Basic principles of building a global network. Principles of building a global Internet network

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The Internet is a worldwide information computer network, which is a union of many regional computer networks and computers that exchange information with each other via public telecommunications channels (dedicated analog and digital telephone lines, optical communication channels and radio channels, including satellite communication lines).

Information on the Internet is stored on servers. Servers have their own addresses and are controlled by specialized programs. They allow you to forward mail and files, search databases, and perform other tasks.

Individual users' access to Internet information resources is usually carried out through a provider or corporate network. Provider - network service provider - a person or organization providing services for connecting to computer networks. The provider is an organization that has a modem pool for connecting to clients and accessing the World Wide Web.

The main cells of the global network are local area networks. If a local network is directly connected to a global network, then every workstation on this network can be connected to it. There are also computers that are directly connected to the global network. They are called host computers (host - master). A host is any computer that is a permanent part of the Internet, that is, connected via the Internet protocol to another host, which in turn is connected to another, and so on.

To connect communication lines to computers, special electronic devices are used, which are called network cards, network adapters, modems, etc. Almost all Internet services are built on the client-server principle. All information on the Internet is stored on servers. Information exchange between servers is carried out via high-speed communication channels or highways. Servers connected by high-speed highways make up the basic part of the Internet.

Individual users connect to the network through the computers of local Internet service providers, Internet providers, which have a permanent connection to the Internet. A regional provider connects to a larger national provider that has nodes in various cities of the country. Networks of national providers are combined into networks of transnational providers or first-tier providers. United networks of first-tier providers make up the global Internet network.

The transfer of information to the Internet is ensured by the fact that each computer on the network has a unique address (IP address), and network protocols ensure the interaction of different types of computers running different operating systems. The Internet primarily uses the TCP/IP family of network protocols (stack). At the data link and physical layers, the TCP/IP stack supports Ethernet, FDDI, and other technologies.

The basis of the TCP/IP protocol family is the network layer, represented by the IP protocol, as well as various routing protocols. This layer facilitates the movement of packets across the network and controls their routing. The packet size, transmission parameters, and integrity control are carried out at the TCP transport layer. The application layer integrates all the services that the system provides to the user. The main application protocols include: telnet remote access protocol, FTP file transfer protocol, HTTP hypertext transfer protocol, email protocols: SMTP, POP, IMAP, MIME.

The Beginnings of Website Building Topic 1. What is a website and how is it structured? The word site (English site) became established in Russian Internet terminology relatively recently. Previously, in 1995 -1996, the combinations “WWW page”, “WWW node” or “WWW server” were used with the same or approximately the same meaning. In fact, a site, as an information unit, is something fundamentally different from a WWW server (i.e., a program) or an Internet node (i.e., a computer). A website is a set of several tens, hundreds or even thousands of web pages linked together by a single theme, general design, mutual hypertext links and, as a rule, placement close to Internet standards (usually within the same domain name).

A domain name is a unique alphanumeric name that identifies a specific website. Domain names usually consist of two or more parts, separated by a period. The left side of the domain name corresponds to the end node of the network (that is, it is the most specific), while the right side is more general. Each machine on the network can have multiple domain names, but each domain name can point to only one machine. The domain name looks, for example, like this: www. ru, www. tomsk. net, www. school. tomsk. ru. A web page is a logical unit of the Internet, uniquely identified by an address (URL).

URL (from the English Uniform Resource Locator) is a unified information resource locator (a standardized string of characters indicating the location of a document on the Internet). A web page can consist of several parts (frames), each of which is a separate page with its own address, and can be static or dynamically generated.

Frames are HTML elements that appeared in browsers versions 3.0. They allow you to divide a page into several independent windows and place your own web page in each of them. A link from one window to another is possible. They are used mainly to organize menus that are constantly on the screen, while the information itself is located in another window. A web page may include text, hyperlinks, graphics, animation, sound, video, and scripts.

Hyperlink – text in an HTML document that denotes a link to other information on the Internet. To differentiate them from plain text, hyperlinks are usually bolded or underlined. A script is a small script program written in a programming language. There are client-side and server-side scripts. Client side scripts are usually written in Java. Script to improve the interactivity of the page. Server scripts are used to dynamically prepare information.

The fundamental difference between a website and material media is nonlinearity. This means that a single page itself does not have a fixed position in the space of the site, and a set of several pages does not have to form a linear (or any other) sequence. At the same time, the main, backbone connections between pages that exist on any site always form a certain structure that reflects the internal connections of the content. There are two main types of such structures: tree (hierarchical) and linear (sequential).

The tree structure of the site assumes that the content of each page (except the first) is included as a subsection in a higher-level page. Such a structure has a beginning - the first page, the root of the tree, but has no end; you can go down and up from level to level and move horizontally until you get bored or exhaust all the contents. The tree structure is best suited for collections of fairly heterogeneous or complexly arranged material - catalogues, collections of articles or references.

