Principles of building a global Internet network. Internet structure: basic principles of operation Network technologies. Global networks and global network technologies
We are starting to publish a series of articles on the topic of deploying a small (within a home or small office) local network and connecting it to the Internet.
I believe that the relevance of this material today is quite high, since just in the last couple of months several of my friends who have a good knowledge of computers in general asked me questions about network topics that I considered obvious. Apparently they are not for everyone ;-)
Throughout the article, terms from the networking field will be used, most of them are explained in the mini-FAQ about networks compiled by Dmitry Redko.
Unfortunately, this material has not been updated for a long time. Although it has not lost its relevance, there are quite a lot of gaps in it, so if there are volunteers to fill these gaps, write to the email listed at the end of this article.
The first time you use a network term, it will provide a hyperlink to an explanation of it in the FAQ. If some terms are not explained throughout the article or in the FAQ, feel free to mention this fact in where this article will be discussed.
So. In the first part, the simplest case will be considered. We have 2 or more computers with a network card built into the motherboard or installed separately, a switch (switch) or even without it, as well as an Internet channel provided by the nearest provider.
Let us note that all computers have the Microsoft Windows XP Professional operating system installed with Service Pack version 1. I will not say that this is the most widespread OS currently installed on computers, but it would take quite a long time to consider all the existing families of the same Microsoft (but if there are many suffering, we will analyze others). OS language version is English. In the Russian version, everything will work in the same way; readers will only need to find the correspondence of the Russian analogues of the names in the screenshots presented below.
If we have only two computers and there is no switch, then to create a network between two computers we need a network card in each of them and a cross-over cable to connect the computers with each other.
Why cross-over and why is a regular cable bad? In the 10 and 100 Mbit Ethernet standards (10Base-T and 100Base-TX), 4 wires are used for a twisted pair (two pairs of wires twisted together). Typically, a twisted pair cable has 8 wires, but only 4 of them are used (all eight are used in Gigabit Ethernet).
After receiving the cable, we connect the network cards of the computers using it and voila - everything should work (at the physical level). To check the functionality of the network at the physical level (signal level), it makes sense to look at the indicators (most often green) that are located on the network card near the RJ-45 connector. At least one of them must be responsible for indicating the presence of a link (physical connection). If the indicators on both network cards light up, then there is a physical link and the cable is crimped correctly. A lit indicator on only one of the two cards does not mean that everything is in order at the physical level. The blinking of these (or adjacent) indicators signals data transfer between computers. If the indicators on both cards do not light up, then the cable is most likely incorrectly crimped or damaged. It is also possible that one of the network cards has failed.
Of course, what is described in the previous paragraph does not mean that the operating system sees the network card. The lighting of the indicators only indicates the presence of a physical link between the computers, nothing more. In order for Windows to see a network card, you need a driver for this card (usually, the operating system itself finds the one you need and installs it automatically). Quote from the forum: " Just yesterday I diagnosed a case with a connected network card that was not fully inserted into the PCI connector. As a result, the network “physically” worked, but the OS did not see it.».
Let's consider the second situation. There is a switch and two or more computers. If two computers can still be connected without a switch, then if there are three (or more), then combining them without a switch is a problem. Although the problem can be solved - to combine three computers, you need to insert two network cards into one of them, switch this computer to router mode and connect it to the two remaining machines. But a description of this process is beyond the scope of this article. Let us dwell on the fact that to unite three or more computers into one local network, you need a switch (however, there are other options: you can connect computers using a FireWire interface or a USB DataLink cable; as well as using wireless (WiFi) cards, transferred to Ad Hoc operating mode... but more on that in the next series).
Computers are connected to the switch using a straight cable. Which termination option (568A or 568B) will be chosen is absolutely not important. The main thing to remember is that on both sides of the cable it (the termination) matches.
After crimping the cable (or purchasing it in a store) and connecting all existing computers to the switch, you should check the presence of a physical link. The check proceeds similarly to the method described above for two computers. The switch should also have indicators next to the ports to indicate the presence of a physical connection. It may well turn out that the indicators are not located next to the port (top, side, bottom) but are placed on a separate panel. In this case, they will be numbered according to port numbers.
Having reached this paragraph, we already have 2 or more computers physically connected to a local network. Let's move on to setting up the operating system.
First, let's check that the IP addressing settings on the network card are correct. By default, Windows OS (2K/XP) itself assigns the necessary IP addresses to the cards, but it’s better to see for yourself.
Let's go to the network card settings. This can be done in two ways, through the control panel (Start -> Control Panel -> Network Connection)
Or, if the Network Places is on the desktop, then just right-click on it and select Properties.
In the window that appears, select the required network adapter (usually there is only one). The new window tells us quite a lot of information. Firstly, the connection status (in this case - Connected, i.e. there is a physical connection) and its speed (100 Mbit). As well as the number of sent and received packets. If the number of received packets is zero, and there is more than one computer on the network (turned on), then this may indicate a malfunction of our network card or switch port (if the computer is connected to it). It is also possible that the cable itself is faulty.
By selecting the Support tab, you can find out the current IP address and subnet mask assigned to the network card. By default, Windows OS gives adapters IP addresses in the range 169.254.0.0 -- 169.254.255.254 with a subnet mask of 255.255.0.0. Discussion of masks, subnet classes, and so on is beyond the scope of this article. The main thing to remember is that the subnet mask of all computers on the same network must be the same, but the IP addresses must be different. But again, the digits of the IP address, which coincide in positions with the non-zero digits of the subnet mask, must be the same on all computers, i.e. in this example, all hosts from the local network in the IP address will have the same first two digit positions - 169.254.
