>>Informatics: How a computer network works
How does a computer network work?
Introduction
Having studied the first part of the “Informatics and ICT” course, you have mastered only some sections of this large scientific and applied field. This textbook will introduce you to new sections of the subject and help you acquire new skills in using information and communication technologies.
This school year you will get to know computer networks, which are used to transmit information. Technologies for working with information in computer networks are called communication technologies. As a result, you will fully understand the meaning of the term “information and communication technologies” - ICT.
A very important application of computer technology is information modeling. You will soon learn what a model is, how information models are created on a computer and why they are used, what ICT tools are used for information modeling. These tools include database management systems (DBMS) and spreadsheet processors. Using a DBMS, information repositories are created on a computer, which are called databases. Table processors are used to organize calculations in spreadsheets. If such calculations relate to some real process, then in this case we can say that a mathematical model of this process is implemented in the spreadsheets.
Management is another broad area of use computers. With the help of computers, airplanes, rockets, industrial installations, production teams, economic sectors, etc. are controlled. It turns out that such various control options have general laws. They were discovered in the science of cybernetics. You will become familiar with the basic concepts of this science.
Any control occurs according to certain rules, which are called a control algorithm. An algorithm written in a programming language that a computer can “understand” is called a computer program. In this part of the course you will learn how to build algorithms and write simple programs in the Pascal programming language.
Inventions of various means and tools for storing, transmitting and processing information have been made from ancient times to the present day. You will learn about the history of such inventions in the last chapter of the textbook. The history of computers and ICT dates back to the mid-20th century. From this time on, the process of informatization of various areas of human activity begins, and the formation of an information-oriented society takes place. The problems of the information society are studied by a branch of computer science called social informatics. You will learn about some issues in social informatics at the end of our course.
So, let's continue our journey across the ocean Computer Science. You visited and explored some of the continents and islands in this ocean in the first part of the journey. But there are still uncharted lands, white spots on the map of the ocean of knowledge. Together with our brave captain - Tochka-RU, you will have to visit these lands and put a detailed description of them on the knowledge map. Good luck to you on this difficult but very interesting journey!
Chapter 1
Transfer of information in computer networks
Here you will learn:
♦ how computer networks are structured;
♦ what are networks used for?
♦ what is the Internet;
♦ how not to get lost on the Internet.
§ 1. How a computer network works
Main topics of the paragraph:
♦ what is a computer network;
♦ local networks;
♦ global networks.
What is a computer network
You already know that when a computer is running, information is constantly exchanged between its component devices. The transfer of information between the user and the computer is carried out through keyboard, display, printer and other input/output devices. Now you will learn how computers exchange information with each other.
A system of computers connected by information transmission channels is called a computer network.
Local networks
Small computer networks operating within one room, one enterprise, are called local networks (LAN). Usually computers of the same local network are separated from each other at a distance of no more than one kilometer.
A local network allows users not only to quickly exchange data with each other, but also to more efficiently use the resources of networked computers. Such resources can be disk memory, a printing device, a scanner and other technical means, as well as software and any information in files.
From the point of view of organizing the interaction of individual elements of the drug system, two types of such systems are distinguished:
Peer-to-peer network; in it all connected computers have equal rights;
network with a dedicated server.
A user of a peer-to-peer network can have access to the resources of all computers connected to it (if these resources are not protected from unauthorized access).
In school computer classes, a LAN with a dedicated server is most often used, organized according to the following principle: there is one central machine, which is called a server, and many computers connected to it - workstations. The central machine usually has a large disk memory; devices that are not on workstations are connected to it: a printer, a scanner, a modem for accessing the global network, etc. The server stores software and other information that can be accessed by network users. The name “server” comes from the English “server” and is translated as “serving device”.
Many enterprises operate information systems based on local networks. For example, in a large shopping center, a database containing information about the goods in stock is stored on the server. Workstations are installed in sales departments. At the request of sellers, they receive information from the server about the availability of the desired type of product. Information about the sold product is transferred from the workstation to the server. After this, the server makes the appropriate changes to the database.
The basis of the LAN software is the network operating system. The most important task of a network OS is to support such a mode of operation of the LAN so that users working in it can use shared network resources without interfering with each other.
Global networks
Another type of computer networks are global networks. Further we will talk about them.
A global network connects many local networks, as well as individual computers that are not part of local networks. The size of global networks is not limited: there can be networks from regional to worldwide.
