How to create a local network between two computers? Building a network diagram: an example. Manufacturing process model

A local area network or LAN is two or more computers connected directly or through a router (router) and capable of exchanging data. These networks usually cover a small office or home space and are used for general 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, there are two ways to combine two PCs into a “LAN” - directly, using a cable, and through a router. Both of these options have their pros and cons. Below we will analyze them in more detail and learn how to configure the system for data exchange and Internet access.

Option 1: Direct Connection

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

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

Please note that for our purposes we need a cable (patch cord), which is designed for direct connection of computers. This type is called a "crossover". However, modern equipment is able to independently determine pairs for receiving and transmitting data, so a regular patch cord will most likely also work fine. If problems arise, then the cable will have to be redone or found in the store, which is very difficult.

The advantages of this option include ease of connection and minimal hardware 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 a high data transfer rate, but this depends on the capabilities of the card.

The disadvantages can be called such with a big stretch - this is a reset when reinstalling the system, as well as the inability to access the Internet when the PC is turned off, which is the gateway.

Setting

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

Now you need to configure the sharing of resources on the local network, as it is limited by default. 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 options.

   

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, turn off public access, set up encryption with 128-bit keys, and turn off password access.

   

6. We 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 options".

   

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

   

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

   

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

   In field "Subnet mask" the correct values ​​will be automatically inserted. Nothing needs to be changed here. This completes the setup. Click OK.

   

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

   We leave the mask by default, but in the fields for the addresses of the gateway and DNS server, specify 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 performed according to the same scenario.

   

The final procedure is to enable internet sharing.

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

Option 2: Connecting through a router

For such a connection, we 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 “straight”, as opposed to crossover, 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.

The router has multiple connection ports. One for receiving the Internet and several for connecting computers. Distinguishing them is easy: LAN connectors (for machines) are grouped by color and numbered, and the port for the incoming signal stands alone 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, on some models, Link or ADSL, and computers to ports signed as "LAN" or Ethernet.

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

The following concepts and terminology are adopted in the network planning and construction management system.

Under the concept of a project, a range of organizational and technical tasks is generalized to be solved to achieve the final results of construction production. These include: the development of a feasibility study for the planned construction, the selection of a construction site, engineering and geological surveys, the design of a territory for development, the development and approval of the technical documentation necessary for construction, including schedules and schemes for the production of construction and installation works before the delivery of those under construction objects in operation.

The set of works performed to achieve a specific goal, which determines a certain part of the project, is called the function of the project. For example, work related to the preparation of construction production (development of working drawings of buildings and structures, a project for the production of works; placing orders for the manufacture of equipment, structures and their delivery to the construction site, etc.) or with the production of construction and installation works, with the construction foundations, (casting, laying out axes, digging pits, harvesting and installing formwork and reinforcement, preparing concrete mix, transporting and laying it into the formwork, stripping and capturing the sinuses of concreted foundations with soil) are functions in the construction project.

The most important performance indicators of the project are the cost and duration of construction, which are directly dependent on similar indicators of individual project functions. If a list of all project functions is established and the sequence of execution and time costs are determined for each of them, then by depicting these functions in the form of a graphical network, you can see which of them determine the timing of the remaining functions and the entire project as a whole.

It follows from this that the network schedule reflects the logical interconnection and interdependence of all organizational, technical and production operations for the implementation of the project, as well as a certain sequence of their implementation.

The main parameters of the network diagram are the work and the event, and the derivatives are the network, the critical path and the time reserves.

Work refers to any process that takes time. In network diagrams, this term determines not only certain production processes that require the expenditure of material resources, but also the expected processes associated with observing technological breaks, for example, for hardening laid concrete.

An event is an intermediate or final result of one or more activities, necessary for the start of other activities. An event is fired after all the jobs included in it have been completed. Moreover, the moment of the completion of the event is the moment of the end of the last (included in it work. Thus, the event is the final results of certain works and at the same time - the starting positions for the beginning of subsequent ones. An event that does not have previous works is called initial; an event that having no subsequent works is called finite.

