Presentation on the topic global network.

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Presentation on the topic:

Global computer networks

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Global computer networks

Slide description:

Global computer networks

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Global computer networks

Computer networks A computer network is a system consisting of two or more spatially separated computers, connected by communication channels, and providing distributed data processing. Computer networks are distributed systems that allow one to combine the information resources of their constituent computers. Slide no. 4 For effective and

collaboration

Global computer networks

several computers they need to exchange information. Computers can exchange information using channels of various natures: cable radio channels, fiber optic channels, information transmission channel, information sender, information recipient. Slide no. 5 Types of computer networks Global network - unites many local, regional and

corporate networks

Global computer networks

History of the global network Chronologically, the first to appear were global networks (Wide Area Networks, WAN), that is, networks that unite geographically dispersed computers, possibly located in different cities and countries. Global computer networks have inherited a lot from other, much older and more widespread networks - telephone networks. Since laying high-quality communication lines over long distances is very expensive, the first global networks often used existing communication channels that were originally intended for completely different purposes. For example, for many years, global networks were built on the basis of voice-frequency telephone channels capable of transmitting only one conversation in analog form at a time. The progress of global computer networks was largely determined by the progress of telephone networks. Since the late 60s, telephone networks have increasingly used digital voice transmission, which has led to the emergence of high-speed digital channels, connecting PBXs and allowing simultaneous transmission of tens and hundreds of conversations. A special technology of plesiochronous digital hierarchy (Plesiochrohous Digital Hierarchy, PDH) was developed, intended for the so-called primary or core networks. Initially, PDH technology supported speeds up to 140 Mbit/s. But in the late 80s, Synchronous Digital Hierarchy (SDH) technology appeared, expanding the range of digital channel speeds to 10 Gbit/s, and spectral multiplexing technology (Dese Wave Division Multiplexing, DWDM) - up to hundreds of gigabits and even several terabits per second. To date, global networks have caught up with local networks in terms of variety and quality of services, which for a long time were leaders in this regard, although they were born much later.

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Global computer networks

Association of computer networks Regional networks– unite computers within one region (city, country, continent). Corporate networks – unite computers of one organization in different countries and cities, protecting them from unauthorized access (for example MicroSoft Network).

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Global computer networks

Internet (translated from English - between networks) is a giant worldwide computer network. Its purpose is to provide anyone with permanent 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. The network size increases monthly by 7-10%. The Internet forms a kind of core that provides communication between various information networks, belonging to various institutions around the world, one with another.

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Global computer networks

Types of connection to the INTERNET 1. Session connection - the user is not connected to the Internet permanently, but only temporarily certain time. Payment is charged for each hour of online work. Data is transmitted to the Network in analog form. 2.Permanent connection - the computer is constantly connected to the network via a fast channel. Payment is charged for the volume of received data (traffic). Data is transmitted to the network in digital form. First of all, to connect to the INTERNET you need a modem and phone line.

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Global computer networks

Hardware networks To transmit and receive information on the network, each computer must have a special board - a network adapter. Computers are connected to each other using cables of various types: coaxial, twisted pair, fiber optic, depending on the type network adapter and cable type, the speed of information transfer over a local network is usually in the range from 10 to 100 Mbit/s.

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Global computer networks

Convergence of local and global networks Gradually differences between local and global types network technologies began to smooth out. Previously isolated local networks began to merge with each other, while global networks were used as a connecting medium. The close integration of local and global networks has led to significant interpenetration of relevant technologies. Convergence in data transmission methods is taking place on the platform of digital data transmission over fiber-optic communication lines. High quality digital channels have changed the requirements for global computer network protocols. New global network technologies such as frame relay and ATM have emerged. In these networks, it is assumed that bit corruption occurs so rarely that it is more profitable to simply destroy an erroneous packet, and delegate all problems associated with its loss to higher-level software that is not directly part of the frame relay and ATM networks. The dominance of the IP protocol has made a major contribution to the convergence of local and global networks. This protocol is used today over any local and global network technologies - Ethernet, Token Ring, ATM, frame relay - to create a single composite network from various subnets.

