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Presentation on the topic: Global computer networks

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Computer networks A computer network is a system consisting of two or more spaced apart computers, united by communication channels, and providing distributed data processing. Computer networks are distributed systems that allow you to combine the information resources of their computers.

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For efficient and collaborative work of several computers, they need to exchange information. Computers can exchange information using channels of various nature: cable radio channels, fiber optics, information transmission channel, information sender, information recipient.

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Types of computer networks Wide area network - combines many local, regional and corporate networks and includes hundreds of millions of computers (INTERNET) resources of computers and their peripheral devices.

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History of the global network Chronologically, the first to appear were wide area networks (WANs), 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, digital voice transmission has been increasingly used in telephone networks, which has led to the emergence of high-speed digital channels connecting exchanges and allowing tens and hundreds of conversations to be transmitted simultaneously. A special technology of plesiochronous digital hierarchy (Plesiochrohous Digital Hierarchy, PDH) was developed, designed for the so-called primary, or core networks. Initially, PDH technology supported speeds up to 140 Mbps. But at the end of the 80s, Synchronous Digital Hierarchy (SDH) technology appeared and expanded the range of digital channel speeds up to 10 Gbps, and Dese Wave Division Multiplexing (DWDM) technology - up to hundreds of gigabits and even several terabits. per second. To date, global networks in terms of the variety and quality of services have caught up with local networks, which for a long time were leaders in this regard, although they appeared much later.

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Combining computer networks Regional networks unite computers within the same 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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Internet (translated from English - between networks) is a giant worldwide computer network. Its purpose is to provide anyone with constant access to any information. The Internet is a global computer network covering the entire world. Today, the Internet has about 15 million subscribers in more than 150 countries around the world. The size of the network increases by 7-10% monthly. The Internet forms, as it were, the core that provides communication between various information networks belonging to various institutions around the world, one with the other.

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

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Network hardware To transmit and receive information on a 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 from 10 to 100 Mbps.

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Convergence of local and global networks Gradually, the differences between local and global types of network technologies began to smooth out. Previously isolated local networks began to unite with each other, while global networks were used as a connecting medium. The tight integration of local and global networks has led to significant interpenetration of the respective technologies. Convergence in data transmission methods occurs on the platform of digital data transmission over fiber-optic communication lines. The high quality of digital channels has changed the requirements for the protocols of global computer networks. New WAN technologies such as frame relay and ATM have emerged. In these networks, it is assumed that bit distortion occurs so rarely that it is more profitable to simply destroy the erroneous packet, and entrust all the 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 great contribution to the convergence of local and global networks. Today this protocol is used over any technologies of local and global networks - Ethernet, Token Ring, ATM, frame relay - to create a single composite network from various subnets.

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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 respect. It became possible to create services whose work is associated with the delivery of 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 the hypertext information service World 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 networks of the scale of a large city, 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 MAN-type networks are distinguished by a variety of services, allowing their customers to combine communication equipment of various types, including office PBXs.

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• In addition to local networks, there are also:
• A corporate network is an association of local networks within a single corporation.
• A regional network is an association of computers and local networks to solve common regional problems.

• The need for the formation of a single global information space led to the creation of the global computer network Internet.

• The global network is an association of computers located at a remote distance for the common use of world information resources.

What is the Internet?

• Internet

• inter- "between"

• net, network- "net"

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

Organization of global networks

• Turning to the Internet, we use the services of an Internet provider. The provider connects clients to its network, which become part of the provider's network and at the same time part of all the interconnected networks that make up the Internet.

Internet addressing.