Work on the network diagram is depicted with one solid arrow. The duration of work in units of time (days, weeks) is put down under the arrow, and the name of the work is above the arrow. Each event is depicted by a circle and numbered (Fig. 115).

Rice. 115. Designation of events and work m - n.

Rice. 116. Designation of the dependence of technological events.

Rice. 117. Designation of the dependence of events of an organizational nature.

The duration of a particular work, established depending on the accepted method of its implementation according to the UNIR or labor costing, is called a time estimate. The dependence between individual events, which does not require the expenditure of time and resources, is called fictitious work and is depicted on the network diagram by a dotted arrow.

These dependencies or fictitious works can be divided into three groups: technological, organizational, conditional.

Dependence of a technological nature means that the execution of one work depends on the completion of another, for example, the walls of the next floor cannot be laid before the floor panels of the lower floor are installed (Fig. 116).

Dependence of an organizational nature shows the transitions of teams of workers, the transfer of mechanisms from one site to another, etc. They arise mainly when work is performed by in-line methods (Fig. 117).

If there are several end events (for example, the commissioning of several objects included in the launch complex of the enterprise), they should be connected by conditional dependencies or fictitious work together - putting the enterprise into operation (Fig. 118, b).

The start event must be one. In cases where there are several initial events (for example, work on excavating the excavations of several objects independently of each other begins), they should be conditionally connected by the designation of fictitious works with a single initial event (Fig. 118, a).

If the timing of the actual initial events of individual objects of the complex is different, the concept of real-time dependencies converging at one initial node should be introduced.

The duration set taking into account single-shift, and for the leading machines two-shift work and the optimal saturation of the front of work, is called the normal duration of work. If the duration of work is due to the maximum load of the front of work for two or three shifts, then it is considered minimal.

Rice. 118. Notation of conditional dependencies.

The term of work differs in terms:

the earliest start date for work is the first day on which work can begin;

the earliest end date of the work - the day the work ends, if it is started at the earliest start date;

the latest start of work - the last day of the start of work without delaying the total construction period;

the latest completion date of the work is the day when the work must be completed without delaying construction, i.e. without disrupting the overall construction period.

The difference between the latest and earliest start dates determines the private slack, that is, the time that work can be postponed without increasing the duration of construction. The time for which work can be postponed without delaying the execution of any subsequent work determines the total (total) slack, which is the difference between the total slack of the considered and subsequent work. In the case of several subsequent jobs, the job that has the smallest amount of total slack is selected.

The continuous sequence of works and events from initial to final, requiring the greatest time for its implementation, determines the critical path, which determines the total duration of construction, since the critical works lying on it do not have time reserves.

In network diagrams, the direction of the arrows depicting jobs can be chosen arbitrarily. Typically, such graphs are built from left to right. However, the arrows for individual jobs can go up, down, or right to left.

When drawing up a network diagram, each activity should be considered from the point of view of its relationship with other activities and the following questions should be answered:

what work should be completed before starting this work;

what other work can be completed simultaneously with the execution of this work;

which work cannot be started before the completion of this work. Let's consider some examples of graphic representation of connections and work sequences in network diagrams.

Rice. 119. Communication schemes between works (a, b, c, d, e, f, g - cases 1,2,3,4,5,6,7).

Case 1 (Fig. 119, a). Relationship between works A (1-2) and B (2-3). Job B cannot start until Job A has finished.

Case 2 (Fig. 119.6). Dependence of two jobs on one. Activities D (7-8) and F (7-9) cannot be started until activity D (6-7) is completed.

Case 3 (Fig. 119, c). The dependence of one job on the completion of two jobs. Job E (10-11) cannot start until jobs D (8-10) and E (9-10) are finished.

Case 4 (Fig. 119, d). The start of the two jobs depends on the completion of the two jobs as well. Works F (15-16) and D (15-17) can only start after the completion of works B (13-15) and C (14-15).