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Global computer networks

Computer global networks of the 90s, operating on the basis of high-speed digital channels, significantly expanded the range of their services and caught up with local networks in this regard. It has become possible to create services whose work involves delivering large amounts of information to the user in real time - images, videos, voices, in general, everything that is called multimedia information. The most striking example is hypertext information World service Wide Web, which has become the main provider of information on the Internet. One of the manifestations of the convergence of local and global networks is the emergence of large city-scale networks, occupying an intermediate position between local and global networks. City networks or networks of megacities (Metropolitan Area Networks, MAN) are designed to serve the territory of a large city. Modern networks type MAN are distinguished by a variety of services, allowing their clients to combine communication equipment various types, including office PBXs.

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Composition of the Internet 2 WWW. (World Wide Web)Email () File servers(FTP)Teleconference (UseNet) Real-time communication systems (ICQ)

WWW – World Wide Web 3 The World Wide Web is Information system, the main components of which are hypertext documents (pages created using the hypertext markup language HTML). Web documents are accessed using web servers. The virtual world of WWW is populated by millions of documents living on hundreds of thousands of servers. The task of the WWW traveler is to find among them the one that contains the necessary information and read it using the viewer program - and for this the viewer program must know the exact location of this document. It is uniquely determined by the server address, port number, directory name and file name with this document.

4 In order to navigate the Web, you need a browser program that can establish a connection to the server on which the website is located and provide the user with access to its resources. Such programs are called browsers, or navigators. In order to navigate the Web, you need a browser program that can establish a connection to the server on which the website is located and provide the user with access to its resources. Such programs are called browsers, or navigators. The most common navigators are Internet Explorer from Microsoft and Netscape Navigator from Netscape. Web document addresses (URLs) identify the location of resources on the Internet and have the same basic structure.

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6 A protocol is a set of rules by which client-server interaction occurs. The “native” WWW protocol is called http. In addition to http, WWW clients can communicate with servers that support the ftp, gopher, and some other protocols. The protocol name is separated from the rest of the URL by a colon. In the protocol name, uppercase Latin letters and corresponding lowercase letters are equivalent.

7 Server address: The beginning of the address is marked with two forward slashes //. It consists of several parts (not necessarily four, as in our example) - so-called subdomains. Subdomains, which are combinations of letters and numbers, are separated by dots, and “clarification of the addressee’s coordinates” from larger to smaller subdomains occurs from right to left. Just like in the name of the protocol, in the server address, uppercase Latin letters and the corresponding lowercase letters are equivalent

Edu - domain top level. It represents either a country code or, as in this case, a network code. edu is the code for the US higher education network. The following top-level domains are also often found: gov - US government organizations, mil - US armed forces, com - commercial organizations, net - network services Internet, org - non-profit organizations, su - CIS countries, ru - Russia.

Uiuc.edu is a second level subdomain. Second-level subdomain names are approved in accordance with the rules developed by top-level domains. In this case, the abbreviation means University of Illinois at Urbana-Champaign.

Scs.uiuc.edu is a third-level subdomain. The names of third-level subdomains are approved in accordance with the rules developed by second-level domains. In our example, scs stands for School of Chemical Sciences.

A subdomain of the fourth, in this case, the youngest, level. Likewise, the names of fourth-level subdomains are approved in accordance with the rules developed by third-level domains. In our example, the subdomain is named www because the WWW server is located on this machine.

12 The port number is expressed as a positive integer and is separated from the address by a colon. A port is like a “door” through which you can enter the server. A server may have multiple ports available; if the WWW server port number is 80, then it can be omitted from the URL.

Electronic mail 15 Electronic mail (English, from English electronic mail) technology and the services it provides for sending and receiving electronic messages (called “letters” or “e-mails”) over a distributed (including global) computer network. Email-this is normal text file containing email address recipient and text of the letter.

