How to build a network diagram. Network planning tasks

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 mode of operation... 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.

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 not required to be entered. 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 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 router mode is activated on the computer, 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 that the address on the local (facing the local network) interface of the router is changed 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 just 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 router computer 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. enable 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 in fact the web server is 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

A network diagram is a table designed to draw up a project plan and monitor its implementation. To build it professionally, there are specialized applications, for example MS Project. But for small businesses, and especially for personal business needs, there is no point in buying specialized software and spending a lot of time learning the intricacies of working with it. The Excel spreadsheet, which is installed by most users, copes quite successfully with constructing a network diagram. Let's find out how to perform the above task in this program.

You can build a network diagram in Excel using a Gantt chart. Having the necessary knowledge, you can create a table of any complexity, from the guard duty schedule to complex multi-level projects. Let's take a look at the algorithm for performing this task by drawing up a simple network diagram.

Stage 1: building the table structure

First of all, you need to create a table structure. It will represent a wireframe network diagram. Typical elements of a network diagram are columns that indicate the serial number of a specific task, its name, the person responsible for its implementation and the deadlines for completion. But in addition to these basic elements, there may be additional ones in the form of notes, etc.

At this point, the creation of the table template can be considered complete.

Step 2: Create a Timeline

Now we need to create the main part of our network graph - the timeline. It will be a set of columns, each of which corresponds to one period of the project. Most often, one period is equal to one day, but there are cases when the period is calculated in weeks, months, quarters and even years.

In our example, we use the option when one period is equal to one day. Let's make a time scale of 30 days.

Let's move on to the right border of our table blank. Starting from this boundary, we select a range of 30 columns, and the number of rows will be equal to the number of lines in the template that we created earlier.

After that, click on the icon "Border" in mode "All Borders".

Once the boundaries are outlined, we will enter the dates into the time scale. Let's say we will control a project with a validity period from June 1 to June 30, 2017. In this case, the names of the time scale columns must be set in accordance with the specified time period. Of course, entering all the dates manually is quite tedious, so we’ll use the autofill tool called "Progression".
Insert the date into the first object of the time jackal header "06/01/2017". Moving to the tab "Home" and click on the icon "Fill". An additional menu opens where you need to select the item "Progression…".

The window is being activated "Progression". In a group "Location" value must be marked "Line by line", since we will fill the header, represented as a string. In a group "Type" option must be checked "Dates". In the block "Units" you should place a switch near the position "Day". In the area "Step" must contain a numeric expression "1". In the area "Limit value" indicate the date 30.06.2017 . Click on "OK".

The header array will be filled with consecutive dates ranging from June 1 to June 30, 2017. But for the network diagram, we have too wide cells, which negatively affects the compactness of the table, and, therefore, its visibility. Therefore, we will carry out a number of manipulations to optimize the table.
Select the header of the time scale. Click on the selected fragment. In the list we stop at the item "Cell Format".

In the formatting window that opens, move to the section "Alignment". In the area "Orientation" set the value "90 degrees", or move the element with the cursor "Inscription" up. Click on the button "OK".

After this, the column names in the form of dates changed their orientation from horizontal to vertical. But due to the fact that the cells did not change their size, the names became unreadable, since they did not fit vertically into the designated elements of the sheet. To change this state of affairs, we again select the contents of the header. Click on the icon "Format" located in the block "Cells". In the list we focus on the option "Auto-fit row height".

After the described action, the height of the column names fit into the boundaries of the cells, but the width of the cells did not become more compact. Again select the range of the time scale header and click on the button "Format". This time, select the option from the list "Auto-fit column width".

Now the table has become compact, and the grid elements have taken a square shape.

Stage 3: filling in data

Step 4: Conditional Formatting

At the next stage of working with the network diagram, we have to fill with color those grid cells that correspond to the period of the specific event. This can be done using conditional formatting.

We mark the entire array of empty cells on the time scale, which is presented as a grid of square elements.

Click on the icon "Conditional Formatting". It is located in the block "Styles" After this, a list will open. You should select the option "Create Rule".

A window opens in which you need to create a rule. In the area for selecting the type of rule, mark the item that implies the use of a formula to designate formatted elements. In the field "Format values" we need to set a selection rule, presented as a formula. For our specific case, it will look like this:
AND(G$1>=$D2;G$1<=($D2+$E2-1))

But in order for you to be able to convert this formula for your network diagram, which quite possibly will have different coordinates, we need to decipher the written formula.