Case 5 (Fig. 119, 6). Dependence of two groups of works. Work B (15-16) depends only on the completion of work A (14-15), and work D (21-22) depends on the completion of works A (14-45) and C (19-21). Network linking is carried out by including fictitious work D (15-21).

Case 6 (Fig. 119, e). Work D (47-48) cannot be started until the end of work C (46-47). In turn, work B (50-51) cannot be started until the end of work C (46-47) and A (49-50). Job E (47-50) is fictitious, which determines the logical linking of the network by holding back the start of job B (50-51) until job C (46-47) is completed.

Case 7 (Fig. 119,g). Work D (8-14) cannot be started until the completion of works A (2-8) and B (4-6); work G (12-16) cannot be started until the completion of Fig. 120. Scheme of the network diagram, works D (10-12), B (4-6); the relationship between these works is indicated by the fictitious work E (6-12). Since work W (12-16) does not depend on the completion of work A (2-8), it is separated from the last fictitious work B (6-8).

Rice. 120. Diagram of a network diagram.

In order to clarify the methodology for constructing network graphs, consider the case when the following conditions arose during the construction of an object:

at the beginning of construction, work A and B must be carried out in parallel;

activities C, D and E can be started before the completion of activity A;

work B must be completed before the start of work F and G;

at the same time, work E also depends on the completion of work A;

activity 3 cannot be started before the completion of activities D and F;

work I depends on the completion of work D and 3;

work K follows the end of work G;

work L follows work K and depends on the completion of work D and 3;

the final work M depends on the completion of works B, I and L.

On fig. 120 shows one of several possible solutions to the problem defined by the given construction conditions. All decisions should be based on the same logical concept, regardless of the grid type. The grid must be considered from the point of view of the logical sequence of work. For this purpose, its review should begin with the last event on the object and go back from event to event, checking such provisions: whether each work starting on the event depends on all the activities leading to the event; whether all activities on which the activity in question should depend are included in the event. If both questions can be answered in the affirmative, then the network schedule satisfies the requirements of the projected construction technology of the facility.

When constructing a network diagram, the concept of “work”, depending on the degree of desired accuracy, can mean certain types of work or complexes of production processes performed at a given facility by one of the organizations participating in the construction. For example, the chief engineer of a trust needs to know fewer details than a foreman. Therefore, to provide construction guidance at the trust level, the network schedule can be compiled on the basis of more aggregated indicators.

If you use at home not only one computer, but also other similar devices, then they can be combined into a home network. In this case, you can create a home network through a router, which will have access to the Internet.

A local network through a router will allow you to simply connect all your devices. You can then exchange files over the local network, play games or use for other purposes.

To do this, you need to purchase only a special device - a router (router). With the help of a router, communication is carried out between devices connected to the network, and a home network is created through a wifi router. If your devices use the same router to access the Internet, then there is a network between these devices. It does not matter how your devices are connected, using a network cable or via wireless Wi-Fi.

To create a local network through a router, you need to connect the necessary devices directly to the router, or use a wireless connection. In all modern routers, you can use a wired or wireless connection option. But you can also use a router to connect several networks to each other.

Creating a home network through a router is usually done using the star principle. When connecting according to this scheme, all devices that you plan to use must be independently connected to the router. The router in this case is such a center of the resulting star, or rather the network. At the same time, the router itself connects to the provider's network and can distribute the Internet to devices connected to it. Schematically, this connection can be seen in the figure below.

Connection with a router of the "Star" type

Router for home network

The router is the main device for creating a network. Before you create a network through a router, you must select a suitable router model. You need to know exactly what type of connection your ISP is using (cable or dial-up). If a cable connection is used, then the router must be selected with a WAN connector, and if a telephone line, then there must be an ADSL connector.

In addition, more options are possible when using a 3G / 4G modem, telephone (“STREAM”) or cable modem (“AKADO”). When using the last two options, a special modem is also required. Such a modem can be a separate device or built into the router itself. You can see the scheme for connecting devices and creating a network through a router in the figure below.