• In order for computers to find each other in the process of exchanging information, there is a unified addressing system on the Internet based on the use of an IP address.
• Every computer connected to the Internet has its own unique 32-bit (binary) IP address.
• The total number of IP addresses is over 4 billion:
• N=232=4294967296

Computer address on the network:

• The address of a computer on a network is called an IP address.
• General form:
• XXX.XXX.XXX.XXX

• octets

• octets

• An IP address consists of four parts written as dotted decimal numbers (for example, 192.168.1.1). Each of these four parts is called an octet. An octet is eight binary digits (for example, 11000000, or 192 in decimal). Thus, each octet can take on binary values ​​from 00000000 to 11111111, or from 0 to 255 in decimal. The following figure shows an example of an IP address where the first three octets (192.168.1) are the network number and the fourth octet (16) is the host ID.

Computer IP address:

• Host - any computer connected to the Internet, regardless of its purpose.
• 195.85.102.14

• 195th subnet of the Internet

• 85th subnet 195th subnet

• 102nd subnet 85th subnet

• 14th computer in 102 subnets

DNS - domain name system

• Domain Name System (DNS)
• DNS converts the numeric IP address of a host (computer) into a set of characters.

• The Internet has a more user-friendly and user-friendly system of addresses, in which the address is indicated by an individual domain name. This is a symbolic name system.
• Each domain name consists of several words separated by dots.
• Domain names are built on a hierarchical basis. The rightmost one is the top-level domain. Further decoding of a domain name is made from right to left.

• Examples of domain names:
• microsoft.com is a commercial organization of the Microsoft Corporation
• www.gov.ru - the official website of the Russian government

• A domain is a group of computers that are grouped together in some way.

• www.qqq.microsoft.ru

• 1st level domain

• 2nd level domain

• 3rd level domain

• 1st level domains (domain zones)

Domain names are divided into levels:

• The first level domain (top level) is 2 - 4 letters that are placed at the end of each domain name after a dot (.ru, .com, .ua, .uz, etc.), and are not used for site names by themselves.
• A second-level domain is obtained by adding the word (website name) before the first-level domain.
• A third-level domain is obtained by adding a word through a dot before the second-level domain.
• There are also fourth-level domains, they are formed according to the same principle, but are used extremely rarely. Fourth-level domain names are quite long and complex, and their names are hard to remember.

• In addition, first-level domain names can be divided into national (geographic) domains, and general use domains (ie, for sites of a certain orientation).
• Examples of geographic domain zones:
• .ru - Russian Federation
• .rf - Russian Federation
• .ua– Ukraine
• .uz – Uzbekistan (domain name registration in Uzbekistan)
• .kz - Kazakhstan
• .am - Armenia

• Examples of public domain zones:
• .info - information nodes.
• .net - providing networking
• .org - non-profit organizations
• .biz - commercial organizations
• .com - commercial
• .gov - government

http://www.myhost.mydomain.spb.ru

• http:// - Hyper Text Transfer Protocol;
• www - World Wide Web - World Wide Web;
• myhost.mydomain - third-level domain;
• spb - second-level domain;
• Ru is the first level domain.

Routing and transportation of data over computer networks

• Internet packet routing ensures that information is delivered from the sending computer to the receiving computer.
• Data is transported by splitting files into Internet packets on the sending computer, routing each packet individually, and reassembling the files from the packets in their original order on the receiving computer.

Internet protocols

• To communicate with each other on the Internet, computers of different types and various operating systems use different protocols - sets of rules and agreements that describe exactly how data is transmitted over the network.

TCP/IP communication protocol

• The Internet functions and develops thanks to the use of a single data transfer protocol TCP/IP. The term TCP/IP includes the names of two protocols:
• Transmission Control Protocol (TCP)
• Internet Protocol (IP)

• The TCP/IP protocol provides for the transfer of information between computers on a network. In order for the letter to reach its destination, the information is packed into an "envelope" on which the IP addresses of the recipient's and sender's computers are "written". For example, "To: 198.78.213.165", "From: 193.124.5.33". The contents of the envelope in computer language is called an IP packet and is a collection of bytes.