A global computer network is called a telecommunications network, and the process of exchanging information over such a network is called telecommunications (from the Greek “tele” - “far”, “far” and the Latin “comunicato” - “communication”).
The organization of communications in global networks is similar to the organization of telephone communications. Each subscriber's phone is connected to a specific switch node. Communication between switches is organized in such a way that any two subscribers, no matter where they are, can talk to each other. And such a telephone network “covers” the whole world. Computer networks work similarly. The personal computer of a network user (it can also be called a subscriber) is connected to a specific network node. The nodes are connected to each other, and this connection operates constantly. In Fig. 1.1 network nodes are designated U1, U2, etc., and subscriber computers are designated A11, A12, etc.
Networks serving some industry of the state (education, science, defense, etc.) are called industry (corporate) networks. If a network exists within a certain region, then it is called regional.
Each regional or industry computer network usually has connections with other networks. For this purpose, one of the network nodes acts as a gateway. It is connected by a communication line with similar nodes of other networks*.
*The need for a gateway only exists if the connected networks use different protocols (agreements). The need for a gateway only exists if the connected networks use different protocols (agreements).
There is a global system of computer networks through which you can establish communications with the most distant corners of the planet. This system is called “Internet” (English: “net” - network; “Internet” - association of networks). We'll talk about the Internet a little later.
Briefly about the main thing
A computer network is a set of computers connected by information transmission lines.
Computer networks are local and global.
In peer-to-peer local networks, all computers have equal rights.
A local network with a dedicated computer includes a server and many workstations. The server is used as a repository of shared information resources, and also contains some public access technical devices.
A global (telecommunications) network is a system of interconnected local networks and computers of individual users. Personal computers of users (subscribers) are connected to nodes of the global network.
There are regional and industry networks. Currently, most of them are united in a global system called the Internet.
Questions and tasks
1. What is a computer network?
2. How does a local network work? What functions does it perform?
3. What is a global network?
4. What is an industry network; regional network?
5. What is the name of the worldwide network, which unites most of the networks existing in the world?
6. Come up with different ways to connect four server computers to a network. Find a method that provides the shortest route for transmitting information between any two subscribers.
I. Semakin, L. Zalogova, S. Rusakov, L. Shestakova, Computer Science, 9th grade
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"Computer networks"
Pyatigorsk 2002
1. What is a computer network?
A certain number of computers connected to each other and having special hardware and software designed to be used together.
A computer network may also have a server or host machine, or be globalized (i.e. be part of Internet).
2. How is a local network organized?
The network structure is designed so that each subscriber can connect to another. For example, networks serving any industry are called sectoral, there are networks that exist within one region - regional networks. A local network usually has connections with other networks; for this, one of the servers acts as a gateway; it connects to similar servers of other networks.
3. What functions does it perform?
Local networks perform quite a lot of functions, the main ones being: e-mail, file transfer, etc. A wide variety of information can be transmitted over the network, in particular, the exchange of letters is possible. All information is in the form of files stored on magnetic disks of PCs or servers.
4. What is a global network?
Global computer network- a set of servers, local networks that form a single “seamless” network and use various IP protocols, as well as providing certain services to their users.
You can also give this definition: Global computer network- technology of network interaction between computers of different types.
5. What are sectoral and regional?
See question 2.
6. What is the name of the worldwide network that connects most computers?
Internet.
7. Come up with different ways to connect 4 computer servers. Find a way to communicate, the shortest route between two computers?
Types of connections are shown in the figure. The shortest route between two computers will be when connected by bus.
8. What is email?
The main type of network services is electronic mail (E-mail). When registering on the network, each user receives a “mailbox” there. In reality, a mailbox is simply a subdirectory on the disk of a network host computer, and the user acquires the right to read files in this area. A special addressing system is used to exchange letters. There are a lot of email addressing systems, but increasingly the one that is accepted in Internet. This is due not only to the scale of the Internet, but also with the fact that many disparate networks are connected to each other not directly by mail, but via the Internet. In this system, addresses are written using Latin letters and numbers, and the address format is always the same:
9. What does an email consist of?
The computer name consists of several words or abbreviations separated by periods. The computer name should be read from right to left. This looks unusual for us, but those who corresponded with friends or colleagues from the USA will remember the sequence of writing an address in the West: first the name of the addressee, then the street, then the city, then the state... - and so it is here.
By e-mail you can conduct private correspondence (one-on-one), you can send copies of your letter to other network users, send faxes and telexes, and also work with information servers, requesting information from them that interests you. By the way, an email is not just text. An email can send a binary file, graphics, or sound.
