Principles of operation of the local network. Technologies for building local computer networks Fundamentals of building LAN and ip networks

Introduction

The purpose of this course project is to build a local area network. LAN - a computer network that usually covers a relatively small area or a small group of buildings (home, office, company, institute). There are also local networks, the nodes of which are geographically separated at distances of more than 12,500 km (space stations and orbital centers). Despite such distances, such networks are still classified as local.

Computers can be interconnected using various access media: copper conductors (twisted pair), optical conductors (fiber optic cables) and through a radio channel (wireless technologies). Wired connections are established via Ethernet, wireless - via Wi-Fi, Bluetooth, GPRS and other means. A separate local area network may have gateways to other local area networks, as well as be part of a global area network (for example, the Internet) or have a connection to it.

Most often, local networks are built on Ethernet or Wi-Fi technologies. To build a simple local network routers, switches, wireless access points, wireless routers, modems, and network adapters are used. Less commonly used are medium converters (converters), signal amplifiers (various repeaters) and special antennas.

In this work, a LAN will be designed using Ethernet technology, while horizontal and vertical cables will be the fifth category of UTP, with the ability to pass 100 Mbps.

1. Technical requirements for LAN

1.1 Network model of LLC "Master"

user computer network local

At the initial stage of development of networks, the organization had its own standards for connecting computers together. These standards described the mechanisms needed to move data from one computer to another. However, these early standards were not compatible with each other.

In subsequent years, the International Organization for Standards (ISO - International Standards Organization) and the Institute of Electrical and Electronic Engineers (IEEE - Institute of Electrical and Electronic Engineers) developed their models, which became generally recognized industry standards for the development of computer networks. Both models describe network technologies in terms of functional layers.

ISO has developed a model that has been called the Open System Interconnection (OSI) model. This model is used to describe the flow of data between a user application and a physical connection to a network.

The OSI model divides communication functions into 7 layers:

Application layer.

The presentation layer.

session level.

The transport layer.

The network layer.

· Link level.

The physical layer.

The concept of the model is that each layer provides a service to the next higher layer. This allows each layer to interact with the same layer on another computer. The concept of the seven-level model is shown in Figure 1.

Figure 1 - ISO OSI seven layer model

Functional purpose of the levels:

The physical layer sends an unstructured stream of data bits through a physical transmission medium (cable).

1. The physical layer acts as a carrier for all signals that transmit data generated by all higher levels. This layer is responsible for the hardware. The physical layer defines the physical, mechanical and electrical characteristics of communication lines (type of cable, number of connector connectors, purpose of each connector, etc.). The physical layer describes the topology of the network and determines the method of data transmission over the cable (electrical, optical).

2. The link layer packs the unstructured data bits with physical layer into structured packages (data frames).

3. The link layer is responsible for ensuring error-free transmission of packets. The packets contain a source address and a destination address, which allows the computer to extract data that is intended only for it.

4. The network layer is responsible for addressing messages and converting logical addresses and names to physical link layer addresses. The network layer defines the path (route) of data passing from the transmitting to the receiving computer. The network layer restructures the data packets (frames) of the link layer (breaks large ones into a set of small ones or combines small ones).

5. The transport layer controls the transmission quality and is responsible for error detection and correction. transport layer

6. Guarantees the delivery of messages generated at the application layer.

7. The session layer allows two applications on different computers to establish, use, and terminate a connection called a session. The session layer coordinates communication between two application programs running on different workstations. The session layer provides task synchronization and implements dialogue control between interacting processes (determines which side transmits, when, for how long, etc.).

8. The presentation layer is used to transform the data received from the application layer into a commonly recognized intermediate format. The presentation layer can be called a network translator. The presentation layer allows you to combine different types of computers (IBM PC, Macintosh, DEC, etc.) into a single network, converting their data into a single format. The presentation layer manages network security and encrypts data (if necessary). Provides data compression to reduce the number of data bits that need to be transmitted.

9. The application layer (application layer) allows application programs to access the network service. The application layer directly supports user applications (software for file transfer, database access, email). The model of the Open Systems Interoperability Standard is considered the best known model and is most often used to describe network environments.

A local area network is the main part of a corporate network that ensures the functioning and interaction of various distributed applications that may be part of an information system (IS). A modern LAN should have the following main characteristics:

performance adequate to modern IS requirements;

· scalability;

· fault tolerance;

Support for all major communication standards and protocols;

· compatibility with the equipment of adjacent subsystems;

the ability to change the logical configuration of the LAN without changing the physical;

manageability.

The LAN architecture uses modern methods, technologies and devices to achieve the best balance between the basic requirements for a LAN and the capabilities of the network. The requirements for modern business and the need to support business applications determine a number of parameters, among which the most important are:

High availability of the network at a level not lower than 99.99%;

high-speed packet switching;

quality of service for users and applications;

rule-based management;

integration with directory services.

As a basis for building a LAN, a strategy should be used that allows you to create and maintain network complexes of any scale, integrate newly emerging technologies and standards, preserving the investments already made and ensuring the minimum level of network support costs.

2. Basic network requirements

One of the most important requirements for a modern LAN is to ensure the safety and security of processes occurring in the LAN, since a network open to outside access is vulnerable. The implementation of a management, statistics and identification system in the LAN allows you to provide control and increase the security of the LAN.

To manage the network and the ability to prevent unwanted situations in the operation of the LAN, the devices of the entire network must have system tools for monitoring the quality of service and security policy, planning the network and services that provide the ability to:

collecting statistics to analyze network performance at all levels;

· traffic redirection of individual ports, groups of ports and virtual ports to the protocol analyzer for detailed analysis;

· monitoring of events in real time for expansion of opportunities of diagnostics in addition to external analyzers.

collecting and saving information about significant network events, including device configuration changes, topology changes, software and hardware errors

A LAN should have a system solution that allows solving the problem in a complex way, which implies the implementation of identification of network resources and users, protection of information and resources from unauthorized access, dynamic active control over the network.

The LAN should provide all departments of the enterprise with:

Possibility of text processing;

· access to the Internet;

Possibility of using e-mail;

work with databases;

access to shared printers;

Possibility of data transfer.

The TCP/IP protocol stack is shown in Figure 2.

Figure 2 - TCP/IP protocol stack

The TCP / IP protocol stack is divided into 4 levels: application (application), transport (transport), internetwork (internet) and the level of access to the transmission medium (network access). The terms used to designate a block of transmitted data are different when using different transport layer protocols - TCP and UDP, therefore, in Fig. 2 shows two stacks.

The relationship between the levels of the OSI and TCP / IP stacks is shown in Figure 3

Figure 3 - Relationship between OSI and TCP/IP stack layers

3. Selection of the necessary material and equipment

Design a local area network of an organization using Ethernet technology, located in two buildings (Fig.).

Organization local area network

The project must meet the following requirements:

1. Each department of the enterprise must have access to the resources of all other departments;

2. Traffic generated by employees of one department should not affect the local networks of other departments, except when accessing the resources of local networks of other departments;

3. One file - the service can support no more than 30 users;

4. File servers cannot be shared among multiple departments;

5. All repeaters, bridges and communicators must be located in wiring closets (WS);

6. The distance between computers on a mono channel should not be less than one meter;

7. Switching equipment and file - servers must be protected against power failure;

8. The designed network must work stably. In cases of network instability, the project must be redesigned;

9. The following combinations of cables are allowed: twisted pair and optical fiber;

10. The project must have a minimum cost;

11. The data transfer rate should not be lower than 10 Mbps;

12. Type of network technology used - Ethernet;

13. In the project, you can only use equipment from Table. 1.

Table 1 List of used equipment

Name	Notional value (y.e.)
Thin coaxial cable (per one meter)
Unshielded twisted pair (per meter)
Two-core fiber optic cable (per meter)
Network adapter with BNC connector
Network adapter with RJ - 45 connector
Dual port repeater (HUB) with BNC connectors
8 Port BNC Switch
Switch with 6 optical ports
Dual-port bridge with any combination of ports for coax, unshielded twisted pair, and fiber optic cables
Switch with 6 optical ports and 24 ports with RJ - 45 connector
Switch for 8 ports with RJ - 45 connector
Switch for 36 ports with RJ - 45 connector
Source uninterruptible power supply for 800 VA
File server based on Pentium processor with pre-installed operating system(maximum for 30 users)

The company has 4 departments. Of which three are located in building 1, and the fourth, in building two, 300 meters away from the first. Each department has a personal computer (PC) in the amount of:

In the marketing department - 7 pcs.

In the department of automated control systems - 10 pcs.

In the production department - 42 pcs.

In the design department - 30 pcs.

The PC connection, within the departments, will be made using a coaxial cable. The first task is to place a PC in each department, ie. PCs should not be located in a random order and not in a heap, but at an acceptable distance from each other. Figure 8 shows PC layouts, with the indicated distances between them.

To optimize performance, the entire local area network (LAN) is divided into segments. Each department has its own segment. All segments will be connected to the main switch. We select from table 1 a switch on 8 optical ports with a BNC connector, which will be the head switch. The switch is protected against mains voltage drop by an 800 VA uninterruptible power supply. This switch will automatically determine the speed of each segment and maintain it. This will allow you to get the required data transfer rate, at least 10 Mbps. The main switch is located in the WS3 wiring closet in the production department.

Marketing department.

The department has 7 PCs and a WC1 switching cabinet. For stable network operation, we divide the department into 2 segments of 3 and 4 PCs. The distance between the last PC in the first segment and the head switch for the segment, which allows it to be used as a single unit, because segment length will not exceed 185 meters.

The WC1 wiring closet houses the department's file server (a file server based on a Pentium processor with a pre-installed operating system), an uninterruptible power supply, and an 8-port switch with BNC connectors. All PCs and the file server are equipped with network adapters with BNC connectors and are interconnected by a thin coaxial cable using BNC T-connectors.

Communication between computers and file server

A “plug” is inserted into the free connector of the last T-connector - a terminator (figure). In order for the thin coaxial cable not to be in a taut state, we leave a margin equal to one meter in each section between computers.