• IP packets on their way to the receiving computer also pass through numerous intermediate Internet servers, on which the routing operation takes place. As a result of routing, IP packets are sent from one Internet server to another, gradually approaching the recipient computer. Computers that forward, receive, and route packets must follow the same strict rules in order to act quickly and smoothly. The set of these rules for the Internet is the Internet Protocol (IP)

• On the Internet, a situation often occurs when you need to send a multi-megabyte file. In such cases, on the sending computer, it is necessary to split a large file into small parts, number them and transport them in separate IP packets to the receiving computer. On the receiving computer, you need to assemble the source file from separate parts. All these actions are performed on the basis of the Transmission Control Protocol, i.e. the transport protocol.

2 What is the Internet? InterNet inter - "between" net, network - "network" The Internet is a global network that unites computer networks. Communication channels: cable fiber optic satellite radio communication A provider is a company that provides end users with access to the Internet through its local network.

4 How did the Internet originate? 1958 Establishment of ARPA (Advanced Research Project Agency) in the USA e ARPANet computer network project there is no single center in the network - survivability; when connecting a 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 In the network - 50 universities and laboratories Development of the TCP / IP data exchange protocol First services: TelNet - remote control of a computer in command line mode FTP (File Transfer Protocol) - receiving and transmitting files E-mail ( , electronic mail) - messaging

5 How did the Internet originate? 1982 European UNIX network (previously USA, Canada, England) 1983 The network is divided into two parts: MilNet - for military purposes USA Internet - public network 1984 Domain Name System (DNS) (addresses of the type On the Internet of computers Web) - T. Bernes-Lee, information exchange in the form of hypertext 1991 Russia connected to the Internet The first Internet stores More than 20 million sites.

6 Internet capabilities (services) WWW (World Wide Web) - hypertext documents Hypertext is a text in which each word or phrase can be an active link to another document Hypermedia - documents with active links containing text, pictures, sound, video . E-mail () FTP (file exchange) Forums (newsgroups, conferences, teleconferences) Newsletter subscriptions Search engines Skype internet phone + speakers + microphone

7 Internet protocols A protocol is a set of agreements and rules that govern how information is exchanged over a computer network. TCP/IP protocol (1974) TCP (Transmission Control Protocol) file is divided into packets no larger than 1.5 KB packets are transmitted independently at the destination packets are assembled into a single file IP (Internet Protocol) determines the best route for packets to travel

8 Internet service protocols HTTP (HyperText Transfer Protocol) - WWW service FTP (File Transfer Protocol) - FTP service SMTP (Simple Mail Transfer Protocol) - sending e-mail messages POP3 (Post Office Protocol) - receiving e-mail messages (password required) 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 of networks Number of computers A1..126wx.yz B w.xy.z C wxyz Classes D and E are used for official purposes.

10 Domain Addresses A domain is a group of computers united by some attribute. 1st-level domain 2nd-level domain 3rd-level domain 4th-level domain 1st-level domains (domain zones) Type of organizationCountry.com commercial organizations.ru Russia.edu education.ua Ukraine.gov US government.by Belarus.mil military departments USA.uk UK.org,.net various organizations.it Italy.info news sites.jp Japan.biz business.cn China

11 Address Translation DNS (Domain Name Service) is a domain name service that translates a domain address into an IP address. query a DNS server to obtain the site's IP address pending response query a Web page at the IP address obtained DNS server DNS server

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

13 WWW service WWW (World Wide Web) is a service for exchanging information in the form of hypertext. Hypertext is text containing active cross-references to other documents. Hypermedia is a document that includes text, pictures, sounds, videos and contains active cross-links to other documents. Browser (browser, browser) - a program for viewing Web pages on the screen: Mosaic (), University of Illinois, USA Netscape Navigator (from 1995 to 2002) Internet Explorer (version 6.0,. 7.0), included in Windows, 70% Mozilla FireFox (version 2.0), 15% Opera (version 9.0), 15% See next section for details. see next section See next section for details. see next section

