Install a connection with a remote computer and ensure the delivery of data. The transmitted data block is divided into packets (the package size does not exceed 1.5 KB), and each packet is transmitted to the following level - the IP protocol driver that sends it to the network at the specified address usually when working on the Internet, computers A and B are not directly related , therefore, the IP protocol task is to determine the node router to which you want to send a package to reach the computer B. When the route is defined, the package (with added service information) is transmitted to the physical level (for example, to a network card), where it is transmitted simply as a chain byte. Physical level protocols can be any, they are not defined in the standard. The IP protocol does not guarantee the delivery of packets, so the TCP driver must check that the data is obtained, and in case of failure, transfer the packet is reused. At the other end of the connection, the TCP driver "collects" packets into a single data block and transmits to the application level (the query has reached the server). Routers exchange information with each other, reporting about the failure or connecting some sections of the network. Routing tables are updated automatically, so when the packet route is selected, the actual network structure is currently taken into account.

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IP address classes There are 5 classes of IP addresses - A, B, C, D, E. Affiliation of the IP address to one or another class is determined by the value of the first octet (W). The following is the compliance of the values \u200b\u200bof the first octet and address classes. Classip addresses A B C D E Range of the first octet 1-127 128-191 192-223 224-239 240-247

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Ranges: class with software 0.0.0.0 127.255.255.255 b 128.0.0.0 191.255.255.255 C 192.0.0.0 223.255.255.255 D 224.0.0.0 239.255.255.2555.255.2555

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Thus, a four-level protocol system is used on the Internet, each of which "is engaged in its business": 1) the level of applications - the format of requests and responses that programs are exchanged; 2) Transport Level (TCP) - Rules for packet data blocks without taking into account their content; 3) Network Level (IP) - route selection rules for individual packages without a guarantee of their delivery; 4) Physical level - rules for the transfer of individual bytes by cable, fiber optic or other communication lines.

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At the application level (which is "closest to the user"), protocols are most often used: HTTP - to transfer web pages; FTP - to transfer files; SMTP - to send email messages to the server; POP3 or IMAP - to receive email messages from the server. There are other protocols (for chats, news groups, etc.), but they all use TCP and IP, respectively, on the transport and network levels

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212.96.118.82, 256 * 256 * 256 * 256 Internet addresses IP addresses on the Internet Any two computers can contact each other. For this, each of them must have a unique address. From the "point of view" of computers, it is more convenient to work with numeric addresses, each of which occupies the same place in memory. Such addresses (they are called IP addresses) consist of four numbers in the range from 0 to 255, for example, 192.168.104.115

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These numbers are encoded network number and computer number on the network. In order to highlight these two parts from the IP address, use masks-templates. Mask is also four numbers in the range of 0-255, but it is based in a special way, according to the principle of "n units, then - zeros" in binary code. For example, a mask 255.255.255.0 in connection with the rapid development of the Internet addresses, which can be used with such coding, will soon not be enough for everyone, therefore it is assumed that a gradual transition to a new (sixth) version of the IP protocol will occur, which is indicated as IPv6. In it, 128 bits are given to each address, and not 32. Already now there are more than 1600 networks, where IPv6 applies; It is supported by all modern operating systems and equipment manufacturers. The full transition to IPv6 will take several years, it will require large cash and replacement of all outdated devices. Generally speaking, the IP address is not assigned to a computer, but the interface - the data channel (network card, modem). Therefore, one computer can have several IP addresses, for example, if two network cards (or network card and modem) are installed on it.

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RU Stavropol Alrus alrus.stavropol.ru Domain of the top level - the country of the lower level domain - the city of the domain of the lower level - the Node of the domain principle of constructing the names system names system (DNS - Domain Name System) puts in accordance with the numerical IP address of the computer a unique domain name .