The IP settings of the network card can also be set manually (Network adapter properties -> Properties -> Internet Protocol (TCP/IP) -> Properties). But in most cases, it makes sense to set the settings to the default value (automatic detection of IP address and DNS) and the operating system will configure the network adapters itself.
In addition to network addresses, all computers must be given the same workgroup name. This is configured in the system settings (System Properties). You can get there through the control panel (System -> Computer Name). Of course, you can give different names to workgroups. This is convenient if you have many computers on the network and need to somehow logically divide the working machines among themselves. The consequence of this will be the appearance of several workgroups in the network environment (instead of one).
or, if the My Computer icon was displayed on the desktop, then right-click on this icon and select (Properties -> Computer Name).
In the window that appears (appearing after clicking the Change button), you can change the computer name (each machine has its own unique name). And then you need to enter the name of the working group. All computers on the local network must have the same workgroup name.
After this, the OS will ask you to reboot, which you will need to do.
On any of the computers you can “share” (i.e. put into public access) directories. This is done as follows:
In Explorer, right-click on the directory and select Properties.
Directories are shared in the Sharing tab. For the first time we will be asked to agree that we understand what we are doing.
In all subsequent ones, you just need to check the Share this folder box (the directory will be accessible over the network only in read mode). If you need to allow changing data over the network, you will have to check the box Allow Network User to Change my Files.
After confirmation (clicking OK), the directory icon will change to the one shown in the screenshot.
From other computers, you can access shared directories by going to the network environment (My Network Places), located in the Start menu or on the desktop, selecting View Workgroup Computers,
and then click on the desired computer name.
The shared directories will be presented in the window that appears.
After selecting any of them, you can work with them in the same way as if they were located on the local computer (but if the permission to change files when sharing a directory was not activated, then you will not be able to change the files, only view and copy).
Please note that the method described above will work without problems if both computers (on which the directory was shared and which is trying to access it over the network) have the same usernames with the same passwords. In other words, if you, working under the user USER1, have shared a directory, then in order to access it from another computer, the user USER1 must also be created on it with the same password (as on the first computer). The rights of the user USER1 on another computer (the one from which they are trying to access the shared resource) can be minimal (it is enough to give him guest rights).
If the above condition is not met, problems may arise with access to shared directories (drop-down windows with messages like access denied, etc.). These problems can be avoided by activating a guest account. True, in this case, ANY user inside the local network will be able to see your shared directories (and in the case of a network printer, print on it) and, if changes to files by network users were allowed there, then anyone will be able to change them, including deleting them.
Activation of a guest account is done as follows:
Start -> Control Panel ->
The control panel looks like the one in the screenshot after clicking the Switch to Classic View button (switch to classic view)
-> administration -> computer management ->
In the computer management window that appears, select the local user and group management tab, find the Guest account and activate it. By default, in Windows, a guest account is already created in the system, but is blocked.
A few words about adding users to the system (more on this in the following articles). In the same local user and group management manager, right-click on an empty space in the user list and select New user(add new user).
In the window that appears, enter the login (in this case, user2 was entered), full name and description, the last two values are optional. Next, assign a password, and in the next field, repeat the same password. Unchecking User must change password at next logon(the user must change the password the next time he logs in), allows the user to log in with the given password and will not require him to change it the first time he logs in. And the jackdaw opposite Password never expires(the password will never become outdated), makes it possible to use the specified password indefinitely.
By default, the newly created user is included in the group Users(users). Those. The user will have fairly limited rights. However, there will be quite a lot of them and you can log in to your local computer under this login and work quite comfortably. You can further limit the rights (to a minimum) of this user by removing him from the group Users and entering into the group Guests(guests). To do this, right-click on the user and select Properties(properties),
Member of -> Add, in the window that appears, click on Advanced(additionally)
Click Find Now(find). And in the list that appears, select the desired group (Guest).
The user has been added to the Guest group. All that remains is to remove it from the Users group: select it and click on the button Remove(delete).
More flexible control of access to shared resources can be obtained by disabling the Simple File Sharing mode in Explorer settings. But this is again beyond the scope of the current article.
Providing public access (sharing) of printers is done in a similar way. On the computer to which the printer is connected, select its icon (via Start -> Printers), right-click on it, select properties.
Printer sharing is managed in the Sharing tab. You need to select the Shared As item and enter the name of the printer under which it will be visible in the network environment.
On other computers connected to the same local network, the network printer will most likely appear in the printer menu. If this does not happen, launch the Add Printer icon (add printer),
which will call a wizard for connecting printers.
We tell him that we want to connect a network printer.
In the next menu we indicate that we want to find the printer in the network environment. You can also enter a direct UNC to the printer, for example, \computer1printer1, using the Connect to this Printer item.
UNC (Universal Naming Convention) - Universal network path, used in operating systems from Microsoft. Represented as \computer_name shared_resource name, where computer_name = NetBIOS machine name, and shared_resource name = name of a shared directory, printer, or other device.
If we selected the item to search for a printer in the network environment, then after clicking the Next button, a network environment viewing window will appear, where you need to select the shared printer. After this operation, you can send documents for printing from the local machine to a remote printer.
So. We now have a working local network. It's time to give her access to the Internet. Later in this article we will tell you how to organize such access using one of the computers as a router. To do this, it must have two network cards. For example, one is built into the motherboard, and the second is external, inserted into the PCI slot. Or two external ones, it doesn’t matter.
We connect the wire coming from the provider to the second network card of the router (the first one looks into the local network). This could be a twisted pair cable (crossover or straight cable) from an ADSL modem, or a twisted pair cable installed by local network installers in your area, or something else.
It is quite possible that the ADSL modem (or other similar device) is connected to the computer via a USB interface, then a second network card is not needed at all. It is also possible that the router computer is a laptop that has one network card connected by wire to the local network and a WI-FI (wireless) network card connected to the provider’s wireless network.