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Working with e-mail Inbox - contains letters received by the addressee; Outbox - contains letters sent by the addressee, from the moment they are created until the moment they are delivered from local computer on mail server; Sent - contains all messages delivered to the mail server; Deleted - contains deleted messages; Drafts - contains blank letters. 17

Mailbox Mailbox is a section external memory mail server reserved for the subscriber. A mailbox has a unique name; the owner gets access to his mailbox via password: 18

Rules for exchanging emails. The email should not contain much text message, if necessary, it is better to attach a text file; Attached emails must be of the size specified in the instructions; Be sure to use archivers to pack attached files; To enhance the emotionality of the letter, you need to use emoticons. 20

Teleconference 22 Teleconference: comfortable communication Communication is the interaction of individuals or social groups, consisting of joint activities, direct exchange of skills, abilities, experience, information and satisfying a person’s needs for contacts with other people. Teleconferencing (UseNet) is a system for exchanging information between many users.

“On line” communication 23 On line communication systems (chat? ICQ) are specialized tools that allow real-time organization of user communication across channels computer communications. Chat (English chat chat, chatter, conversation) is a means of exchanging messages over a computer network in real time, as well as software, allowing such communication to be organized. A characteristic feature is communication in real time or close to it, which distinguishes chat from forums and other “slow” means. The word chat usually refers to group communication, although it can also include one-on-one text exchange via instant messaging programs such as ICQ or even SMS. Chat (eng. chat chat, chat, conversation) is a means of exchanging messages over a computer network in real time, as well as software that allows you to organize such communication. A characteristic feature is communication in real time or close to it, which distinguishes chat from forums and other “slow” means. The word chat usually refers to group communication, although it can also include one-on-one text exchange via instant messaging programs such as ICQ or even SMS. Databases with remote access

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28 People's Library Biographies of famous people Science and education Collection of abstracts

Description of the presentation by individual slides:

Global computer networks

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Global computer networks

2 slide History of the Internet. The Internet is the World Wide Web, global. The history of the emergence and development of this world wide web is bright and unusual, because already 10 years after its appearance it conquered many organizations and countries that began to actively use the network for work. At first, the Internet served exclusively groups of researchers and scientists; soon the military squeezed into this group, and then businessmen. After this, the popularity of the Internet grew rapidly. Users were seduced by the speed of information transfer, cheap global communications, a lot of easy and available programs, unique database, etc. Today, at a low cost of services, every user can access information services from all countries of the world. Also, the Internet today provides global communication opportunities around the world. Naturally, this is convenient for companies that have branches in different parts of the world, for transnational corporations, as well as for management structures.

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Global computer networks

How and when did the Internet appear? This happened more than 50 years ago. Back in 1961, on instructions from the US Department of Defense. began work on an experimental project to create a network between computers to transmit data packets. Each node has the authority to originate, transmit, and receive messages from other computers. In this case, messages are divided into standardized elements called “packets”. Each package is assigned an address, ensuring correct and complete delivery of documents. The first theoretical development of the predecessor of the modern World Wide Web, which was published in 1964 by Paul Baran, argued that all nodes on the network should have the same status. This network was called ARPANET, and it was intended to explore various options for ensuring reliable communication between different computers. It became the immediate predecessor of the Internet. -Paul Baran - thanks to whom the network appeared in 1964 - the progenitor of the modern Internet.

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For eight years, DARPA worked on the project and in 1969, the Department of Defense approved ARPANET as the leading organization for research in the field of computer networks. From this time on, nodes began to be created new network. The following year, ARPANET hosts used NCP for communication. A year later, there were already 15 nodes in the network. 1972 is the year in which addressing development groups were created to harmonize different protocols. At the same time, TCP/IP data transfer protocols were developed. In 1973, the first international connections were made. The countries that joined the ARPANET network were England and Norway. The ARPANET project turned out to be so successful that soon many organizations in the USA, England and Norway wished to join it. The history of the Internet is just beginning here. In 1976, the UUCP protocol was developed, and three years later they launched USENET, which runs on UUCP. The US Department of Defense declared TCP/IP its standard in 1983. 1984 was the year the DNS system was introduced, and the total number of hosts exceeded 1000. The formation of CSNET accelerated significantly in 1986, when they began to create supercomputer centers. By 1987, the number of hosts had exceeded 10 thousand. And in 1988, NSFNET began using the T1 channel. -DISA - Defense Information Systems Agency - defense information systems agency.