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The top-level domains are of two types: geographical (two-letter - each country corresponds to two-letter code) and administrative (two-three-letter). Domain System Names Main Server Company Microsoft www.microsoft.com Microsoft Advisory Type of Organization COM Commercial EDU General Education GOV Government US INT International MIL Military US Net Computer Network Org Nonphone Country Canada Germany Japan Russia Former USSR England / Ireland US Geographical CA de JP RU SU UK US COM WWW

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COM - Commercial ORG - Non-Profit Gov - Government EDU - Educational MIL - Military Net - Work on the Biz Business Network; Info - information sites; Name - personal sites; Museum - museums; The main names of the top level domains

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rU - Russia Au- Australia by - Belarusian CA - Canada DE - Germany FR - France JP - Japan In addition, each country has its own two-letter domain of the first level. Basic top-level domain names for countries

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The distribution of IP addresses and domains of the first level is engaged in the international organization ICANN (English Internet Corporation for Assigned Names and Numbers). Russian domain.ru was registered in 1994. A second-level free domain can register anyone wishing for a small fee. Such services provide special organizations - domain name recorders, for example, RU-CENTER (NIC.ru). The third level domains can often be obtained free of charge. For example, the site narod.yandex.ru provides all the wishing space for the site and domain of the third level of the form ivanov.narod.ru.

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Previously, only Latin letters, numbers and hyphen were allowed to use in the domain names. Now you can register domains containing other signs included in Unicode encoding, for example, the letters of the Russian alphabet. Domain.rf is enshrined for Russia, in which everyone can register second-level domains. Thus, two addresses are used on the Internet: IP addresses and domain names. To establish a correspondence between them, on special servers that are called DNS servers, tables consisting of "IP address - domain name" pairs are stored. Their task is to return an IP address for a given domain name (or vice versa) upon request.

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When registering the address, the Provider provides the following data: IP-address Network Mask Same Gateway Server Phone Number Modem Provider Instructions for logging in the system and others

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In order for the computer to establish communication with the network, in the settings of the network card (or modem), the IP address, network mask and the address of the DNS server are specified. Sometimes this data is determined automatically when the provider is connected to the network. When you enter the site address (domain name) in the address bar of the browser, first sends a request to the DNS server, the purpose of which is to determine the server's IP address. If it was possible, a request to receive a web page is sent, and the IP protocol driver uses the resulting IP address, not a domain name. Note that several IP addresses may correspond to one domain name. This technique is used to distribute the load on sites with a large number of visitors (for example, www.yandex.ru, www.google.com). Thus, the correspondence between domain names and IP addresses can be described as "many to many": several domain names can be associated with one IP address and vice versa.

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Resource address (URL) Accurate address has not only every computer on the Internet, but also every document. For such an address, the English abbreviation of the URL \u003d Uniform Resource Locator is most often used. The typical URL consists of four parts: a protocol, server name (or its IP address), directory and document name (file). This recording system was invented in 1990 by the creator of the World Wide Web T. Bernosis. For example, the address http://example.com/doc/new/vasya-new.htm includes the HTTP protocol - a protocol for exchanging hypertext documents (this is a web page); Domain name Server Example.com; directory on server / doc / new; Vasya-New.htm file name.

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In other words, to access the Vasya-New.htm document, which is located in the / doc / new directory on the EXAMPLE.COM server you need to use the HTTP protocol. Sometimes the directory and file name do not indicate, for example, http://example.com. This means that we appeal to the main page of the site. It can have different names, depending on the server settings (most often - index.htm, index.html, index.php). FTP protocol is often used to download and download files, then the document address looks like this: ftp://files.example.com/pub/new/vasya-new.zip

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Examples of Internet addresses https://www.yandex.ru http://www.mail.ru http://www.rp5.ru/ http: //askhk.rf http://support.kaspersky.ru/ Protocol Transfer Zone Web (Internet)

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Basic Internet services Storage and provision of information Email Search Systems Voice and video Communication Transfer Files forums and blogs Social networks Online stores Electronic payment systems, etc.

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The peculiarity of the modern web is to attract users to filling the websites of information and its adjustment. This led to the emergence of the term "Web 2.0", which sometimes denote the modern stage of the development of the World Wide Web. Sites using Web 2.0 technologies typically require user registration, for this you need a valid email address. Anyone can create a "personal zone" with its own settings and store there files, photos, videos, notes. Others can comment on these materials. Users are united in groups (communities) in order to discuss their questions together. Often, participants can evaluate each other's messages, therefore, "reputation" (or "karma") of participants changes, some rivalry appears