The main thing is that two network interfaces are visible in the Network Connections window. In this case (see screenshot), the left interface (Local Area Connection 5) is responsible for access to the local network, and the right (Internet) is responsible for access to the global Internet. Of course, the names of the interfaces will differ in each specific case.
Before implementing the following steps, the front end (facing the Internet) must be configured. Those. From the computer-future-router, Internet access should already work. I omit this setting, since it is physically impossible to provide for all possible options. In general, the interface should automatically receive the necessary settings from the provider (via a DHCP server). You can check whether the network card has received any addresses, similar to the method described above in this article. There are options when a representative of the provider gives you a list of parameters for manually configuring the adapter (as a rule, this is an IP address, a list of DNS servers and a gateway address).
To activate Internet access for the entire local network, right-click on the external (facing the Internet) interface.
Select the Advanced tab. And here we check the box next to the item Allow other Network Users to Connect through this Computer's Internet Connection. If you need this Internet access to be controlled from other computers on the local network, enable Allow other Network Users to Control...
If the machine does not use any additional firewall (firewall), in addition to the one built into Windows (i.e., a program that was additionally installed on the machine), then be sure to turn on the firewall (protecting our router from the outside world) - Protect my Computer and Network . If an additional firewall is installed, then the built-in protection can not be activated, but only the external firewall can be configured. The main thing is that the firewall on the interface facing the Internet must be turned on, built-in or external.
After confirmation (pressing the OK button), the computer activates the router mode, implemented through the NAT mechanism. And above the network interface where this mechanism is activated, a palm symbol appears (a lock on top means that firewall protection is enabled for this interface).
A direct consequence of this mode is a change in the address on the local (facing the local network) interface of the router to 192.168.0.1 with a subnet mask of 255.255.255.0. In addition, on the computer acting as a router, the DHCP service is activated (the router begins distributing the necessary IP addressing parameters to all computers on the local network), and DNS (converting IP addresses to domain names and vice versa). The router becomes the default gateway for all other computers on the network.
And here's what it looks like from the point of view of the rest of the computers on the local network. They all receive the necessary IP addressing settings from the router via DHCP. To do this, of course, their network cards must be configured to automatically obtain an IP address and DNS. If this has not been done, then nothing will work. Setting up automatic acquisition of an IP address and DNS was described above. It is possible that the computer will not receive the necessary addresses from the router immediately; in order not to wait, you can click the Repair button, which will force the DHCP service to provide the necessary information.
If the network card is configured correctly, computers will receive addresses from the range 192.168.0.2---254 with a mask of 255.255.255.0. The default gateway (default gw) and DNS server will be set to 192.168.0.1 (router address).
From this moment on, computers on the local network must have access to the Internet. You can check this by opening a website in Internet Explorer or pinging any host on the Internet, for example, www.ru. To do this, click Start -> Run and in the window that appears, type
ping www.ru -t
Of course, instead of www.ru, you can choose any other host on the Internet that works and responds to pings. The “-t” switch allows infinite ping (without it, only four packets will be sent, after which the command will complete its work and the window with it will close).
If the Internet channel is operating normally, the screen output from the ping command should be approximately the same as in the screenshot, i.e. replies must go. If the host does not respond (i.e. the Internet channel does not work or something is configured incorrectly on the router), then timeouts will appear instead of replies. By the way, not all providers allow the ICMP protocol, which is used by the ping command. In other words, it is quite possible that “ping does not work”, but there is Internet access (sites open normally).
Finally, I’ll dwell a little more on the NAT mechanism. NAT - Network Address Translation, i.e. technology for broadcasting (converting) network addresses. Using this mechanism, several machines from one network can access another network (in our case, several machines from a local network can access the global Internet) using only one IP address (the entire network is masked under one IP address). In our case, this will be the IP address of the external interface (second network card) of the router. The IP addresses of packets from the local network, passing through NAT (towards the Internet), are rewritten with the address of the external network interface, and returning back, the correct (local) IP address of the machine that sent the original data packet is restored on the packets. In other words, machines from the local network work under their own addresses without noticing anything. But from the point of view of an external observer located on the Internet, only one machine is working on the network (our router with the NAT mechanism activated), and another two, three, hundred machines from the local network located behind the router are not visible to the observer at all.
On the one hand, the NAT mechanism is very convenient. After all, having received only one IP address (one connection) from the provider, you can connect at least a hundred machines to the global network, literally by making a few mouse clicks. Plus, the local network is automatically protected from intruders - it is simply not visible to the outside world, with the exception of the computer-router itself (numerous vulnerabilities of the Microsoft OS family are again beyond the scope of this article, I will only note that to activate the protection, i.e. turn on the firewall on external interface of the router, as mentioned above, is required). But there is also another side to the coin. Not all protocols (and therefore not all applications) will be able to work through NAT. For example, ICQ will refuse to transfer files. Netmeeting most likely will not work, there may be problems with access to some ftp servers (working in active mode), etc. But for the vast majority of programs, the NAT mechanism will remain completely transparent. They simply won’t notice it, continuing to work as if nothing had happened.
But. What to do if there is a WEB or some other server inside the local network that should be visible from the outside? Any user contacting the address http://my.cool.network.ru (where my.cool.network.ru is the router address) will be sent to port 80 (by default WEB servers respond on this port) of the router, which does nothing does not know about the WEB server (because it is not located on it, but somewhere inside the local network BEHIND it). Therefore, the router will simply respond with a reply (at the network level), thereby showing that it really has not heard anything about the WEB (or any other) server.
What to do? In this case, you need to configure redirection (redirection) of some ports from the external interface of the router to the local network. For example, let's configure port 80 redirection inward, to the web server (which we have on the computer 169.254.10.10):
In the same menu where NAT was activated, click the Settings button and select Web Server (HTTP) in the window that appears.