If the material is arranged in a logical structure - such as, for example, chapters of one book or sequential steps of placing an order in an electronic store - it is more convenient to use a linear structure. A linear chain of pages must have a beginning and an end, and there is usually no point in starting to get acquainted with the site from one of the intermediate pages, since it will be much more difficult for you to catch the thread of presentation than with a tree-like arrangement of the material.

Dynamic pages blur the harmonious structure of the site. On many modern sites it is simply impossible to tell exactly how many pages they consist of and how many links they contain. Dynamic page – in relation to an HTML page, this is a page of data elements that are generated from a database, i.e. a page generated “on the fly”, in the process of accessing the database. These pages change as the visitor reads and interacts with them.

IP addressing on the Internet Each computer connected to the Internet has a unique address. Computer addresses are double encoded: 1. Digital IP address 2. DNS address (domain address) IP addresses, represented in digital form (IP numbers), consist of four bytes, i.e., a 32-bit binary number, which is divided into four blocks of 8 bits. A digital IP address can be written as four decimal numbers separated by dots. For example: 195. 82. 54. 17. Each number should not exceed two hundred and fifty-six.

A domain address (DNS address) consists of several domains (alphanumeric symbols), which are separated from each other by a dot. The domain address is built on the basis of a hierarchical classification, i.e. the domain address includes several levels of domains, for example: lessons-tva. info. The top-level domain is located to the right of the name, and the lower-level domain is to the left. An Internet user does not work with IP addresses, but only with domain addresses. The DNS address is converted to a digital IP address by the Domain Name Server (DNS).

An IP address consists of two parts: the network number and the node (computer) number on the network. If an individual computer (host computer) or network is part of the Internet, then the IP address is assigned by a special division of the Internet. The distribution of IP addresses is carried out by the organization ICANN (Internet Corporation for Assigned Names and Numbers), and in Europe the distribution of IP addresses between regional providers is carried out by RIPE. The addresses of computers on the network are determined by network administrators.

There are several classes of IP addresses: A, B, C. Class A includes addresses in which the network number occupies one byte and the host number takes three bytes. The number of nodes in this network can reach 224. The range of network numbers A: 1. 0. 0. 0 - 126. 0. 0. 0. Class B includes addresses in which the network number occupies two bytes. The number of nodes in this network can reach 216. The range of network B numbers is: 128. 0. 0. 0 191. 255. 0. 0.

Class C includes addresses in which the network number occupies three bytes. The number of nodes in this network can reach 28 or 256. The range of network numbers C: 192.0.1.0 - 223.255.0.

When working on the Internet, it is not domain names that are used, but universal resource locators called URLs (Universal Resource Locator). A URL is the address of any resource (document, file) on the Internet; it indicates which protocol should be used to access it, which program should be run on the server, and which specific file should be accessed on the server. General view of the URL: protocol: //host computer/file name (for example: http: //lessons-tva. info/book. html).

Programs for viewing Web pages One of the main tasks of the Internet is storing and providing (upon request) the necessary information to users. To find the necessary information on the Internet, you need to know the address of the Web page (site) on which this information is located, have at least one of the Web page viewing applications installed on your PC, and have access to the global network.

A program for navigating (searching for information on the Internet) and viewing Web pages is called a browser. There are many browsers available nowadays. The most popular graphical browsers (two-dimensional): Internet Explorer, Mozilla Firefox, Flock (Firefox and Flock are based on Netscape code), Opera, Netscape Navigator, Google Chrome and others. The Safari browser for Windows is gaining popularity. The first graphical browser, Viola, appeared in 1992. Currently, three-dimensional browsers are being developed, for example the Clara browser

Popular text browsers (console browsers) are Lynx and Links (Links 2 supports graphics). Lynx and Links can be used on various platforms: Unix, Macintosh, Windows and other operating systems. These browsers are advisable to use for weak PCs and low-speed Internet connections. In addition, these browsers can be used for powerful PCs and high-speed lines for the purpose of navigation or Internet surfing (for quick access to the required information on sites), and to view the required Web pages, it is advisable to use browsers with a graphical interface.

Browsers are a client of the World Wide Web, that is, an application program that, upon request, receives documents from Web servers, interprets data from Web pages and displays them on the screen.

Using a browser, you can easily search for a desired web page on the Internet by typing one or more words in the address bar (search bar) of the browser and pressing Enter to begin the search. Browsers provide access not only to Web servers, but also to other Internet servers (FTP servers, Gopher servers and Use.Net teleconferencing servers). One of the most popular browsers is Internet Explorer, since the Internet Explorer application is included in the Windows operating system.

Mail applications, mail interface MAIL email appeared before the creation of the Internet, that is, before the advent of packet-switching networks based on the TCP/IP protocol stack. At that time, email transfer between computers was carried out via a modem connection using the UUCP (Unix-to-Unix Co. Py) protocol.