After typing the address and message, we press the Send button. Using the Attach button, you can attach an arbitrary file to a message.
Email is designed to be read by a specific user. But what if you need to contact everyone or a large group of users at once? Of course, you can send a letter to a list, and this method is widely used in networks. But there is another, often more convenient approach - to place the message in some area of the network, which (unlike a mailbox) is accessible to all users. To make this area easier to navigate, it has a clear structure: it is divided into separate sections called teleconferences. Of course, each user decides for himself which conferences he is interested in viewing and which ones he is not. Conferences are usually structured according to a single scheme: each conference consists of topics, and each topic contains sequentially numbered responses. You can think of a conference as a bulletin board divided into vertical columns with headings, each column containing a string of notes pinned one below the other.
Such teleconferences are classified as so-called “delayed”, when their participants communicate with each other over a short time interval. However, there is now another form of communication - Internet Relay Chat (IRC), which gives users the opportunity to chat with each other (by entering words directly from the keyboard) through one of thousands of constantly active IRC communication channels.
10. Where is the subscriber's mailbox located and what is stored in it?
See question 8.
11. What is an email address?
See question 8.
12.
See question 9.
13. What are teleconferences and how to become a participant?
Computer network services include: remote control, fax transmission, bulletin boards, software distribution and much more.
14. What is included in the technical means of computer networks?
By technical means are host computers, personal computers of subscribers (terminals), communication lines, modems.
15. Why are telephone lines used as a communication line?
Information in a computer has a discrete binary form, while telephone lines transmit a continuous electrical signal.
16. What is a modem? Its purpose in the network?
Modems(modulator - demodulator) is a device that connects a personal computer with a remote computer or server via telephone communication. A modem is used if the communication channel is a telephone line. The modem converts the computer's binary code into an analog electrical signal from the telephone information transmission network (modulation) and performs the reverse conversion while receiving information.
17. What quantity is the main characteristic of the modem and in what units is it measured?
The main characteristic of a modem is the speed of receiving and transmitting information, which is measured in bits/s or bot/s.
18. What capabilities does a smart modem have?
The smart modem can monitor and, in some cases, correct errors.
19. What is a network protocol?
Protocol network operation– this is a standard, a certain form of presentation and methods of sending information, procedures for their interpretation, rules for the compatible operation of various equipment.
20. What is the client-server model?
The organization of software adopted in modern networks is called "client-server technology". The client program prepares the user's request, transmits it over the network, and then receives the response and transmits it to the user.
21. What job does a mail server do?
Server - an e-mail program organizes the distribution of correspondence from subscribers' mailboxes over a network, as well as the reception of incoming information.
22. What work does an email client program do?
Purpose of the client program: preparation of sending subscriber letters, receiving incoming correspondence and a number of services.
23. What's happenedInternet?
Internet– worldwide global computer network.
24. How to translateWorld Wide Web (WWW)?
World Wide Web- "The World Wide Web".
25. What's happenedWWW?
WWW is a hyperconnected information system distributed throughout the world, existing on the technical basis of the Internet.
26. What information can be obtained fromWWW?
The information can be very different: text, drawing, photograph, multimedia, advertising, background information, latest news, etc.
27. How is the connection betweenInternetpages?
The most important property of the WWW is the hypertext organization of connections between WEB pages. The connection between pages is organized through hyperlinks.
28. What's happened Hypertext?
Hypertext is a way of organizing textual information within which semantic connections are established. Between its various fragments.
Functional
Speaking about what functions a local network server performs, you need to know what tasks are assigned to it. Basically, auxiliary capabilities are transferred to them. So, a local network server can look like:
- file device;
- print server;
- database storage;
- main operating point in the terminal network, etc.
Speaking about the first three cases, it is meant that the server is used as a large device on which there is certain data. So, it can be a storage for files of an automated enterprise management system, simply save the work of personnel and be used in a similar way.
A terminal network is usually used to reduce the cost of existing equipment. Thus, for work in such cases, employees are offered computers with a minimum configuration, the task of which is simply to connect to local servers. All necessary actions, calculations, processing, etc. take place on them, and the data is only transferred to the user’s computer, where it is displayed on the monitor and from where instructions to change them come.
There is also a certain range of other functions. But they are so specialized that it is very inconvenient to talk about each of them - it will take a lot of time and will only be interesting to certain people. Therefore, we will omit information about them.