"AND" is a built-in Excel function that checks whether all values supplied as its arguments are true. The syntax is:

AND(logical_value1;logical_value2;…)

In total, up to 255 boolean values are used as arguments, but we only need two.

The first argument is written as an expression "G$1>=$D2". It checks that the value in the time scale is greater than or equal to the corresponding value for the start date of a particular event. Accordingly, the first link in this expression refers to the first cell of the row in the timeline, and the second - to the first element of the event start date column. Dollar sign ( $ ) is set specifically so that the coordinates of the formula that have this symbol do not change, but remain absolute. And for your case, you should place dollar signs in the appropriate places.

The second argument is represented by the expression "G$1<=($D2+$E2-1)» . It checks that the indicator on the time scale ( G$1) was less than or equal to the project completion date ( $D2+$E2-1). The time scale indicator is calculated as in the previous expression, and the project completion date is calculated by adding the project start date ( $D2) and its duration in days ( $E2). In order to include the first day of the project in the number of days, one is subtracted from this amount. The dollar sign plays the same role as in the previous expression.

If both arguments of the presented formula are true, then conditional formatting will be applied to the cells in the form of filling them with color.

To select a specific fill color, click on the button "Format…".

In a new window, move to the section "Fill". In a group "Background Colors" Various shading options are presented. We mark the color with which we want the cells of the days corresponding to the period of completion of a specific task to be highlighted. For example, let's choose green. After the shade is reflected in the field "Sample", click on "OK".

After returning to the rule creation window, click on the button "OK".

After the last action was completed, the grid arrays corresponding to the period of the specific activity were colored green.

At this point, the creation of the network diagram can be considered complete.

As we worked, we created a network diagram. This is not the only version of such a table that can be created in Excel, but the basic principles for performing this task remain unchanged. Therefore, if desired, each user can improve the table presented in the example to suit their specific needs.

Hello.

Even 10-15 years ago, having a computer was almost a luxury, but now even having two (or more) computers in the house does not surprise anyone... Naturally, all the advantages of a PC appear when you connect it to a local network and the Internet, for example: network games, disk space sharing, fast file transfer from one PC to another, etc.

Not long ago I was “lucky” to create a home local network between two computers + “share” the Internet from one computer to another. I’ll tell you how to do this (from fresh memory) in this post.

1. How to connect computers to each other

The first thing you need to do when creating a local network is to decide how it will be built. A home local network usually consists of a small number of computers/laptops (2-3 pcs.). Therefore, 2 options are most often used: either computers are connected directly using a special cable; or use a special device - a router. Let's look at the features of each option.

Connecting computers “directly”

This option is the simplest and cheapest (in terms of equipment costs). In this way you can connect 2-3 computers (laptops) to each other. At the same time, if at least one PC is connected to the Internet, you can allow access to all other PCs on such a network.

What is needed to create such a connection?

1. A cable (also called twisted pair), slightly longer than the distance between the connected PCs. It’s even better if you immediately buy a crimped cable in the store - i.e. already with connectors for connecting to the computer’s network card (if you crimp it yourself, I recommend that you familiarize yourself with it:).

By the way, you need to pay attention to the fact that the cable is needed specifically to connect a computer to a computer (cross connection). If you take a cable to connect a computer to a router - and use it to connect 2 PCs - such a network will not work!

2. Every computer must have a network card (all modern PCs/laptops have one).

3. Actually, that’s all. Costs are minimal, for example, a cable in a store to connect 2 PCs can be bought for 200-300 rubles; There are network cards in every PC.

All that remains is to connect 2 system units with a cable and turn on both computers for further settings. By the way, if one of the PCs is connected to the Internet via a network card, then you will need a second network card - to be used to connect the PC to the local network.

The advantages of this option:

Fast creation;

Easy setup;

The reliability of such a network;

High speed when exchanging files.

Cons:

Extra wires around the apartment;

To have access to the Internet, the main PC that is connected to the Internet must always be turned on;

Inability to gain access to the network for mobile devices*.

Creating a home local network using a router

A router is a small box that greatly simplifies the creation of a local network and Internet connection for all devices in the house.

It is enough to configure the router once - and all devices will be able to immediately connect to the local network and access the Internet. Nowadays you can find a huge number of routers in stores, I recommend reading the article:

Desktop computers connect to the router via a cable (usually 1 cable is always included with the router), laptops and mobile devices connect to the router via Wi-Fi. You can see how to connect a PC to a router (using the example of a D-Link router).

The organization of such a network is described in more detail in this article:

Pros:

Set up the router once, and Internet access will be available on all devices;

No extra wires;

Flexible Internet access settings for different devices.