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Internet in Russia. The network came into operation in 1995. In 1996-98, a backbone network for science and higher education was built. At the same time, networks of commercial suppliers emerged and developed. At first they focused on connecting organizations. In 1998, Rostelecom, together with Relcom, formed the company Relcom - DS. Today it is the largest Internet service provider in Russia. Today, the Internet already has a huge database of information in Russian. According to sociologists, at the end of 1998, about 1.5 million people in Russia were Internet users, and more than half of these users lived outside of Moscow. In 1999, the number of users exceeded 5 million people.

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Negative influence of the Internet on humans. -Internet and vision. -Computer and poor health. -The Internet is an addiction.

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Global computer networks

1.1Internet and vision. In fact, it is not the Internet that has a bad effect on vision, but the computer, but the Internet is definitely to blame for this. Let's look at the statistics of whose vision deteriorates more. This means that those users who communicate on the computer are more likely to worsen their vision. Such users communicate using the Internet, which means the Internet negatively affects our vision. Vision deteriorates due to greater fatigue, when a person sits at the computer for a very long time and continuously, vision weakens. Vision also deteriorates when reading from a monitor screen. 1.2Computer and poor health. Man working at a computer long time must maintain a relatively motionless position, which negatively affects the spine and blood circulation throughout the body (blood stagnation). Long-term use of the keyboard leads to overstrain of the joints of the hand and forearm muscles. Working at a computer involves processing a large amount of information and constant concentration of attention, therefore, when working at a computer for a long time, mental fatigue and impaired attention often develop. Working at a computer often absorbs all the attention of a working person and therefore such people often neglect normal nutrition and work from hand to mouth all day. This is directly related to the Internet, because a person will spend more time at a computer only when he is on the Internet, a person will absorb a large amount of information, communication, and he will lose track of time, and his health will deteriorate every minute. 1.3The Internet is an addiction. Computer addiction is no less dangerous than drug addiction, as it leads to a significant disruption of adaptation in society (inability to work, inability to start a family or simply take care of oneself). Internet addiction is a mental disorder, an obsessive desire to connect to the Internet and a painful inability to disconnect from the Internet in time.

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Positive influence of the Internet on people. Positive features of the influence of the Internet on a person - Earning money online, finding a job. - Possibility of paying and ordering many services via the Internet. - Show yourself, show yourself to the world. - Talk to people, find old friends, classmates. - On the Internet you can always get the latest news on any topic.

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We have looked at some of the negative aspects of the Internet, but you can also find positive ones. We can communicate with people who are thousands of kilometers away from you, we can exchange information at a distance, we can make all kinds of purchases without leaving home, etc. Let's consider useful features Internet. 2.1 Online purchases. Nowadays, shopping through online stores is becoming very popular; you choose the product you need, put it in the online shopping cart and pay using a card, ATM or web wallet. It is very comfortable. 2.2Internet money. Now at this time it has become popular to have an online wallet. This is a kind of wallet, but we cannot see or touch it because... it is in an interactive space. It is visual, but the money it contains is a real means of payment. With this money we can pay for other goods from online stores. And these are just the main advantages. The needs and requests of Internet users are very different. Some want to get new software. Others are looking for certain documents they need for their professional activities. Still others connect online to receive email. The Internet helps everyone.

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Global computer networks

28 People's Library Biographies of famous people Science and education Collection of abstracts

Description of the presentation by individual slides:

Global computer networks

1 slide

Global computer networks

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Global computer networks

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

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Global computer networks

Global computer network Internet The Internet is a global computer network that unites many local, regional and corporate networks and includes tens of millions of computers. The Internet is effectively a networked database. Hyperlinks link hundreds of millions of documents together into a single network database. Internet

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The word Internet, meaning a global computer network, originated as an abbreviation for Interconnected Networks - interconnected networks or “network of networks.” Unlike local networks, its “elements” are not individual 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 client-server technology: a client program on the user’s computer requests information, and the server returns a response.