Thus, the question of what functions the local network server performs can be considered clarified. Now let's talk about how to prepare it for work.
Setting up a local network server
There are many software products available to achieve this task. Therefore, to make the information more specific, let’s consider an example of work in Denver. Its basic package contains all the necessary tools, which means that setting up a local network server will be simple.
To do this, you need to download the software (you can use the official website, since it’s all free). During installation, specify the directory where the files are located. We create a virtual disk on the computer that will always work when the computer is turned on. Next, you need to configure it to work on a specific port (choose above 1024), and indicate to other computers where to connect.
Now let's talk about how to make it a local network proxy server. To do this, you must have a static IP address for constant stable operation. Then you should disable the Windows Firewall (but you must understand that this will reduce the level of security, which will need to be compensated using specialized software). Then we create the following directive: /home/"Your ip"/www. There you need to place a file that will be sent to the address that the user enters. That's it, the proxy server is ready!
Conclusion
As you can see, working with a local server is not a difficult task. Creating various websites on it will not be difficult for almost anyone. Which means it’s worth a try!
Why are local networks needed, and what are they? How to connect several computer devices to one Internet channel at once? What equipment is required to build a home network? You will receive answers to all these and other equally important questions in this material.
Introduction
Before you learn how to design and configure home local networks yourself, let’s immediately answer the most important question: “Why are they needed?”
The concept of a local network itself means the unification of several computers or computer devices into a single system for the exchange of information between them, as well as the sharing of 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 this to be done directly from a remote computer or multimedia device.
Connect several devices simultaneously to the global Internet through one access channel. This is probably one of the most popular functions of local networks, because these days 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 participants in 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 productivity 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 combined performance to perform resource-intensive tasks.
As you can see, creating a local network even within one apartment can bring a lot of benefits. Moreover, having several devices at home that require an Internet connection has long been not uncommon, 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 - via wire, such networks are called cable and use Ethernet technology, and also 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.
Today, wired networks still provide the highest bandwidth, allowing users to exchange information at speeds of 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 Gbit/s (Wi-Fi 802.11ac standard), in practice this figure looks much more modest and in most cases does not exceed 150 - 300 Mbit/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 home networks are arranged according to the same principle: user computers (workstations) equipped with network adapters are connected to each other through special switching devices, which can be: routers (routers), switches (hubs or switches), points access 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 be possible to combine several computers into one system at once. The maximum that can be achieved is to create a mini-network of two PCs by connecting them to each other.
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 network is combined and can include several types of switching devices. For example, desktop computers can be connected to the network using wires, and various mobile devices (laptops, tablets, smartphones) can be connected via Wi-Fi.
For example, consider the diagram of one of the possible options for a home local network. It will involve electronic devices designed for various purposes and tasks, as well as using different types of connections.
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. Now let's figure out what equipment you will 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 can be divided into two large groups by type - wired and wireless. Wired network cards allow you to connect electronic devices to a network using Ethernet technology using a cable, while 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 cards, for example, to equip the system unit with a Wi-Fi wireless communication module.
Based on their design implementation, individual network cards are divided into two groups - internal and external. Internal cards are designed for installation in desktop computers using interfaces and their corresponding PCI and PCIe connectors. External cards are connected via USB connectors or legacy 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 one single channel provided to you by your provider.
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A router is a multifunctional device or even a minicomputer with its own built-in operating system, which has at least two network interfaces. The first one is 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 (Wide Area Network) is used to connect a local network (LAN) to other networks and the World Wide Web - the Internet.
The main purpose of devices of this type is to determine the routes of data packets that the user sends to or requests from other, larger networks. It is with the help of routers that huge networks are divided into many logical segments (subnets), one of which is the home local network. Thus, at home, the main function of a router can be called organizing the transfer of information from a local network to a global one, and vice versa.
Another important job of a router is to limit access to your home network from the World Wide Web. Surely you are unlikely to be happy 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 boundaries. Therefore, from the general internal traffic generated by local network participants, the router 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 limit or prevent access from the public network (outside) to devices on your local network is called NAT (Network Address Translation). It also provides all users of your home network with access to the Internet by converting multiple internal device addresses into one public external address that is provided to you by your Internet service provider. All this makes it possible for computers on a 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 access to it can be provided at any time at your request.
In general, routers can be divided into two large groups - wired and wireless. Already from the names it is clear that all devices are connected to the first ones only using cables, and to the second ones, both with the help of wires and without them using Wi-Fi technology. Therefore, at home, wireless routers are most often used to provide Internet access and network 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 your ISP cable.