Terminator

Department of ACS.

The department has 10 computers and a WC2 switching cabinet. In the WC2 cabinet there is a switch, an uninterruptible power supply, which is connected to the file server. The file server based on the Pentium processor with a preinstalled operating system is located directly in the department. All PCs and file server are equipped with network adapters with BNC connectors. Personal computers and the file server are interconnected by a thin coaxial cable using BNC T-connectors. A “plug” is inserted into the free connector of the last T-connector - a terminator. Segment LS2 for more stable operation, divided into 2 segments of 5 PCs. The switch is connected to the main switch in cabinet WC3 in the production department. In order for the thin coaxial cable not to be in a taut state, we leave a margin equal to one meter in each section between computers. The length of the LS2-a segment from the last PC to the head switch, and taking into account the cable margin between the PCs, is, for the LS2-b segment, which does not exceed the allowable 185 meters.

Production Department.

The department has 42 computers and a WC3 wiring closet. In connection with a large number computers, it is advisable to separate them. Thus, we get 7 segments LS3-a, LS3-b, LS3-c, etc., each of which has 6 PCs. The segments are interconnected by 8-port switches with BNC connectors (3 pcs.). Using a switch allows you to bypass the 5-4-3 rule without loss in speed, in addition, using a switch provides greater security against collisions than following the above rule. This department will use two file servers.

In the wiring closet of the WC3 department there will be an uninterruptible power supply, which is connected to the file server; switches of this department connecting separate segments; the main switch of the entire network.

All PCs and file servers are equipped with network adapters with BNC connectors and are interconnected by a thin coaxial cable using BNC T-connectors. In order for the thin coaxial cable not to be in a taut state, we leave a margin equal to one meter in each section between computers. A "plug" - a terminator - is inserted into the free connector of the last T-connector.

The total length of the LS3-a segment from the last PC to the switch is. The total length of the LS3-b segment from the last PC to the switch is. The total length of the LS3-in segment from the last PC to the switch is. The total length of the LS3-r segment from the last PC to the switch is. The total length of the LS3-d segment from the last PC to the switch is. The total length of the LS3-e segment from the last PC to the switch is. The total length of the LS3-g segment from the last PC to the switch is. The length of any of the segments does not exceed the allowable 185 m.

Project department

The department has 30 PCs and a WC4 wiring closet. The S4 segment is divided into 5 segments for more stable operation. In the switching cabinet, we install an uninterruptible power supply that protects file servers from power drops, an 8-port switch with BNC connectors that combines segments. All PCs and file servers are equipped with network adapters with BNC connectors and are interconnected by a thin coaxial cable using BNC T-connectors. A “plug” is inserted into the free connector of the last T-connector - a terminator. In order for the thin coaxial cable not to be in a taut state, we leave a margin equal to one meter in each section between computers. The length of the LS4-a segment from the last PC to the WC4 wiring closet is. The length of segment LS4-b from the last PC to the switching cabinet WC4 is. The length of the LS4-B segment from the last PC to the WC4 wiring closet is. The length of the LS4-r segment from the last PC to the WC4 wiring closet is. The length of the LS4-d segment from the last PC to the WC4 wiring closet is. The length of any of the segments does not exceed the allowable 185 m.

Connecting departments to each other

Building 2 is removed from building 1 by 300 meters. The buildings are interconnected by a pipeline. In order to connect the WC4 segment with the main switch, we lay a two-core fiber optic cable in the pipeline (Table 1). The cable length is 320 meters. On each side we leave a margin of 10 meters, two of which are required for cutting the cable, the remaining eight are placed in rings in the cabinet due to technological requirements. In order to switch from one data transmission medium to another, we select from table 1 a two-port bridge with a combination of ports "coaxial cable - fiber optic cable", which is installed in the WC4 cabinet, and "optical cable - coaxial cable", which is installed in the WC3 cabinet. Both bridges are protected from voltage drop by an uninterruptible power supply. The fiber optic cable - coaxial cable bridge in the WC3 cabinet, in turn, is connected via a thin coaxial cable directly to the main switch.

Thus, we got a network connecting two buildings, which has a minimum cost, but at the same time there is no broadcast traffic in it and the data transfer rate reaches at least 10 Mbps. Figures 8 and 9 show, respectively, the layout of personal computers that are part of the local area network and the connection diagram of personal computers with a diagram of cable gaskets and cable segment lengths.

WS1: File - Department Server

8 port marketing switch with BNC connectors.

WS2: File - Department Server

Uninterruptable power source;

ACS department switch for 8 ports with BNC connectors.

WS3: 2 uninterruptible power supplies;

2 file - department servers;

2 switches for 8 ports with BNC connectors;

Head switch for 8 ports with BNC connectors;

Two-port bridge "coaxial cable - optical fiber".

WS4: File - Department Server

Uninterruptable power source;

8-port design department switch with BNC connectors;

Bridge "coaxial cable - fiber optic cable"

Figure 12 shows the layout of equipment in cable cabinets and the switching line of this equipment.

In order for the network to work stably, that is, there is no distortion of the transmitted information or its loss, the following conditions must be met:

1. The length of the segment must not exceed the allowable value:

thin coax - 185 m;

optics - 2000 m (we have a maximum of 320 m).

2. The total length of the network should not exceed 2.5 km.

3. The number of computers in the network should not exceed 90 pcs. (We have 89 computers + 5 departmental file servers).

4. One file server can support no more than 30 users (we have a maximum of 30 users).

5. File servers cannot be shared among multiple departments.

6. All repeaters, bridges, and switches must be located in wiring closets.

7. The 5-4-3 rule must be followed (is being done).

There is not a single excess of the required parameters. Therefore, it is not necessary to perform robustness checks using PDV (double-interval time - must not exceed 575 bit intervals) and PVV (inter-frame interval reduction must not exceed 49 bit intervals). Compliance with these requirements ensures stable operation of the network even in cases where the above conditions are violated. This test will be performed to ensure that the network is up and running.

To simplify calculations, reference data from the IEEE organization is used, containing data on signal propagation delays in repeaters, transceivers and various physical environments.

Table 4 Data for calculating PDV

To calculate stability, draw a section with the most remote stations.

The left segment is the segment where the signal starts from.

The right segment is the segment where the signal arrives.

Intermediate segment - the segment between the left and right segments.

The calculation should be carried out twice, when the signal propagates in both directions, because the result may be different in the case of an asymmetric network. If in at least one case PDV fails, the network will lose frames due to missing collisions.

The calculation will be made for the two most distant from each other computers from the marketing department and from the design department. A schematic representation is shown in Figure 13.

Let's calculate the stability of the network using PDV and PVV

4. Economic calculation of the project

The practical use of LAN models in many cases presupposes the availability of information about the actual characteristics of the computing process. Such information can be obtained by empirical methods, on the basis of which tools are currently being created for studying the hardware and software components of a LAN. The necessary information is collected using special means,

which provide the measurement of parameters characterizing the dynamics of the LAN operation in the modes of experimental and normal operation. These tools include network analyzers, protocol analyzers, etc. The creation of tools for measuring the parameters of LAN functioning, including LAN operating systems, is one of the new tasks in computer technology. Experimental methods make it possible to create a basis for quantifying the effectiveness of VS to achieve the following practical goals: analysis of existing LANs, selection of the best one, and synthesis of a new LAN. Evaluation of the characteristics of hardware and software is associated with experiments and measurements, which from a practical point of view can be considered as a process of obtaining useful information. Measurement data are presented in a form suitable for subsequent analysis. This is done using special processing tools, the creation of which is associated with the development of analyzers. This relationship concerns, for example, the choice common formats data, convenient not only for measurements, but also for processing their results. In the general case, the measurement stage precedes the processing stage, and processing tools should be designed for efficient application to large amounts of information, since measurements on a LAN are characterized, as a rule, by large volumes and high density of recorded data. At the final stage of experimental studies, the analysis of the measurement results is carried out, which consists in obtaining meaningful conclusions about the studied LAN. An important condition for the formation of such conclusions is the successful presentation of the measurement results. The effectiveness of experimental methods largely depends on the quality of experiment design and the correct choice of the type of load. An experiment consists of a set of tests that are performed during the research, and the test, in turn, consists of a series of sessions or "runs". The term "session" is more often used for measurements, and "run", as a rule, for simulation. During a session or run, information about system behavior and possibly workload is accumulated. As the workload varies, the number of observations required for each quantity of interest to the user must be such that the distributions for those quantities and their moments can be estimated with the required accuracy. Thus, the duration of the session depends on the required number of observations.

A one-session experiment is sufficient to evaluate, if necessary, consider only one system configuration and one type of workload. For example, if measurements are made to find out whether a given LAN provides satisfactory performance for a given workload (traffic), i.e. whether it meets certain requirements. Experiments lasting several sessions are necessary if it is necessary to determine the influence of certain factors on system performance or if the system is being optimized by successive iterations.

5. Setting up network equipment and end users

Setting up the equipment is the most difficult stage in the network installation. The more complex the network, the more heterogeneous technically complex equipment is used in it, the more profound knowledge and experience is required from an engineer to configure this equipment. The final setup and debugging of equipment for the customer's goals sometimes takes much more time than installation. Performance depends on the optimization of a large number of parameters of each network device future network. This means that the productivity of the company's staff depends on it.

Setting up the equipment may include, at the request of the customer, the following steps and work:

1. configuring switches, routers and firewalls (Firewall). Configuration usually includes dividing the network into virtual local networks, developing and configuring routing rules, ensuring quality of service, ensuring security, ensuring encryption of critical data, and organizing remote secure access to corporate network data. The list of configurable equipment includes active devices in the network environment, such as multiplexers, switches, routers, firewalls, service servers (DNS, DHCP, HTTP, MAIL), and very often backbone copper and optical multiplexers.

2. At present, with the development of wireless technologies, not a single corporate data transmission network can do without a WI-FI network. Therefore, wireless access points also fall into the setting. The organization of a convenient, scalable, managed from a single point network requires knowledge of modern technologies. A properly configured network provides high reliability, centralized management, as well as additional services such as authorization, handover, and others.

