Local computer network is an association of several computers. Open lesson on the topic: “Combining computers into a local network

Network is a single complex that includes a geographically dispersed system of computers united into a single system by means of communication using communication equipment, software and protocols for solving information, management, computing and/or other problems.

The local network(Local Area Network - LAN) connects computers and peripheral equipment within one or more adjacent buildings. The network organized within the office is also local. The main purpose of a local network is to share the resources of one computer with another computer(s). Thus, the local network allows you to share files, applications, peripheral devices (printers, scanners, etc.), work with by email, use instant messaging, participate in electronic conferences, etc.

The principle of construction (configuration) of network connections is called topology. Based on topological characteristics, local networks can be represented by three basic topologies: common bus, star, ring.

By topology common bus(backbone) all computers are connected to one cable (Fig. 118).

At the ends of the cable there are terminators(energy absorbers) that serve to prevent signal reflection. The message sent by the workstation is distributed to all computers on the network. Each machine checks who the message is addressed to, and if it is addressed to her, then processes it. In order to exclude the simultaneous sending of data, either a “carrier” signal is used, or one of the computers is the main one and “gives the floor” to the other stations.

Rice. 118.

Advantages of such a construction are:

• - simple structure, which allows you to expand the network by adding an additional number of computers;
• - low cost of implementation;
• - the network is easy to set up and configure.

Flaws:

• - low efficiency due to loss of productivity with the addition of new workstations;
• - network problems, such as a cable break, completely block the operation of the entire network.

This topology is used in local networks with architecture Ethernet(technology and architecture for building large local computer networks). Data transmission in networks of this type is possible via coaxial cable at a speed of 10 Mbit/s (10Base-5 and 10Base-2 standards), twisted pair cable (10Base-T standard) and fiber optic cable (10Base-F standard).

In a topology like "star"(Fig. 119) each computer is connected by a cable (twisted pair) to hub(habu). The hub provides parallel connection workstations, and thus all computers connected to the network can communicate with each other.

The workstation from which data needs to be sent sends it to the hub, which determines the recipient and gives him the information. At a given time, only one machine on the network can send data; if two packets arrive at the hub at the same time, both packets will be rejected and the senders will have to wait a random period of time to resume data transmission.

Advantages topologies:

• - failure of one computer does not affect the operation of the entire network as a whole;
• - good network scalability - easy to connect a new computer;
• - easy troubleshooting and network breaks;
• - high network performance.

Flaws star topologies:

• - failure of the central hub will result in the inoperability of the network (or network segment) as a whole;
• - high cable consumption, especially if the hub is not located in the center of the topology;
• - the finite number of workstations in a network (or network segment) is limited by the number of ports in the central hub.

Rice. 119 .

In a network with a topology "ring"(Fig. 120) all nodes are connected by communication channels into an unbreakable ring through which data is transmitted. All data on this network is transmitted from one station to another in one direction. Each computer works as a repeater, restoring and amplifying signals.

TO merits Ring topologies include:

• - ease of installation;
• - almost complete absence of additional equipment;
• - the possibility of stable operation without a significant drop in data transfer speed under intense network load.

Flaws Ring topologies are as follows:

• - if one computer fails or the cable breaks, the ring “breaks”;
• - connecting a new computer leads to a short-term network shutdown;
• - complexity of configuration and setup;
• - Difficulty in troubleshooting.

Rice. 120.

Exists two main types of local networks, based on the computer connection scheme: client/server and peer-to-peer network.

IN networks server based(rice. 121) there is a dedicated server- a specialized computer that controls the use of resources shared between workstations, such as external memory, printers, databases, etc.

Rice. 121.

There are several types of servers, in particular:

• - mail server- manages the transmission of electronic messages between network users;
• - file server- manages the creation and use of local network information resources, including access to its databases and individual files, as well as their protection. For example, when working with a test editor, the file is stored on a file server and will be loaded into the memory of your computer;
• - application servers- controls the operation of the local network when performing any application tasks. Examples of this kind of tasks can be: ensuring communication with other local and/or telecommunication systems, collective use of printing devices, etc.;
• - proxy servers- can store frequently requested information in cache memory on a local disk, quickly delivering it to users without re-accessing the Internet;
• - print servers- allow all computers connected to the network to print documents on one or more shared printers. In this case, there is no need to equip each computer with its own printing device. In addition, by taking on all the worries about printing documents, the print server frees up computers for other work.

The advantages of a network with a dedicated server include, in particular, the following.

• 1. High performance, since a high-performance computer is installed as a server, with significant amounts of internal and external memory, a powerful central processor, etc.
• 2. Support for a significant number of workstations.
• 3. The ability to implement access control, which means that you can limit the user’s access to various resources, which increases the security and protection of data.
• 4. Possibility of backup storage, since the data is stored on the server.

There is no dedicated server in a peer-to-peer network (Fig. 122), all computers

equal rights, i.e. each user personally decides what data on his computer to provide for public use.

To organize constant communication between computers on a peer-to-peer local network, they are combined into work groups.

Working group- this is a group of people (for example, employees of an organization) who are engaged in one project. The computers in each workgroup form a separate segment.