With the introduction of the domain name system (Domain Name Server, DNS - domain name server), domain names were introduced into the email address: user_name@domain_name (user such and such on computer such and such.), for example tva-web@narod. ru. The @ symbol - “this is commercial” in the email address was used by the developer instead of the preposition at (at). Dedicated servers began to be used for e-mail; mailboxes were located on mail servers where mail was received and from where users took it. Special protocols have been developed for the operation of mail clients and servers.

Currently, the most common email protocols are: SMTP and POP 3. Emails are sent to the outgoing mailbox using SMTP and received from the incoming mailbox using POP 3 or Internet Message Access Protocol l. MAP 4. In a global network, email is transmitted between nodes (mail servers) using mail forwarding programs. Message switching is used to transmit emails over the network.

Message switching is the process of sending data, including reception, storage, selection of the initial direction and further transmission of message blocks (without breaking them into packets). Currently, both mail clients and web mail interfaces are used to work with e-mail, which are located on mail web servers and are designed to work with e-mail. Mail application programs include, for example, applications: Outlook Express, The Bat, and mail web interfaces are hosted on mail servers: mail. ru, hotmail. ru and so on.

Why are local networks needed, and what are they? How to connect several computer devices to one Internet channel at once? What equipment is required to build a home network? You will receive answers to all these and other equally important questions in this material.

Introduction

Before you learn how to design and configure home local networks yourself, let’s immediately answer the most important question: “Why are they needed?”

The concept of a local network itself means the unification of several computers or computer devices into a single system for the exchange of information between them, as well as the sharing of their computing resources and peripheral equipment. Thus, local networks allow:

Exchange data (movies, music, programs, games, etc.) between network members. At the same time, to watch movies or listen to music, it is absolutely not necessary to record them on your hard drive. The speeds of modern networks allow this to be done directly from a remote computer or multimedia device.

Connect several devices simultaneously to the global Internet through one access channel. This is probably one of the most popular functions of local networks, because these days the list of equipment that can use a connection to the World Wide Web is very large. In addition to all kinds of computer equipment and mobile devices, TVs, DVD/Blu-Ray players, multimedia players and even all kinds of household appliances, from refrigerators to coffee makers, have now become full participants in the network.

Share computer peripherals , such as printers, MFPs, scanners and network attached storage (NAS).

Share the computing power of computers of network participants. When working with programs that require complex calculations, such as 3D visualization, to increase productivity and speed up data processing, you can use the free resources of other computers on the network. Thus, having several weak machines connected to a local network, you can use their combined performance to perform resource-intensive tasks.

As you can see, creating a local network even within one apartment can bring a lot of benefits. Moreover, having several devices at home that require an Internet connection has long been not uncommon, and combining them into a common network is an urgent task for most users.

Basic principles of building a local network

Most often, local networks use two main types of data transfer between computers - via wire, such networks are called cable and use Ethernet technology, and also using a radio signal over wireless networks built on the basis of the IEEE 802.11 standard, which is better known to users under the name Wi -Fi.

Today, wired networks still provide the highest bandwidth, allowing users to exchange information at speeds of up to 100 Mbps (12 Mbps) or up to 1 Gbps (128 Mbps) depending on the equipment used (Fast Ethernet or Gigabit Ethernet). And although modern wireless technologies, purely theoretically, can also provide data transfer up to 1.3 Gbit/s (Wi-Fi 802.11ac standard), in practice this figure looks much more modest and in most cases does not exceed 150 - 300 Mbit/s. The reason for this is the high cost of high-speed Wi-Fi equipment and the low level of its use in current mobile devices.

As a rule, all modern home networks are arranged according to the same principle: user computers (workstations) equipped with network adapters are connected to each other through special switching devices, which can be: routers (routers), switches (hubs or switches), points access or modems. We will talk in more detail about their differences and purposes below, but for now just know that without these electronic boxes, it will not be possible to combine several computers into one system at once. The maximum that can be achieved is to create a mini-network of two PCs by connecting them to each other.

At the very beginning, you need to determine the basic requirements for your future network and its scale. After all, the choice of the necessary equipment will directly depend on the number of devices, their physical placement and possible connection methods. Most often, a home local network is combined and can include several types of switching devices. For example, desktop computers can be connected to the network using wires, and various mobile devices (laptops, tablets, smartphones) can be connected via Wi-Fi.

For example, consider the diagram of one of the possible options for a home local network. It will involve electronic devices designed for various purposes and tasks, as well as using different types of connections.

As can be seen from the figure, several desktop computers, laptops, smartphones, set-top boxes (IPTV), tablets and media players and other devices can be combined into a single network. Now let's figure out what equipment you will need to build your own network.

LAN card

A network card is a device that allows computers to communicate with each other and exchange data on a network. All network adapters can be divided into two large groups by type - wired and wireless. Wired network cards allow you to connect electronic devices to a network using Ethernet technology using a cable, while wireless network adapters use Wi-Fi radio technology.