3. In addition to network equipment, network printers, multifunctional printers, and copiers also require settings. Currently, they are stand-alone network devices and, like computers, require professional configuration. It is better to entrust the input of settings to specialists, because. unprofessional handling of high-tech equipment can disable it. In addition, unauthorized installations are not welcomed by manufacturers, and self-configuration and installation of equipment, without the involvement of an authorized service center, is the risk of losing the warranty for expensive equipment.

4. Data transfer technologies are improving, and today the list of equipment frequently used by corporate customers traditionally includes video conferencing systems. Proper system setup allows you to get a high-quality image, save on bandwidth, and fully use all the functionality of the system for the end user. The video conferencing system includes not only video conferencing servers, but also end terminal devices - IP video phones, video terminals, collective video communication systems. Proper configuration of the entire class of devices, together with the central system, will ensure the implementation of quality services and services for the user.

A modern broadband wireless router is a multifunctional device that combines:

a router

Fast Ethernet network switch (10/100 Mbit/s);

a wireless access point;

firewall

NAT device.

The main task assigned to wireless routers is to unite all computers home network into a single local network with the ability to exchange data between them and the organization of a high-speed, secure Internet connection for all home computers.

Using a wireless router to connect

Currently, the most popular methods are connecting to the Internet via a telephone line using an ADSL modem and via a dedicated Ethernet line. Based on this, all wireless routers can be divided into two types:

for connecting via a dedicated Ethernet line;

for telephone connection.

In the latter case, an ADSL modem is also built into the router.

According to statistics, the method of connecting via a dedicated Ethernet line is becoming more and more popular among providers. At the same time, the routers designed for this can also be used to connect to the Internet via a telephone line, but for this you will have to purchase an ADSL modem additionally.

In the future, we will consider only routers designed to connect to the Internet via a dedicated Ethernet line.

So, routers are network devices installed on the border of the internal local home network and the Internet, and therefore, they act as a network gateway. From a constructive point of view, routers must have at least two ports, one of which connects the local network (this port is called the internal LAN port), and the second is the external network, that is, the Internet (this port is called the external WAN port). Home routers have one WAN port and four internal LAN ports, which are combined into a switch (Fig. 2). Both the WAN and LAN ports have a 10/100Base-TX interface and can be connected to an Ethernet network cable.

LAN and WAN - router ports

The wireless access point integrated into the router allows you to organize a wireless network segment, which for the router belongs to the internal network. In this sense, computers connected to the router wirelessly are no different from those connected to the LAN port.

The task of the firewall integrated into the router is to ensure the security of the internal network. To do this, firewalls must be able to mask the protected network, block known types of hacker attacks and information leakage from the internal network, and control applications that access the external network.

In order to implement these functions, firewalls analyze all traffic between the external and internal networks for its compliance with certain established criteria or rules that determine the conditions for the passage of traffic from one network to another. If the traffic meets the specified criteria, then the firewall passes it through itself. Otherwise, that is, if the established criteria are not met, the traffic is blocked. Firewalls filter both incoming and outgoing traffic, and allow you to control access to certain network resources or applications.

By their purpose, firewalls resemble a checkpoint of a guarded facility, where the documents of all those entering the territory of the facility and all those leaving it are checked. If the pass is in order, access to the territory is allowed. Firewalls operate similarly, only in the role of people passing through the checkpoint, they act network packages, and the pass is the match of the headers of these packets to the given set of rules.

All modern routers with built-in firewalls are NAT devices, that is, they support the NAT (Network Address Translation) network address translation protocol. This protocol is not an integral part of the firewall, but it helps to improve network security. Its main task is to solve the problem of the shortage of IP addresses, which is becoming more and more urgent as the number of computers grows.

The NAT protocol defines how network address translation takes place. The NAT device translates IP addresses reserved for private use on local networks into public IP addresses. Private addresses include the following IP ranges: 10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255, 192.168.0.0-192.168.255.255. Private IP addresses cannot be used on the WAN, so they can only be used freely for internal purposes.

In addition to the listed functionality, some models of wireless routers have a number of additional ones. For example, they can be equipped with USB 2.0 ports, to which you can connect external devices with the ability to organize shared network access to them. So, when connected to a printer router via a USB 2.0 interface, we also get a print server, and when connecting an external hard drive- network storage device type NAS (Network Attached Storage). In addition, in the latter case, the software used in routers even allows you to organize an FTP server.

There are router models that have not only USB ports, but also a built-in HDD, and therefore can be used for network storage, as FTP servers for access both from the outside and from the internal network, and even serve as multimedia centers.

Despite the seeming similarity in functionality of broadband wireless routers, there are significant differences between them, which ultimately determine whether a particular router is suitable for your purposes or not. The fact is that different Internet providers use Various types Internet connection. If we are talking about connecting a single computer (without using a router), then there are no problems, since user operating systems (for example, Windows XP / Vista) contain software tools that support all types of connections used by providers. If a router is used to connect the home network to the Internet, then it is necessary that it fully supports the type of connection used by the provider (we will consider connection types in the section on configuring the WAN interface).

Almost all routers aimed at home users have built-in quick setup software (setup wizards) or auto-configuration tools - for example, Quick Setup, Smart Setup, NetFriend, etc. However, you need to keep in mind that there can always be a provider that does not will support the automatic configuration function of a specific router. In addition, the presence of such functions does not mean at all that by pressing one "magic" button you will immediately cope with all the problems and configure your router. After all, even in order to get to this “magic” button, you will have to perform some network interface settings on your computer.

For the above reasons, we will not rely on the automatic configuration capabilities of the router and will consider the most universal way to manually configure it step by step.

It is advisable to configure the router in the following sequence:

· Gaining access to the web-interface of the router.

· Configuring the LAN interface and the built-in DHCP server.

· Setting up a WAN interface with the organization of an Internet connection for all computers on the local network.

· Setting up a wireless network (if there are wireless clients).

· Firewall settings.

· Configuring the NAT protocol (if required).

The first step in configuring the router is to gain network access to its settings via the web interface (all routers have a built-in web server).

Let's take a closer look at the steps for configuring the LAN interface and the built-in DHCP server, as well as configuring the WAN interface. We will not talk about setting up a wireless network, firewall and NAT protocol in this article - separate publications will be devoted to these issues.

Getting access to the web- Androuter interface

To access the web interface of the router, you need to connect a computer (laptop) to the LAN port. The first thing you need to find out is the IP address of the LAN port of the router, the default login and password. Any router, being a network device, has its own network address (IP address). In order to find out the IP address of the LAN port of the router and the password, you will have to scroll through the user manual.

If the router has not been used before, then its settings are the same as the default (factory) settings. In most cases, the IP address of the LAN port of the router is 192.168.1.254 or 192.168.1.1 with a subnet mask of 255.255.255.0, and the password and login are admin. If the router has already been used and the default settings have changed in it, but you do not know the IP address of the LAN port, or the login and password, then the first thing to do is reset all settings (return to factory settings). To do this, all routers have a special recessed reset button (Reset). If you press it (when the router is powered on) and hold for a few seconds, the router will reboot and restore its factory settings.

In addition to the ability to quickly reset to factory settings, most routers have a built-in DHCP server that is enabled by default. This makes it easy to connect to the router, because the computer connected to the LAN port of the router will automatically be assigned an IP address on the same subnet as the LAN port of the router itself, and the IP address of the default gateway will be set to the IP address of the router. router LAN port address. But in order to use this feature, you need to make sure that the network connection properties of the computer used to connect to the router's LAN port have the Obtain IP address automatically function set. It is enabled by default for all network interfaces, and if after installing the operating system network connections were not specially configured on the computer, then most likely you will be able to access the router settings immediately after connecting to its LAN port on the computer.

If it is not possible to connect to the router in this way, then you will have to first configure the network interface of the computer connected to the router. The meaning of the setting is that the network interface of the computer that connects to the LAN port of the router and the LAN port of the router have IP addresses belonging to the same subnet. Let's say the router's LAN port has an IP address of 192.168.1.1. Then the network interface of the connected computer must be assigned a static IP address 192.168.1.x (for example, 192.168.1.100) with a subnet mask of 255.255.255.0. In addition, you must specify the IP address of the router's LAN port as the default gateway IP address (in our case, 192.168.1.1).

The configuration of the computer's network interface depends on the operating system you are using.

Conclusion

In this paper, the main components of the LAN were considered, as well as the process of data transfer in the network at all levels (logical and hardware). The local computer network of a trade enterprise is modeled taking into account the requirements for the future structure. Based on the size of the room, the length of the cable connecting all network components was found and optimized as much as possible.

To date, the development and implementation of LAN is one of the most interesting and important tasks in the field of information technology. The need to control information in real time is growing more and more, the traffic of networks of all levels is constantly growing. As a result, new technologies transmission of information in the LAN.

For example, among the latest discoveries, it should be noted the possibility of data transmission using conventional power lines, and this method allows you to increase not only the speed, but also the reliability of transmission.

Network technologies are developing very rapidly, in connection with which they begin to stand out as a separate information industry. Scientists predict that the next achievement of this industry will be the complete exclusion of other means of information transmission (television, radio, print, telephone, etc.). These "obsolete" technologies will be replaced by a computer, it will be connected to some global information flow, perhaps even the Internet, and from this flow it will be possible to obtain any information in any representation.

Bibliography

1. SPb1. Kuznetsov M.A., "Modern technologies and standards of mobile communication".: Link, 2006.

2. McCullough D., "Secrets of wireless technologies" / - M .: NT-Press, 2010.

3. Maufer T., "WLAN: a practical guide for administrators and professional users" / - M .: KUDITS-Obraz, 2011.

4. Novikov Yu.V., Kondratenko S.V. Fundamentals of local networks. Lecture course. - M.: Internet University of Information Technologies, 2010.

