Classification of computer networks. Computer networks

A computer network is a collection of interconnected computers distributed over a certain territory. TYPES OF NETWORKS Global WN Network complex structure based on three main principles: the presence of a single center in charge of coordinating activities and developing the network; the use of a routing system that allows a message to move along a chain of network nodes without additional human intervention; the use of a single standard addressing making the network transparent to external networks and the latter accessible...


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Lecture No. 23

Subject: Computer networks: concept, purpose.

1. CONCEPT OF COMPUTER NETWORK. PURPOSE.

When working on a PC in offline mode, users can exchange information (programs, documents, etc.) only by copying it to floppy disks. However, in the process of exchanging information between computers, problems arise:

  1. moving a floppy disk is not always possible (lack of a disk drive on one of the computers);
  2. floppy disk is not a reliable means (for example, physical damage);
  3. The information capacity of a floppy disk is limited (from 720 bytes to 1.44 MB), and recording information on a floppy disk is not always possible;
  4. Moving a floppy disk and exchanging information can take quite a long time.

Computer networkis a set of interconnected computers distributed over a certain territory. The creation of computer networks is caused by a practical need:

  1. information sharingusers working on computers remote from each other;
  2. simultaneous operationwith documents and programs;
  3. sharingprinters and other peripheral devices.

Main purposecomputer networks sharing of resources and implementation of interactive communication within one company and beyond its borders. Resources ) these are data, applications and peripheral devices (external drive, printer, mouse, modem or joystick). Conceptinteractive communicationcomputers involve the exchange of messages in real time.

2. TYPES OF NETWORKS

  1. Wide Area Network (WAN) complex structure based on three main principles:
  • availability of a single center, in charge of coordinating activities and developing the network;
  • using a routing system, allowing a message to move along a chain of network nodes without additional human intervention;
  • application of a single standard addressing, making the network “transparent” to external networks, and the latter accessible to any subscriber point in the system.
  1. Regional network(MAN) a network that serves the information needs of a specific region, republic or region.
  2. City network a network that serves the information needs of a large city.
  3. Corporate network – a network that serves the information needs of a specific organization.
  4. Local computing network ( LAN - a set of computers and other computer equipment (network equipment, printers, scanners), connected via cables and network controllers, running a network operating system.

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Today’s article opens a new section on the blog, which will be called “ Networks" This section will cover a wide range of issues related to computer networks. The first articles in the section will be devoted to explaining some of the basic concepts that you will encounter when working with the network. And today we will talk about what components are required to create a network and what exist types of networks.

Computer network is a collection of computer and network equipment connected via communication channels into a single system. To create a computer network we need the following components:

  • computers that have the ability to connect to a network (for example, a network card, which is found in every modern PC);
  • transmission medium or communication channels (cable, satellite, telephone, fiber optic and radio channels);
  • network equipment (for example, a switch or router);
  • network software (usually included with the operating system or supplied with network equipment).

Computer networks are usually divided into two main types: global and local.

Local networks(Local Area Network - LAN) have a closed infrastructure before accessing Internet service providers. The term “local area network” can describe both a small office network and a network of a large factory covering several hectares. In relation to organizations, enterprises, firms, the term is used corporate network – a local network of a separate organization (legal entity), regardless of the territory it occupies.
Corporate networks are closed networks; access to them is allowed only to a limited number of users (for example, company employees). Global networks are focused on serving any users.

Global network(Wide Area Network - WAN) covers large geographic regions and consists of many local networks. Everyone is familiar with the global network, which consists of several thousand networks and computers - this is the Internet.

The system administrator has to deal with local (corporate) networks. An ordinary user computer connected to a local network is called workstation . A computer that makes its resources available for shared use by other computers on the network is called server ; and the computer accessing shared resources on the server is client .

There are various types of servers: file servers (for storing shared files), database servers, application servers (providing remote operation of programs on clients), web servers (for storing web content) and others.

Network load is characterized by a parameter called traffic. Traffic is a flow of messages in a data network. It is understood as a quantitative measurement of the number of data blocks passing through the network and their length, expressed in bits per second. For example, the data transfer speed in modern local networks can be 100 Mbit/s or 1 Gbit/s

Currently, in the world there is a huge amount of all kinds of network and computer equipment that allows you to organize a wide variety of computer networks. The entire variety of computer networks can be divided into several types according to various criteria:

By territory:

  • local – cover small areas and are located inside individual offices, banks, corporations, houses;
  • regional – formed by combining local networks in separate territories;
  • global (Internet).

According to the method of computer connection:

  • wired (computers are connected via cable);
  • wireless (computers exchange information via radio waves, for example, using WI-FI or Bluetooth technology).

By control method:

  • with centralized control - one or more machines (servers) are allocated to manage the data exchange process on the network;
  • decentralized networks - do not contain dedicated servers; network management functions are transferred in turn from one computer to another.