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Social networks: VKontakte (VK.RU), Odnoklassniki (www.odnoklassniki.ru), Facebook (www.facebook.com) For many, we became a venue with friends and classmates. Special sites appeared, where users can lead blogs - network diaries (www.livejournal.com, - www.blogspot.com). The influence of blogs has increased so much that they began to equate with the media / Wiki-Systems (English) are actively developing - websites, structure and contents of which users can change using the tools that are on the site itself. The most famous wiki site is the free encyclopedia of Wikipedia (the Russian version is posted on the website RU.Wikipedia.org

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Domain names unlike computers, a person is inconvenient to work with numeric addresses. They are badly remembered, when entering an IP address, it is easy to make a mistake, and it is sometimes difficult to notice it. Therefore, in 1984, domain name system was developed (English DNS \u003d Domain Name System), which allowed the use of symbolic names of sites, for example, www.mail.ru. Domain (eng. Domain - area, district) is a group of symbolic addresses on the Internet. Domains form a multi-level structure (hierarchy, wood), they are invested in each other, as a matryoshki such a system resembles a postal address in which the country, city, street, house, apartment indicates. The point in the root of the tree is the root domain. First-level domains (they are called domain zones) can designate the type of organization, for example

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The search for information on the Internet on the Internet now contains a huge amount of data, while finding the necessary information is sometimes quite difficult. The search engine is a website that is intended to search for information on the Internet. At the beginning of the development of the Internet, when sites were a bit, a web master (site creators) constituted lists of links to interesting sites. When there were many references, they began to merge into groups on topics. As a result of the development of this idea, catalogs appeared. Catalog (Eng. Web Directory) is a list of links to sites with their brief description. The catalogs usually use a multi-level linkage of links (wood): in each of the largest topics (news, science, education, etc.) are sections, in sections - subsections, etc. The first major catalog was Yahoo (www.yahoo.com), created in 1995. The largest of Russian catalogs is Yandex Catalog (yaca.yandex.ru) and [email protected] (list.mail.ru). Catalogs are filled with manually by people experts (editors of the catalog), each of which is responsible for a specific section. In addition, the web wizard can offer editors their sites for inclusion in the directory (free or paid).

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The search engine is an automatic system that stores information about all web pages known to it and issues the address of those from those where keywords entered by the user are found. A search engine browser (it is often called "spider", eng .crawler pumps from the websites of a web page, moving on all the links that meets on them, which is a set of words and expressions that reflect the required information. The search robot with the help of the index finds those pages where these words are found. Each search engine has its own language that allows you to compose complex requests, for example, to exclude some keywords from the search or search one of the specified set of words. In many systems to designate a logical operation "or" (one of the specified words) is used symbol |, and for a logical operation "and" (both words are needed) - symbol &. If you need to find the phrase, it takes it in quotes in the query. Typically, the search robot finds thousands of pages corresponding to the request. They are issued to the user in the order that is determined by the developers. The quotability is most often taken into account - the number of links from other sites on this page; What references are larger than the higher "rank" of this page and the higher it is located in the search results.

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5. What family of protocols is used on the Internet? 6. Explain why several protocol levels are applied. Tell us about the role of protocols of different levels. 7. What is the role of nodes-routers? 8. How is the guaranteed delivery of messages on the Internet? 9. Name the most well-known application level protocols. Where do they apply control questions how to use the client-server technology on the Internet? What is a provider? Tell us how to get access to the Internet. What are the advantages of the disadvantages of different ways? What ideas were based on a global computer network?

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How much space in memory is the IP address? 3. What do you think, can two computers have the same IP address? Justify the answer. 4. What IP addresses are used for local networks? Why is it necessary to transition to the IPv6 protocol? What is a domain? In the form of which structure you can submit a domain name system? What domains can you register (if they are free)? What do you think will be the popularity of domains with Russian letters? Justify the answer. What is a DNS server? What functions does it perform? What is URL? What parts does it usually consist of?

2 What is the Internet? Internet Inter - "Between" Net, Network - "Network" Internet is a global network that combines computer networks. Communication channels: Cable fiber optic satellite radio provider is a firm providing end users with Internet access through its local network.