5. Kuznetsov M.A., "Modern technologies and standards of mobile communications" - St. Petersburg: Link, 2006.

6. Kuznetsov M.A., “Modern technologies and standards of mobile communications” / Ryzhkov A.E. - St. Petersburg: Link, 2009.

7. McCullough D., "Secrets of wireless technologies" / - M .: NT-Press, 2010.

8. Maufer T., "WLAN: a practical guide for administrators and professional users" / - M .: KUDITS-Obraz, 2011.

9. Novikov Yu.V., Kondratenko S.V. Fundamentals of local networks. Lecture course. - M.: Internet University of Information Technologies, 2010.

10. Olifer VG, Fundamentals of data transmission networks. - M.: Publisher: Piter, 2008.

11. Olifer V.G., "Basic technologies of local networks" - St. Petersburg: Peter, 2009.

12. V. G. Olifer, Computer networks. Principles, technologies, protocols. Textbook. - St. Petersburg, Peter, 2011.

13. Pejman R., “The basics of building wireless local area networks of the 802.11 standard. A Practical Guide to Learning, Designing, and Using 802.11 Wireless LANs / Jonathan Leary. - M.: Cisco Press Translation from English Williams Publishing House, 2009.

14. Shakhnovich S. Modern wireless technologies. - PETER, 2008.

15. Shcherbo V.K. Computer network standards. - M.: Kudits - Obraz, 2010.

Star topology.

The concept of a star network topology comes from the field of mainframe computers, in which the host machine receives and processes all data from peripheral devices as an active data processing node. This principle is applied in data communication systems such as RELCOM e-mail. All information between two peripheral workstations passes through the central node of the computer network.

fig.1 Star topology

Network throughput is determined by the computing power of the node and is guaranteed for each workstation. Collisions (collisions) of data do not occur.

The cable connection is quite simple as each workstation is connected to a node. Cabling costs are high, especially when the central site is not geographically located in the center of the topology.

When expanding computer networks, previously made cable connections cannot be used: a separate cable must be laid from the center of the network to a new workplace.

The star topology is the fastest of all computer network topologies, since data transmission between workstations passes through the central node (if it performs well) on separate lines used only by these workstations. The frequency of requests for information transfer from one station to another is low compared to that achieved in other topologies.

The performance of a computer network primarily depends on the capacity of the central file server. It can be a bottleneck in a computer network. If the central node fails, the operation of the entire network is disrupted.

Central control node - file server can implement an optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center.

Ring topology.

With a ring network topology, workstations are connected to each other in a circle, i.e. workstation 1 with workstation 2, workstation 3

fig.2 Ring topology

with workstation 4, etc. The last workstation is linked to the first. Communication link closes in a ring.

Laying cables from one workstation to another can be quite complex and expensive, especially if the workstations are geographically located far from the ring (for example, in a line).

Messages circulate regularly around the circle. The workstation sends information to a certain end address, having previously received a request from the ring. Message forwarding is very efficient as most messages can be sent "on the road" over the cable system one after the other. It is very easy to make a ring request to all stations. The duration of information transfer increases in proportion to the number of workstations included in the computer network.

The main problem with a ring topology is that each workstation must actively participate in the transfer of information, and if at least one of them fails, the entire network is paralyzed. Faults in cable connections are easily localized.

Connecting a new workstation requires a short-term shutdown of the network, since the ring must be open during installation. There is no limit on the extent of the computer network, since it is ultimately determined solely by the distance between two workstations.

With a bus topology, the information transmission medium is presented in the form of a communication path, accessible to all workstations, to which they must all be connected. All workstations can communicate directly with any workstation on the network.

fig.3 Bus topology

Workstations at any time, without interrupting the operation of the entire computer network, can be connected to it or disconnected. The functioning of a computer network does not depend on the state of a separate workstation.

In a typical situation for an Ethernet bus network, a thin cable or a Cheapernet cable with a tee connector is often used. Turning off and especially connecting to such a network requires a bus break, which causes a disruption in the circulating flow of information and a system hang.

The tree structure of the LAN.

Along with the well-known topologies of computer networks ring, star and bus, a combined one is also used in practice, for example, a tree structure. It is formed mainly in the form of combinations of the above topologies of computer networks. The base of the computer network tree is located at the point (root) where communication information lines (tree branches) are collected.

Computing networks with a tree structure are used where it is impossible to directly apply the basic network structures in their pure form.

fig.4 Tree structure

3 .3. Network devices and means of communication.

The most commonly used means of communication are twisted pair, coaxial cable, and fiber optic lines. When choosing the type of cable, the following indicators are taken into account:

· installation and maintenance cost,

· information transfer rate,

· restrictions on the value of the information transmission distance without additional repeater amplifiers (repeaters),

· data transmission security.

The main problem is to achieve these indicators at the same time, for example, the highest data transfer rate is limited by the maximum possible data transfer distance, which still provides the required level of data protection. Easy scalability and ease of expansion of the cable system affect its cost.

3.3.1. Types of cables used.

twisted pair.

The cheapest cable connection is a twisted two-wire wire connection often referred to as a "twisted pair" (twisted pair). It allows you to transfer information at speeds up to 10 Mbit / s. It can be easily increased, but is not protected from interference. The cable length cannot exceed 1000 m at a transmission rate of 1 Mbps. The advantages are low price and ease of installation. To improve the noise immunity of information, a shielded twisted pair is often used, i.e. a twisted-pair cable placed in a shield, similar to the screen of a coaxial cable. This increases the cost of twisted pair and brings its price closer to the price of coaxial cable.

Ethernet cable.

The Ethernet cable is also a 50 ohm coaxial cable. It is also called thick Ethernet (thick), yellow cable (yellow cable) or 10BaseT5. It uses a 15 pin standard switch. Due to its noise immunity, it is an expensive alternative to conventional coaxial cables. The maximum available distance without a repeater does not exceed 500 m, and the total distance of the Ethernet network is about 3000 m. The Ethernet cable, due to its backbone topology, uses only one terminating resistor at the end.

Cheapernet cable.

Cheaper than an Ethernet cable is the Cheapernet cable or, as it is often called, thin Ethernet or 10BaseT2 connection. It is also a 50-ohm coaxial cable with a transmission rate of ten million bits per second.

When connecting segments of a Shearegnet cable, repeaters are also required. Computing networks with Cheapernet-cable have a low cost and minimal costs when building up. Network board connections are made using widely used small bayonet connectors (CP-50). Additional shielding is not required. The cable is connected to the PC using tee connectors (T-connectors).

The distance between two workstations without repeaters can be a maximum of 300 m, and the total distance for a network on a Cheapernet cable is about 1000 m.

fiber optic lines.

The most expensive are optical conductors, also called fiberglass cable. The speed of information propagation through them reaches several billion bits per second. Permissible removal of more than 50 km. There is practically no external influence of interference. This is currently the most expensive LAN connection. They are used where electromagnetic interference fields occur or information is required to be transmitted over very long distances without the use of repeaters. They have anti-fluff properties, since the tapping technique in fiber optic cables is very complex. Optical conductors are combined in JIBC using a star connection.

Network adapter cards act as physical interface, or connections between the computer and the network cable. Boards are inserted into special sockets (expansion slots) of all computers and servers. To provide a physical connection between the computer and the network, a network cable is connected to the appropriate connector, or port, of the card (after it is installed). Purpose of the network adapter board:

Preparation of data coming from a computer for transmission over a network cable;

Transferring data to another computer;

Data flow control between computer and cable system;

The network adapter card takes data from the network cable and translates it into a form understandable by the computer's central processing unit.

The network adapter card consists of hardware and firmware stored in ROM (Read Only Memory). These programs implement the functions of the logical link control sublayers and access control to the medium of the link layer of the OSI model.

The splitter serves as the central node in networks with a star topology.

When transmitting over a network cable electrical signal gradually weakens (fades out). And, it is distorted to such an extent that the computer ceases to perceive it. To prevent signal distortion, a repeater is used that amplifies (restores) the weakened signal and transmits it further along the cable. Repeaters are used in networks with a bus topology.

3.4. Types of building networks by methods of information transfer.

Local network Token Ring.

This standard was developed by IBM. The transmission medium is unshielded or shielded twisted pair (UPT or SPT) or optical fiber. Data transfer rate 4 Mbps or 16 Mbps. As a method of controlling the access of stations to the transmission medium, the method is used - a token ring (Token Ring). The main provisions of this method:

Devices are connected to the network in a ring topology;

All devices connected to the network can only transmit data if they receive permission to transmit (token);

At any given time, only one station in the network has this right.

There are three main types of packets used in IBM Token Ring:

Package control / data (Data / Command Frame);

Marker (Token);

Reset package (Abort).

Control/Data package. With the help of such a packet, data or network control commands are transmitted.

Marker. The station can start data transmission only after receiving such a packet. There can be only one marker in one ring and, accordingly, only one station with the right to transmit data.

Reset package. The sending of such a packet calls the termination of any transmissions.

Computers can be connected in a network in a star or ring topology.

Ethernet local area network.

The Ethernet specification was proposed by the Xerox Corporation in the late seventies. Later, Digital Equipment Corporation (DEC) and Intel Corporation joined this project. In 1982, the specification for Ethernet version 2.0 was published. On the basis of Ethernet and the IEEE Institute, the IEEE 802.3 standard was developed. The differences between them are minor.

Basic principles of work.

At the logical level, Ethernet uses a bus topology:

All devices connected to the network are equal, i.e. any station can start transmission at any time (if the transmission medium is free);

Data transmitted by one station is available to all stations on the network.

10BaseT

In 1990, the IEEE released the 802.3 specification for building a twisted-pair Ethernet network. 10 BaseT (10 - transmission rate 10 Mbps, Base - narrowband, T - twisted pair) - an Ethernet network that usually uses unshielded twisted pair (UTP) to connect computers. Most networks of this type are built in the form of a star, but the signaling system is a bus, like other Ethernet configurations. Typically, a 10BaseT network splitter acts as a multiport repeater. Each computer connects to the other end of a cable connected to a splitter and uses two pairs of wires, one for receiving and one for transmitting.