On the back or side of the router are the device ports used for connection. The port that is used to connect to the Internet is called the WAN port. Ports for wired connection of a computer, network drive or other devices to a local network are called LAN ports. There are several such ports, but basically there are four of them. If the number of ports does not suit you and you need to connect more devices, you can use a network switch. When installing such a switch with eight ports, you connect one port to the router, and you can use the remaining seven to connect your devices. Switches are 100-megabit and gigabit. The use of a gigabit switch makes sense if you need to quickly connect a computer to a network drive. This will not affect the speed of the Internet itself. Network configuration through the router can be performed through the settings in the web interface of the router.

In addition to wired connection of devices using Ethernet technology, other options are possible. The network can be created via electrical wiring (HomePlug). But most often a wifi network is created through a router using a wireless connection. These methods differ in different maximum speeds and these characteristics can be seen in the table below.

When choosing a router for a WIFI home network, the router using 802.11n gives the best results, as it provides, compared to 802.11g technology, better performance and signal coverage. In addition, you should pay attention to other useful features, such as the built-in FTP client or USB port, which can be used to connect a USB flash drive, printer or network drive.

How to make a network through a router

Opening a port on a TP-LINK TL-WR841N router

For example, here we will describe setting up a home network through a router using a TP-Link TL-WR841N router model that connects to the Internet. In this case, one of the computers will be connected to the router using a network cable, and the second computer via a wireless connection. The local network can also be configured for more computers. On each computer, you need to share the necessary resources in order to be able to access them from every device on the network.

First, you need to check that the Internet is supplied to the router. When you connect the cable from the provider to the WAN port on the router, the corresponding indicator on the front panel should flash. If the indicator is not lit, then you need to update the firmware of the router. To do this, download the latest firmware from the manufacturer's website. And perhaps a bad cable connection and you need to re-compress the cable connector. If everything works fine, then you can start creating a local network through a router.

Checking the physical connection

It is necessary to check the connection between computers before setting up a network through a router. You need to ping between them. For this check, you need to go to the router menu from the computer and find the value of the IP address of another computer in the settings.

To do this, type the network address of the router in the browser, usually 192.168.1.1 and go to the router settings. Open the settings tab called "DHCP", and then "DHCP Clients List". In this window, you will see the devices connected to your router. Remember the address assigned to the second computer in order to ping it. Then you need to click the computer's Start menu and type cmd in the search bar to find a utility with that name and run it.

In the window that appears, you need to enter the ping command and write the address of the second computer. After that, press enter and see the result of the command. If the packet exchange goes through, then the connection between the computers is established and it is already possible to set up a home network through a router.

If there is no packet transmission, then the router does not see the network. Perhaps the reason is in the settings of the antivirus program. Then you need to disable the firewall and antivirus. You can go to the antivirus network settings and find the option to change the network security mode for the computer. There you need to check the option to allow sharing.

Setting up a local network through a router

First you need to check which workgroup each of the computers is connected to, and set the name accordingly. It is necessary to see that the name is written in Latin characters and, if necessary, change it. To do this, you need to right-click on the My Computer icon and select Properties. Then select the Advanced settings option and open the Computer name item there. Here you can change the computer name and group. After all the settings, you need to click Ok and restart the computer. Now you can configure the local network through the router.

All these actions must be performed on all connected computers that will use the local network through a wifi router. After that, you need to open the computer's start menu and open the Control Panel item. Here we are interested in the Network Control Center. It is important that the Home network is selected in the network settings. If so, you can click the Ready to Create button.

Now you need to click the appropriate button to create a homegroup.

Now you need to specify which elements you want to share.

After that, a window with a password will open, you need to write it down and click Done. In the next window, you need to click the button to change additional parameters.

In the advanced sharing settings, you need to disable the option to require a password on the local network. Then the General tab also opens and this item is disabled with password protection. Now don't forget to click Save Changes.