Since we have chosen the standard HTTP protocol, which was already included in the list before us, there is no need to select the external port (External Port) to which the router will receive connections and the internal port (Internel Port) to which the connection to the local network will be redirected , - the standard value 80 is already set there. The protocol type (TCP or UDP) is also already defined. All that remains is to set the IP address of the machine on the local network, where the incoming Internet connection to the web server will be redirected. Although, as I was correctly corrected in the forum, it is better to set not the IP address, but the name of this machine. Since the IP address (which is issued automatically by the DHCP server) may well change, but the machine name will not (it can only be changed manually).
Now, from the point of view of an external observer (located on the Internet), a web server has appeared on port 80 on the router (the local network behind it is still not visible). He (the observer) will work with it as usual, without assuming that the web server is actually located on a completely different machine. Comfortable? I guess so.
If you need to give external access to some non-standard service (or a standard one, but not included in the list in advance), then instead of selecting services from the list in the above screenshot, you will need to click the Add button and enter all the required values manually.
Instead of a conclusion
In the first part of the series of articles, the possibility of organizing local network access to the Internet using the built-in capabilities of Windows XP from Microsoft was considered. We should not forget that the computer-router obtained as a result of configuration must work constantly, because if it is turned off, other hosts on the local network will lose access to the Internet. But a constantly running computer is not always convenient (it makes noise, gets hot, and also eats up electricity).
Options for organizing access of local networks to the global one are not limited to those described above. The following articles will look at other methods, for example through hardware routers. The latter have already appeared in reviews on our website, but in those articles the emphasis was on testing the capabilities, without much explanation of what these capabilities give the user. We will try to correct this annoying omission.
Navigation
- Part one - building a simple wired network
- Part three - using WEP/WPA encryption in wireless networks
Internet technologies, connection methods and speed characteristics, provider
1. A brief history of the Internet.
The birthplace of the Internet is the USA. In 1961, the Defense Advanced Research Agency (DARPA), on behalf of the US Department of Defense, began a project to create an experimental network for data exchange in packet mode.
The main disadvantage of the centralized network was its lack of stability: if any of the nodes failed, the entire sector behind it also completely failed, and if the control center failed, the entire network failed.
The largest university and scientific centers in the United States became testing grounds for new principles, between which computer communication lines were laid. The first non-departmental national computer network was called ARPANET. Its implementation took place in 1969.
The ARPANET experiment was so successful that many organizations wanted to log on to exchange email and files on a daily basis. And in 1975, ARPANET moved from the category of an experimental network to a working network. The second birth date of the Internet is considered to be 1983. This year the first standard for the TCP/IP protocols was released, which was adapted into a publicly available standard. The problem of global network stability has been resolved. In 1983, MILNET was spun off from ARPANET and became part of the US Department of Defense.
The term Internet began to be used to refer to a single network: MILNET plus ARPANET. And although ARPANET ceased to exist in 1991, the Internet continues to develop.
Organizational characteristics of the Internet
In fact, the Internet consists of many local and global networks belonging to various companies and enterprises, interconnected by various communication lines. Currently, almost all known communication lines are used on the Internet: from telephone lines to digital satellite channels.
A host on the Internet is a computer running a modern operating system (Unix, VMS), supporting TCP/IP protocols and providing users with any network services.
At low cost, users can access commercial and non-commercial information services in many countries. The Internet provides unique opportunities for reliable and confidential global communications around the world.
The Internet is an all-volunteer organization. The ultimate authority on the Internet remains with the ISOC (Internet Society) in each country, a voluntary membership society. Its goal is to facilitate the global exchange of information via the Internet. It defines a council that is responsible for technical policy, support and governance of the Internet.
The board is a group of invited volunteers called the IAB (Internet Architecture Board). The IAB regularly evaluates and selects standards and allocates resources.
Internet users make suggestions at IETF (Internet Engineering Task Force) meetings. The IETF is also a voluntary organization that functions to solve current operational and strategic technical problems.
If a certain network joins the Internet, then it becomes part of it. The fundamental principle of the Internet is the equivalence of all physical networks connected through it: any communication system is considered as a component of the Internet, regardless of its physical parameters, the size of transmitted data packets and geographic scale.
The failure of any node or the emergence of a new node does not have any impact on the overall performance of the network. However, the architecture of the Internet communication system has a very definite hierarchical nature.
In this hierarchical architecture, a limited set of high-cost, high-bandwidth backbones, called the backbone or core network, connect medium-bandwidth networks to which individual organizations in turn connect.
No one pays for the Internet centrally. Instead, everyone pays their share. So what is the Internet?
From an information point of view, the Internet is a collection of millions of information centers, called websites, containing terabytes of various information and closely connected by many interconnections.
From a social and economic point of view, the Internet is a unified environment for communication, communication, entertainment and business.
From a technical point of view, the Internet is a collection of tens of thousands of independent networks and millions of computers.
The definition of the Internet, given by the Federal Networking Council, states: “The Internet is a global information system, the parts of which are logically interconnected through a unique address space based on the IP protocol (InetrnetProtocol) or its subsequent extensions, capable of communicating through the TCP/IP (TransmissionControlProtocol/InternetProtocol) protocol suite, its subsequent extensions, or other IP-compatible protocols, and publicly or privately providing, using, or making available a high-level communications service.” In other words, the Internet can be defined as an interconnection of networks based on a single communication protocol - TCP/IP.
Principles of building the Internet
The main and most common Internet access device for the end user is a computer. To expand its capabilities, it can be equipped with a microphone, video camera, sound speakers and other devices that turn it into a multimedia center. The computer can be located in any place that has modern means of communication.