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World Wide Web The World Wide Web or “web” (English I/I/I/ = World Wide Web) is a service for accessing hypertext documents (web pages) stored on servers. Now WWW is the most popular Internet service. Hypertext is text that contains active links (hyperlinks) to other documents. Hyperlinks are usually underlined and highlighted in color (blue by default). When you left-click on a hyperlink, the document that the link points to is loaded into your browser window. Modern web pages contain not only text, but also graphics, sound, video, and each element can be a hyperlink. Such documents are called hypermedia. A site (website) is a group of web pages that are located on the same server, united by a common idea and connected using hyperlinks. In order for the site to become accessible to other computers, a special program must be running on the server - a web server. The most popular web servers:

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Global computer networks

Apache (httpd.apache.org), a free web server for various operating systems, including Windows, Linux, Mac OS; IIS (www.iis.net) - commercial web server for Windows; nginx (sysoev.ru/nginx) is a free web server and mail server for large websites (there are versions for Windows and UNIX-like systems). Browsers (Internet Explorer, Mozilla Firefox, Safari, Chrome, Opera). The browser sends a request to the web server containing the URL of the document (web page, picture, file, etc.), and the server responds with the requested data. The exchange takes place via the HTTP protocol.

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Methods of connecting to a provider: The user gains access to the global network through a provider - a company whose local network is directly connected to the Internet. using a modem over a regular telephone line; the data exchange speed does not exceed 56 kbit/s, so this method is practically no longer used; using an ADSL modem, which also uses a telephone line, but allows you to simultaneously talk on the phone and surf the Internet; the speed of data transfer from the Internet to the user can reach 25 Mbit/s, however, additional equipment must be installed at the telephone exchange (a splitter that separates the low-frequency telephone signal from the high-frequency signal transmitting digital data); through the provider’s local network (if it exists in your home); in this case the telephone line is not used; using wireless modems (USB modems) that use networks mobile operators and work wherever mobile communications are available; The data transfer speed for 3rd generation networks (English 3G = 3rd generation) reaches 10 Mbit/s, and in 4th generation networks (4G) - up to 1 Gbit/s.

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New generations 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. A sufficient amount of time passed from the start of development to actual implementation (for example, 1G networks were introduced in 1984, 2G networks in 1991). In the 1990s, the 3G standard 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 is a generation of mobile communications with increased requirements. The fourth generation includes promising technologies that allow data transmission at speeds exceeding 100 Mbit/s for mobile subscribers and 1 Gbit/s for stationary subscribers. LTE Advanced (LTE-A) and WiMAX 2 (WMAN-Advanced, IEEE 802.16m) technologies have been officially recognized wireless standards fourth generation communications 4G (IMT-Advanced) by the International Telecommunication Union at a conference in Geneva in 2012. 100 Mbit/s speed should be provided to high mobility subscribers (such as trains and cars), and low mobility subscribers (such as pedestrians and fixed subscribers) should be provided with 1 Gbit/s speed

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Working sketch of the first global network ARPA NETWORK The first network consisted of 4 computers

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Global computer networks

Short story In the 1960s, the US Department of Defense began developing computer system data transmission, which was called ARPANET (Advanced Research Projects Agency Network, network of advanced research agency). This project was based on the following ideas: a network connects computers with different hardware and software;

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when connecting a new network, no modification of the existing part is required; there is no single center (such a network is called distributed), this ensures survivability in the event of failure of any node; packet data transmission: the transmitted data is divided into small packets; one communication line is used to simultaneously transmit several blocks of data.

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In 1969, the first data exchange took place over a network between computers installed at the University of California and the Stanford Research Center. In 1971, a program for working with e-mail was created, which immediately became very popular. Since 1973, universities and colleges not only in the USA, but also in Europe have been connected to the new network. In 1983, the network splits into two parts: the military network MilNet and public network, which was called the Internet. Story Russian Internet begins in 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 hypertext - text with active links to other documents. Now called the World Wide Web (English WWW = World Wide Web) and is the most powerful service on the Internet. Many people mistakenly believe that the Internet and the World Wide Web are one and the same. In fact, this is not true, because there are other services on the Internet - email, file sharing, chat rooms, forums, etc.

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Graphic image connections between Internet networks. Only connections between servers are shown

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The Internet operates and develops through the use of a single data transfer protocol, TCP/IP. The TCP/IP Internet Protocol (IP) is a routing protocol that provides routing of IP packets, i.e. delivery of information from the sending computer to the receiving computer. Transmission Control Protocol (TCP) - a transport protocol - ensures that transmitted files are split into IP packets during transmission and file assembly during reception.