In order not to overload the article with redundant information, we will not consider in detail the main technical characteristics of routers in this chapter; I will talk about them in a separate article, on choosing a router.
In many cases, a router may be the only component needed to build your own local network, since there is simply 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 be in the tens, or even hundreds.
If, at some point, the number of LAN ports on the router is no longer enough, then to expand the cable network, you can connect one or more switches to the router (discussed 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 regular 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 a computer via a USB interface and provide network access to only one specific PC, to which the modem is directly connected. In the second group, the already familiar LAN and/or Wi-Fi interfaces 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 are located side by side: modems with built-in routers and routers with built-in modems. What is the difference between them?
These two groups of devices practically do not have any key differences. Manufacturers themselves position a router with a built-in modem as a more advanced option, equipped with a large number of additional functions and improved performance. But if you are only interested in basic capabilities, for example, such as connecting all computers on your 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 as an external network interface.
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 individual devices, for example a desktop PC, or entire groups of devices united into an independent network segment. Unlike a router, a switch has only one network interface - LAN and is used at home as an auxiliary device primarily for scaling local networks.
To connect computers using wires, like routers, switches also have special socket ports. In models aimed at home use, their number is usually five or eight. If at some point the number of ports on the switch 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 suggests, can be controlled from the network using special software. Although they have advanced functionality, they are expensive and not used at home. Unmanaged switches distribute traffic and regulate the speed of data exchange between all network clients automatically. These devices 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, switches can provide a maximum data transfer speed of either 100 Mbit/s (Fast Ethernet) or 1000 Mbit/s (Gigabit Ethernet). Gigabit switches are best used for building home networks where you plan 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 a network with a wireless router may be justified in cases where a large Wi-Fi coverage area is required. For example, the signal strength of a wireless router alone may not be enough to completely cover the entire area in a large office or multi-story country house.
Access points can also be used to organize wireless bridges, allowing you to connect individual devices, network segments or entire networks with each other using a radio signal in places where laying cables 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 connection to your network from the outside.
To create a wired local 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 pairs of wires twisted together (to reduce interference).
When building computer networks, predominantly unshielded cable of the CAT5 category is used, and more often its improved version CAT5e. Cables of this category allow you to transmit a signal at a speed of 100 Mbit/s when using only two pairs (half) of wires, and 1000 Mbit/s when using all four pairs.
To connect to devices (routers, switches, network cards, and so on), 8-pin modular connectors, commonly called RJ-45 (although their correct name is 8P8C), are used at the ends of the twisted pair cable.
Depending on your desire, you can either buy ready-made (with crimped connectors) network cables of a certain length, called “patch cords”, at any computer store, or purchase twisted pair cables and connectors separately, and then make your own cables of the required size in the right quantity. You will learn how this is done in a separate material.
Using cables to connect computers into a network, of course, you can connect them directly from switches or routers to the connectors on the PC’s 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, into the external connector of which you can subsequently connect computer or network devices.
Network sockets can be either built into the wall or mounted externally. Using sockets instead of protruding cable ends will give a more aesthetically pleasing look to your workspace. 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 an apartment, and then thoroughly route cables from it to sockets located in all the necessary rooms. Thus, you will receive several points located in different parts of the apartment, to which you can at any time connect not only computers, but also any network devices, 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 cord that can be used to connect two twisted pairs with already crimped RJ-45 connectors.
In addition to their intended purpose, extension cords are convenient to use in cases where the end of the cable ends not with one connector, but with two. This option is possible when building networks with a capacity of 100 Mbit/s, where it is enough to use only two pairs of wires 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 speed will be limited to 100 Mbit/s.
For more information about crimping twisted pair cables, connecting sockets and the characteristics of network cables, read the special material.
Now that we've become familiar with the basic components of a local area network, it's time to talk about topology. In simple terms, a network topology is a diagram that describes the locations and methods of connecting network devices.
There are three main types of network topologies: Bus, Ring and Star. With a bus topology, all computers on the network are connected to one common cable. To unite PCs into a single network using the “Ring” topology, they are connected in series with each other, with the last computer connecting to the first. In 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 predominantly used, where routers and switches are used as hub devices.
Creating a network using the Star topology does not require deep technical knowledge and large financial investments. For example, using a switch that costs 250 rubles, you can connect 5 computers into a network 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 expandability and ease of upgrading. Thus, network branching and scaling is achieved by simply adding additional hubs with the necessary functionality. You can also change the physical location of network devices or swap them at any time in order to achieve more practical use of the equipment and reduce the number and length of connecting wires.