Cons:

Additional costs for purchasing a router;

Not all routers (especially those from a low price category) can provide high speed on the local network;

It is not always so easy for less experienced users to set up such a device.

2. Setting up a local network in Windows 7 (8)

After the computers are connected to each other by any of the options (whether they are connected to a router or directly to each other), you need to configure the Windows OS for full operation of the local network. Let's show the example of Windows 7 OS (the most popular OS today; in Windows 8 OS the setting is similar + you can familiarize yourself with it).

2.1 When connecting via a router

When connecting via a router, the local network, in most cases, is configured automatically. The main task comes down to setting up the router itself. Popular models have already been discussed on the blog pages earlier; I will provide several links below.

After setting up the router, you can start setting up the OS. So…

1. Setting up a workgroup and PC name

The first thing you need to do is set a unique name for each computer on the local network and set the same workgroup name.

For example:

1) Computer No. 1

Working group: WORKGROUP

Name: Comp1

2) Computer No. 2

Working group: WORKGROUP

Name: Comp2

To change the PC name and workgroup, go to the control panel at the following address: Control Panel\System and Security\System.

Windows 7 System Properties

2. File and Printer Sharing

If you do not take this step, then no matter what folders and files you provide for public access, no one will be able to access them.

To enable the option to share printers and folders, go to the control panel and open the “Network and Internet” section.

Now click in the left column on the item “ change advanced sharing options«.

Several profiles 2-3 will appear in front of you (in the screenshot below there are 2 profiles: “ Home or work" and "General "). In both profiles you need to allow file and printer sharing + disable password protection. See below.

Setting up sharing.

More sharing options

After making the settings, click " save changes" and restart your computer.

3. Sharing shared folders

Now, in order to use files on another computer, the user needs to share folders on it (give general access to them).

This is very easy to do - in 2-3 mouse clicks. Open File Explorer and right-click on the folder you want to open. In the context menu select " Sharing - HomeGroup (Reading)«.

Next, you just have to wait about 10-15 seconds and the folder will appear in public access. By the way, to see all the computers on your home network, click on the “Network” button in the left column of Explorer (Windows 7, 8).

2.2 When connecting directly + sharing Internet access on a second PC

In principle, most of the steps for setting up a local network will be very similar to the previous option (when connecting through a router). To avoid repetition, I will mark steps that are repeated in parentheses.

1. Setting up the computer name and workgroup (similarly, see above).

2. Setting up file and printer sharing (similarly, see above).

3. Configuring IP addresses and gateways

The setup will need to be done on two computers.

On this page you will find solved standard tasks from tests on network planning - a section of economic and mathematical methods and models.

As part of the study of network analysis, students usually learn to: build a network graph using a tabular or verbal description of a project (and vice versa), find early and late start and finish dates for work, reserves, the critical path and the minimum time for completing a project. More complex tasks involve various options for adjusting and optimizing the network schedule (with an increase in time and a decrease in costs, or vice versa, with a decrease in time and an increase in costs), and resource allocation tasks. Various graphical methods of displaying both a network graph (see tasks below) and other diagrams for the project (Gantt chart, line graph) are studied.

Examples of solutions to network planning problems online

Task 1. For a given network model of a certain set of works, determine the time and critical path.

Task 2. The publisher has a contract with the author to publish his book. Below is a sequence (simplified) of processes leading to the implementation of a book publishing project. It is necessary to develop a network for this project.

Task 3. 1. Based on the given list of works, build a network diagram.
2. Determine the duration of complete paths of the schedule.
3. Identify and highlight the critical path.
4. Determine the reserve time for each route.
5. Determine the track tension coefficients.
6. Determine the early and late start and finish dates of work.
7. Determine the full reserve time for each job.

Task 5. On the network diagram, find early and late dates for the occurrence of events, determine the critical path and time reserves of each event.

Task 6. Construct a network diagram. Solve the problem of optimal distribution of resources among jobs at constant intensities. Availability of resource R=10. Work does not allow interruption in its execution.

Task 7. This option requires:
1) build a network model;
2) determine the critical paths of the model;
3) carry out the maximum possible reduction in project completion time at the minimum possible additional costs

Every project manager is faced with such a typical task as constructing a network diagram. Currently, this process is completely automated and, as a rule, the manager does not have any big problems. For a long time now there is no need to draw graphs on paper, calculate early and late starts or finishes of tasks, connect tasks with arrows, or calculate the length of the critical path. ISUP successfully solves all these problems.