14 FTP service (file archives) Capabilities downloading files from the server (download) uploading files to the server (upload), including Web sites Access rights login: user code name password: password Anonymous login (in browsers - automatically) login: anonymous password: any Search for a file on the FTP server dirinfo, readme, index ftpsearch.com ftp:// user: files.vasya.ru ftp:// files.vasya.ru

15 Distribution of software via FTP freeware – free software registerware – free registration by e-mail shareware (try before you buy) – shareware (time limit, annoying messages) demo versions – demonstration of software capabilities (limited functions) beta versions – preliminary (debugging) versions of commercial programs, the goal is to find errors

16 E-mail () commercial "at" "dog" (Russia) "cat" (Poland) "rose" (Turkey) XVI century: weight 10 kg, volume 15 l 1972 R. Tomlison SMTP POP3 mail server mailbox mail server mail server

17 E-mail Message Buying an Elephant Buying an Elephant To: From: Reply To: CC: Bcc: BC: Subject: Email Header Hello John! Do you have desires to buy an elephant? Sincerely, Vasily Pupkin, General Director, Horns and Hooves LLC, St. Petersburg, st. Rogokopytnaya, 2 tel. +7 (812) fax +7 (812) greeting body text signature company details attached files (attachments) attached files (attachments)

18 Mail programs Outlook Express - included in Windows Outlook - included in Microsoft Office TheBat (Features: creating messages, attaching files receiving and sending messages forwarding messages (forward) automatic checking of mail at a specified interval address book (list of contacts) sorting messages into folders many servers can work with mail through a Web site (Web interface)! ! !

19 Teleconferences, forums Teleconferences (conferences, newsgroups) 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 obscene language FAQ (Frequently Asked Questions) FAQ (Frequently Asked Questions) - a list of the most frequent questions of newcomers and answers to them . A thread is a chain of related messages that contains a question, answers to it, and comments. avatar nickname (pseudonym) quote Nick (English nickname) - nickname, pseudonym.

20 Search Engines Indexes are robots that constantly crawl the Internet and populate databases. Catalogs are databases that are filled manually by human experts (guides). give out a lot of links 1) some links do not correspond to the topic 2) it is difficult to select the right links correspond to the headings of the catalog fewer links list.mail.ru, Hybrid systems - index + catalog.

21 Real-time communication (online) Chats (English chat - chatter) real-time text messaging Web-chats (on Web-pages): all equal IRC-chats (Internet relay Chat, 1988) "talk" on channels, there are channel operators with privileges

22 Communication in real time (online) ICQ (English I Seek You), "ICQ", Internet pager. Registration: number Opportunities: dialog group discussion file exchange Russian version icq.rambler.ruicq.rambler.ru

23 Skype Internet phone (real-time conversation Skype PHONE STATION Free Skype to Skype calls File transfer Group and individual chats Teleconferencing (up to 9 people) Paid Calls to landlines and mobiles Receive Skype calls from regular phones Send and receive voice messages and SMS

24 Internet via mobile phone WAP (Wireless Application Protocol) download toys, music, weather only carrier sites, weather sites, e-mail, online shopping 1) high cost (old technology) 2) few GPRS (General Packet Radio Service) capabilities or EDGE (Enhanced Data for Global Evolution) built-in browser (Opera Mini - page compression) Java language support built-in program for can be used instead of a modem for a computer Smartphones: also music playback, video shooting, photo and video operating system, office programs

25 Ethics on the Internet Tolerance: do not suppress the statements of others do not harass or threaten others Ethics of trust: do not distribute the statements, images and opinions of others without their consent do not distort the facts, your own and others' opinions do not request or transmit information created by coercion to warn if the information can be misjudged by a naive person

26 Netiquette Netiquette (net + etiquette) - good manners when communicating on the Internet. E-mail: message subject, greeting, signature do not type sentences in capital letters do not send large files without agreement do not send executable files (*.exe) do not use obscene and slang expressions Forums: read the list of questions and answers (FAQ, FAQ) do not deviate from forum topics (off-topic - “off topic”) do not type sentences in capital letters do not insult participants Chats: do not interfere in someone else's conversation do not be offended if he left

• develop curiosity,
• ability to work in a group
• Teach students basic networking skills.