Despite the fact that the Star 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 devices being connected and how they are connected to the network. This will minimize the risks associated with purchasing unsuitable or redundant equipment and optimize the amount of your financial costs.
Conclusion
In this material, we examined the general principles of 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 them all with an Internet connection through one single channel.
Switches, which are essentially splitters, are used as auxiliary equipment for expanding connection points to a local network using cables. To organize 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 to connect entire segments of the local network together in a “bridge” mode.
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 devices participating in the network that will require 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; layout and size of the room; requirements for the aesthetic appearance 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 select and purchase the necessary equipment, install it and configure it. But we will talk about these topics in our next materials.
This article will discuss what functions a local network server performs. This is a hardware and software complex, with its help the operation of all user computers is regulated. It is based on a very powerful computer with high performance, good optimization, and multitasking. This is what makes it possible to quickly process commands from clients’ personal devices.
Features of server equipment
The server must be multi-core, with a high degree of fault tolerance. It should also have a hot-swappable hardware feature. In other words, any part can be replaced without disconnecting the server from clients and the power grid. As for client computers, they much more often require repairs due to the failure of some parts.
An operating system is used, a kind of layer necessary for communication between executable programs and hardware.
File server
It is worth noting that this is one of the most important functions of any server equipment. Local networks provide all users with access to stored files on a central PC. In addition, they can manage all directories. For example, any user on the network can access the storage for the necessary documents, reports, projects, tables, even multimedia.
Planned work on a file server can never do without publishing some documents. This will significantly reduce time and speed up task completion. Any participant can view changes, track the status of document corrections or any reports.
The main feature of such a server is that you can control access to files. Assign public or personal access. This means that all users of client personal computers will be able to read and change any file. If only personal access is open, then only a few people can view and change documents.
Terminal server
This is a server that provides computing resources to all its users. As a rule, when using it, it is allowed to run only the licensed software necessary for operation. All users have a client called the “desktop protocol” installed on their computers. If the connection with the server is correct, then the user will definitely see all the content on the desktop. Now you know what functions the local network server performs when organizing access to files.
He will also be able to work with all programs remotely; for this, only his resources are used, there is no load on the client computer. It is worth noting about the features of working with a client. And it lies in the fact that information coming from the client to the server is intercepted through the clipboard.
Print server
The functions of this type of server include organizing access to printing devices. Sometimes it is called a print server, it is necessary so that several workers can use one fax or printer at once. This method implies that remote printing will be performed on the device. Moreover, this printer does not connect directly to one specific work computer. These are the functions that a local network server performs in the case of shared access to printers and faxes.
The print server allows you to process several flows of operations at once, and ensures printing documents from several personal computers without significant downtime. It is also worth noting that installing all printers in one room will greatly simplify office work. If you know the address, then you just need to select the one you need from the list of public devices.
Database server
It is necessary in order to work with SQL queries that come from a personal computer user to a specific database. With the help of such a server, the safety and integrity of all data is ensured. This tool allows you to work with sections, tables, formulas, and reports.
Now you know about databases and what a local network is. The functions of the computer network in this case are to provide access to specific documents to PC users.
When a user connects to a database, he uses only the computing power of the server hardware. An example is computers with the most common versions of software, for example “1C:Enterprise”, “Parus-Accounting”, etc. On such platforms you can implement a server that uses a database management system:
- Oracle Database Server.
- Microsoft SQL Server.
- My-SQL.
- Informix.
- Firebird.
There are other similar DBMSs. But what functions does a local network server perform besides these? He can play the role of a “postman” who delivers letters from the boss to the workers and back.
Mail server
It is necessary in order to store letters, as well as exchange information between all users of the local network. Moreover, the functions of such a server include storing all user addresses that are available on the network.
In addition, correspondence is exchanged between all participants, you can send reports, participate in the mailing list, and also create calendar projects for any meetings and events. In this case, the server and local stations must be on the same network.
Flaws
Now we need to consider what disadvantages server-based local networks may have:
- In the event of a server emergency, there is a very high probability of downtime of the entire network. This usually happens when the integrity of network equipment is compromised.
- High costs, from a financial point of view, for the purchase of licensed software and equipment.
- Setting up all equipment is quite complex, so qualified technical personnel are required.
Now you know what functions the local network server performs. We briefly listed all his responsibilities in the article.