LAN segment- part of the network cable, limited routers(a device designed to provide access to remote local networks and the Internet, as well as to organize communication between networks and their interaction), repeaters, terminators and other additional devices.

IN separate group Print servers with several conventional printers connected to them can be considered, which at the same time acquire network capabilities and can work over the network, regardless of whether they support this operating mode. Typically print servers have LPT connectors. Such servers are used in large organizations, but at home it is quite enough to have one printer on a computer connected to a local network so that all computers in the workgroup have access to it. All of the above can be expressed in a single term - "shared access to resources."

Rice. 122.

Thus, a peer-to-peer network is convenient to use in teams of up to ten people, taking into account the fact that the network is not expected to scale in the near future.

The advantages of a peer-to-peer network include:

• 1. Cheapness of building a network due to the use of shared printers and other peripheral devices.
• 2. No special software or powerful computer is required as a server.
• 3. High qualifications are not required when installing and administering the network.

The disadvantages include:

• 1. Low security, since insufficient security of one workstation can lead to infection of other computers with viruses.
• 2. Quite low productivity, since no special requirements are imposed on the workstation.
• 3. Users must have sufficient qualifications to solve problems that arise during operation.

Currently, in any store, office or enterprise it is impossible to work quickly and fully without a local network into which all employee computers are connected. LAN is also used at home or other places where there are multiple computers.

To organize user work on a local computer network, a number of requirements must be met, including:

• 1. A network cable must be connected to the computer.
• 2. A network card is installed as an additional device.
• 3. The connection to the local network has been configured.

Other settings can be made even by an inexperienced user. In particular, in order to set the workgroup name, which other computers, say, in your office or organization have. To do this, click on the button Start, go to item Computer, by clicking the right mouse button go to the menu item Properties. The window shown in Fig. will open. 123.

Rice. 123.

Let's pay attention to the bottom part of the window, labeled as Computer name, domain name, and workgroup settings. There is a link on the right Change settings by clicking on which the user can change the computer name and workgroup name.

Another setting is related to providing shared access to folders. To make a folder visible on the network, you must perform the following steps:

• 1. Find the folder to which you are going to share access, suppose the folder Documentation.
• 2. Right-click on it.
• 3. Go to item Specific users and in the window that opens (see Fig. 124) press the button General access.

Rice. 124.

After this, the folder will be shared with all users on the local network. If you need to deny access to a folder to which it was previously granted, then you should follow the steps described above, only when you complete step 3, click on the button Terminate access.

When working together on a local network, other users can use your printer, scanner, fax, etc. In order to provide access to your resources, you must complete the following steps:

• 1. Enable the printer sharing feature. To do this, run the following command Start/Control Panel/Network and Internet/Network and Sharing Center. On the left side of the window, select Change advanced sharing settings.
• 2. Select the desired profile. Activate option Enable file and printer sharing. A similar situation is shown in Fig. 125.

Rice. 125.

• 3. Run the command Start/Devices and Printers. Right-click on the desired device, select Printer properties.
• 4. Go to tab Access and check the option Share this printer. The network name of the printer is also set here.
• 5. Click on the button OK.

• 1. Define the concept of “network”? What is the main purpose of local networks?
• 2. What is topology?
• 3. Draw a diagram of how computers are connected using a common bus topology. What are the advantages and disadvantages of this topology? What are terminators used for?
• 4. Draw a diagram of how computers are connected using a star topology. List the advantages and disadvantages of this topology. What does the hub provide?
• 5. Draw a diagram of how computers are connected using a “ring” topology. Explain the advantages and disadvantages of this topology.
• 6. Draw a diagram for constructing a local network based on a server and describe it.
• 7. Name the types of servers and give them characteristics.
• 8. List the advantages of a dedicated server network.
• 9. Draw a diagram of a peer-to-peer network and describe it.
• 10. For what purposes are working groups created? What is a LAN segment?
• 11. Name the advantages and disadvantages of peer-to-peer networks.
• 12. Determine what type of network is used in your computer classroom. Draw its diagram.
• 13. Together with your teacher, try to graphically construct a diagram of the networks of your educational institution.
• 14. What are the requirements for organizing user work on a local network?
• 15. Show practically how to set a workgroup name and share folders on a specific computer.
• 16. Demonstrate how you can provide access to local computer resources to other users.

Workshop

Concept of system administration

With the increasing use of computers, systems administration is becoming a key area in more and more organizations. The administrator must understand his system, know its users and their occupation. The main thing in administration is the ability to plan, since in the conditions of creation, modernization and expansion of systems, an attempt to improvise and develop network solutions on the fly is doomed to failure.

Network administrator (system administrator)- a specialist whose responsibilities include performing the following main functions:

• - installation of the operating system and application programs;
• - description of the information environment;
• - setting up the operating environment;
• - setting up network printing;
• - network monitoring and management of network resources;
• - archiving and restoring network data.

Let's look at them in more detail.

Installation(English, installation) - the process of installing software on a computer. During the operating system installation process, the administrator must answer a number of questions interactively.

Description of the information environment- includes the following actions:

• - creation of user directories;
• - assigning access rights to directories and files;
• - assigning attributes to directories and files.