Now the basic settings of the local network are done, and you need to restart all configured computers. Check if all configured computers can see each other in the created network. To do this, you just need to go to My Computer and click on Network. All computers connected to the network, both wired and wireless, using the wifi network through the router should be displayed.

Now you can use the network through the wi fi router. But, if you go to another computer over the network, you will only get access to the Shared folder. To access a particular disk or individual files, you need to make the appropriate settings.

Setting up sharing

To set up shared access to a folder or drive, you need to open the folder or drive, respectively, and click on Sharing, and then select the advanced settings item.

In the window that appears, select the option to open sharing by checking the box there and clicking Ok. Optionally, you can also specify a name for the share.

After this setting, all devices connected to your network will have shared access to the specified resource. When you set up a local network, it is recommended that you keep a backup copy of the network configuration on your computer. This will save you from repeating the steps taken.

Two routers on the same network

Sometimes it becomes necessary to connect two routers to a network. This can be done by connecting several routers together.

Before you create a router router network, you need to imagine the end result of such work. Routers can be connected to combine two local networks, can be used as a common Internet access point or to connect various devices to a second router via a wired or wireless connection.

You can connect two routers using a network cable or a Wi-Fi wireless connection and set up a wifi network through a router. When choosing a wired connection of routers, when one of them is connected to the Internet, you need to perform the following steps.

First you need to connect one end of the network cable to the LAN port of the router that is accepted as the main one. You must connect the other end of the cable to the WAN port of the second router.

Setting up a home network router router begins with setting up the main router. You must enable the DHCP function in the settings. After that, you need to open the “IP address” menu for the second router and check the item to automatically obtain an IP address.

If you need to connect two routers wirelessly, then in the settings of the second router you need to enable the option to search for wireless networks. Now you can connect to the Wi-Fi network created by the first router. To complete the setup, you also need to enable the DHCP function in the router settings, and then configure the automatic receipt of an IP address. Now you know how to connect a router to a WiFi network created by another router.

network printer via router

You can set up network access to the printer. A method that is suitable for a printer that does not have a special built-in Wi-Fi module will be described here. All you need to connect is a router that has a built-in USB printer port. For the above connection, an ASUS WL-520GU and Xerox Workcenter PE114e router will be used.

The printer can only be connected via a USB port, so the standard connection to a computer using sharing imposes some restrictions. To always access the printer, the host computer to which the printer is connected must always be on. This is not always convenient and in such a situation it is better to use the connection of the printer to the router.

To properly configure the connection of the printer to your router, you need to open the computer's Start menu and select the Devices and Printers item there. In this window, you need to open the Add Printer item. When a new window opens, you need to select the type of printer to be added (local) and click Next to continue the setup.

Now you need to configure the printer port. You need to select the option -Create a new port, and select the port type as Standard TCP, as in the figure below, and then click Next to continue the configuration.

In the next window, you need to enter the printer's network IP address. Here you need to enter the address of the router, which in our case will be 192.168.1.1. The value of the port name can be entered any name, but you can leave what will be the default after entering the IP address of the printer (network address of the router). The option to poll the printer and select a driver can be left enabled (tick below). This option will not affect the speed of the process.

The computer will then take some time to find the TCP/IP Port you specified. This will be indicated by the corresponding window.

If the port is not found, a window will appear asking you to enter additional information about the port. In this case, you must select Device Type - Custom by ticking the appropriate box and click Next.

If everything went well, a window with port settings will open. Make sure that all settings are set as shown in the figure below.

In the next printer driver installation window, you need to select the name of your printer and its model. It is possible that you will not find the name of your printer in the list. Then you just need to click the button to install the printer driver from the disc. In this case, you must specify the exact path to the driver file in the appropriate field. You can download the latest version of the driver on the Internet from the printer manufacturer's website.

If you have already installed drivers for such a printer, a corresponding window will appear asking which version of the driver to use. It is recommended to leave the default selection and use the installed driver.

After that, you can set any suitable name for the printer, which will then be visible in the Devices and Printers menu. You can leave the name for the printer and the one that will be the default, and then click Next.