The maximum length of a 10BaseT segment is 100 m. The minimum cable length is 2.5 m. A 10BaseT LAN can serve up to 1024 computers.

To build a 10BaseT network, use:

RJ-45 connectors at cable ends.

The distance from the workstation to the splitter is no more than 100 m.

10Base2

According to the IEEE 802.3 specification, this topology is called 10Base2 (10 is a 10Mbps transmission rate, Base is narrowband transmission, 2 is a transmission over a distance approximately twice as long as 100m (actual distance 185m).

This type of network is focused on thin coaxial cable, or thin Ethernet, with a maximum segment length of 185 m. The minimum cable length is 0.5 m. In addition, there is a limit on the maximum number of computers that can be connected on a 185 m cable segment - 30 things.

Thin Ethernet Cable Components:

BNC barrel - connectors (connectors);

BNC T - connectors;

BNC - terminators.

Thin Ethernet networks usually have a bus topology. The IEEE standards for thin Ethernet do not require a transceiver cable between the T-connector and the computer. Instead, the T-connector is located directly on the network adapter board.

BNC barrel - connector, connecting cable segments, allows you to increase its overall length. However, their use should be kept to a minimum as they degrade signal quality.

Thin Ethernet networking is a cost-effective way to implement networks for small offices for workgroups. The cable used in this type of networks is relatively inexpensive, easy to install, and easy to configure. A thin Ethernet network can support up to 30 nodes (computers and printers) per segment.

A thin Ethernet network can consist of a maximum of five cable segments connected by four repeaters, but workstations can be connected to only three segments. Thus, two segments remain reserved for repeaters, they are called inter-repeater links. This configuration is called the 5-4-3 rule.

10Base5.

According to the IEEE specification, this topology is called 10Base5 (10 is 10Mbps transmission rate, Base is narrowband transmission, 5 is 500-meter segments (5 times 100 meters)). There is another name for it - standard Ethrnet.

Networks on thick coaxial cable (thick Ethrnet) usually use a bus topology. Thick Ethernet can support up to 100 nodes (workstations, repeaters, etc.) per backbone segment. Trunk, or trunk segment, is the main cable to which transceivers are connected with workstations and repeaters connected to them. A thick Ethernet segment can be 500 meters long with a total network length of 2500 meters. Distances and tolerances for thick Ethernet are greater than for thin Ethernet.

Cable system components:

Transceivers. Transceivers, providing communication between the computer and the main LAN cable, are combined with a "vampire tooth" connected to the cable.

Transceiver cables. The transceiver cable (drop cable) connects the cable to the network adapter card.

DIX - connector, or AUI - connector. This connector is located on the transceiver cable.

Barrel - connectors and terminators.

A thick Ethernet network can consist of a maximum of five backbone segments connected by repeaters (according to the IEEE 802.3 specification), but computers can be connected to only three segments. When calculating the total length of the thick Ethernet cable, the length of the transceiver cable is not taken into account, i.e. only the length of the thick Ethernet cable segment is taken into account. The minimum distance between adjacent connections is 2.5 meters. This distance does not include the length of the transceiver cable. Thick Ethernet was designed to build a LAN within a large building department.

Typically, large networks share thick and thin Ethernet. Thick Ethernet works well as a backbone, and thin Ethernet is used for branching segments. You probably remember that thick Ethernet has a larger copper core and can transmit signals over longer distances than thin Ethernet. The transceiver is connected to the “thick Ethernet” cable, AUI - the connector of the transceiver cable is included in the repeater. The branching segments of the “thin Ethernet” are connected to the repeater, and computers are already connected to them.

10BaseFL.

10BaseFL (10 - 10 Mbps transmission rate, Base - narrowband transmission, FL - fiber optic cable) is an Ethernet network in which computers and repeaters are interconnected by fiber optic cable.

The main reason for the popularity of 10BaseFL is the ability to lay cable between repeaters over long distances (for example, between buildings). The maximum length of a 10BaseFL segment is 2000 meters.

8-pin modular sockets (modular jack) are used to connect cables. 8-pin RJ-45 connectors are installed on the cables using special crimping pliers.

Fig.5 Modular socket Rice. 6 8-pin RJ-45 connectors

When exchanging data between two devices, the receiver of one of the devices must be connected to the transmitter of the other and vice versa. Pair twisting (cross-over) is usually implemented inside one of the devices when wiring the cable in the connector. Some ports of hubs and switches support the ability to change the type of wiring in the connector (MDI-X or Normal). Computer network adapters usually do not allow you to change the type of port pinout and are referred to as devices with an MDI or Uplink port.

Figures 7 and 8 show straight and cross-over port connection options.

Cable joints must provide at least 750 connection-disconnect cycles.

The category of the patch cable must match the category of the cable in the horizontal system.

· Patch cables must have stranded conductors to ensure sufficient flexibility.

Cable routing

1. In order to avoid breaking the conductors, the tension should not exceed 110N.

2. The bending radius should not be less than 4 cable diameters for horizontal wiring.

3. Avoid pinching cables, which can be caused by:

Twisting cables during installation;

Inaccurate hanging of cables;

Too dense laying of cables in the channel;

Cable specifications: diameter 0.2", RG-58A/U 50 Ohm;

Acceptable connectors: BNC;

Maximum segment length: 185 m;

Minimum distance between nodes: 0.5 m;

Maximum number of nodes in a segment: 30

Cable specifications are shown in table 1.

Table 1. 10BASE2 (ThinNet) RG 58 A/U and RG 58 C/U cable specifications

Table 2. Electrical Specifications for Category 3, 4, and 5 Cables

Wave impedance: 50 ohm

Maximum segment length: 500 meters

Minimum distance between nodes: 2.5 m

Maximum number of nodes in a segment: 100

AUI cables are used to connect AUI ports to thick coaxial cable trunks. The maximum cable length is 50 meters.

Table 3 AUI Cable Specifications

Conclusion

In this paper, the main components of the LAN were considered. To date, the development and implementation of IVS is one of the most interesting and important tasks in the field of information technology. The need for operational information is growing more and more, the traffic of networks of all levels is constantly growing. In this regard, new technologies for transferring information to IVS are emerging. Among the latest discoveries, it should be noted the possibility of data transmission using conventional power lines, and this method allows you to increase not only the speed, but also the reliability of transmission. Network technologies are developing very rapidly, in connection with which they begin to stand out as a separate information industry. Scientists predict that the next achievement of this industry will be the complete exclusion of other means of information transmission (television, radio, print, telephone, etc.). These "obsolete" technologies will be replaced by a computer, it will be connected to some global information flow, perhaps even the Internet, and from this flow it will be possible to obtain any information in any representation. Although it cannot be argued that everything will be exactly like this, since network technologies, like computer science itself, are the youngest sciences, and everything young is very unpredictable.

Bibliography:

1. N. Malykh. Local networks for beginners: Textbook. – M.: INFRA-M, 2000.

2. N. Olifer, V. Olifer. Basic technologies of local networks. Textbook. - M.: Dialogue - MEPhI, 1996.

3. Computer networks. Training course / Per. from English. - M .: Publishing Department "Russian Edition" LLP "Channel Trading Ltd.", 1997.

4. Barry Nance. Computer networks: Per. from English. - M: Eastern Book Company, 1996.

Application

Option 5. .

Option 5.

Table 5

Turnover sheet for accounting

diet food

Product name	Unit	Incoming balance	Turnovers		Outgoing balance
			Coming	Consumption

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

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

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

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

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

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

Basic principles of building a local network

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

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

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

We must not forget that the local network is a "product" with individual solutions for each specific case, which does not tolerate an ill-conceived approach. That is why, like any quality product, a local network must be built by professionals. Let's take a look at what we need to know in order to conduct a quality installation.

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

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

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

LAN card

A network card is a device that allows computers to communicate with each other and exchange data on a network. All network adapters by type can be divided into two large groups - wired and wireless.

Wired network cards allow you to connect electronic devices to a network using Ethernet technology using a cable, and wireless network adapters use Wi-Fi radio technology.

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

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

According to their constructive implementation, individual network cards are divided into two groups - internal and external. Internal cards designed for installation in desktop computers using interfaces and their corresponding PCI and PCIe slots. External boards are connected via USB connectors or outdated PCMCIA (laptops only).

Router (Router)

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

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

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

Another important task of a router is to restrict access to your home network from the World Wide Web. Surely you are unlikely to be satisfied if anyone can connect to your computers and take or delete from them whatever they want.

To prevent this from happening, the data flow intended for devices belonging to a specific subnet must not go beyond its limits. Therefore, the router from the total internal traffic generated by the members of the local network selects and sends to the global network only that information that is intended for other external subnets. This ensures the security of internal data and saves overall network bandwidth.

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

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

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

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

If, nevertheless, at some point the number of LAN ports of the router ceases to be enough, then to expand the cable network, one or more switches can be connected to the router (we will discuss them below), which act as splitters.

Modem

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

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

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

There are practically no key differences between these two groups of devices. Manufacturers themselves position a router with a built-in modem as a more advanced option, endowed with a large number of additional features and improved performance. But if you are only interested in basic features, such as, for example, connecting all computers on a home network to the Internet, then there is not much difference between modem routers and routers where a DSL modem is used as an external network interface.

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

Switch

A switch or switch is used to connect various nodes of a computer network and exchange data between them via cables.

The role of these nodes can be either separate devices, such as a desktop PC, or entire groups of devices already combined into an independent network segment. Unlike a router, the switch has only one network interface - LAN and is used at home as an auxiliary device, mainly for scaling local networks.

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

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

Depending on the model, the switches can provide a maximum data transfer rate of either 100 Mbps (Fast Ethernet) or 1000 Mbps (Gigabit Ethernet). Gigabit switches are best used for building home networks in which it is planned to frequently transfer large files between local devices.

Wireless access point

To provide wireless access to the Internet or local network resources, in addition to a wireless router, you can use another device called a wireless access point.

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

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

Access points can also be used to organize wireless bridges that allow you to connect individual devices, network segments or entire networks using a radio signal in places where cabling is undesirable or difficult.