Setting up the operating environment includes:

• - installation of configuration files for workstations;
• - development of system and user procedures for connecting to the network;
• - workstation management.

Setting up network printing suggests description:

• - print objects (queues, printers, print servers);
• - print forms (paper size);
• - configurations of print jobs.

Network monitoring- assessment of its performance and reliability characteristics. Using special software packages you can implement:

• - monitoring of file servers and network segments;
• - management of a file server, hubs, workstations.

Archiving and restoring network data. IN case of large volume

of archived data, all computers involved in the archiving process must have a high-speed (100 Mbit/s or higher) connection to the local network. Otherwise, the archiving process may take considerable time.

In addition to the above functions, the system administrator must know the basics of information security. This concept includes the protection of information located on personal computers and servers of the enterprise local network from unauthorized access, intentional distortion and damage. This concept also includes anti-virus protection of the local network and individual computers from virus attacks, all kinds of Trojan programs, malicious macros and software bookmarks.

In addition to the listed professional knowledge, the administrator must have communication skills, non-conflict, patience, know the basics of psychology and conflict management, since he is the link between computer technology and those who work on it.

The risks of the Internet are associated solely with its uncontrollability. Being a colossal source of information, the Internet does not divide it into good and bad or useful and useless. In addition, the Internet is ultimately a paid resource, i.e., the consumption of information from it must be paid for by someone.

The main disadvantages of uncontrolled use of the Internet in organizations are the following:

• - user access to harmful and useless information, which entails distraction from the work process;
• - penetration of viruses and worms into the enterprise network;
• - cost overruns due to unrelated labor activity Internet activity of users.

To effectively combat the risks described above, you need a system that performs three critical functions:

• 1.Accounting for the consumption of Internet resources. If employees know that their every “step” on the global network is monitored, this will reduce traffic and prevent misuse of the institution’s funds. It will be possible to easily find out which resources are visited by users during working hours.
• 2. Internet access control. In order to be able to specify which employees can have access, when and where. This will reduce lost work time and improve safety.
• 3.Network protection from information leakage, hacker attacks, network viruses and worms. This component is necessary to ensure the security of the enterprise network.

Differentiation of access rights in the network

Provide information security allows differentiation of user access rights to working documents and annexes. Each employee gets the opportunity to work only with those resources that he needs, while all documents are protected from accidental or intentional viewing or modification.

Currently, there are a number of programs on the market that provide, in particular, control and management of Internet access, protection of users and enterprise networks, traffic accounting, anti-virus protection and content filtering of web traffic. Conventionally, they can be divided into several categories:

Free programs, which can be downloaded from the Internet. But, as a rule, such programs are designed to solve individual problems. There are programs for collecting statistics, but they do not have the ability to process data according to various parameters. Conversely, there are programs for limiting resources that do not have statistics collection functions, etc.

An example is the BWMeter program, designed for graphically displaying and counting traffic that is transmitted over a local network. Using the utility, you can count transmitted packets, as well as find out where and from where they are sent, through what protocol and to what port.

Paid solutions on the protection and control of corporate information can be purchased on CDs on the Internet. Professional solutions of this kind from well-known foreign manufacturers, as a rule, meet all the above requirements, but are expensive. This category includes programs such as Kerio WinRoute Firewall, Ideco ICS Standard Edition, UserGate proxy server, Windows Svr Ent 2008.

Hardware and software systems to control Internet connection. They are convenient because their functionality is focused specifically on the end user, i.e., companies of any level, meet all requirements and are easy to use. Their main advantage is that you do not need to select equipment and install software. A hardware and software complex or simply a server connects to the network, is configured to its characteristics and works. An example is the Internet Control Server 2.x software package, which is installed on a computer and separates the corporate network from the Internet, controlling all information flows and accounting for traffic between the institution’s network and the Internet.

On the tasks of delimiting access rights in the network can be attributed:

• 1. Distribution of users into groups and creation account for each group and user separately.
• 2. User authorization.
• 3. Prohibition of access to certain objects.
• 4. Setting restrictions on the consumption of Internet resources.

In order to distribute users into groups, it is necessary to create a user structure using an analysis of the organization, for example, highlight all departments, think through the characteristics for identifying user groups. For example, the following structure is possible: planning and financial department, accounting department, personnel and office management department, etc. For dedicated departments, you need to create groups and create users within them, or do it differently - create users without groups. In principle, there is not much difference here. The only advantage of creating groups is the ability to track consumption for the group as a whole. With access profiles, you can easily set the same access rights for individual users who are not grouped. Of course, for groups there is no need to create an access profile.

How does user authorization work? When opening a new browser window and requesting a resource from the Internet, the user receives a window asking for a login and password. In this window, you should enter the login and password for this user, which were assigned to him during creation. If the login and password are correct, the user gains access to the Internet.

For implementation prohibiting access to certain objects you need to create a locking system that works according to the following example:

User 1

User 2

User 3

With this structure, “user 3” will be denied all three resources (www.yandex.ru, www.google.com and www.auto.ru), “user 2” will have only the top two - Yandex and Google, “User 1” will have access to any resource except www.yandex.ru.