Internet access, which is provided by organizations called Internet Service Providers, can be obtained by the user via a modem or the organization's local network. To connect to the provider, various communication lines can be used (regular telephone lines, cable television networks, radio communication channels or satellite communications).
The ISP has one or more connections to the backbones or large networks that form the Internet's main bloodstream. In this case, a dial-up connection or a leased line connection is offered. In any case, there must be a line of communication of some kind.
The boundaries of the Internet are quite blurry. Any computer connected to it can already be considered part of it, and even more so this applies to the local network of an enterprise with Internet access. Web servers on which information resources are located can be located in any part of the Internet (at the provider, in the local network of the enterprise). The main condition: they must be connected to the Internet so that Internet users can access their services. The services can be email, FTP, WWW and others. The information component of the services comes from a wide variety of sources. This could be data, photographs, sound clips, videos: everything that users strive for and achieve through an Internet connection.
TCP/IP protocol family
The main difference between the Internet and other networks lies precisely in its TCP/IP protocols, which cover a whole family of protocols for interaction between network computers. TCP/IP is an Internet technology. The TCP/IP protocol consists of two parts - IP and TCP.
The IP protocol (Internet Protocol) implements the dissemination of information in the IP network. It provides packet delivery, its main task is packet routing.
The high-level TCP protocol (TransmissionControlProtocol) is a protocol that establishes a logical connection between the sender and the recipient. It provides session communication between two nodes with guaranteed delivery of information, monitors the integrity of transmitted information, and maintains the order of the packet flow.
Being the basic protocol, TCP/IP has undeniable advantages: openness, scalability, versatility and ease of use, but this family of protocols also has disadvantages: the problem of information security, the disorder of packet transmission and the inability to track the route of their progress, the amount of address space.
New versions of protocols are being developed that should solve these shortcomings.
Addressing in IP networks
To identify computers (host nodes) connected to the Internet and internetwork routing of packets, each computer is assigned a unique four-byte address (IP address). An IP address entry consists of four segments separated by dots. Each segment is a decimal number ranging from 0 to 255, which corresponds to one byte. An example of an IP address entry is the line: 197.25.17.34. The numbers 0.127 and 255 are reserved for special needs and cannot be used in a regular IP address.
IP addresses are the main type of address used to transmit packets between networks. An IP packet contains two addresses - a sender and a recipient. Both addresses are static, i.e. do not change throughout the entire packet path.
Domain Name System. In order to make access to all Internet resources as simple and transparent as possible from the point of view of users, the Internet has a DNS domain name system. It is designed to ensure that any resource, in addition to a unique IP address, has an easy to remember domain name.
The Domain Name Service is designed to match IP addresses with a machine's domain name, and vice versa. The domain name of any resource consists of the following main parts: the name of the machine name, the proper domain name and the zone name.
For example, www.rbk.ru (this domain name says that the resource is located in the geographical domain ru, has its own name rbc and the functional name www, that is, it performs the functions of a WWW server).
The names of zones can be divided into “organizational” and “geographical”. The following organizational zones are registered in first-level domains: com - commercial; edu - educational; gov - government; mil - military; net - organizations that ensure the operation of the network; org - non-profit organizations.
Each country (state) has its own two-letter geographic domain. Here are the domains of some of the countries: ca - Canada (Canada); fi - Finland (Finland); fr - France (France); jp - Japan (Japan); ru - Russia (Russia); ua - Ukraine (Ukraine); uk - UnitedKingdom (England).
A number of specialized organizations are involved in the process of registering and maintaining domain names.
Internet technologies are technologies for creating and supporting various information resources on the Internet computer network: websites, blogs, forums, chats, electronic libraries and encyclopedias.
The Internet and Internet technologies are based on hypertexts and sites located on the global Internet or on local computer networks.
To record hypertexts, the hypertext markup language HTML is used, which is understood by all browsers on all personal computers.
The HTML language is an international standard, so all hypertexts are perceived and displayed in the same way on all personal computers around the world.
To prepare hypertexts, visual hypertext editors are usually used, in which you can immediately see what the hypertext will look like on a computer and it is possible to insert hyperlinks to sites on the Internet.
One of the best visual hypertext editors is the free office editor Writer in the free office suite OpenOffice.
Interactive sites are sites that use interactive hypertext routines that allow dialogue with computer users connected to the computer network.
Hypertext routines are included in hypertexts along with hypertext forms and routines called scripts.
To write hypertext subroutines (hypertext scripts), the JavaScript language is often used, which is an extension of the hypertext markup language HTML.
JavaScript is an extension of HTML hypertext markup and for these reasons the JavaScript interpreter is built into all browsers and all hypertext editors.
The JavaScript language is an international standard. For this reason, interactive JavaScript programs run in the same way on every computer in the world.
More than 60% of the world's programs are written in the hypertext script language JavaScript.
JavaScript programs can not only be executed on any computer connected to the Internet, but their source texts can also be read on the Internet.
JavaScript programs are the best example of Open Source on the Internet - they can be read, executed, and modified by anyone familiar with the JavaScript programming language.
Modern Internet technologies:
1. web server
2. hypertexts and websites;
3. email;
4. forums and blogs;
5. chat and ICQ;
6. television and video conferences;
7. wiki encyclopedia;
Internet technologies in computer science - various kinds of workshops on creating websites, blogs, electronic libraries and encyclopedias on the Internet.
Internet sites are sets of hypertexts with hyperlinks located on servers and portals on the Internet computer network.
Blogs on the Internet are Internet sites combined with interactive forums for communication and publication of messages and comments by site visitors.
Creating websites on the Internet is one of the most important tasks of computer science courses in universities and schools by students and schoolchildren.
Electronic libraries and encyclopedias are the latest technologies for publishing scientific and educational literature on the Internet.