4 How did the Internet originate? 1958 Creation of ARPA (Advanced Research Project Agency) in the USA E project of the ARPANET computer network on the network does not have a single center - vitality; When connecting the new network, it does not require alteration; communication between networks through special nodes - gateways; packet data exchange; 1968 The first network of a new type of 4 computers on the network - 50 universities and laboratories Development of the TCP / IP data exchange protocol. First services: Telnet - Remote computer management in the FTP command line mode - receiving and transmitting files Email (File Transfer Protocol) , ELECTRONIC MAIL) - Messaging

5 How did the Internet originate? 1982 European Unix Network (before this - USA, Canada, England) 1983 Network divided into two parts: MILNET - For US military purposes Internet - Public Network 1984 Domain Names System (DNS Addresses Online Computers Development WWW (WORLD WIDE Web) - T. Bernosis, the exchange of information in the form of hypertext 1991 Russia connected to the Internet the first online stores more than 20 million sites.

6 Internet Opportunities (Service, Services) WWW (World Wide Web) - Hypertext documents Hypertext is a text in which each word or phrase can be an active link to another Hypermedia document - Documents with active references containing text, drawings, sound, video . Email () FTP (File Sharing) Forums (Newsgroups, Conferences, Teleconferences) Subscribe to news Search engines Chats (Chat - chatter) Personal communication in real time ICQ (I Seek You) - Conversation 1-1, in group, exchange Files Internet Phone Skype + Columns + Microphone

7 Internet Protocols Protocol is a set of agreements and rules determining the procedure for exchanging information in a computer network. TCP / IP (1974) TCP (TRANSMISSION CONTOCOL) Protocol (TRANSMISSION Control Protocol) is divided into packets of no more than 1.5 kb packets are transmitted independently from each other at the destination Packages are collected in one IP file (Internet Protocol) defines the best packet movement route

8 Internet Service Protocols HTTP (Hypertext Transfer Protocol) - WWW FTP Service (Simple Mail Transfer Protocol) - sending emails POP3 (Post Office Protocol) - Receive Email Messages (Password) TCP / IP HTTP FTP SMTP POP3 All service protocols are based on TCP / IP! ! !

9 IP Addresses IP Address: WXYZW.xyz Network number + Computer number in the network Network class W Network Number Computer number Number Networks Number of computers A1..116WX.YZ B W.xy.z C WXYZ Classes D and E Used For service purposes.

10 Domain Domain Addresses is a group of computers combined by some feature. The domain of the 1st domain of the 2nd domain domain of the domain of the 4th level of the 1st level domains (domain zones) view of the organization. Commercial organizations.ru Russia.edu Education.ua Ukraine.gov US government.by Belarus.mil United States Military Office.uk United Kingdom.org, .net Different organizations.it Italy.info information sites.jp Japan.biz Business.cn China

11 DNS address conversion is a domain name service that converts a domain address to an IP address. Request DNS Server To get the IP address of the site Waiting for the answer WEB-Page Request for the received IP address DNS server DNS server

12 Document Address on the Internet URL (Uniform Resource Locator) - universal document address on the Internet. http: // / images / new / qq.jpg site address directory (folder) file name http: // Main page site: index.html, index.htm ftp: // files.vasya.ru / public / download / qq .zip file on FTP server protocol

13 WWW WWW (World Wide Web) - service for sharing information in the form of a hypertext. Hypertext - text containing active cross references to other documents. Hypermedia is a document that includes text, pictures, sounds, video and contains active cross references to other documents. Browser (Browser, Browser) - a program to view Web pages on the screen: Mosaic (), Illinois University, USA Netscape Navigator (from 1995 to 2002) Internet Explorer (version 6.0, 7.0), as part of Windows, 70% Mozilla Firefox (version 2.0), 15% Opera (version 9.0), 15% details can be viewed in the next section. The next section details can be viewed in the next section. In the next section

14 FTP (File archives) Features for downloading files from server (download) Download files to the server (upload), including Web sites Login access rights: Code name Password user: password anonymous input (in browsers - automatically) Login: Anonymous Password: Any file search on the FTP server Dirinfo, Readme, index ftpsearch.com FTP: // User: Files.vasya.ru FTP: // Files.vasya.ru

15 Program distribution via FTP Freeware - Free Registerware Programs - Free Email Email Shareware (TRY BEFORE You Buy) - Conditional Free Programs (Time Restrictions, Irritating Messages) Demo version - Demonstration of programs (limit functions) beta - preliminary (debugging) versions of commercial programs, goal - finding errors