It is also worth noting that each of the users from the example above must have explicit permission to access any (!) resources. There will be no disruption as the rules of higher groups will also apply. That is, taking this into account, the example will look like this.

All users (www.yandex.ru is prohibited)

User 1 (all allowed)

User 2 (all allowed)

User 3 (all allowed)

The sequence in which rules are added affects the priority of the rules (the higher the rule is located, the higher its priority over the others).

The network administrator may need to set a certain set of prohibiting/permitting rules for a whole set of users who are located in different groups. So that he does not have to manually add this set of rules separately for each user, it is possible to create a so-called access profile with the appropriate set of rules and then add it to the list of access rules for each individual user.

As already mentioned, the Internet is a paid and public resource. That's why great importance have savings Money educational institution and, in addition, limiting channel capacity for specific users in order to more equitably distribute channel capacity across all users. To do this you need to set restrictions on resource consumption Internet.

In this regard, the following characteristic is introduced: the maximum volume of traffic consumption (quota), if exceeded, the network administrator can take various punitive measures.

By tracking the dynamics of traffic consumption by users, the network administrator can determine the average maximum traffic volume, if exceeded, it is possible, for example, to disconnect the user who has violated the rules from the Internet without warning.

Not a single network administrator of an educational institution will allow ordinary users (students) to carry out the above-described functions of delineating access rights in the network during practical classes. However, on a regular school or home computer you can consider, in particular, account creation process. The fact is that quite often situations arise when several people work on one computer, and in this case you can make sure that each user has their own Windows settings. In addition, you can give some users the opportunity to install new software, and others should be banned. It is also possible to prohibit the use of certain programs on the computer.

There are three types of accounts. Each type gives the user different options for controlling the computer:

• - regular user accounts are intended for everyday work;
• - administrator accounts provide full control over the computer and are used only when necessary;
• - Guest accounts are intended for temporary access to the computer.

In other words, when you log into Windows using the normal

account can perform the same actions as an administrator account, but Windows may require an administrator password to make changes that affect all users on the computer (for example, installing software or changing security settings).

To create a new account, run the command Start/Control Panel/User Accounts and Family Safety. The window shown in Fig. will open. 126.

Rice. 126.

Let's select an item Adding and removing user accounts. IN

in the window that appears (Fig. 127), select the item Create an account.

Rice. 127.

Rice. 128.

Next you need to specify the account name and access rights (Administrator or Regular access) which the owner of the account being created will have to have (Fig. 128), and click the button Create an account.

Your account has been created and now you need to configure it. To do this, double-click on the created account.

In the window shown in Fig. 129, there are the following points:

• 1. Change the account name.
• 2. Create a password.
• 3. Changing the pattern.
• 4. Set up parental controls.
• 5. Changing the account type.
• 6. Managing another account.

Rice. 129.

Let's comment on some of them. First, after creating an account, you need to create a password for it (Fig. 130). Using a password increases system security. Field Enter a password hint may not be filled out. After entering the password and duplicating it, click on the button Create a password.

Rice. 130.

Set up parental controls. A new feature in Windows 7 allows you to set the time when the user (child) can use the computer, as well as determine what games and programs will be available to him. With parental controls you can:

• - limit the time spent by the user (child) at the computer. You can limit the amount of time children are allowed to log in. For each day of the week, you can set aside a time to log in to the system, even if the user works at the computer, the system will automatically log out;
• - set a ban on access to certain games. You can control access to games, choose the appropriate age rating, what types of content should be blocked, and set whether or not to allow or deny access to specific or uncategorized games;
• - establish a ban on the user (child) using certain programs.

For implementation prohibiting access to certain objects, in particular, for Internet resources, you should install the additional module “Family Safety”, located at http://windows. microsoft.com/ru-RU/windows-live/essentials-other-programs (Fig. 131). However, in this case, you will first need to obtain a Windows Live ID from the Windows Live service at http://www.home.live.ru.

By installing the core components of Windows Live on your computer, you can enhance your experience with photos, videos, and email. The core components of Windows Live are free and include Windows program Live Messenger, Photo Album and Film Studio. With a Windows Live ID, you can access all Windows Live services, including Hotmail, SkyDrive, and Messenger, with one sign-in.

Rice. 131.

After registering and installing the Family Safety component, options will become available for filtering and blocking Internet resources that, in your opinion, are undesirable for the user to visit. They include the following sections:

• 1. Web filter.
• 2. Create an action report.
• 3. Contact management.
• 4. Requests.
• 5. Time restrictions.
• 6. Game restrictions.
• 7. Program limitations.

The settings will be available at http://familysafety.live.com if the system administrator first enters a Windows Live ID and password.

After entering the password, a window with the above parameters will appear on the screen (Fig. 132).

Let's look at some of the parameters.

Web filter. With its help, you can control what types of websites users (children) can view and track the sites they visit (Fig. 133). In particular, you can allow visiting web resources only from the white list, added by the administrator (parent), block adult sites, allow or prohibit communication on social networks.

Rice. 132.

Rice. 133.