Network printer name

In the next window, you can set up printer sharing. But since the printer will already be connected to your router, you can not use the printer sharing option. It is recommended to leave the default value, do not use sharing.

You can allow the printer to be used over the network

On the last page of printer settings, you can leave or remove the option to use a custom printer by default. After that, you can check the printer and print a test page. Click Finish to complete printer setup.

Your computer is now configured to access the printer. To access the printer from other computers, you need to repeat the same settings for each of your computers.

Optimization of the work of the company, especially the manufacturing enterprise, is one of the most important conditions for the existence of the company. Not only competition requires the uninterrupted flow of the production process. Current trends in minimizing the cost of manufactured products involve, first of all, the elimination of downtime and the consistency of operations.

To solve these problems, a technique for optimizing activities and calculating the timing of work is used. The developed network schedule allows you to determine the logical sequence of individual operations, the possibility of combining them in time, as well as the timing of the entire production cycle of work.

What's this?

One of the methods for effective planning of the activities of a manufacturing enterprise is the construction of a network diagram. Initially, it was used in construction and determined not so much the sequence of work as the timing of the arrival of teams of workers of different specialties on the construction site. It's called the "work schedule".

In modern conditions, when large enterprises mass-produce products, the whole process is broken down into simple operations to facilitate and increase productivity. Therefore, the network schedule "migrated" from construction to almost all industries.

So what is displayed in this document? First, all the operations necessary for the release of goods (production of services) are listed in detail. Secondly, the logical interdependence between them is determined. And, finally, thirdly, not only the timing of each specific work is calculated, but also the time required to complete the production process.

By exposing the internal dependencies of project activities, the network schedule becomes the basis for scheduling equipment and workforce utilization.

The concept of "operation" in network planning

In the network schedule, you can evaluate the periods of start (end) of work, forced downtime and, accordingly, the maximum delay in the production of certain operations. In addition, critical operations are identified - those that cannot be performed with a deviation from the schedule.

Understanding the terminology of planning, it is necessary to clearly understand what an operation is. Most often, this is understood as an indivisible part of the work that requires time to complete. Further, we understand that the operation is associated with costs: time and resources (both labor and material).

In some cases, no resources are needed to perform some actions, only time is required, which takes into account the network schedule. An example of this is the expectation of concrete hardening (in construction), the cooling time of rolled parts (metallurgy), or simply the approval (signing) of a contract or permits.

Most often, operations in planning are given a name in the imperative mood (develop a specification); sometimes verbal nouns are used for names (specification development).

Operation types

When compiling a network schedule, there are several types of work:

• merge - this operation is immediately preceded by more than one work;
• parallel operations are performed independently of each other and, at the request of the design engineer, can be performed simultaneously;
• a crushing operation implies that after its execution, several unrelated jobs can be performed at once.

In addition, there are a few more concepts necessary for planning. The path is the time to complete and the sequence of interdependent operations. A critical path is the longest path of the entire system of work. In the event that some operation on this path is not performed on time, the deadlines for the implementation of the entire project are disrupted.

And the last: event. This term usually refers to the beginning or end of some operation. The event does not require resources.

What does the chart look like

Any graph familiar to us is represented by a curve located on a plane (less often in space). But the type of network plan is significantly different.

The network diagram of the project may look two ways: one technique involves the designation of operations in the nodes of the block diagram (OS), the second uses connecting arrows (OS) for this. It is much more convenient to use the first method.

The operation is indicated by a round or rectangular block. The arrows connecting them define the relationships between the actions. Since the titles of works can be quite long and voluminous, the numbers of operations are put down in the blocks, and a specification is drawn up for the schedule.

Schedule Design Rules

For proper planning, you need to remember a few rules:

1. The graph unfolds from left to right.
2. Arrows indicate links between operations; they may intersect.
3. Each simple work must have its own serial number; any subsequent operation cannot have a number less than that of the previous one.
4. The graph cannot have loops. That is, any looping of the production process is unacceptable and indicates an error.
5. You cannot use conditions when a network graph is built (an example of a conditional order: “if an operation is performed .., perform work ... if not, do not take any action”).
6. To indicate the beginning and end of work, it is more convenient to use one block that defines the initial (final) operations.