16 Email () Commercial "AT" "Dog" (Russia) "Nature" (Poland) "Rose" (Turkey) XVI century: Weight 10 kg, volume 15 l 1972 R. Thomlison SMTP POP3 Mail Server Mailbox Mail Server Postal server

17 Email Message about the purchase of an elephant about buying an elephant who (to): from anyone: Reply: Copy (CC): Hidden Copy (BC): Topic (Subject): Letter heading Hello, John! Do you have a desire to buy an elephant? Sincerely, Vasily Pupkin, General Director, Rog and Hoof LLC, St. Petersburg, ul. Rorn, 2 tel. +7 (812) Fax +7 (812) Greeting Main Text Signature Requisites Company Attachments (Attachments) Attachments (ATTACHMENTS)

18 Outlook Express Mail Programs - As part of Windows Outlook - As part of Microsoft Office Thebat (Opportunities: Create Message, File Connection, Receive and Send Message Messages (Forward) Automatic Mail Verification Via the Added Interval Address Book (Contact List) Sorting Messages by folders on Many servers can work with mail via the Web site (Web interface)!!!

19 Teleconferences, Teleconference Forums (Conferences, News Groups) are discussions in the form of messaging. Moderator (Administrator) - a conference participant who has the right to delete messages for: OFF-TOPIC (extraneous messages, advertising) Insulting participants in obscene Brani FAQ (Frequently Asked Questions) FAQ (Frequently Asked Questions) - a list of the most frequent issues of beginners and answers to them . Tred (thread, thread) Chain related messages, which contains a question, answers to it and comments. Avatar Nick (nickname) quote Nick (English Nickname) - nickname, pseudonym.

20 Search Engines Indexes - Robots, which constantly examine the Internet and fill databases. Catalogs - databases that are filled by manually by people experts (guides). Give a lot of links 1) Some links do not match theme 2) It is difficult to select the desired links correspond to the catalog rubrics fewer links list.mail.ru, hybrid systems - index + directory.

21 Real Time Communication (Online) Chats (English Chat - Chat) Sharing text messages in real-time Web chats (on web pages): All Equal IRC Chats (Internet Relay Chat, 1988) "Conversation" on channels, There are channel operators with privileges

22 Real Time Communication (Online) ICQ (English I Seek You), ICQ, Internet pager. Registration: Room Features: Dialogue Discussion in the File Sharing Group Russian version icq.rambler.ruikq.rambler.ru

23 Skype internet phone (real-time conversation Telephone station Skype free calls Skype - Skype sending files Group and individual teleconference chat rooms (up to 9 people) for fee calls to stationary and mobile phones receiving calls from ordinary phones in Skype Sending and receiving voice messages and SMS.

24 Internet via WAP Mobile Phone (Wireless Application Protocol) Loading toys, Music, Weather Only Sites Communication Operators, Meteosites, Email, Online Stores 1) High Cost (Old Technologies) 2) Some GPRS options (General Packet Radio Service) or EDGE (Enhanced Data for Global Evolution) Built-in Browser (Opera Mini - Pages Compression) Supports Java Language Built-in Program for You can use instead of a computer smartphones instead of a modem: In addition, playing music, video shooting photos and video operating system, office programs

25 Ethics on the Internet Tolerance: Do not suppress the statements of others do not disturb others and not threaten them ethics of confidence: do not disseminate the statements, images and opinions of others without their consent, do not distort the facts, their own and other people's opinions do not request and not transmit information created by coercion to warn if information may be incorrectly appreciated by naive

26 Netyquette Net + etiquette - the rules of good tone when communicating on the Internet. Email: Message Theme, Greeting, Signature Do not dial off with capital letters Do not send large files without arrangement Do not send executable files (* .exe) Do not use obscene and jargonal forums: Read the list of questions and answers (FAQ, FAQ) Do not deviate from Forum themes (OFF-Topic - "Outside the topic") Do not dial off sentences with capital letters not to insult participants chats: do not meet in someone else's conversation, if he left

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Presentation on the topic: Global computer networks

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Computer Networks Computer Network is a system consisting of two and more computers in the space of computers, combined communication channels and providing distributed data processing. Computer networks are distributed systems that allow you to combine information resources included in their composition of computers.