As a rule, all modern desktop computers are already equipped with Ethernet network cards built into the motherboard, and all mobile devices (smartphones, tablets) are equipped with Wi-Fi network adapters. At the same time, laptops and ultrabooks are mostly equipped with both network interfaces at once.

Despite the fact that in the vast majority of cases, computer devices have built-in network interfaces, sometimes it becomes necessary to purchase additional cards, for example, to equip the system unit with a Wi-Fi wireless communication module.

Based on their design implementation, individual network cards are divided into two groups - internal and external. Internal cards are designed for installation in desktop computers using interfaces and their corresponding PCI and PCIe connectors. External cards are connected via USB connectors or legacy PCMCIA (laptops only).

Router (Router)

The main and most important component of a home local network is a router or router - a special box that allows you to combine several electronic devices into a single network and connect them to the Internet through one single channel provided to you by your provider.

A router is a multifunctional device or even a minicomputer with its own built-in operating system, which has at least two network interfaces. The first one is LAN (Local Area Network ) or LAN (Local Area Network) is used to create an internal (home) network, which consists of your computer devices. The second - WAN (Wide Area Network) or WAN (Wide Area Network) is used to connect a local network (LAN) to other networks and the World Wide Web - the Internet.

The main purpose of devices of this type is to determine the routes of data packets that the user sends to or requests from other, larger networks. It is with the help of routers that huge networks are divided into many logical segments (subnets), one of which is the home local network. Thus, at home, the main function of a router can be called organizing the transfer of information from a local network to a global one, and vice versa.

Another important job of a router is to limit access to your home network from the World Wide Web. Surely you are unlikely to be happy if anyone can connect to your computers and take or delete from them whatever they want. To prevent this from happening, the data flow intended for devices belonging to a specific subnet must not go beyond its boundaries. Therefore, from the general internal traffic generated by local network participants, the router selects and sends to the global network only that information that is intended for other external subnets. This ensures the security of internal data and saves overall network bandwidth.

The main mechanism that allows the router to limit or prevent access from the public network (outside) to devices on your local network is called NAT (Network Address Translation). It also provides all users of your home network with access to the Internet by converting multiple internal device addresses into one public external address that is provided to you by your Internet service provider. All this makes it possible for computers on a home network to easily exchange information with each other and receive it from other networks. At the same time, the data stored in them remains inaccessible to external users, although access to it can be provided at any time at your request.

In general, routers can be divided into two large groups - wired and wireless. Already from the names it is clear that all devices are connected to the first ones only using cables, and to the second ones, both with the help of wires and without them using Wi-Fi technology. Therefore, at home, wireless routers are most often used to provide Internet access and network computer equipment using various communication technologies.

To connect computer devices using cables, the router has special sockets called ports. In most cases, the router has four LAN ports for connecting your devices and one WAN port for connecting your ISP cable.

In order not to overload the article with redundant information, we will not consider in detail the main technical characteristics of routers in this chapter; I will talk about them in a separate article, on choosing a router.

In many cases, a router may be the only component needed to build your own local network, since there is simply no need for the rest. As we have already said, even the simplest router allows you to connect up to four computer devices using wires. Well, the number of equipment that receives simultaneous access to the network using Wi-Fi technology can be in the tens, or even hundreds.

If, at some point, the number of LAN ports on the router is no longer enough, then to expand the cable network, you can connect one or more switches to the router (discussed below), which act as splitters.

Modem

In modern computer networks, a modem is a device that provides access to the Internet or access to other networks through regular wired telephone lines (xDSL class) or using wireless mobile technologies (3G class).

Conventionally, modems can be divided into two groups. The first includes those that connect to a computer via a USB interface and provide network access to only one specific PC, to which the modem is directly connected. In the second group, the already familiar LAN and/or Wi-Fi interfaces are used to connect to a computer. Their presence indicates that the modem has a built-in router. Such devices are often called combined, and they should be used to build a local network.

When choosing DSL equipment, users may encounter certain difficulties caused by confusion in its names. The fact is that often in the assortment of computer stores, two very similar classes of devices are located side by side: modems with built-in routers and routers with built-in modems. What is the difference between them?

These two groups of devices practically do not have any key differences. Manufacturers themselves position a router with a built-in modem as a more advanced option, equipped with a large number of additional functions and improved performance. But if you are only interested in basic capabilities, for example, such as connecting all computers on your home network to the Internet, then there is not much difference between modem-routers and routers where a DSL modem is used as an external network interface.

So, to summarize, a modern modem with which you can build a local network is, in fact, a router with an xDSL or 3G modem as an external network interface.

A switch or switch is used to connect various nodes of a computer network and exchange data between them via cables. The role of these nodes can be either individual devices, for example a desktop PC, or entire groups of devices united into an independent network segment. Unlike a router, a switch has only one network interface - LAN and is used at home as an auxiliary device primarily for scaling local networks.