Web filter lists. With their help (Fig. 134), you can manage the list of websites that are allowed or blocked for the user (child). By compiling a list of specific sites in advance, the administrator (parent) can allow or block access to them.

Time restrictions. In a special dialog box (Fig. 135) you can select the time when the user (child) is allowed to use the computer. In the clock grid, white rectangles indicate allowed hours of access to the computer, and blue rectangles indicate prohibited hours.

Rice. 134.

Rice. 135.

Game restrictions. Each game has its own rating, i.e. the rating of the category of people for which it is intended, for example, the game is allowed for children over 3 years old, over 6 years old, over 10 years old, etc. In accordance with these assessments, one or another category of games can be allowed/prohibited. The window for setting game restrictions is shown in Fig. 136.

Rice. 136.

Application restrictions. The corresponding window (Fig. 137) will list the programs installed on the computer, from which you can select those that are not allowed to be used.

Connecting your computer to the network

So, we have considered issues related to the differentiation of access rights on the network and on the user’s computer, and we have gained the concept of system administration. However, we assumed that the local network was already configured and the computer with the operating system installed was connected to the local network. Now it's time to meet connecting your computer to the network and settings associated with this process. It should be noted that such actions will most likely be prohibited by the educational institution’s network administrator, so you can view the general progress of connection work on your personal computer without changing its settings in any way.

Firstly, a network card must be installed on the computer connecting to the network, secondly, a network cable must be connected to it, and thirdly, an agreement must be concluded in advance with the network service provider.

By executing the command Start/Control Panel/Network and Internet/View network status and tasks, the user will see the window shown in Fig. 138.

Rice. 138.

Typically, within a few seconds of turning on your computer, Windows 7 detects and configures your home network settings. Otherwise (in our example), the straight line connecting the SERGEY-VAIO section (this computer) - Multiple networks would be crossed out with a red cross. If a red cross appears on the site Internet(Fig. 139), this means that there is no connection to the Internet.

Rice. 139.

If you place your mouse pointer over the red cross, the message “Click here to troubleshoot” will appear. After clicking the mouse it will start Troubleshooting Wizard. However, those recommendations that Master will be issued at the end of the diagnostic process; only an experienced user can help. Even if you forcefully disconnect the network cable, Master will not display the message “Your network cable is disconnected”, but will inform you that you need to restart the modem.

In order to configure the computer’s connection to the network, in the window Network and Sharing Center(see Fig. 138) select item Internet Options/Connections. A similar situation is presented in zis. 140. Next, click the button Add VPN...

Rice. 140.

What is a VPN? Various computer companies often have the problem of combining several local networks that are located at a great distance from each other. In addition, there is also the problem of connecting remote users and providing them necessary protection from unauthorized access. If a company uses its own or leased communication channels or telephone lines, then this is a rather expensive solution that only large and very successful companies can afford. That is why, in order to reduce the cost of data transmission, virtual network technology (English: Virtual Private Network VPN) was developed.

The main feature of this technology is that a special channel is organized on top of the available network in a connection that has already been established. This channel allows for very high and reliable protection the information that is transmitted through this channel (the so-called tunnel) from the subscriber to the provider. For these purposes it is used PPTP protocol(English: Point-to-Point Tunneling Protocol), a point-to-point tunnel protocol that allows a computer to establish a secure connection with a server by creating a special tunnel in a standard, unsecured network.

Let's return to the VPN connection settings. Pressing the button Setting, should be entered Username: Password And domain. The window shown in Fig. 141.

All data must have been previously issued to the user by the network service provider. Next in the window Properties: Internet button should be pressed Network configuration. A window will open Configuring local network settings(Fig. 142), in which you will need to check the box Use a proxy server for LAN connection. When finished, press the button OK.

Next, you need to manually set/clarify network settings. To do this, in the window at Start/Control Panel/Network and Internet/Network Connections(Fig. 143) you need to double click on the icon LAN connection.

Rice. 141.

Rice. 142.

Rice. 143.

This action will cause a window to appear in which you should click the Properties button. The Local Area Connection - Properties window will open, shown in Fig. 144.

Rice. 144.

Rice. 145.

Next, from the list of components you need to select the option Internet Protocol Version 4 (TCP/IPv4) and press the button Properties. The window shown in Fig. 145 in which the options should be activated Obtain an IP address automatically And Obtain the DNS server address automatically.

Each computer on the network must have its own unique IP address, determining its location on the Internet. IP addressing is a 32-bit digital system designed to identify network computers in the Internet. Consists of four sets of numbers, where each number can range from 0 to 255, and is separated from the other values ​​by a dot, e.g.

Domain name system looks like a phone book. The user finds the name of the person or the name of the organization with which he wants to contact - a telephone number is indicated next to it. Similarly, a computer accesses DNS (Domain Name System) using the name of another computer or domain, and the name server issues an 1P address corresponding to this name.

A domain (area) name allows a person to work not with digital addresses of computers, but with familiar symbolic names (website addresses). The domain name is read from left to right from minor domains to domains top level(in order of increasing importance).