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For effective and collaboration of multiple computers, they need information sharing. Computers can exchange information using channels of various nature: cable radio channels fiber-and-channel transmission information information card information recipient Recipient

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Types of computer networks Global network - combines many local, regional and corporate networks and includes hundreds of millions of computers (Internet) Local network - this is a computer network that connects a group of computers, covers relatively small distances (for example within one building) and allows users to share Computer resources and their peripheral devices.

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The history of the global network is chronologically the first to appear global networks (Wide Area Networks, WAN), that is, networks uniting geographically dispersed computers, possibly located in various cities and countries. Global computer networks inherited a lot from others, much older and common networks - telephone. Since the gasket of high-quality communication lines over long distances costs very expensive, then in the first global networks, already existing communication channels were often used, initially intended for other purposes. For example, during many years, global networks were built on the basis of telephone channels of tone frequency capable of carrying out only one conversation in analog form. The progress of global computer networks was largely determined by the progress of telephone networks. Since the late 60s, telephone networks have become increasingly used in digital form, which led to the appearance of high-speed digital channels connecting the PBX and allowing simultaneously to transmit tens and hundreds of conversations. A special technology of a PlesiOhron Digital Hierarchy (PLESIOCHROHous Digital Hierarchy, PDH) was developed, designed for the so-called primary, or reference networks. Initially, PDH technology, maintained speeds up to 140 Mbps. But in the late 80s, synchronous digital hierarchy technology appeared (Synchronous Digital Hierarchy, SDH) expanded the range of digital channels to 10 Gbit / s, and the spectral multiplexing technology (DWDM) technology (DWDM) technology (Dese Wave Division Multiplexing, DWDM) - per second. To date, global networks on the diversity and quality of services caught up with local networks, which for a long time were leaders in this regard, although they were born much later.

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Combining computer networks Regional networks - combine computers within one region (city, country, continent). Corporate networks - combine computers of one organization in various countries and cities, protecting them from unauthorized access (for example, Microsoft Network).

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Internet (translated from English - Between Networks) - Gigantic World Computer Network. It is an appointment - to provide anyone who wants to constant access to any information. Internet is a global computer network covering 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.

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Types of connection to the Internet. 1.Sean-connection - the user is connected to the network not constantly, but only for a certain time. Payment is charged for every hour of work on the network. Data is transmitted to the network in analog form. 2. Connect connection - the computer is connected to the network constantly to the rapid channel. Payment is charged for the amount of data taken (traffic). Data is transmitted to the network in digital form. First of all, a modem and telephone line are needed to connect to the Internet.

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Network hardware To transmit and receive information in the network, each computer must have a special board - a network adapter computers. Computer connection is performed using cables of various types: Coaxial-activated packet-folk connotations of the type of network adapter and the cable type of information on the local network is usually in the range From 10 to 100 Mbps.

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Racing by local and global networks gradually the differences between local and global types of network technologies began to smooth. Insulated earlier, local networks began to be combined with each other, while global networks were used as a binder. Close integration of local and global networks led to a significant interpenetration of relevant technologies. Rapid in data transfer methods occurs on the digital data transfer platform for fiber optic communication lines. High quality digital channels has changed the requirements for global computer network protocols. There are new global network technologies such as Frame Relay and ATM. These networks assume that bit distortion occurs so rarely that the erroneous package is more profitable to just destroy, and all the problems associated with its loss, pass the higher-level software, which is not directly included in the Frame Relay and ATM networks. A great contribution to the approach of local and global networks made an IP protocol dominance. This protocol today is used on top of any technology of local and global networks - Ethernet, Token Ring, ATM, Frame Relay - to create from various subnets of a single composite network.

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Computer global networks 90s, based on high-speed digital channels, significantly expanded the set of their services and caught up with local networks in this regard. It became possible to create services whose work is associated with the user's delivery of large amounts of information in real-time - images, video films, voices, in general, the whole thing that got the name of multimedia information. The most striking example is the WORLD WIDE WEB Hypertext Information Service, which has become the main information provider on the Internet. One of the manifestations of rapprochement of local and global networks is the emergence of networks of a large city scale, occupying an intermediate position between local and global networks. City Networks or MetroPolitan Area Networks, Man) are designed to maintain the territory of a major city. Modern networks of type MAN are distinguished by a variety of services, allowing their customers to combine communication equipment of various types, including office PBX.

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