Creating hypertext programs in JavaScript is one of the best examples of teaching programming because these programs can be published and tested on the Internet.
The following programs in JavaScript were written and published on the Internet and are still functional and available for imitation and the development of new Internet textbooks.
JavaScript is one of the best languages for teaching programming on the Internet.
Internet provider (sometimes just provider; from English. internetserviceprovider, abbr. ISP- Internet service provider) - an organization providing Internet access services and other Internet-related services.
The main services of Internet providers include:
· broadband Internet access,
Dial-up Internet access
· wireless Internet access,
· allocation of disk space for storing and ensuring the operation of sites (hosting),
· support for electronic mailboxes or virtual mail server,
· placement of the client’s equipment on the provider’s site (colocation),
· rental of dedicated and virtual servers (VPS, VDS),
· data backup.
According to the services provided, they can be divided into categories:
· access providers,
· hosting providers,
· main lines (English) backbone) providers,
· channel providers,
last mile providers.
Among access providers, we can distinguish primary (backbone) ones, which own backbone communication channels, and secondary (city, house) ones, which rent communication channels from primary ones. Primary providers usually sell traffic only in large volumes and provide services to other providers, not individual users, although there are exceptions.
6. CONNECTING TO THE INTERNET
Every day, more and more different devices are able to connect to the Internet. These are personal and mobile computers, servers and local networks, telephones, game consoles and music centers. Their access to the Internet and service is provided by Internet providers - organizations that provide Internet services.
Connecting to the Internet can be done in various ways. The most common are:
1. Dial-up access via telephone line.
2.Access via ADSL digital subscriber line.
3.Access via a dedicated communication channel.
4.Wireless digital communication.
5.Wireless connection via mobile phone.
The conversion of information from digital form into electrical signals for transmission over communication lines and vice versa is carried out using a modem (short for “modulator-demodulator”).
The choice of modem type is determined by the method of connecting to the network: analog – for a regular telephone connection, digital – for an ADSL connection, radio modem – for a wireless connection.
For personal computers, an internal modem is most often used, which is connected to a slot on the motherboard using a standard connector. Most modern laptops have a built-in modem.
An important characteristic of any computer network is the speed of information transfer, i.e. the amount of information that is transmitted per unit of time. The unit of transmission speed is 1 bit/s. The speed of information transfer in modern computer networks reaches hundreds of millions of bits per second. Therefore, derived units are used: kilobits per second or megabits per second.
With dial-up access over a telephone line, the modem, at the command of the computer, dials the provider's telephone number and, if the telephone line is not busy, establishes a connection with the provider's modem. Therefore, this connection method is called Dial-Up (by call). Then the username and password are verified. If authorization is successful, you are connected to the Internet. For the duration of the session, the computer is assigned a temporary address. During an Internet session, no one can reach the subscriber - the telephone line is busy.
The data transmission reception speed for analog modems reaches 56 kbit/s. The actual speed of dial-up access depends on many factors: the throughput of the external communication channel, the number of simultaneously connected users, and the state of the telephone line.
The more users connect, the greater the external channel bandwidth should be. Therefore, the provider must have a multi-channel telephone and a high-speed external communication channel, for example, with a speed of 30-60 Mbit/s and higher. More promising is ADSL technology (AsymmetricDigitalSubscriberLine - asymmetric digital subscriber line), which allows you to transfer data over telephone networks at speeds of up to 8 Mbit/s to the subscriber and up to 1.5 Mbit/s from the subscriber (hence the name asymmetric). The actual transmission speed depends on the length and quality of the line. Data exchange does not interfere with telephone conversations due to the separation of signal frequency ranges in the telephone line. ADSL connection requires a digital modem and a signal splitter. Access via a dedicated channel is carried out by permanently connecting the user’s computer to the provider’s server. The provider runs a dedicated line to the subscriber's computer and issues a permanent address. The user receives a constant connection to the Internet, high quality connection and data transfer, high speed (up to 100 Mbit/s). The only equipment required is a network card.
The cost of laying a leased line depends on the distance to the provider’s connection point. For individual users, this access method is justified only when laying the line itself does not require significant costs. The best option is to connect to home or city local networks, which provide shared access to high-speed Internet connections. You can connect to such networks in various ways - in fact, these are ordinary local networks. Recently, connecting to the Internet via cable television networks has become widespread. There are two options. With the individual option, the cable modem is installed separately for each computer. With the collective option, one modem is installed in a house for several users. Then a local network is installed and the necessary equipment is installed. Advantages: good speed, ability to view digital cable TV channels. Wireless digital WiFi allows you to access the Internet using a special adapter. Most modern laptops have it built in. There are several WiFi standards. They differ in data transfer speed, which can reach 50 Mbit/s. The actual data transfer speed is much lower, but this is still enough for convenient Internet browsing. Using WiFi is possible if you are within the range of receiving devices. Advantages: mobility, good speed, minimum equipment. Disadvantages: small radius of coverage of one access point, problem of line of sight, limitation of the number of users in the WiFi coverage area.
Wireless Internet connection via mobile phone is carried out using special mobile communication protocols.
One of the services of the most common communication networks today is GPRS. The maximum data transfer rate using the GPRS standard reaches 170 kbit/s. The actual speed does not exceed 30-40 kbit/s and depends on the workload and capabilities of the cellular operator’s network, the distance to the antenna, and the characteristics of a particular mobile phone.
Sometimes GPRS networks are called second generation networks. Third generation networks are also beginning to develop. For example, these include CDMA and EDGE mobile connection standards.
Principles of building the Internet
Internet (eng. Internet, from Inter connected Net works - interconnected networks) - a global telecommunications network of information and computing resources. Serves as the physical basis for the World Wide Web. Often referred to as the World Wide Web, Global Network, or simply the Network.