For example, the domain name krf.ane.ru has three components called levels and separated by dots:

ru- 1st (top) level domain name;

ane.ru- 2nd level domain name (second level domain in the w zone); krf.ane.ru- 3rd level domain name (third level domain in the ane.ru zone). In terms of purpose, the following domain designations are accepted:

Cell - for commercial sites;

Info - for companies or sites providing information;

Net - for telecommunications companies or companies doing business online;

Org -- for non-profit organizations;

Biz - zone for business sites as an alternative to the.cell zone;

Ru, .de, .tk, .cn, .us, .ca, etc. - domains different countries(geographical). Let's go back to the settings. Being in the window shown in Fig. 145, go to the tab Alternative configuration(see Fig. 146). Values ​​for IP address, DNS server, etc. issued by your network service provider.

Next in all open windows button pressed OK. The computer's network connection setup is complete, but you should restart the computer. After the reboot, double-click on the network connection name shortcut (it is specified during setup). The window shown in Fig. will open. 147.

The username and password will be the default and will not need to be entered again. All you have to do is press the button Connection. After which the connection to the Internet is considered established and the user is taken to the home page (specified in the settings).

Rice. 146.

Test questions and assignments

Rice. 147.

• 1. What functions does a system administrator perform?
• 2. List the administrator's steps to configure the operating environment.
• 3. What is the network printing setup?
• 4. Describe the administrator action known as network monitoring.
• 5. What knowledge should a network administrator have in such an area as information security?
• 6. What are the disadvantages of uncontrolled use of the Internet in organizations? What should a system provide to reduce such disadvantages?
• 7. What software is used to control and manage Internet access? Give examples.
• 8. List the tasks of differentiating access rights in the network.
• 9. How does user authorization work?
• 10. How does the locking system work to deny access to certain objects?
• 11. Why is an access profile created?
• 12. What are the three types of accounts? Tell us about each one.
• 13. What steps do I need to take to create an account?
• 14. What is the Windows 7 feature called parental controls?
• 15. Tell us about such a protection option as a web filter.
• 16. What needs to be done in order to connect a computer to the network?
• 17. Show practically the sequence of actions required to connect a computer to the network.
• 18. For what purposes is the PPTP protocol used? What is special about VPN technology?
• 19. Explain what IP addressing is for.
• 20. Tell us about the domain name system. Give examples of domain names. Explain what levels a domain name consists of.

Local network Local network A local network unites computers installed in one room (classroom, office, etc.), in one building or in several nearby buildings. Typically, local network computers are located at a distance of no more than one kilometer. As the distance increases, special equipment is used.

Server Server (from the English server - service device) is a computer that distributes resources between network users. The server has a powerful processor, large RAM and disk memory, and stores the bulk of software and network data that can be used by all network users.

In networks with a dedicated server, client-server technology is implemented. Server software is installed on the server: server operating system; WEB server (Intranet organization); proxy server (ensuring work with Internet workstations); file server (providing file sharing), etc. Dedicated server network software

Most common following methods computer connections: bus (usually used for peer-to-peer networks); star (used for any local networks); ring. Network hardware (Computer network topology) LAN topology –. LAN topology is the physical arrangement of network computers relative to each other and the way they are connected by lines.

To organize a local network you must: determine the name of the Working Group; assign each computer a unique name and IP address in this Workgroup, and also set a subnet mask address (in some cases, an explicit IP address and subnet mask address may not be set).

Local resource. Network users are prohibited from accessing computer resources. To ensure the availability of local resources, you need to set the switch to the Shared resource position. Shared resource. Allows the use of computer resources (disk memory and peripheral devices - printer, modem) to network users. To do this, you need to allow Sharing the folder. In this case, it is necessary to determine the access level. Modes of access to network resources

Read only Allows network users to open or copy files and folders. Full access Allows network users to perform all operations on files and folders (move, delete, edit, rename, etc.). Password access This mode Grants different categories of users different access rights, such as read-only or full access.

When working on a personal computer in offline mode, users can exchange information (programs, documents, etc.) only by copying it to floppy disks, disks, or flash memory.

The creation of computer networks is caused by the practical need to share information between users working on computers remote from each other. Networks provide users with the opportunity not only to quickly exchange information, but also to share printers and other peripheral devices and even work with documents simultaneously.

The local network combines computers installed in one room (for example, a school computer lab) or in one building (for example, a school building can be combined into local network several dozen computers installed in various subject rooms).

LAN Hardware

Local network equipment generally includes:

· computers (servers and workstations);

· network cards;

· channels of connection;

· special devices, supporting the functioning of the network (routers, hubs, switches).

The simplest type of local network is peer-to-peer network. From the name of such a network it follows that all computers in it have the same importance (status) and none of them is subordinate to another.

More developed networks, in addition to end user computers - workstations, include special computers - servers.

A server is a computer dedicated to the network that performs the functions of servicing workstations. Eat different types servers: file servers, database servers, etc.

Each computer connects to the network using network card- an adapter that supports a specific connection scheme. Thus, Ethernet adapters with a bandwidth of 10 or 100 Mbit/s are widely used.

A network cable is connected to the network card. If you are using radio or radio communications infrared rays, then no cable is required.