According to the composition of computing tools:

  • homogeneous – combine homogeneous computing means (computers);
  • heterogeneous - combines various computing tools (for example: PCs, trading terminals, web cameras and network data storage).

By type of transmission medium networks are divided into fiber optics, with the transmission of information via radio channels, in the infrared range, via a satellite channel, etc.

You may come across other classifications of computer networks. As a rule, a system administrator has to deal with local wired networks with centralized or decentralized control.

After personal computers were created by humanity, it was necessary to create a new approach to the organization of systems that process data, as well as the creation of new technologies in the field of storage, transmission and use of information. Somewhat later, the need arose to move from the use of individual computers operating in systems that process data centrally to systems capable of processing data in a distributed manner.

Distributed data processing is the type of processing that is performed by independent but interconnected computers that form a distributed system.

A computer network is a collection of computers that are connected to each other by communication channels, which makes it possible to create a single system that fully satisfies the requirements of the rules of distributed information processing. Thus, the main purpose of computer networks is joint data processing, in which all components of the system participate, regardless of their physical location.

The classification involves dividing them into types of computer networks, depending on the territorial location of computers and other components relative to each other. Thus, the classification involves their division into:

Global networks are computer networks that connect subscribers who are located at a great distance from each other - from hundreds to tens of thousands of kilometers. Such networks make it possible to solve the problem of uniting all of humanity, as well as organize instant access to these resources;

Regional are computer networks connecting subscribers who are located at smaller but still significant distances. An example would be the network of a large city or a separate state.

Local are those that unite subscribers who are located at relatively short distances from each other - most often in one building or several nearby buildings. These are networks of enterprises, company offices, firms, etc.

In addition, the classification of computer networks suggests that global, regional and local networks can be combined, which makes it possible to create multi-network hierarchies, which are powerful tools that allow processing huge amounts of information and providing virtually unlimited access to information resources.

Among other things, the classification of computer networks, or rather its understanding, makes it possible to build just such a system that will fully satisfy the information needs of a particular enterprise, office, city or state. In general, computer networks consist of three subsystems nested within each other: a network of workstations, a network of servers, and a core data network.

A workstation (can be represented by a client machine, a workstation, a subscriber point, or a terminal) is a computer on which a computer network subscriber works. A network of workstations is a collection of workstations, as well as communication means that are designed to ensure interaction between the workstations and the server.

A server is a computer that performs general network tasks and provides workstations with various services. A server network is a collection of network servers, as well as communication facilities designed to connect servers to the core network.

The core network is a set of means for transmitting information between servers. The core network includes communication channels and communication nodes. is a set of switching means, as well as information transmission, concentrated at one point. The purpose of the communication node is to receive data that arrives through communication channels, as well as their transmission to channels that lead to subscribers.

Developed by Shamsutdinov Rail Rafaelevich, computer science teacher at Kazan Energy College

Test on the topic “Computer networks”.

1. A set of computers connected by channels for exchanging information and located within one (or more) premises, building, is called:

    global computer network;

    regional computer network.

    local computer network;

2. Local network is

    a set of computers connected via a cable connection;

    a set of computers united on the basis of telephone communication channels;

    a set of computers connected via satellite communications.

3. Specify software tools to support local networks

4. Global computer network is:

    information system with hyperlinks;

    many computers connected by information transmission channels and located within the same room or building;

    a set of host computers and file servers;

    a system for exchanging information on a specific topic;

    a set of local networks and computers located over long distances and connected via communication channels into a single system

5. A set of hardware and software that allows computersexchangedata is:

    highway;

    interface;

    data buses;

  1. computer network.

6 . Internet access is provided:

    router

    provider

  1. domain name registration organizations

    all of the above

7. What is the name of the computer that stores information intended to be transmitted to Internet users?

a. web server

c. firewall

d. router

8. ICQ is:

    Instant Messaging

    FAQ

    Dating service

9. The browser is called:

    mail delivery program

    mail client

    web browser

10. WEB pages have the extension:

11. Hypertext is:

    a method of organizing textual information within which semantic connections are established between its various fragments;

    ordinary, but very large text;

    text in large font size;

    distributed collection of databases containing texts;

    very valuable text.

12. Electronic mail (e-mail) allows you to transmit:

    messages and attached files;

    text messages only;

    executable programs;

    www-pages;

    exclusively databases.

13. A computer connected to the Internet must have:

    Domain name;

    WEB page;

  2. home WEB page.

14. HTML (HYPER TEXT MARKUP LANGUAGE) is:

    programming system;

    graphic editor;

    database management system;

    a tool for creating WEB pages;

    expert system.

15. Teleconference is:

    exchange of letters in global networks;

    information system in hyperlinks;

    service for receiving and transmitting files of any format;

    the process of creating, receiving and transmitting WEB pages;

    a system for exchanging information between subscribers of a computer network.

16. Internet FTP service is designed to:

    for creating, receiving and transmitting WEB pages;

    to ensure the functioning of email;

    to support teleconferencing;

    for receiving and transmitting files of any format;

    for remote control of technical systems.