However, without understanding the basics and rules of constructing network graphs, mistakes are often made. Despite the fact that modern ones are quite “smart” and protect the project manager in many moments related to the project schedule, nevertheless, there remain “blind” spots that lie only in the area of responsibility of the project manager.

In order to get real benefit from it, you need to be able to use it competently, like any other tool.

What is a network diagram

Network diagram (English, Project Network) is a dynamic project model that reflects the dependence and sequence of project work, connecting their completion in time, taking into account resource costs and the cost of work.

A network diagram can be built in two ways:

The vertices of the graph reflect the state of a certain object (for example, construction), and the arcs represent the work being carried out at this object.
The vertices of the graph reflect the jobs, and the connections between them represent the dependencies between the jobs.

Rules for constructing a network graphic

First of all, constructing a network diagram consists of correctly connecting events together (indicated in the diagram in circles) with the help of work (indicated in the diagram arrows). The correct connection of the arrows is as follows:

each job in the network diagram must exit from an event, which means the end of all jobs, the result of which is necessary to start the job;
an event marking the commencement of a particular activity must not include the results of activities the completion of which is not required for the commencement of that activity;
The network graph is built from left to right, and each event with a higher serial number must be located to the right of the previous one. Arrows representing work should also be positioned from left to right.

Original works

The construction of a schedule begins with the depiction of work that does not require the results of other work to begin. Such work can be called initial work, since all other work of the complex will be carried out only after they are fully completed.

Depending on the specifics of the planned complex, there may be several initial works, or there may be only one. When placing initial works, it is necessary to take into account that there should be only one initial event on the network diagram.

Figure 1 shows an example of the start of a network diagram with one initial job (job A), and in Figure 2 there is an example of the beginning of a network diagram with three initial works (works A, B, C).

Figure 1. Network diagram with one source work

Figure 2. Network diagram with three original works

Consecutive works

If work B should only be performed after the work has been completed A, then on the graph this is depicted as a sequential chain of works and events.

Figure 3. Sequentially performed work

If to perform multiple jobs, e.g. B And C the result of the same work is required A, then on the graph this is depicted by “parallel” arrows emanating from the event that is the result of the work A.

Figure 4. Jobs performed after the same job

If to get the job done C the result of the work is required A And B, then on the graph this is depicted by “parallel” arrows entering the event, after which the work follows C.

Figure 5: Job done after multiple jobs

If to perform work B And C intermediate result of work is required A, then work A is divided into subtasks in such a way that its first subtask ( A1) was executed until the intermediate result necessary to begin work was obtained B, and the second subtask was executed until the intermediate result needed to start working was obtained C, the subsequent part A3 can be performed in parallel with the work A1 And A2.

Figure 6. Work performed after partial completion of other work

Two adjacent events can be combined by one and only one activity. To depict parallel work on a network diagram, a so-called intermediate event and fictitious work are introduced.

Figure 7. Jobs that have common start and end events

If doing the work D possible only after receiving the total result of the work A And B, and doing the work C– after receiving only the result of work A, then it is necessary to enter an additional event and fictitious work in the network diagram.

Figure 8. Use of dummy works

"Tails" and "dead ends"

There should be no “dead ends” in the network, i.e. intermediate events from which no work comes out. In Figure 9, the deadlock event is the event 6.

There should also be no “tails”, i.e. intermediate events that are not preceded by at least one activity. In Figure 9, the tail event is the event 3 .

Figure 9. “Tails” and “dead ends” in a network diagram

Cycles

The network diagram should not contain cycles consisting of interconnected works that create a closed chain - a chain of works D->F->G in Figure 10. This situation most likely indicates an error in compiling a list of works and determining their relationships.

Figure 10. Cycle on a network diagram

In this case, it is necessary to analyze the source data and, depending on the conclusions drawn from the analysis, either redirect the work creating the cycle to another event (if the work starting in this event requires its result, or if it is part of the overall result), or completely eliminate it from the complex (if it is determined that its result is not required).

Figure 11 shows an example of loop elimination when operation G becomes part of the overall result.

Figure 11. Eliminating a loop in a network diagram

Naming jobs and numbering events

Each job in the network diagram should be uniquely defined, only by its inherent pair of events, just as there should not be events with the same numbers on the diagram.

To correctly number events, proceed as follows: numbering of events begins with the initial event, which is given a number 0 . All works emanating from it are deleted from the initial event, and an event is again found on the remaining network, which does not include any work. This event is given a number 1 . Then the works that come out of the event are crossed out. 1 , and again find an event on the remaining part of the network that does not include any work, it is assigned a number 2 , and so on until the final event.