To connect computers using wires, like routers, switches also have special socket ports. In models aimed at home use, their number is usually five or eight. If at some point the number of ports on the switch is no longer enough to connect all devices, you can connect another switch to it. Thus, you can expand your home network as much as you like.

Switches are divided into two groups: managed and unmanaged. The first, as the name suggests, can be controlled from the network using special software. Although they have advanced functionality, they are expensive and not used at home. Unmanaged switches distribute traffic and regulate the speed of data exchange between all network clients automatically. These devices are ideal solutions for building small and medium-sized local networks, where the number of participants in the exchange of information is small.

Depending on the model, switches can provide a maximum data transfer speed of either 100 Mbit/s (Fast Ethernet) or 1000 Mbit/s (Gigabit Ethernet). Gigabit switches are best used for building home networks where you plan to frequently transfer large files between local devices.

Wireless access point

To provide wireless access to the Internet or local network resources, in addition to a wireless router, you can use another device called a wireless access point. Unlike a router, this station does not have an external WAN network interface and is equipped in most cases with only one LAN port for connecting to a router or switch. Thus, you will need an access point if your local network uses a regular router or modem without Wi-Fi support.

The use of additional access points in a network with a wireless router may be justified in cases where a large Wi-Fi coverage area is required. For example, the signal strength of a wireless router alone may not be enough to completely cover the entire area in a large office or multi-story country house.

Access points can also be used to organize wireless bridges, allowing you to connect individual devices, network segments or entire networks with each other using a radio signal in places where laying cables is undesirable or difficult.

Network cable, connectors, sockets

Despite the rapid development of wireless technologies, many local networks are still built using wires. Such systems have high reliability, excellent throughput and minimize the possibility of unauthorized connection to your network from the outside.

To create a wired local network in home and office environments, Ethernet technology is used, where the signal is transmitted over the so-called “twisted pair” (TP-Twisted Pair) - a cable consisting of four copper pairs of wires twisted together (to reduce interference).

When building computer networks, predominantly unshielded cable of the CAT5 category is used, and more often its improved version CAT5e. Cables of this category allow you to transmit a signal at a speed of 100 Mbit/s when using only two pairs (half) of wires, and 1000 Mbit/s when using all four pairs.

To connect to devices (routers, switches, network cards, and so on), 8-pin modular connectors, commonly called RJ-45 (although their correct name is 8P8C), are used at the ends of the twisted pair cable.

Depending on your desire, you can either buy ready-made (with crimped connectors) network cables of a certain length, called “patch cords”, at any computer store, or purchase twisted pair cables and connectors separately, and then make your own cables of the required size in the right quantity. You will learn how this is done in a separate material.

Using cables to connect computers into a network, of course, you can connect them directly from switches or routers to the connectors on the PC’s network cards, but there is another option - using network sockets. In this case, one end of the cable is connected to the switch port, and the other to the internal contacts of the socket, into the external connector of which you can subsequently connect computer or network devices.

Network sockets can be either built into the wall or mounted externally. Using sockets instead of protruding cable ends will give a more aesthetically pleasing look to your workspace. It is also convenient to use sockets as reference points for various network segments. For example, you can install a switch or router in the hallway of an apartment, and then thoroughly route cables from it to sockets located in all the necessary rooms. Thus, you will receive several points located in different parts of the apartment, to which you can at any time connect not only computers, but also any network devices, for example, additional switches to expand your home or office network.

Another little thing that you may need when building a cable network is an extension cord that can be used to connect two twisted pairs with already crimped RJ-45 connectors.

In addition to their intended purpose, extension cords are convenient to use in cases where the end of the cable ends not with one connector, but with two. This option is possible when building networks with a capacity of 100 Mbit/s, where it is enough to use only two pairs of wires to transmit a signal.

You can also use a network splitter to connect two computers to one cable at once without using a switch. But again, it is worth remembering that in this case the maximum data exchange speed will be limited to 100 Mbit/s.

For more information about crimping twisted pair cables, connecting sockets and the characteristics of network cables, read the special material.

Now that we've become familiar with the basic components of a local area network, it's time to talk about topology. In simple terms, a network topology is a diagram that describes the locations and methods of connecting network devices.

There are three main types of network topologies: Bus, Ring and Star. With a bus topology, all computers on the network are connected to one common cable. To unite PCs into a single network using the “Ring” topology, they are connected in series with each other, with the last computer connecting to the first. In a star topology, each device is connected to the network through a special hub using a separate cable.

Probably, the attentive reader has already guessed that to build a home or small office network, the “Star” topology is predominantly used, where routers and switches are used as hub devices.

Creating a network using the Star topology does not require deep technical knowledge and large financial investments. For example, using a switch that costs 250 rubles, you can connect 5 computers into a network in a few minutes, and using a router for a couple of thousand rubles, you can even build a home network, providing several dozen devices with access to the Internet and local resources.