In modern local networks, two types of network cables are most often used:

· unshielded twisted pair;

· fiber optic cable.

twisted pair is a set of eight wires twisted in pairs in such a way as to provide protection against electromagnetic interference. Each twisted pair connects only one computer to the network, so a connection failure affects only that computer, allowing you to quickly find and fix problems.

Fiber Optic Cables transmit data in the form of light pulses over glass wires. Most LAN technologies now allow the use of fiber optic cables. Fiber optic cable has significant advantages over any copper cable option. Fiber optic cables provide the highest transmission speeds; they are more reliable because they are not subject to electromagnetic interference. Optical cable is very thin and flexible, making it easier to transport than heavier copper cable. The data transfer speed over an optical cable is hundreds of thousands of megabits per second, which is about a thousand times faster than through twisted pair wires.

Wireless connection on radio waves can be used to organize networks within large premises where the use of conventional communication lines is difficult or impractical. In addition, wireless lines can connect remote parts of the local network at distances of up to 25 km (subject to line of sight).

Shared external devices include external memory drives connected to the server, printers, plotters and other equipment that becomes accessible from workstations.

In addition to cables and network adapters, twisted pair local networks use other network devices - hubs, switches and routers.

Hub(also called a hub) is a device that unites several (from 5 to 48) branches of a star-shaped local network and transmits information packets to all branches of the network equally. A switch (switch) does the same thing, but, unlike a hub, it ensures the transmission of packets to specified branches. This ensures optimization of data flows in the network and increased security against unauthorized penetration.

Router(router) - a device that transfers data between two networks, including between local and global networks. A router, in fact, is a specialized microcomputer that has its own processor, RAM and ROM, and operating system.

Network topologies

General scheme The connections of computers on a local network are called network topology. Network topologies can be different:

· ring;

· bus – computers are connected to a common channel (bus), through which they can exchange messages;

· radial (“star”) – each computer is connected to a separate cable from one central node;

· tree-like – hierarchical subordination of computers.

Organization of data transmission on the network

A necessary condition The operation of a unified local network is the use of a network operating system. Such OS provide sharing not only of network hardware resources (printers, drives, etc.), but also of distributed collective technologies when performing a variety of work. The most widely used network operating systems are Novell NetWare, Linux and Windows.

Information in networks is transmitted in separate portions - packets, and the length of these packets is strictly limited (usually several kilobytes). This transmission method is due to the fact that the local network must provide high-quality communication for all computers on the network within a reasonable access time - the time the user waits for the connection to begin.

Computer networks have given rise to new information processing technologies - network technologies that allow the sharing of hardware and software. It has become commonplace for employees of many institutions to use e-mail to exchange messages and documents, and to collaborate. At enterprises, automated enterprise and technological process management systems are created on the basis of local networks.

A common way of organizing information processing on a network is called client-server technology. It assumes a deep separation of the functions of computers on the network.

The main function of the server is to perform specific actions based on client requests (for example, solving a complex mathematical problem, searching for data in a database, connecting a client to another client, etc.).

Global network is constructed in such a way that data transfer processes, management procedures and administrative services of individual subnets do not change significantly. Each of the subnets retains its autonomy, although the requirements for network management and control are tightened.

The local network designed as a single distribution system, in which priority is given to the requirements for standard protocols and the efficiency of network-wide management procedures.

In the first approach, the aggregation of subnets is concentrated in gateway (internetwork) devices. The network becomes unified primarily from the user's point of view. This approach is most consistent with the global Internet, implemented by the mechanism of virtual network addresses of client computers.

The second approach is implemented in practice in cases where the network physically connects user computers to each other and manages them on a server basis. A set of computers that have the ability to communicate with each other is usually called local computer (computer) network or LAN(LAN - Local Area Network). The most common local computer network technology since the mid-1990s. became Ethernet. Let's consider general structure LAN.

LAN composition:

computers;

cables;

node devices.

Local computer networks can be single- and double-rank (hierarchical).

In large networks with a large number of computers, they organize two-rank (hierarchical) local network with a dedicated, more powerful computer called server. The server must be configured in such a way that it can receive requests for network resources from the client computer, determine the client's authority to execute a particular request, and, if the client has authority, execute its request and transmit the result of this request to it. To solve all these problems, both the client computer and the server must have network operating system.

Components local network.

Work station- this is a PC turned on and a local network for exchanging information.

Server this is a specially dedicated computer for processing requests coming from workstations, which provides workstations (clients) with its resources (for example, “hard” drives, application software). File server, application server, database server, remote access server, print server, backup server.

Cables designed for transmitting information via wired communication channels.

When connecting computers to a LAN, they can be used wireless communication devices. In this case, there is no need to lay cable networks.

One of the trends in the development of intracorporate networks is Wi-Fi wireless technology(Wireless Fidelity - wireless accuracy). In this case, any access point includes a Wi-Fi antenna for transmitting a radio signal, special Wi-Fi equipment - a network adapter (wireless network card), wireless access points (routers) and various switching devices.

Bluetooth is also a wireless networking technology. Physically, a typical Bluetooth device is a radio receiver and a radio transmitter operating at specific frequencies.