Construction and analysis of the graph

For each job, three things need to be clarified:

1. A list of operations that must be completed prior to this job. They are called preceding in relation to the given one.
2. A list of operations that are performed after a given action. Such works are called the following.
3. The list of tasks that can be carried out simultaneously with the given one. These are parallel operations.

All the information received gives analysts the necessary basis for building logical relationships between the operations included in the network diagram. An example of building these relationships is shown below.

The real schedule requires a serious and objective assessment of the production time. Determining the time and entering it into the schedule makes it possible not only to calculate the duration of the entire project, but also to identify the most important nodes.

Graph Calculation: Direct Analysis

Estimation of time costs for the performance of one operation is made on the basis of standard labor costs. Thanks to the direct or inverse calculation method, you can quickly navigate the order of work and identify critical steps.

Direct analysis allows you to determine the early start dates for all operations. Reverse - gives an idea of ​​late dates. In addition, using both analysis techniques, you can not only establish the critical path, but also identify the time intervals for which you can delay the execution of individual works without disrupting the overall timing of the project.

Direct analysis looks at the project from start to finish (if we talk about the drawn up schedule, then the movement along it occurs from left to right). During the movement along all chains of operations, the time for completing the entire complex of works increases. Direct calculation of the network diagram assumes that each subsequent operation begins at the moment when all previous ones end. At the same time, it must be remembered that the next job starts at the moment when the longest of the immediately preceding ones ends. At each step of direct analysis, the execution time of the settlement operation is added. This gives us the values ​​of early start (ES) and early finish (EF).

But you need to be careful: the early end of the previous operation becomes the early start of the next one only if it is not a merge. In this case, the start will be the early end of the longest of the previous works.

reverse analysis

The reverse analysis takes into account such parameters of the network schedule: late completion and late start of work. The name itself suggests that the calculation is carried out from the last operation of the entire project towards the first (from right to left). Moving towards the start of work, you should subtract the duration of each activity. Thus, the latest start (LS) and end (LF) dates for the production of work are determined. If the time frame of the project is not initially set, then the calculation starts from the late end of the last operation.

Calculation of temporary reserves

Having calculated the network schedule of work in both directions, it is easy to determine temporary downtime (sometimes the term “fluctuation” is used). The total possible delay time for the execution of an operation is equal to the difference between the early and late start of a particular action (LS - ES). This is the time reserve that will not derail the overall time frame for the project.

After calculating all the fluctuations, they begin to determine the critical path. It will go through all operations for which there is no timeout (LF = EF; and respectively LF - EF = 0 or LS - ES = 0).

Of course, in theory, everything looks simple and uncomplicated. The developed network schedule (an example of its construction is shown in the figure) is transferred to production and implemented. But what is behind the numbers and calculations? How to use possible technological downtime or, conversely, avoid force majeure situations.

Management experts suggest assigning the most experienced employees to perform critical operations. In addition, when assessing the risks of a project, it is necessary to pay special attention not only to these steps, but also to those that directly affect the critical path. If it is not possible to control the progress of work as a whole, then it is necessary to find time to obtain primary information from the operations of the critical path. It is about talking directly with the performers of such works.

Network diagram - a tool for optimizing the company's activities

When it comes to the use of resources (including labor), it is much easier for a manager to manage them if there is a network schedule for the production of work. It shows all the downtime and employment of each individual employee (team). The use of an unemployed worker at one facility to implement another allows you to optimize the company's activities as a whole.

Do not neglect another practical advice. In reality, project managers are faced with the "desires of senior management" to see the work done "yesterday". In order to avoid panic and the release of marriage, it is necessary to strengthen resources not so much on the operations of the critical path, but on those that directly affect it. Why? Yes, because there is no downtime on the critical path, and it is often impossible to reduce the time of work.