Educational:

• instill interest in the subject
• develop self-reliance and self-discipline skills.

Equipment: computer, interactive whiteboard, projector, presentation on the topic.

Lesson type: explanation of new material.

During the classes.

1. Organizing time(checking absentees, preparing for the lesson).
2. Checking homework using a presentation(2nd and 3rd slide). front poll.
3. Formulation of the problem.

When working on a personal computer offline, users can exchange information (programs, documents, etc.) using floppy disks, optical disks and flash memory. However, moving a storage medium between computers is not always possible and can take quite a long time. If there is only one printer in use, then printing documents also takes a lot of time. How to improve the user experience? (Answer: creating a computer network)

1. Explanation of the new topic.

The creation of computer networks is caused by the practical need for quick access to the information resources of other computers, as well as printers and other peripheral devices.

A local computer network is a network connecting two or more computers, allowing them to work together with programs and data. .

A local computer network unites computers installed at a relatively small distance from each other (in the same room or building). For example, in a school computer room.

What she does?

• Connects computers to share information
• Allows you to share common resources (printer, modem, disk memory, etc.)

In small local networks, all computers are usually equal, i.e. users themselves decide which resources of their computer to make available to other network users. Such networks are called peer-to-peer. For example, in our class there is a peer-to-peer computer network. All computers are equal in relation to each other. The disadvantage of such networks is the weak security of information from unauthorized access.

To increase productivity, as well as to ensure greater information security when storing information on the network, some computers are specially allocated to store the most important information. Such computers are called servers, and the local area network is called a server-based network. The rules for accessing information are set by one person - the network administrator.

Computers connected to a local network in the Windows operating system are included in the network folder. Each of the computers on the network is also a folder, which in turn contains folders of drives. If access is granted to the disks and folders of a computer or a connected printer, then any network user can use them as their own.

Every computer or printer connected to the local network must have a network card. The main function of the network card is to transmit and receive information from the network. Computers (network cards) are connected using a twisted pair cable. Computers can be either wired or wireless. Wireless LANs use an access point, and each computer must have a dedicated Wi-Fi type wireless network card installed.

Primary fastening. Answers to the questions posed.

5. Homework.

Before we do the practical part, let's write down the homework: pp. 81 - 84, Test questions after the paragraph.

Consolidation of what has been learned.

Create a Christmas card in Paint and send it over the network to a friend.

To receive a postcard, you need to open the Public Folder on your computer. The best postcards to print on the printer.

7. Completion of the lesson. Grading.

Guys, today we learned what a local network is and learned how to transmit and receive data over the network.

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"Presentation on the topic "Global network INTERNET. Search for information in it"»

Internet is … … a network that includes …, … and … networks and connects millions of … around the world.

Searching for information is one

of the most requested

in practice tasks that

have to decide

any user

Internet.

"An educated person is one who knows where to find what he does not know."

Georg Simmel

This is the least convenient

way, because with it

you can search for documents

only close in meaning

current document.

Search system

provides the ability to search for information on the Internet.

Most search engines look for information on World Wide Web sites.

www. yandex.ru

www. google.ru

www. rambler.ru

www. mail.ru

www. yahoo.com

www. nigma. en

www. aport. en

www. altavista.com

Yandex - Russian

web search engine.

Company website, Yandex.ru,

distinctive

Yandex feature -

possibility of accurate

search engine settings

Google . en

The leader of search engines on the Internet.

According to one version, Google is a distorted

spelling of the English word googol.

"Googol (googol)" is a mathematical

term for unit

100 zeros.

Rambler . en

Rambler created

in 1996.

search engine

understands and

distinguishes words

Russian,

English and

Ukrainian

languages. By

default

search in progress

in all forms

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1. What is the Internet?

2. What is a search engine?

3. What search engines do you know (learn)?