Network cable, connectors, sockets

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

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

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

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

Depending on your desire, you can either buy ready-made (with crimped connectors) network cables of a certain length, called “patch cords” in any computer store, or purchase twisted pair and connectors separately, and then make cables of the required size yourself in the right amount.

Using cables to connect computers to a network, of course, you can connect them directly from switches or routers to connectors on PC network cards, but there is another option - using network sockets.

In this case, one end of the cable is connected to the switch port, and the other to the internal contacts of the socket, in the external connector of which you can later connect computer or network devices.

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

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

In addition to their direct purpose, extension cords are convenient to use in cases where the end of the cable ends with not one connector, but two. This option is possible when building networks with a bandwidth of 100 Mbps, where only two pairs of wires are sufficient to transmit a signal.

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

Read more about twisted pair crimping, connecting sockets and the characteristics of network cables in a special material.

Network topology

Now that we've seen the basic components of a LAN, it's time to talk about topology. If to speak plain language, then a network topology is a diagram that describes the locations and how network devices are connected.

There are three main types of network topology: Bus, Ring, and Star. With a bus topology, all computers on the network are connected to one common cable. To combine PCs into a single network using the "Ring" topology, they are serially connected to each other, while latest computer connects to the first. With a star topology, each device is connected to the network through a special hub using a separate cable.

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

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

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

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

Conclusion

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

Switches are used as ancillary equipment to expand the points of connection to the local network using cables, which are essentially splitters. For the organization of wireless connections, access points are used, which allow using Wi-Fi technology not only to connect all kinds of devices wirelessly to the network, but also in the "bridge" mode to interconnect entire segments of the local network.

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

So, as soon as you have a detailed plan for your future network, you can begin to move on to the selection and purchase of the necessary equipment, its installation and configuration. But we will talk about these topics in our next materials.

In today's world, LANs have become more than just a necessity - they're actually required to achieve a good level of productivity. However, before you start using such a network, you should create and configure it. Both of these processes are quite difficult and require maximum concentration, especially the first of them. A poorly designed and configured LAN will not work at all, or it will not function at all as it should, so creating a local network should be the focus of the person doing it.

What is a local network

As a rule, the creation of such communication systems is caused by the need to share data by users who work on remote computers. A LAN not only enables near-instantaneous exchange of information and simultaneous file sharing, but also allows remote use of network printers and other devices.

A local network is a complete set of software and hardware resources aimed at creating a single information space. In fact, this is a number of computers located at a distance from each other and connected by a communication line - a cable. The main difference between a LAN and other types of networks is the short distance at which workstations are located.

Pre-project preparation and design

Before you create a local network, you must first design it, that is, plan the process of its creation. This stage is one of the most significant, since the LAN includes a huge number of components and nodes.

Initially, the terms of reference are drawn up on the basis of primary data, defining several points:

Functions and tasks of the LAN.
Selected topology.
List of available equipment.

Once you have these points in mind, you can start designing. The project itself should contain LAN schemes, network equipment placement points, a list of required software and hardware.

A local area network is a complex mechanism, but if it is designed correctly and the equipment is selected in accordance with the requirements, then the likelihood of problems in the operation of the communication mechanism becomes minimal.

Required Hardware

There is a list of equipment without which no LAN can function. It includes:

Data lines. The most commonly used coaxial cable and optical fiber. In this case, the length of the coaxial cannot exceed several hundred meters, however, if it is necessary to extend the network over long distances, special repeaters are used - signal repeaters that do not allow it to fade.
Communication equipment: network cards (devices that perform duplex exchange of information between a computer and a data transmission medium), hubs (break the network into separate segments, structuring the network physically), routers (take on the choice of the packet transmission route), switches (logically divide the LAN into segments, combining several physical circuits), repeaters (provide signal recovery, allowing you to increase the length of the transmission medium), transceivers (amplify the signal and convert it to other forms, allowing you to use different data transmission media).

List of software

No LAN is complete without software. Required LAN programs include:

Operating systems of work nodes. The most commonly used operating system remains Windows 7, although Windows XP is also not losing ground.
Network operating systems installed on servers are the basis of the LAN, since it is impossible to set up a local network without them. It is these software tools that take control of all data flows between the main and secondary nodes, providing the possibility of collective access to network resources. As a rule, the following Microsoft operating systems are used: Windows Server 2003 or 2008.

Network services and applications that allow users to access remote files, print documents to a network printer, view networked work sites, and send email. The implementation of such services is carried out using software.

Creation and installation of a LAN

Installation and commissioning work takes the most time, since it is necessary to create a local network in several stages:

Before starting the installation of communication lines and switching devices, you must first prepare the room.
Next, you can lay the cable, as well as install the necessary equipment.
Devices of the server and workstations should be connected to the cable communication line.
After that, the software is installed and configured.

Installation of cable and equipment has a number of features, therefore, if there are difficulties with how to connect a local network, better solution entrust this issue to specialists.

Joining two computers in a LAN

In some cases, it may be necessary to combine two computers into one network, for example, to create a common information space. This is not very difficult to do if you follow a certain algorithm of actions:

If necessary, install network adapters in both computers, not forgetting the drivers.

Purchase a crimped network cable for connection. If you have the necessary knowledge and skills, crimping can be done on your own - the local network of two computers will not become worse quality from this.
Connect both workstations with a communication line.
Set up the LAN in a specific order.

Algorithm for setting up a local network between two computers for Windows 7

Select the Start menu, then press right click mouse on the "Computer" icon, enter the "Properties" submenu.
You need to find in the list "Computer name and domain", and then select the item with the change in settings.
The working name of the computer must be changed by clicking on the appropriate icons.
The group name should remain unchanged - "Workgroup", but the computer names are changed to "pc1" and "pc2" for the first and second subscriber, respectively.
You can now click OK and restart your computer.

In most cases, you may want to give each host a unique IP address:

From the Start menu, select Settings and then Network Connections.
Right-click to open the "Properties" submenu next to the "Local Area Connection" icon.
In the "General" tab, select "Properties" of the item "Internet Protocol".
Make the line "Use the following IP address" active and enter the value 192.168.0.100. After that, save the changes made.

Local network and internet

Work nodes connected in a LAN can be connected to the Internet. A local network, to which the Internet can be connected in two ways, will work at a speed divided in two.

The first way to connect is to use a router, which is assigned an identifying IP address. And in the second case, you can use a wireless connection.

In this case, the local network is the interaction of two computers, master and slave, so the IP address is written in the gateway of the main one, previously connected to the worldwide network.

If the LAN is based on the use of a server, each workstation must have an individual IP address, and the proxy server through which the Internet is accessed must be specified in the browser settings.

Wireless LAN

A wireless local area network is a type of LAN that uses high-frequency radio waves to transmit information. WLAN is an excellent alternative to the conventional cable communication system, having a number of advantages:

Improving labor productivity. WLAN makes it possible to use the Internet without being tied to one room. You can freely change your location without losing your internet connection.
Easy installation and configuration, financial savings and reliability - all these factors are due to the absence of a cable communication line.
Flexibility. Installing a wireless network is real where there is no way to stretch the cable.
Possibility of expansion. Network scalability is greatly simplified with wireless network adapters that can be installed on any work node.

WLAN has a certain range, which depends on the characteristics of the network devices and the noise immunity of the building. As a rule, the range of radio waves reaches 160 m.

Necessary equipment for creating a wireless LAN

An access point is used to connect other workstations to the network. This device is equipped with a special antenna that controls duplex data transmission (sending and transmitting) using radio signals. Such a point can transmit a signal at a distance of up to 100 m indoors and up to 50 km in an open area.

Access points significantly expand the computing power of the entire communication system, allowing users to freely move between each of them without losing connection to the LAN or the Internet. In fact, these radio points act as hubs, providing a connection to the network.

Using access points allows you to scale up your entire wireless LAN by simply adding new devices. The number of subscribers that one radio point can withstand generally depends on the network load, since the traffic is divided equally between each of the users.

Wireless LAN: Windows 7 Setup Flow

First you need to prepare an ADSL modem with WiFi technology, as well as client points with connected to them wireless adapters. After that, you can start building a wireless LAN:

Connect the modem to the electrical network.
Run the WLAN setup wizard on the client device.
Select the SSID from the list of found wireless networks.

Access point setup:

The first step is to configure the TCP/IP protocol properties by specifying the IP address and subnet mask.
Then enter the value DNS servers, since it is not possible to fully configure the local network without this parameter. In most cases, it is enough to make the automatic assignment of the DNS address active.
It is also mandatory to configure the parameters of the wireless network itself, in which security is important.
At this stage, you need to configure the Internet connection and filtering for the Windows 7 firewall.
And lastly, the wires are connected and the WLAN network is tested.

To create an optimal information space, you can combine types of networks - cable and wireless, allowing you to use the advantages of each of them for the benefit of the enterprise. However, it is important to remember that in our time, it is more and more used precisely wireless network WLAN, which has all the advantages of cable networks and is devoid of their disadvantages.

After completing the creation and configuration of the local network, it is important to provide for its administration and the possibility of maintenance. Even if the LAN installation is perfect, during its operation various hardware or software malfunctions are almost inevitable, which is why maintenance should be regular.

Let's decide on the starting points: a small company, let's say about 15-50 employees. As a rule, there is no qualified network specialist. And most likely it was the "dedicated" for working with the network, the network administrator by state. Let's agree - your specialist is still needed. And he needs to be paid money, and good money at that (what a horror, right? That's news for many directors). I will try in this article (perhaps with a continuation) to act as a network administrator for such a small company. So, we build a network ourselves. Why not? There are many arguments "against" "home-made", and all of them are true (unless, of course, this is not outright "noodles" from a potential contractor). But still, you can do it yourself. Arguments "for" also abound. We will not bring them here - we believe that we decided to do it ourselves. We will not make newfangled radio, Wi-Fi and other networks, but an inexpensive, but high-quality traditional wired cable network for the daily work of the company. However, one must understand that the work must be performed by a specialist (or several).