Another undoubted advantage of this topology is good expandability and ease of upgrading. Thus, network branching and scaling is achieved by simply adding additional hubs with the necessary functionality. You can also change the physical location of network devices or swap them at any time in order to achieve more practical use of the equipment and reduce the number and length of connecting wires.

Despite the fact that the Star topology allows you to quickly change the network structure, the location of the router, switches and other necessary elements must be thought out in advance, in accordance with the layout of the room, the number of devices being connected and how they are connected to the network. This will minimize the risks associated with purchasing unsuitable or redundant equipment and optimize the amount of your financial costs.

Conclusion

In this material, we examined the general principles of building local networks, the main equipment that is used and its purpose. Now you know that the main element of almost any home network is a router, which allows you to network many devices using both wired (Ethernet) and wireless (Wi-Fi) technologies, while providing them all with an Internet connection through one single channel.

Switches, which are essentially splitters, are used as auxiliary equipment for expanding connection points to a local network using cables. To organize wireless connections, access points are used, which allow, using Wi-Fi technology, not only to connect all kinds of devices wirelessly to the network, but also to connect entire segments of the local network together in a “bridge” mode.

To understand exactly how much and what kind of equipment you will need to purchase to create a future home network, be sure to first draw up its topology. Draw a diagram of the location of all devices participating in the network that will require a cable connection. Depending on this, select the optimal location for the router and, if necessary, additional switches. There are no uniform rules here, since the physical location of the router and switches depends on many factors: the number and type of devices, as well as the tasks that will be assigned to them; layout and size of the room; requirements for the aesthetic appearance of switching nodes; possibilities for laying cables and others.

So, as soon as you have a detailed plan for your future network, you can begin to select and purchase the necessary equipment, install it and configure it. But we will talk about these topics in our next materials.

Internet– worldwide information computer network.

Basic principles of building the Internet

1.Decentralization of management– there is no single control center for the Internet.

2. The failure of one computer or part of the network does not lead to the inoperability of the entire network.

3. Model of information transfer based on packet switching( at the transport level is implemented in the form TCP/IP transmission protocols). Before transmission, any array of information is first divided into the required number of small portions (packets). Each packet is assigned a number, and it is supplied with the sender's address, the recipient's address and some service information. Further, packets are transmitted over the network independently of all others, and, in principle, can follow different routes. After all packets arrive at their destination, the original message is assembled from them, according to the numbers received. The integrity of the packets is checked, and if information is damaged during transport, the receiving system requests the retransmission of only one small packet, and not the entire array.

4. The use of TCP/IP protocols ensures reliable delivery of information on the Internet.

TCP/IP (Transmission Control Protocol/Internet Protocol, Transmission Control Protocol/Internet Protocol)– a protocol (family of protocols), which is a standard for transmitting data between networks, including the Internet. The TCP (Transmission Control Protocol) breaks information into chunks (packets) and numbers them. The Internet Protocol (IP) then adds service information to each packet with the source and destination addresses and ensures that all packets are delivered. Thanks to this method of transmitting information, there is no need to establish a separate communication channel between two computers on the Internet. Each computer can simultaneously receive packets from a large number of other computers. TCP/IP is the main protocol of the Internet, therefore, in order to work on the global network, the operating system installed on the user's computer must provide support for the specified protocol. All modern operating systems (MS Windows, Unix-like) contain tools for installing and configuring the TCP/IP network protocol

Internet addressing. To distinguish computers on the Internet, each of them is assigned an address, which is a unique chain of numbers or a symbolic computer name corresponding to this chain. There is a special organization on the Internet that checks and issues addresses. When sending information using TCP/IP protocols, the digital (IP) address of the computer is used.

IP address– a four-byte binary number, represented as four decimal numbers (octets), separated by a dot, and allowing one to uniquely identify a computer connected to the Internet.

Example IP address: 193.233.85.46.

The host address is logically divided into two parts, one of which is called the Network ID, and the other is called the Host ID (Fig. 1).

Fig.1. Components of an IP Address

A global network can connect many networks, each of which has its own Network ID. Each network can contain a number of nodes, each of which has its own Host ID. Thus, using a pair of numbers (Network ID, Host ID) you can address any node connected to a global network based on the TCP/IP protocol. There are three classes of addresses, designated by the letters A, B and C, for which different bit widths of the Network ID and Host ID fields are used

As can be seen from the table, the address belongs to class A if the first bit is 0, B - if 10, C-110.

Networks with class A addresses are large networks that connect a maximum of 16,777,214 nodes. Due to the selected network number range, there may be as few as 126 such large networks.

There can be up to 16384 networks with class B addresses, since two bytes are allocated for the identifier of such networks. Moreover, the first byte can take values in the range from 128 to 191. Two bytes are also allocated for the node identifier. As a result, up to 65,534 nodes can be connected to a network with Class B addresses. There can be 2,097,151 networks with class C addresses, in which the network identifier is specified by three bytes and the node identifier by one byte, uniting up to 254 nodes each.