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In order to account for millions of PCs on the network using unique codes, network protocols TCP/IP. 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 Protocol). Possibly 232 = 4,294,967,296 IP addresses, written as four decimal numbers from 0 to 255, separated by a dot: 123.45.67.89. Internet addressing

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Protocols You already know that to transmit information, the source and receiver must use the same protocol - a set of rules and agreements that determine how data is exchanged on the network. The Internet uses the TCP/IP protocol, developed in 1974, as a standard. Generally speaking, this is not one protocol, but a whole family, the name of which comes from the two most important protocols - TCP (Transfer Control Protocol) and IP (Internet Protocol). Let's try to figure out why you need to use several protocols to work on the Internet. Let's assume that the browser on computer A requests a web page from a server located on computer B. The “conversation” between the browser and the server takes place using the HTTP protocol (HyperText Transfer Protocol). The browser and web server cannot communicate directly. To send a request to a server, the browser passes the server's address and the request text to the operating system, which calls the TCP protocol driver.

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The TCP driver's job is to establish a connection with remote computer and ensure data delivery. The transmitted data block is divided into packets (the packet size usually does not exceed 1.5 KB), and each packet is transmitted to the next level - the IP protocol driver, which sends it to the network at the specified address. Usually, when working on the Internet, computers A and B are not directly connected , therefore, the task of the IP protocol is to determine the router node to which the packet needs to be sent so that it reaches computer B. When the route is determined, the packet (with added service information) is transmitted to physical layer(for example, to a network card), where it is transmitted simply as a chain of bytes. Physical layer protocols can be anything; they are not defined in the standard. The IP protocol does not guarantee the delivery of packets, so the TCP driver must (using an established connection) check that the data has been received and, if it fails, retransmit the packet. At the other end of the connection, the TCP driver “collects” the packets into a single block of data and transmits it to the application level (the request has reached the server). Routers exchange information with each other, reporting failure or connection of some parts of the network. Routing tables are updated automatically so that when choosing a route for packets, the actual network structure at that moment is taken into account.

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Classes of IP addresses There are 5 classes of IP addresses - A, B, C, D, E. Whether an IP address belongs to one class or another is determined by the value of the first octet (W). The correspondence between the values ​​of the first octet and the address classes is shown below. IP address class A B C D E First octet range 1-127 128-191 192-223 224-239 240-247

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Ranges: Class C To A 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 224.0.0.0 239.255.255.255 E 240.0.0 .0 255.255.255.255

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Thus, the Internet uses a four-level system of protocols, each of which “does its own thing”: 1) application level - the format of requests and responses exchanged between programs; 2) transport layer (TCP) - rules packet transmission blocks of data without taking into account their contents; 3) network layer (IP) - rules for choosing a route for individual packages without guarantee of their delivery; 4) physical layer - rules for transmitting individual bytes over a cable, fiber optic or other communication line.

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At the application level (which is “closest” to the user), the following protocols are most often used: HTTP - for transferring web pages; FTP - for file transfer; SMTP - for sending messages to the server Email; POP3 or IMAP - for receiving email messages from the server. There are other protocols (for chats, newsgroups, etc.), but they all use TCP and IP at the transport and network layers respectively

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Global computer networks

212.96.118.82, 256*256*256*256 Internet addresses IP addresses On the Internet, any two computers can communicate with each other. To do this, each of them must have unique address. From the “point of view” of computers, it is more convenient to work with numeric addresses, each of which takes up the same space in memory. These addresses (called IP addresses) consist of four numbers ranging from 0 to 255, for example, 192.168.104.115

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These numbers encode the network number and the computer number on the network. In order to isolate these two parts from the IP address, template masks are used. The mask is also four numbers in the range 0-255, but it is constructed in a special way, according to the principle of “n ones, then zeros” in binary code. For example, the mask is 255.255.255.0 Due to the rapid development of the Internet, addresses that can be used for such encoding will soon not be enough for everyone. Therefore, it is assumed that there will be a gradual transition to a new (sixth) version of the IP protocol, which is designated as IPv6. It allocates 128 bits for each address, not 32. There are already more than 1,600 networks that use IPv6; it is supported by all modern operating systems and equipment manufacturers. A complete transition to IPv6 will take several years, it will require large financial expenditures and replacement of all outdated devices. Generally speaking, an IP address is assigned not to a computer, but to an interface - a data transmission channel (network card, modem). Therefore, one computer can have several IP addresses, for example, if it has two network cards installed (or a network card and a modem).