Introduction

Let's decide on the starting points: a small company, let's say about 15-50 employees. As a rule, there is no qualified network specialist. And most likely it was the "dedicated" for working with the network, the network administrator by state. If there is - a jack of all trades, and often forced to do some "urgent" business like installing Windows or drivers on some computer, instead of working with the network. Together with other "computers" (if any). Is the network working? Let the deck through the stump, well, okay, a little later we will do it (let's do it).

Let's agree - your specialist is still needed. And he needs to be paid money, and good money at that (what a horror, right? That's news for many directors). I will try in this article (perhaps with a continuation) to act as a network administrator for such a small company.

Initial data

So, we build a network ourselves. Why not? There are many arguments "against" "home-made", and all of them are true (unless, of course, this is not outright "noodles" from a potential contractor). But still, you can do it yourself. Arguments "for" also abound. We will not bring them here - we believe that we decided to do it ourselves.

However, one must understand that the work must be performed by a specialist (or several). You can’t train (“though inferior, but your own”) and raise your specialist in this way. You can put your own into practice to the person doing the work (we will not take into account drilling holes with a puncher in the walls and fixing the cable channel - any man should be able to do this).

One more factor, let's add, so to speak, "pepper" - our company, in addition to the office, has a store and a warehouse, which are quite remote.

We will not make new-fangled radio, Wi-Fi and other networks, but an inexpensive, but high-quality cable network of a traditional wired type for the daily work of the company. For work, not for surfing news and/or porn sites from a laptop from a hotel couch. We may return to these issues in the sequel (not to the hotel and others like it, of course, but to modern technologies).

Last, and also very important: we count money, but we are not greedy.

Plan

At the very beginning, you must definitely do one very simple, but very important thing - take a few pieces of paper, a pencil and sit down for a draft business plan. It is very important to more or less clearly "pencil" all the keywords that come to mind from the question "what do I want from the network." Sketch these positions on the first sheet. On the second - to group them into separate categories. For example - the category "services". What kind of services do we want to receive from the network, and what quality? What do we need? File-, ftp-, print-, internet service?

It would seem that everything is clear, why write, draw? But, if you do not take everything on a pencil - then it will be worse. For example, it turns out that you need to go to the director and / or to the accounting department: “Sorry, we bought the wrong piece of iron here, and not for 100 USD. necessary, but for 500.

Now you can take a break to add what you need, throw away the excesses. And put it all aside for at least a day. Then the draft can be transferred to the third sheet. With "final" additions and corrections. Why quotes - you yourself understand, this is not the last sheet, and far from the last "sketches".

Services are services, however, the base is SCS, that is, a structured cabling system. Let's try not to run too far ahead of the horse.

Usually there are two options - an office "from scratch" and an office "ready". The first case - bare walls and ceiling, repair - ours, and that's good. The second option is "done". Those. - we begin the external laying of the SCS. But, let's not start with that, yet.

Electricity

An important stage, because God forbid, not just one or two ordinary computers “fly”, everything can “fly”. Well, we believe that everything is in order with the power network in our office. There is only one important point here - uninterruptible power supplies (UPS). They are necessary. Believe me. A diesel generator is, of course, good, but not necessary in all cases, but sparing money on installing a UPS on each server or communication closet is simply stupid. However, we will return to the issue of UPS in due time.

SCS and basic active equipment

Structured Cabling System (SCS) is one of the cornerstones. SCS must be properly designed and built. Let's break the question into sections:

* Communication cabinet (with "stuffing")
* cable lines
* Subscriber sockets

This is where the plan of the premises, with clearly marked places for employees, is very useful. It must be borne in mind - it’s also good to note power sockets. Next - in order, let's start with the closet.

Communication cabinet: find a convenient place to install a cabinet with equipment. It is important to find the optimal distance to workstations in order to reduce the cost of twisted pair, cable channel and other "little things". There are many factors: limiting the length of the line to 100 meters (or rather, 90 meters, according to the classical formula 90 + 5 + 5); office layout (where is it convenient to put or hang a cabinet, is it convenient to pass the walls when pulling the cable, will the cooling not put pressure on the ears of customers or employees, etc.); in fact, the design of the cabinet (floor, wall, its height in U, the amount of equipment that needs to be installed in it, whether there will be a cooling unit).

There are a wide variety of cabinets, you need to carefully look at the prices and quality of the proposed purchase, do not forget to stock up on capacity (!) In those very U. Be sure to have at least one shelf. However, in some places it is quite possible to get by with wall brackets to secure equipment. But this is specificity. We will assume that for the office we chose a 12-14-height cabinet with a glass door. Looking ahead a little, it is necessary to mention what will be installed inside:

Shelf: it will always come in handy, even if it is empty (I doubt it) - it can be removed. You should not spare 10-20 dollars when you have to "suddenly" put a device or two in the closet, remember these lines.

Switch (switch): 24 ports at the lower limit of the company's employees in the office - let there be 10-20 people in the office (and do not forget about servers and other network equipment). However, if there is a high density of jobs, there will be no problems adding the required number of switches and other related equipment.

Distribution panel (patch panel): 24 ports, everything is the same with the switch. It is on the patch panel that all lines from workstations and servers will be reduced.

Panel (block) of power sockets: by the number of connected equipment in the cabinet, plus a supply of 1-2 sockets on the panel. Here we may well expect an "ambush" if we have to connect power supplies - it may not be enough (recall about 99.9% of the market filled with network filters with tightly-obliquely planted rosettes).

You can put a cheap, simple option (that's when a shelf comes in handy, but you can also put it on the floor of a cabinet), you can also use a 19 ”UPS designed for installation in a cabinet.

So, having looked at the products offered on the market, we believe that we have decided on a cabinet: 14-height (14 U). For example, Molex MODBOX II 14U:

Suitable for 19" 1U fan cabinet
. Standard cabinet set:
. Lightweight steel profile provides the cabinet with greater rigidity and strength
. Aesthetic glass door with lock
. Door of universal design with the possibility of hanging (left, right)
. 19" depth adjustable frame
. Grounding of all cabinet elements
. The cable entry holes are equipped with a protective brush to prevent dust from entering the cabinet

Switch. His choice is a more complex issue. Absolutely cheap switches do not want to be considered. There are devices that are more expensive (and very expensive), but you still have to choose from two types: unmanaged and managed.

Let's take a look at the following two devices: ZyXEL Dimension ES-1024 and ES-2024:

It is a cost-effective Fast Ethernet solution and can be used to build highly efficient switched networks. The data staging feature significantly reduces latency on high-speed networks. The switch is designed for workgroups, departments or backbone computing environments for small and medium enterprises. Due to the large address table and high performance, the switch is an excellent solution for connecting departmental networks to a corporate backbone or for connecting network segments.

Specifications:

24-port Fast Ethernet switch
. IEEE 802.3, 802.3u and 802.3x compliant
. RJ-45 Ethernet ports with 10/100 Mbps auto-speed selection
. Automatic connection detection cross cable on all RJ-45 10/100 Mbps Ethernet ports
. Back-Pressure-Base flow control support on half-duplex ports
. Pause-Frame-Base flow control support on full duplex ports
. Store-and-forward switching support
. Support for automatic address detection
. Maximum Wired Transfer Rate
. Built-in MAC address table (8K MAC address capacity)
. Power LEDs, LK/ACT and FD/COL

Application of ES-2024 switch will allow you to unite a group of users and connect them with high-speed lines to the corporate network. Additionally, it will be possible, thanks to the use of iStackingTM technology, to combine a group of switches for network management, regardless of their location.

Specifications:

24 RJ-45 ports with automatic 10/100 Ethernet speed selection and automatic crossover cable connection detection
. 2 x 10/100/1000 Ethernet ports
. 2 mini-GBIC standard slots, combined with ports
. 8.8 Gbps non-blocking switching bus
. Support for IEEE 802.3u, 802.3ab, 802.3z, 802.3x, 802.1D, 802.1w, 802.1p protocols
. MAC address table 10Kb
. VLAN support: Port-based and 802.1Q
. Possibility to limit the rate on the port
. 64 static VLANs and up to 2Kb dynamic VLANs
. MAC address filtering
. Support for ZyXEL iStacking™, up to 8 switches (up to 24 in the future) managed by a single IP address
. Control via RS-232 and WEB-interface
. Telnet CLI
. SNMP V2c(RFC 1213, 1493, 1643, 1757, 2647)
. Control over IP: static IP or DHCP client
. Firmware update via FTP
. Updating and Saving System Configuration
. Standard 19" Rack Mount

As you can see, there is a difference, and a very significant one. As there is a difference in price - approximately 100 and 450 dollars. But, if the first switch is a decent, but "stupid" box, then the second one is in some sense intelligent, with much more functionality and manageability, with potential strengths. We choose the second option. We want to build a good network, don't we?

By the way, right now it is quite time to ask yourself why, in fact, we are building a “hundredth” network? Today, every second computer has not just a gigabit network interface, but two gigabit ones?

This is the case where you can safely save. The fact is that a 100-megabit network is more than enough for an office to work. If, moreover, the switch is decent! Yes, but on the two gigabit interfaces of the selected switch - safely "sit down", for example, two servers. Here they are, the servers, it's just for the benefit.

Of course, you can take something like ZyXEL GS-2024 and put everyone on a gigabit channel, but this is just a case of unreasonable spending of money, and for that kind of money we can buy a complete cabinet with a more complete filling.

Patch panel. Also the case when you should not save much. Choose a panel like Molex 19" 24xRJ45, KATT, 568B, UTP, PowerCat 5e, 1U.

Compliance with the requirements of category 5e. The compensation system is implemented directly on the printed circuit board. The use of CATT type connectors speeds up and simplifies cable installation. Dedicated space for labeling channels. The panel is powder coated. All necessary fastening and marking elements are supplied in the kit.