When configuring the TCP/IP network component, you will need to specify a parameter such as a subnet mask. The subnet mask is a 32-bit number that is used to separate the Network ID and Host ID components from a 32-bit address. Network identifier extraction is performed by a logical AND operation between the address and the subnet mask. By default, the subnet mask uses the following values (which depend on the network address class):

A subnet mask can also be used to divide networks into subnets.

Some IP addresses are reserved for special purposes (examples):

· address 127.0.0.1 is used for testing network applications;

· an address in which the network number is indicated, and the node number is zero, is used to designate the network (an example of such an address is 193.24.2.0);

· if all bits of the node number field are equal to one (for example, 193.24.2.255), then this is a broadcast address, using which you can transmit packets to all nodes of the specified network at once;

For the convenience of Internet users, a digital address can be represented as a chain of characters. This means that the computer has a name or domain address.

Domain address– representation of a computer’s address on the Internet in the form of several chains of characters (domains), separated by a dot.

Example domain name: inf.susu.ac.ru.

On the Internet, there is a DNS database that stores information about the correspondence of domain and digital addresses, as well as a DNS server program that automatically resolves addresses.

DNS server (Domain Name System)– a program that converts a domain address into a digital (IP) address and vice versa.

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1. Networking BasicsInternetand its basic protocols

The Internet is a worldwide information computer network, which is a union of many regional computer networks and computers that exchange information with each other via public telecommunications channels (dedicated telephone analog and digital lines, optical communication channels and radio channels, including satellite communication lines).

Information exchange between network servers is carried out via high-speed communication channels (dedicated telephone lines, fiber optic and satellite communication channels). Individual users' access to Internet information resources is usually carried out through a provider or corporate network.

Provider - network service provider - a person or organization providing services for connecting to computer networks. The provider is an organization that has a modem pool for connecting to clients and accessing the World Wide Web.

The main cells of the global network are local area networks. If a local network is directly connected to a global network, then every workstation on this network can be connected to it.

There are also computers that are directly connected to the global network. They are called host computers (host - master). A host is any computer that is a permanent part of the Internet, i.e. connected via Internet protocol to another host, which in turn is connected to another, and so on.

To connect communication lines to computers, special electronic devices are used, which are called network cards, network adapters, modems, etc.

Almost all Internet services are built on the client-server principle. All information on the Internet is stored on servers. Information exchange between servers is carried out via high-speed communication channels or highways. Servers connected by high-speed highways make up the basic part of the Internet.

Individual users connect to the network through the computers of local Internet service providers, Internet Service Providers (ISPs), which have a permanent connection to the Internet. A regional provider connects to a larger national provider that has nodes in various cities of the country. Networks of national providers are combined into networks of transnational providers or first-tier providers. United networks of first-tier providers make up the global Internet network.

The Internet primarily uses the TCP/IP family of network protocols (stack). At the data link and physical layers, the TCP/IP stack supports Ethernet, FDDI, and other technologies. The basis of the TCP/IP protocol family is the network layer, represented by the IP protocol, as well as various routing protocols. This layer facilitates the movement of packets across the network and controls their routing. The packet size, transmission parameters, and integrity control are carried out at the TCP transport layer.

The application layer integrates all the services that the system provides to the user. The main application protocols include: telnet remote access protocol, FTP file transfer protocol, HTTP hypertext transfer protocol, email protocols: SMTP, POP, IMAP, MIME.

2. ProtocolsInternet

internet network protocol server

It is obvious that sooner or later computers located in different parts of the globe, as their number increased, had to acquire some means of communication. Computer networks became such means. Networks are local and global. A local area network is a network that connects computers geographically located a short distance from each other - for example, in the same building. Global networks serve to connect networks and computers that are separated by long distances - hundreds and thousands of kilometers. The Internet belongs to the class of global networks.

Simply connecting one computer to another is a necessary step to create a network, but not sufficient. To start transmitting information, you need to make sure that computers “understand” each other. How do computers “communicate” over a network? To provide this opportunity, special tools called “protocols” were developed. A protocol is a set of rules according to which information is transmitted through a network. The concept of a protocol is not only applicable to the computer industry. Even those who have never dealt with the Internet have most likely worked in everyday life with some devices whose functioning is based on the use of protocols. Thus, a regular public telephone network also has its own protocol, which allows devices, for example, to establish that the handset has been picked up at the other end of the line or to recognize a disconnection signal and even the caller’s number.

Based on this natural need, the world of computers needed a single language (that is, a protocol) that would be understandable to each of them.

The main protocols used in the Internet:

3. Brief description of protocols

The best minds of humanity worked on creating the protocols necessary for the existence of a global network. One of them was Vinton G. Cerf. Now this man is called the “father of the Internet.” In 1997, US President Bill Clinton awarded Vinton Cerf and his colleague Robert E. Kahn the National Medal of Technology, recognizing their contributions to the development of the Internet. Vinton Cerf is currently Senior Vice President of Internet Architecture at MCI WorldCom Inc.