The Internet consists of many thousands of corporate, scientific, government, and home computer networks. The combination of networks of different architectures and topologies has become possible thanks to the IP protocol (Internet Protocol) and the principle of routing data packets.
What is a protocol? A protocol is the rules for transmitting data between nodes of a computer network. In order for different computers on a network to communicate, they must “speak” the same “language,” that is, use the same protocol. The main protocols used on the Internet for data transfer are TCP/IP (Transmission Control Protocol/Internet Protocol), HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol - “file transfer protocol”).
Every computer connected to the Internet has a unique address. To record addresses, two equivalent formats are used - IP and DNS addresses.
An IP address consists of four numbers with values from 0 to 255, separated by dots (for example, 195.27.38.172), and includes two logical parts - the network number and the host number on the network. This numbering scheme makes it possible to have more than four billion computers on the network. When a local network or an individual computer first joins the Internet, a special organization (provider) assigns it an IP address, guaranteeing its uniqueness and correct connection.
For convenience, computers on the Internet are assigned their own names in addition to digital addresses. In this case, as in the case of IP addresses, the uniqueness of this name is necessary. For this purpose, a special addressing system was created - DNS (Domain Name System). Domain names, unlike IP addresses, are optional and must be purchased separately. The DNS address contains letters instead of numbers, separated by dots into separate levels. The first name in the DNS address is the name of the real computer with its IP address. Next, there are sequential addresses of the domains to which the computer belongs, up to the country domain (a two-letter encoding is adopted for them). Consider the DNS name dit.isuct.ru. Here ru is the national first-level domain denoting Russia; isuct – second-level domain name denoting the ISUTU organization; dit – third level domain name. All DNS names are built according to this hierarchy principle.
The main services of the Internet are the World Wide Web, electronic mail, search engines, web forums, various mailing lists, file-sharing servers and newsgroups (Usenet). You can find a web page or file on the Internet using the Uniform Resource Locator (URL).
URL is a standardized way of writing the address of a resource on the Internet. It includes the document access protocol, the server's domain name or IP address, and the full path to the file on the web server. For example, the address of the “Internet” article on the Wikipedia portal looks like
http://ru.wikipedia.org/wiki/Internet,
where http:// is the access protocol, ru.wikipedia.org is the domain name of the server, /wiki/Internet is the path to the file.
Web pages are viewed using special viewing programs – browsers. The browser allows the user to open and view web pages, as well as navigate between documents in the web space. Currently, the most common browsers are Mozilla Firefox, Opera and Internet Explorer.
The Internet is a global computer network that hosts various services (E-mail, Word Wide Web, FTP, Usenet, Telnet, IP radio, IPTV, IRC (chat), etc.). The date of its foundation can be considered October 29, 1969. On this day at 21:00, a communication session was held between the first two nodes of the ARPANet (Advanced Research Projects Agency) experimental network, located at a distance of 640 km - at the University of California Los Angeles (UCLA) and at the Stanford Research Institute (SRI).
ARPANet was created using packet switching technology based on Internet Protocol - IP or the TCP/IP (Transmission Control Protocol) family of protocols (stack), i.e. is based on independent promotion of packages on the network. It was the use of the TCP/IP network protocols that ensured the normal interaction of computers with various software and hardware platforms on the network and, in addition, the TCP/IP stack ensured high reliability of the computer network (even if several computers failed, the network continued to function normally).
After the open publication in 1974 of a description of the IP and TCP protocols (a description of the interaction of computers on a network), the rapid development of networks began, based on the TCP/IP family of protocols. TCP/IP standards are open and are constantly being improved. Currently, all operating systems provide support for the TCP/IP protocol.
In 1983, ARPANet split into two networks, one - MILNET became part of the US Defense Data Network, the other was used to connect academic and research centers, which gradually developed and in 1990 transformed into the Internet.
TCP/IP protocols have ensured absolute decentralization of the global Internet; no state controls its operation. The Internet is developing democratically and any computer network or individual computer can connect to it. There is no single owner and control center of the Internet.
Among all the network services, the Web (English network, web) has become the most popular. Many Internet users believe that the World Wide Web is the global Internet. It should be noted that this is not true. WWW is one of the Internet services, but it is its basis; it is a distributed hypermedia (hypertext) system in which documents are hosted on Internet servers and linked to each other by links.
To view web pages on the Internet, users use special programs called browsers. The most common include Internet Explorer, Google Chrome, Mozilla FireFox, Safari, Opera. The user types the address of an Internet web page into his browser. If he types it in digital form (IP address of the form 5.45.110.50), then the browser directly contacts the Internet site located at this address. If the address is specified in text form, for example, “site,” then the browser contacts the DNS server (prescribed in the computer’s network settings), which replaces the text name with the corresponding IP address.
The site name in text form is also called a domain name. So “site” is a second-level domain in the first-level domain “.ru”. The most common first-level domain names include “.com”, “.org”, “.net”, “.ru”.
Each DNS server stores data (a table of correspondence between all known text domain names and digital IP addresses). This is a large amount of information. Therefore, DNS servers are divided into several levels, each of which regularly (about 2 times a day) receives updates from a higher-level DNS server. The most senior level DNS servers receive data from registrars (companies responsible for registering domain names).
Registrars provide the opportunity for legal entities and individuals to rent domain names from them for a long period of time. The cost of initial registration depends on many factors, such as the simplicity of the name, the length of the word, the presence of a commercial component, connection with the brand, etc. After a certain period (usually 1 year), the domain name registration is required to be renewed.
Having received a domain name, you need to add it to the DNS database. To do this, on the registrar’s website we indicate the IP address of the DNS server (or servers), which knows where physically (at what IP address) the web page corresponding to our domain is located. Provided that the DNS server is configured correctly and the page exists, it will become available to users around the world in approximately one to two days.