There are many options here, as already mentioned, you can put any cheap one, it can be more expensive, you can use a 19” rack-version - there will be beauty at all. Who doesn't know APC? You can see for example this UPS:

APC Smart-UPS SC 1500VA 230V - 2U Rackmount/Tower

Or, like this:

Without delving into the characteristics, we note that many devices are equipped on request with guides for installing the UPS in a 19 "rack. Also, it is possible to equip, if desired, with an SNMP module for monitoring and managing the UPS over a computer network. Of course, this will cost money, but It can be very convenient.Let's opt for IPPON.It should be noted that models 1500, 2000 and 3000 can be equipped with SNMP support, but not 750 and 1000.

Power outlet block:

Without any special comments - maybe you can find something cheaper, easier. But a dozen "strangled raccoons" will not make the weather.

It remains to remember to decide whether a fan unit is needed in the cabinet? Expensive pleasure, especially when paired with a thermostat unit. However, we will attribute this to the specifics of the place / office.

We more or less figured out the closet, there were all sorts of “little things”, without taking into account which there will be annoying delays later:

* Screws with nuts for mounting equipment in the cabinet;
* Nylon non-opening ties for laying and fastening the cable (packs of 100 pieces, 100, 150, 200 mm long);
* Marking for the cable (adhesive sheets with a protective layer).

In fact, we got to the SCS itself. A very important "detail" is the cable, which will be used for wiring the SCS. Yes, again a call not to save. A good twisted pair cable is a good investment. We take Molex, unshielded UTP PowerCat 5e cable.

The cable is the core element of the PowerCat product line. The line is designed for use in high-speed telecommunication networks (eg GigaEthernet 1000Base-T).

We, of course, will come to subscriber sockets, and then what? Next - buy the required number of patch cords to connect workstations. Naturally, you need to think over the length, look at the office plan mentioned above. But that is not all. You also need a strainded cable (normal - solid). This is a special twisted pair, "soft", from which patch cords are made. After all, sooner or later you will definitely need a patch cord of a greater length than there are ready-made ones at hand (if at all by that time they remain). it will be necessary - as you wish) to make short - 30-50 cm, patch cords for crossing SCS lines and active equipment in the cabinet itself. Therefore, we "take a pencil" a couple more packages of RJ45 connectors, in common parlance - "chips". And packaging of rubber caps for them.It is better to take soft caps and with a slot for the "chips" retainer, and not with a "pimple" for the retainer.

We have almost reached the network interfaces on user computers, but subscriber sockets are still needed. Someone against such a wonderful thing as Molex OFFICE BLOCK 2xRJ45? ;-)

Compliance with the requirements of category 5e. The modules are designed for high-speed telecommunication networks. Possibility of cable entry from the sides, top or rear. As standard, the modules are equipped with dust shutters. Ease of labeling channels. The built-in magnet simplifies mounting the modules to metal surfaces. Possibility of fastening with screws. Cable fastening inside the module without cable ties. Free choice of connection sequence (568A/B). Connector type "KATT" facilitating installation. The kit includes mounting elements. .

Here it is necessary to determine the quantity. After all, there are single options. Again we take the plan of the office. There is another important point in determining the installation locations for sockets - it is advisable to add one or two additional SCS lines to each cabinet. One is just "just in case". What if the layout in the office changes a little or someone will need to connect a laptop? The second one is not bad to have based on the print server, for organizing network printing. It is very nice to have one or two network printers for your office or office that work without problems and whims of the owner (or Windows).

Do you think that's all? No. Another factor that is present in any office is forgotten - telephony. It's a good idea to think about this too: if telephones should be wired to some workplaces, then why not make a wiring in the general SCS? After all, the issue can be solved simply: throw a line or two to the necessary places, put an RJ-12 socket next to the RJ-45, even in one housing (unit). In the socket - DECT, for example, with several handsets, and in the cabinet we draw a line (lines) from the PBX - they can be put on sockets, neatly glued with Velcro inside and on the side. Lines from jobs - on them.

It seems like it's time to take on the cable channel and dowel-nails? Yes. It is time. But this is already clear to any handy man, we will not dwell on this for a long time. You just need to take into account the number of lines laid in the cable channel. And, of course, a small margin is needed. It is very good if the office has a suspended ceiling, the lines can be pulled behind it right to the workplace and lowered in a cable channel along the wall. When drawing lines, it’s a good idea to mark them (as well as sockets in the future). The easiest method is the first socket to the left of the door - No. 1, further in a circle.

After stretching the lines, you can start splitting the patch panel and sockets. Needless to say, this job requires accuracy and skill. It is at this moment that line marking will come in handy for us - if all the lines are split in order, then in the further operation of the SCS it will be possible to practically do without an installation map (layout), something like this:

Socket

However, this card is still needed in the future. Will definitely come in handy.

When laying cables, you must follow a few simple rules (just simple ones, we will not delve into standards and other ISOs now):

* Do not severely bend, rub or step on the cable. Cable bending is allowed: during installation - 8, and, during operation - 4 radii of the cable itself;
* Do not lay lines near power lines: if necessary, lay them in parallel - at a distance of at least 20 cm;
* Crossing power lines is allowed, at a right angle;
* Mandatory testing by a cable tester.

Separately, about the last point. Remember the joke about the Japanese supply of something there? “Dear customers! We don't know why you need this, but we still decided to put in the boxes one defective chip for every ten thousand, according to your requirements. Yes, you can just split and forget. An experienced installer is not mistaken. However, a really experienced installer will definitely check, and not only the layout of the line, but also the quality.

Here we come to the most interesting moment. If we check a trifle with a simple and cheap tester, then to carry out tests and certify lines - no, it will not work:

Which exit? I really don't want to leave the issue of line quality unresolved. There are three options. The first is to buy a good tester, for example:

But, alas, we are very sorry for $6,000, even if it is for such a wonderful and necessary device.

It is a compact, portable tool used for qualification, testing, and troubleshooting of coaxial and twisted-pair cable in local computer networks. The tester is recommended by leading manufacturers of information cabling systems for testing for system certification up to Class E inclusive. The high level of reliability, convenience and accuracy of the device provided him with one of the first places among the products of this class. For fast and high-quality testing of cable connections in an extended frequency range up to 350 MHz, technologies are used digital processing pulse signal.

The second option is to invite a familiar admin or installer who has such or a similar device. Of course, having previously bought a case of good beer. Half an hour of work, plus a beer evening in the pleasant company of a friend.

The third option is to officially invite specialists from a company that provides such services. and pay for these services. This is not so much, especially if you do not require a certificate on paper.

Remote workstations

Having "finished" (quotation marks because we must first still plan everything and make the necessary purchases and negotiations) with the work at the main office, we remember the warehouse and the store.

Now (in these notes) we will consider not a "tricky" solution like VPN, but the simplest one - organizing the connection of computer networks with subnets (workstations with a network) over a dedicated line. Effective, cheap and cheerful. By the way, allotments, of course, should be placed in a closet and connected to sockets, like telephones.

If the distance and, accordingly, the resistance of the leased line are small, you can try to install a pair of "bridges", for example, the already mentioned firms ZyXEL Prestige 841С and ZyXEL Prestige 841. Model "C" is "master", so this device is best installed at the head office. These are inexpensive VDSL devices, but they give the necessary results for our task. What ZyXEL says:

Depending on the type and condition of the cable, as well as on the distance, the Prestige 841 paired with the Prestige 841C provides the following data exchange rate:

In the direction to the subscriber - within the range from 4.17 to 18.75 Mbps
. in the direction from the subscriber - from 1.56 to 16.67 Mbps
. the total bandwidth of the line can reach 35 Mbps

Specifications:

VDSL Ethernet Bridge
. LAN connection at 15 Mbps up to 1.5 km
. Plug&Play, transparent to all protocols
. Working in pairs
. Desktop execution
. Non-volatile memory (Flash ROM)
. Size: 181 x 128 x 30 mm

This option will give 18 Mb in each direction, ideally, of course. This is VDS.

When using Prestige 841 there is another plus. These devices have a built-in splitter, and we can get "free" telephony from a remote location. It is enough to plug into the “phone” socket on the one hand the telephone of the remote workplace, and on the other hand, connect the office mini-PBX.

If the VDSL bridges don't "stretch" the line, you need to look at other devices, xDSL. For example - something from the 79 series ZyXEL, SHDSL.

Optimization of the hardware and the use of advanced technologies have made it possible not only to reduce the dimensions of the device, but also to reduce the cost and improve functional characteristics. provide symmetrical connection at speeds up to 2.3 Mbps and can work on a leased 2-wire line both in point-to-point mode and as a client of an Internet provider hub.

Specifications:

. SHDSL router
. G.991.2 support up to 2.3 Mbps symmetrical
. Connecting networks or accessing the Internet on long distances
. Encapsulation PPPoA, PPPoE, RFC-1483
. TCP/IP Routing, Full NAT, Packet Filtering
. Support for IP Policy Routing, UPnP, connection redundancy
. Management via console, Telnet, Web, SNMP

The ideal speed is 2.3Mb over two wires. If you "charge" 4 wires, the speed will be correspondingly greater. However, these devices cost a large amount- 400-500 dollars for a pair. In any case, roughly speaking, the worse the quality of the line, the lower the speed and the higher the costs. However, we will postpone the tuning (tuning) of devices for the future, this is a separate conversation, especially since in the case of VDSL 841 this does not make too much sense at all. xDSL devices should be placed on a shelf in a closet. I told you it wouldn't be empty.

Internet connection

ZyXEL Prestige-660

A modern office is unthinkable without the Internet. To connect, we can use ADSL technology, for example - ZyXEL Prestige 660.

As ZyXEL describes this device:

Modem P-660R belongs to fourth generation ADSL modems and combines in one device the functionality necessary to connect an existing office or home network to the Internet: ADSL2 + modem, router and firewall. Modem will provide your office permanent connection to the Internet, working quickly and safely. Installation and maintenance of the P-660R modem is simple and will not cause any problems even for inexperienced users.

Main advantages of ZyXEL Prestige 660:

* High Speed Internet- up to 24 Mbps
* Reliable connection on problematic lines
* Free phone
* Permanent connection
* Does not require driver installation
* Works with W

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