Each computer connected to the network must be equipped network adapter(or network card). The most famous adapters are the following types: Arc-Net, Token Ring, Ethernet. Of these, the latter is used most widely in Russia.

To combine computers into a network consisting of more than two computers using a physical star topology, you need a device that acts as the center of the star. Such a device is most often hub, or hub(from English hub - hub).

Router(router) is a device for separating or combining several computer networks. The method of organizing communication between LAN computers is called local network topology(architecture, configuration). There are three main topologies that make up a LAN: bus, ring, and star.

To send data from one computer to another, you need to know and specify its address. Modern networks use three types of addresses: physical, numeric and symbolic.

Every network adapter, bridge, router, and other network equipment has a unique digital hardware address called physical, which is used for addressing on the local network. This address is called a MAC address (Media Access Control). The MAC address of the device can be seen on its back side. Usage numeric addresses is associated with the operation of TCP/IP, which is one of the main protocols that ensures the delivery of information from the source to the destination.

Assignment: outline the topic.

A local network or LAN is two or more computers connected to each other directly or through a router (router) and capable of exchanging data. Such networks usually cover a small office or home space and are used to share an Internet connection, as well as for other purposes such as file sharing or online gaming. In this article we will talk about how to build a local network of two computers.

As it becomes clear from the introduction, you can combine two PCs into a local area in two ways - directly, using a cable, and through a router. Both of these options have their pros and cons. Below we will look at them in more detail and learn how to configure the system for data exchange and access to the Internet.

Option 1: Direct connection

With this connection, one of the computers acts as a gateway for connecting to the Internet. This means that it must have at least two network ports. One for the global network, and the second for the local one. However, if the Internet is not required or it “comes” without the use of wires, for example, through a 3G modem, then you can get by with one LAN port.

The connection diagram is simple: the cable is plugged into the corresponding connectors on the motherboard or network card of both machines.

Please note that for our purposes we need a cable (patch cord) that is designed for direct connection computers. This type is called a “crossover”. However, modern equipment is capable of independently determining pairs for receiving and transmitting data, so a regular patch cord will most likely also work normally. If problems arise, you will have to redo the cable or find the right one in the store, which can be very difficult.

The advantages of this option include ease of connection and minimal equipment requirements. Actually, we only need a patch cord and a network card, which in most cases is already built into the motherboard. The second plus is high data transfer speed, but this depends on the capabilities of the card.

It's a stretch to call the disadvantages such - they reset the settings when reinstalling the system, as well as the inability to access the Internet when the PC, which is the gateway, is turned off.

Settings

After connecting the cable, you need to configure the network on both PCs. First, we need to assign a unique name to each machine in our local area. This is necessary so that the software can find computers.

Now you need to configure shared access to resources on the local network, since by default it is limited. These steps also need to be performed on all machines.

1. Right-click on the connection icon in the notification area and open "Network and Internet settings".

   

2. Let's move on to setting up sharing parameters.

   

3. For a private network (see screenshot), enable discovery, enable file and printer sharing, and let Windows manage connections.

   

4. For the guest network we also enable discovery and sharing.

   

5. For all networks, we disable general access, configure encryption with 128-bit keys, and disable password access.

   

6. Save the settings.

   

In Windows 7 and 8, this block of parameters can be found like this:

1. On the first PC (the one that connects to the Internet), after going to the parameters (see above), click on the menu item "Configuring adapter settings".

   

2. Here we select "LAN connection", right-click on it and go to properties.

   

3. In the list of components we find the protocol IPv4 and, in turn, move on to its properties.

   

4. Switch to manual input and in the field "IP address" enter the following numbers:

   In field "Subnet mask" the required values ​​will be automatically entered. There is no need to change anything here. This completes the setup. Click OK.

   

5. On the second computer, you must set the following IP address in the protocol properties:

   We leave the mask as default, but in the fields for the gateway and DNS server addresses we indicate the IP of the first PC and click OK.

   

   In the "seven" and "eight" you should go to "Network Control Center" from the notification area, and then click on the link "Change adapter settings". Further manipulations are carried out according to the same scenario.

   

The final procedure is to allow shared access to the Internet.

Now on the second machine it will be possible to work not only on the local network, but also on the global one. If you need to exchange data between computers, you will need to perform one more setup, but we will talk about this separately.

Option 2: Connection via router

For such a connection, we will need, in fact, the router itself, a set of cables and, of course, the corresponding ports on the computers. The type of cables for connecting machines to a router can be called “direct”, as opposed to a crossover cable, that is, the cores in such a wire are connected “as is”, directly (see above). Such wires with already mounted connectors can be easily found in retail stores.

The router has several connection ports. One for receiving the Internet and several for connecting computers. It’s easy to distinguish them: LAN connectors (for cars) are grouped by color and numbered, and the port for the incoming signal stands apart and has a corresponding name, usually written on the case. The connection diagram in this case is also quite simple - the cable from the provider or modem is connected to the connector "Internet" or, in some models, "Link" or "ADSL", and computers to ports signed as "LAN" or "Ethernet".

The advantages of this scheme are the possibility of organizing a wireless network and automatic detection system parameters.