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RU STAVROPOL ALRUS alrus.stavropol.ru Top-level domain - Country Low-level domain - City Low-level domain - Node Domain principle of naming The Domain Name System (DNS - Domain Name System) assigns a unique domain name to the numerical IP address of the computer .

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Top-level domains are of two types: geographical (two-letter - each country has a two-letter code) and administrative (two- or three-letter). Domain name system Main server of Microsoft www.microsoft.com microsoft Administrative Type of organization com Commercial edu General education gov Government USA int International mil Military USA net Computer network org Non-profit Country Canada Germany Japan Russia former USSR England / Ireland USA Geographic 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 network Biz - business; Info - information sites; Name - personal sites; Museum - museums; Basic Top Level Domain Names

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ru - Russia au- Australia by - Belarus ca - Canada de - Germany fr - France jp - Japan In addition, each country has its own two-letter top-level domain Basic top-level domain names for countries

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The distribution of IP addresses and first-level domains is carried out by the international organization ICANN (Internet Corporation for Assigned Names and Numbers). Russian domain.ru was registered in 1994. Anyone can register a free second-level domain for a small fee. Such services are provided by special organizations - domain name registrars, for example, RU-Center (nic.ru). Third-level domains can often be obtained for free. For example, the site narod.yandex.ru provides everyone with space for a site and a third-level domain of the form ivanov.narod.ru.

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Previously, only Latin letters, numbers and hyphens were allowed in domain names. Now you can register domains containing other characters included in the UNICODE encoding, for example, letters of the Russian alphabet. The domain.rf is assigned to Russia, in which everyone can register second-level domains. Thus, there are now two addressing systems used on the Internet: IP addresses and domain names. To establish a correspondence between them, on special servers, which are called DNS servers, store tables consisting of “IP address - domain name” pairs. Their task is to return the IP address for a given domain name upon request from a client computer (or vice versa).

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Global computer networks

When registering an address, the provider provides the following data: IP address Network mask Name server Gateway Phone number of the provider’s modem Instructions for logging in, etc.

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Global computer networks

In order for the computer to establish a connection to the network, the IP address, network mask and DNS server address are specified in the settings of the network card (or modem). Sometimes this data is detected automatically when connecting to the provider's network. When you enter a website address (domain name) in address bar browser, a request is first sent to the DNS server, the purpose of which is to determine the IP address of the server. If this succeeds, a request is made to retrieve the web page, with the IP protocol driver using the resulting IP address rather than the domain name. Note that one domain name can correspond to several IP addresses. 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 mapping 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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Global computer networks

Resource address (URL) Not only every computer on the Internet has an exact address, but also every document. For such an address, the English abbreviation URL = Uniform Resource Locator is most often used. A typical URL has four parts: the protocol, the server name (or its IP address), the directory, and the document (file) name. This recording system was invented in 1990 by the creator of the World Wide Web, T. Bernes-Lee. 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); server domain name example.com; directory on the server /doc/new; file name vasya-new.htm.

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Global computer networks

In other words, to access the document vasya-new.htm, 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 are not specified, for example, http://example.com. This means that we are turning to home page site. It can have different names, depending on the server settings (most often - index.htm, index.html, index.php). To download and upload files, the FTP protocol is often used, then the document address looks something like this: ftp://files.example.com/pub/new/vasya-new.zip

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Global computer networks

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

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Basic Internet services Storage and provision of information E-mail Search engines Voice and video communications File transfer Forums and blogs Social media Online stores Electronic payment systems, etc.