17. The configuration (topology) of a local computer network, in which all workstations are connected to a file server, is called:

    annular;

    radial;

  1. tree-like;

    radial-ring.

1 8 . The modem provides:

    analog signal amplification;

    exclusively converting binary code into an analog signal;

    only converting an analog signal to binary code;

    conversion of binary code to analog signal and vice versa;

    weakening of the analog signal.

19. The email subscriber's mailbox is:

    regular mailbox;

    file server RAM area;

    part of the memory on the mail server hard drive allocated for the user;

    part of the memory on the hard drive of the workstation;

    a special electronic device for storing text files.

2 0 . Routing Protocol (IP) provides:

    interpreting data and preparing it for the user level;

    preservation of mechanical, functional parameters of physical communication in a computer network;

    control of data transmission equipment and communication channels;

    delivery of information from the sending computer to the receiving computer;

21 To store files intended for public access by network users, the following is used:

    host computer;

    file server;

    client-server;

    switch;

    work station.

2 2 Transport Protocol (TCP) provides:

    reliable, streaming, connection-oriented data delivery.

    user access to processed information;

    delivery of information from the sending computer to the receiving computer;

    splitting files into IP packets during transmission and assembling files during reception.

23. The configuration (topology) of a local computer network, in which all workstations are connected in series to each other, is called:

  1. radial;

  2. tree-like;

    annular.

Answers to the test “Computer networks”

№ question

Possible answer

What is a computer network?

Parameter name Meaning
Article topic: What is a computer network?
Rubric (thematic category) Computers

Computer network(English: Computer NetWork, from net - network and work - work) - a set of computers connected using communication channels and switching means into a single system for messaging and user access to software, technical, information and organizational resources of the network .

A computer network is represented as a collection of nodes (computers and network equipment) and branches connecting them (communication channels). A network branch is a path connecting two adjacent nodes. There are terminal nodes, located at the end of only one branch, intermediate nodes, located at the ends of more than one branch, and adjacent nodes - such nodes are connected by at least one path that does not contain any other nodes. Computers can be networked in different ways.

The logical and physical ways of connecting computers, cables and other components that make up a network are usually called topology. Topology characterizes the properties of networks that do not depend on their size. This does not take into account the performance and operating principle of these objects, their types, and channel lengths, although these factors are very important when designing.

Topology as a mathematical concept:

Topology(from the Greek topos - place and... logic - study), a branch of mathematics that studies the topological properties of figures, ᴛ.ᴇ. properties that do not change under any deformations performed without tearing or gluing. Examples of topological properties of figures are dimension, the number of curves limiting a given area, etc. Thus, a circle, an ellipse, and the outline of a square have the same topological properties, because these lines are deformed one into another in the manner described above; at the same time, the ring and the circle have different topological properties: the circle is limited by one contour, and the ring by two.

The most common types of network topologies:

Linear network. Contains only two end nodes, any number of intermediate nodes, and has only one path between any two nodes.

Ring network. A network in which each node is connected to two and only two branches.

Tree network. A network that contains more than two end nodes and at least two intermediate nodes, and in which there is only one path between the two nodes.

Star network. A network in which there is only one intermediate node.

mesh network. A network that contains at least two nodes that have two or more paths between them.

Fully connected network. A network in which there is a branch between any two nodes. The most important characteristic of a computer network is its architecture.

Network architecture- ϶ᴛᴏ the implemented structure of the data transmission network, which determines its topology, the composition of devices and the rules for their interaction in the network. Within the framework of the network architecture, issues of information coding, its addressing and transmission, message flow control, error control and analysis of network operation in emergency situations and when performance deteriorates are considered.

The most common architectures:

· Ethernet(English ether – broadcast) – broadcast network. This means that all stations on the network can receive all messages. Topology – linear or star-shaped. Data transfer speed 10 or 100 Mbit/s.

· Arcnet(Attached Resource Computer Network - computer network of connected resources) - broadcast network. Physical topology is a tree. Data transfer rate 2.5 Mbit/s.

· Token Ring(relay ring network, token passing network) – a ring network in which the principle of data transmission is based on the fact that each ring node waits for the arrival of some short unique sequence of token bits from an adjacent previous node. The arrival of the token indicates that it is possible to transmit a message from this node further along the flow. Data transfer speed 4 or 16 Mbit/s.

· FDDI(Fiber Distributed Data Interface) is a network architecture for high-speed data transmission over fiber optic lines. Transfer speed – 100 Mbit/sec. Topology – double ring or mixed (including star or tree subnets). The maximum number of stations in the network is 1000. Very high cost of equipment.

· ATM(Asynchronous Transfer Mode) - a promising, yet very expensive architecture, provides the transfer of digital data, video information and voice over the same lines. Transfer speed up to 2.5 Gbps. Optical communication lines.

What is a computer network? - concept and types. Classification and features of the category "What is called a computer network?" 2017, 2018.



 

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