Scheme for obtaining an IP address by domain name
Thus, in order for a site to appear on the Internet and access it using its domain name, you need a registered domain name, a dedicated IP address and a computer connected to the Internet with a configured server. Hosting companies provide the services of providing an IP address and a configured computer. The cost varies greatly depending on the range of services offered and the resource provided. Hosting can be virtual (it's cheaper). In this case, several websites of different owners are running simultaneously on one computer. Hosting can be dedicated (this is more expensive). In this case, a separate computer is allocated for the site.
Main characteristics of hosting:
- Dedicated or virtual hosting;
- Availability and magnitude of restrictions on traffic volume;
- The amount of allocated disk space;
- Software used;
- The number of domains that can be linked to your hosting account.
Most hosting providers provide access to and management of the site both through a web interface and via ftp. After the hosting is configured, a domain name is attached to it, the start web page of the site is created, users can go to this site..html, index.htm or index.php (if at least one of the pages with this name is on the site ).
The Internet is a worldwide information computer network, which is a union of many regional computer networks and computers that exchange information with each other via public telecommunications channels (dedicated analog and digital telephone lines, optical communication channels and radio channels, including satellite communication lines).
Information on the Internet is stored on servers. Servers have their own addresses and are controlled by specialized programs. They allow you to forward mail and files, search databases, and perform other tasks.
Information exchange between network servers is carried out via high-speed communication channels (dedicated telephone lines, fiber optic and satellite communication channels). Individual users' access to Internet information resources is usually carried out through a provider or corporate network.
Provider - network service provider - a person or organization providing 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.
The history of the Internet began in the late 50s of the twentieth century, namely, when the first artificial satellite was launched in the USSR in 1957. At the height of the Cold War, the Soviet Union's "conquest" of outer space posed a serious threat to the United States.
It was necessary to accelerate the pace of development of the latest defense systems. For this purpose, the Advanced Research Projects Agency of the US Department of Defense - ARPA - was created in 1957. This organization was interested in the question of whether it was possible to connect computers located in different places using telephone lines. Their goal was to organize a data transmission network capable of functioning in conditions of a nuclear conflict. In January 1969, a system was launched for the first time, connecting 4 computers in different parts of the United States. A year later, a new information network, called ARPAnet, has already started working.
Every year, ARPAnet grew and developed and from a military and classified network became more and more accessible to various organizations.
In 1973 the network became international.
In 1983, a new mechanism for accessing the ARPAnet, called the TCP/IP protocol, was introduced. This protocol made it easy to connect to the Internet using a telephone line.
In the late 1980s, the military's patience came to an end as the network turned from secret to public. Therefore, they separated a part of the network for their needs, called MILNet.
At the end of the 90s, it became possible to transmit not only text, but also graphic information and multimedia over the network.
One of the first Russian networks connected to the Internet was the Relcom network, created in 1990 on the basis of the Russian Center “Kurchatov Institute”. Specialists from the Demos cooperative (now the Demos-Internet company) took part in the creation of the network. By the end of the year, 30 organizations were connected to the Internet. In 1991, the first news (electronic conference) server appeared on the Relcom computer network. And very soon it united many large cities of Russia (Ekaterinburg, Barnaul, etc.), as well as some other CIS countries and the Baltic countries.
Today, the Internet consists of millions of computers connected to each other using a variety of channels, from ultra-fast satellite data backbones to slow dial-up telephone lines.
Currently, there are many ways to connect to the Internet, from connecting a computer via an analog modem to connecting methods using high-speed technologies.
The method of connecting a computer to the Internet depends on the level of services used by the user that he wants to receive from the provider (service provider), on the speed and quality of data transfer. Services provided by the Internet include: E-mail, WWW, FTP, Usenet, IP telephony, video streaming, etc.
Methods of connecting to the Internet can be classified into the following types:
dial-up access;
access via dedicated lines;
access via broadband network (DSL - Digital Subscriber Line);
Internet access via local network;
satellite Internet access;
access to the Internet using cable television channels;
wireless technologies.
Dial-up access typically uses an analog modem and an analog telephone line, but dial-up access over the ISDN (Integrated Services Digital Network) digital telephone network is also used. An ISDN adapter is used to connect a PC to a digital network with integration of ISDN services. In addition, dial-up access to the Internet can be provided using wireless technologies: mobile GPRS - Internet and mobile CDMA - Internet.
Access via dedicated communication channels involves a permanent communication channel from the premises with the computer to the switch belonging to the ISP (provider). This access method ensures your computer is connected 24 hours a day. A promising method of connecting to the Internet for both individuals and companies is a DSL broadband network. Digital Subscriber Line is a family of digital subscriber lines designed to provide access over an analog telephone network using a DSL/cable modem. This method provides data transfer up to 50 Mbit/s.
Access to the Internet via a local network with Fast Ethernet architecture provides the user with access to global Internet resources and local network resources. The connection is made using a network card (10/100 Mbit/s) with data transfer speeds of up to 1 Gbit/s on the backbone sections and 100 Mbit/s for the end user.
Satellite Internet access (DirecPC, Europe Online) is popular for users in remote areas. The maximum data reception speed is up to 52.5 Mbit/s (real average speed is up to 3 Mbit/s).
Cable television users can use cable television network channels to connect to the Internet, with data reception speeds ranging from 2 to 56 Mb/sec. To organize a connection to a cable television network, a cable modem is used.
Recently, wireless methods of connecting to the Internet have become increasingly popular. Last mile wireless technologies include: WiFi, WiMax, RadioEthernet, MMDS, LMDS, mobile GPRS - Internet, mobile CDMA - Internet.