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Peculiarity modern web- involving users in filling sites with information and updating it. This led to the emergence of the term “Web 2.0,” which is sometimes used to describe the current stage of development of the World Wide Web. Sites using Web technologies 2.0 generally require user registration, which requires a valid email address. Anyone can create a “personal zone” with their own settings and store files, photos, videos, notes there. Others may comment on these materials. Users unite in groups (communities) in order to discuss issues that interest them together. Often participants can evaluate each other's posts, thus the "reputation" (or "karma") of the participants changes, and some rivalry appears

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Global computer networks

Social networks: VKontakte (vk.ru), Odnoklassniki (www.odnoklassniki.ru), Facebook (www.facebook.com) have become a place for many to communicate with friends and classmates. Special sites have appeared where users can write blogs - online diaries (www.livejournal.com, - www.blogspot.com). The influence of blogs has grown so much that they have come to be equated with means mass media/ Wiki systems are actively developing - websites, the structure and content of which users can change using tools that are on the site itself. The most famous wiki site is the free encyclopedia Wikipedia (the Russian version is posted on the site ru.wikipedia.org

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Global computer networks

Domain names Unlike computers, humans are not comfortable working with numeric addresses. They are difficult to remember; it is easy to make a mistake when entering an IP address, and sometimes it is quite difficult to notice it. Therefore, in 1984, a domain name system (DNS = Domain Name System) was developed, which allowed the use of symbolic website names, for example, www.mail.ru. A domain (English domain - region, region) is a group of symbolic addresses on the Internet. Domains form a multi-level structure (hierarchy, tree), nested within each other, like nesting dolls. In some ways, this system resembles mailing address, which indicates the country, city, street, house, apartment. The point at the root of the tree is the root domain. First-level domains (called domain zones) can indicate the type of organization, for example

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Global computer networks

Searching for information on the Internet The Internet now contains a huge amount of data, and finding the information you need can sometimes be quite difficult. Search system is a website that is designed to search for information on the Internet. At the beginning of the Internet, when there were few websites, webmasters (website creators) compiled lists of links to interesting sites. When there were a lot of links, they began to be combined into groups by topic. As a result of the development of this idea, catalogs appeared. A directory (English: web directory) is a list of links to sites with a brief description, broken down by topic. Directories usually use a multi-level grouping of links (tree): each of the major topics (News, Science, Education, etc.) has sections, sections have subsections, etc. The first major directory site was Yahoo (www.yahoo.com), created in 1995. The largest of the Russian catalogs are Yandex catalog (yaca.yandex.ru) and [email protected] (list.mail.ru). Catalogs are filled in manually by human experts (catalogue editors), each of whom is responsible for a specific section. In addition, webmasters can offer their sites to editors for inclusion in the catalog (free or paid).

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Global computer networks

A search engine is automatic system, which stores information about all web pages known to it and, upon request, provides the addresses of those where the keywords entered by the user are found. A search engine robot browser (often called a “spider”, English crawler) downloads web pages from sites, following all the links found on them. Keywords are a set of words and expressions that reflect the required information. The search robot uses an index to find those pages where these words appear. Each search engine has its own language that allows you to compose complex queries, for example, exclude some keywords from the search or search for one of a given set of words. In many systems, the logical OR operation (requiring one of the specified words) is represented by the symbol |, and the logical operation AND (both words are required) is the symbol &. If you need to find a phrase, it is placed in quotation marks in the query. Typically, a search robot finds thousands of pages that match a query. They are issued to the user in the order determined by the developers. Most often, citation is taken into account - the number of links from other sites to this page; The more links there are, the higher the “rank” of a given page and the higher it is located in the search results.

Global computer networks

5. What family of protocols is used on the Internet? 6. Explain why multiple layers of protocols are used. Explain the role of protocols at different levels. 7. What is the role of router nodes? 8. How is guaranteed delivery of messages on the Internet ensured? 9. Name the most well-known application layer protocols. Where are they used? Review questions How is client-server technology used on the Internet? What is a provider? Tell us how you can access the Internet. What are the advantages and disadvantages different ways? What ideas formed the basis of the global computer network?

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How much memory space does an IP address take? 3. Do you think it is possible for two computers to have the same IP address? Justify your answer. 4. What IP addresses are used for local networks? Why is it necessary to switch to IPv6? What is a domain? What kind of structure can a domain name system be represented in? What domains can you register (if they are available)? Do you think domains with Russian letters will be popular? Justify your answer. What is a DNS server? What functions does it perform? What is a URL? What parts does it usually consist of?