In 1972, a group of developers led by Vinton Cerf developed the TCP/IP protocol - Transmission Control Protocol/Internet Protocol.

The experiment to develop this protocol was commissioned by the US Department of Defense. This project is called ARPANet (Advanced Research Projects Agency Network). Obviously, in a war situation, when the need for information exchange is more acute than ever, the problem arises of the unpredictability of the state of the path along which this or that information will be transmitted - any of the transmission nodes can be disabled by the enemy at any time. Therefore, the main task when developing a network protocol was its “unpretentiousness” - it had to work with any network environment and, in addition, have flexibility in choosing a route when delivering information.

TCP/IP later outgrew its original purpose and became the basis for the rapidly developing global network now known as the Internet, as well as smaller networks using Internet technologies - intranets. TCP/IP standards are open and are constantly being improved.

In fact, TCP/IP is not one protocol, but a whole set of protocols that work together. It consists of two levels. The upper-level protocol, TCP, is responsible for the correct conversion of messages into information packets, from which the original message is assembled at the receiving side. The lower layer protocol, IP, is responsible for ensuring that messages are correctly delivered to the specified address. Sometimes packets of the same message can be delivered via different paths.

The HTTP protocol (Hypertext Transfer Protocol) is a higher-level protocol than the TCP/IP protocol, an application-level protocol. HTTP was designed to transport Web pages efficiently over the Internet. It is thanks to HTTP that we have the opportunity to contemplate the pages of the Web in all their splendor. The HTTP protocol is the basis of the World Wide Web.

You issue HTTP commands using the browser interface, which is an HTTP client. When you click on a link, the browser requests the Web server for data from the resource to which the link points - for example, the next Web page.

In order for the text that makes up the content of Web pages to be displayed on them in a certain way - in accordance with the intent of the page creator - it is marked up using special text marks - HyperText Markup Language (HTML) tags.

The addresses of Internet resources that you access via the HTTP protocol look something like this: http://www….

The FTP (File Transfer Protocol) protocol is specifically designed for transferring files over the Internet. We'll talk about it in detail later. Now let's just say that the address of the FTP resource on the Internet looks like this: ftp://ftp....

Using this protocol, you can connect to a remote computer as a user (if you have the appropriate rights, that is, you know the username and password) and perform actions on its files and applications in the same way as if you were working on your own computer.

Telnet is a terminal emulation protocol. You can work with it from the command line. If you need to use the services of this protocol, you should not scour the wilds of the Internet in search of a suitable program. A Telnet client is supplied, for example, with Windows 98.

To command the Telnet client to connect to a remote computer, connect to the Internet, select Run from the Start menu and type in the input line, for example, the following: telnet lib.ru

WAIS stands for Wide-Area Information Servers. This protocol was developed for searching information in databases. The WAIS information system is a distributed database system where individual databases are stored on different servers. Information about their content and location is stored in a special database - the server directory. Information resources are viewed using the WAIS client program.

Information is searched using keywords specified by the user. These words are entered for a specific database, and the system finds all the corresponding fragments of text on all servers where the data in this database is located. The result is presented as a list of links to documents indicating how often the searched word and all searched words in the aggregate appear in this document.

Even today, when the WAIS system may be considered obsolete, experts in many fields, when conducting scientific research, nevertheless turn to it in search of specific information that they cannot find through traditional means.

The WAIS resource address on the Internet looks something like this: wais://site.edu.

The Gopher protocol is an application layer protocol developed in 1991. Before the widespread use of the World Wide Web hypertext system, Gopher was used to extract information (mostly text) from a hierarchical file structure. Gopher was the forerunner of the WWW, allowing you to navigate from one page to another using a menu, gradually narrowing the range of information displayed. Gopher client programs had a text interface. However, Gopher menu items could point not only to text files, but also, for example, to telnet connections or WAIS databases.

Gopher translates as “gopher”, which reflects the glorious university background of the developers of this system. The student sports teams at the University of Minnesota were called the Golden Gophers.

Gopher resources can now be viewed using a regular Web browser, as modern browsers support this protocol.

Gopher information resource addresses look something like this: gopher://gopher.tc.umn.edu.

WAP (Wireless Application Protocol) was developed in 1997 by a group of companies Ericsson, Motorola, Nokia and Phone.com (formerly Unwired Planet) in order to provide access to Internet services to users of wireless devices such as mobile phones, pagers, electronic organizers etc., using different communication standards.

For example, if your mobile phone supports the WAP protocol, then by typing the address of the desired Web page on its keyboard, you can see it (in a simplified form) directly on the phone’s display. Currently, the vast majority of device manufacturers have already switched to producing models with WAP support, which also continues to improve.

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Basic principles of building a global network. Principles of building a global Internet network

Introduction

Basic principles of building a local network

LAN card

Router (Router)

Modem

Wireless access point

Network cable, connectors, sockets

Conclusion

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