When constructing network graphs, you must adhere to the following rules.

• 1. The number of each subsequent event must be greater than the number of any previous event. The implementation of this rule allows you to ensure that the logical sequence of work is followed.
• 2. There should be no events from which no work comes out (the exception is the last event), if this rule is not met, then the network schedule is built incorrectly or extra work is planned (see Fig. 10.7).

Rice. 10.7. An example of an incorrect network diagram with extra workAT

3. There must be no events that do not include any work (the exception is the start event). If this rule is not met, then this means that an error was made when drawing up the network schedule or work was not planned, the result of which (for example, event 5 in Fig. 10.8) is necessary to start work E.

Rice. 10.8.

BUT. There should be no closed loops in the network diagram, as this leads to a situation where the result of the execution of the work sequence (B-C-D-E) is event 2, from which this sequence began (Fig. 10.9).

Rice. 10.9.

5. Any two events must be connected by no more than one work. Such errors occur most often when depicting parallel work (Fig. 10.10, a). For the correct representation of these works, it is necessary to introduce additional fictitious events 2" and 2" and fictitious works 2"-2 and 2"-2 (Fig. 10.10, b).

Rice. 10.10.

6. If any intermediate work of the network schedule can be started before the complete completion of the previous work, then the latter should be divided into several sequential works, each of which is sufficient to start any of the previously indicated. An example of incorrect and correct construction of such a network graph is shown in Fig. 10.11.

Rice. 10.11.

If, in order to continue work at any stage, it is necessary to obtain the results of other work, then the specified work should be divided into parts using intermediate events (in this example, event 4 in Fig. 10.12).

Rice. 10.12.

If before the complete completion of the work it is necessary to see the intermediate result required before the next work begins, you should also divide the work into parts by introducing intermediate events (Fig. 10.13, b), work 2-4).

Figure 10.13.

In conclusion, we note that the effective application of the methodology of network planning and project management on this basis can be quite a difficult task. In general, the following principles must be observed:

• provide an image of each individual task, with the exception of tasks without an agreed deadline;
• avoid details that are more appropriate in calendar plans (plans of key events) or lists of sequence of actions;
• use the network plan to test, justify and determine how to eliminate deviations from the schedule;
• if necessary, use computer programs, given that not all software is suitable for solving various planning tasks;
• conduct appropriate training of project staff in network planning methods;
• present the results of network planning to the top management of the organization in which the project is being carried out.

conclusions

Successful implementation of the project is possible only on the basis of the project plan, which performs a number of functions: gives a general, holistic picture of the project and the sequence of work; allows you to determine for each point in time to what extent the project is moving towards completion and what obstacles exist or may arise along the way; presents the general economic model of the project, it indicates the main activities and schedules for the implementation of work.

Drawing up a plan or planning performs the following functions: determines the duration, structure of the project, the amount of necessary resources and the sequence of their use, the sequence of work and their financing.

Depending on the underlying principles, four types of plans are distinguished: object-oriented, function-oriented, phase-oriented and mixed-oriented.

The set of works that ensure the implementation of an integral part of the plan is called a work package. The work package contains information about the expected results of the work, specific tasks, the deadlines for their execution and those responsible, information regarding the resource costs for the work package.

Planning is carried out using certain methods, which are called planning tools. They allow you to plan uniformly, ensure the coordination of the execution of work and tasks of the project, increase the efficiency of control and implementation of project operations.

The following planning methods are distinguished:

• 1) drawing up a plan of key events and a phased plan (sequence plan);
• 2) planning with bar charts;
• 3) network planning.

Each of these methods has its own advantages and is used to solve certain problems. So, in particular, the compilation of action lists is used for small projects, where it is easy to coordinate the execution of individual works, which, as a rule, follow one after another.

Bar charts provide a visual representation of the progress of a number of parallel project activities.

Network diagrams allow you to manage a series of related activities in a project and calculate the critical path.