home Garage heating Information networks definition of information network and network. Basic concepts of information networks and communications What are information networks

Information networks definition of information network and network. Basic concepts of information networks and communications What are information networks

Results of mastering the topic

Studying this topic, you will know:

what do networks include? information Technology;
what types of network information technologies are there;
how to work collaboratively online.

Basic concepts:

Computing, communication and information network;
Local, regional (territorial) and global networks;
Internet technologies. Online and offline technologies;
Real, artificial and peer-to-peer networks;
Network topology and protocols. Plastic bag. Traffic;
Web technologies, Internet services.

In the 1960s, the first computer networks (CN) with computers appeared. Since that time, network information technologies have actually appeared, making it possible to combine technologies for collecting, storing, transmitting and processing information on a computer with communication technology.

A Network is an interacting collection of objects connected to each other by communication lines.

In information processes, systems and technologies, the term “network” refers to at least several computers and other computers connected to each other using special equipment to provide calculations and exchange various types information. Complex networks imply a large number of users, a branched structure, switching and communication nodes that connect everyone into a single structure.

The basis of network technologies is computer networks - means of communication (telecommunications), with the help of which computers distributed in space are combined into a system.

computer network also called computer network or computer network(Computer network). It represents a computing complex that includes a geographically distributed system of computers and their terminals, combined into a single system.

Almost immediately with the advent of computer networks, they began to be used for the exchange of various kinds of data (data networks) and information. The development of computer networks and network technologies has shown the possibility of using them to organize large-scale information support for people.

This led to the fact that computer networks providing the exchange of information resources began to be called “ information networks”, representing a type of communication networks.

At the same time, it is not expected to abandon network computing; moreover, this technology is constantly being improved, and supercomputers now connected to an information network make it possible to carry out ultra-fast calculations related to the needs of any subject areas.

Note that by area of use(distribution) distinguish local, regional (territorial) and global networks .

They have a less developed architecture compared to WAN and use simpler methods for managing the interaction of network nodes. Short distances between network nodes and ease of management of the communication system allow for high data transfer rates.

In a LAN, the distance between computers is usually limited to 1–2.5 km, and the information transfer speed is more than one Mbit/s. Such a network consists of three main components: one or more central (main) machines (servers), workstations and communications.

LANs are easily adapted to changed operating conditions and modernized. They have a flexible architecture, which makes it easy to change the location of the corresponding RS. Although there is no clear classification of LANs, the following characteristics are usually distinguished: purpose, topology, types of computers used, organization of management, information transfer, methods of teleaccess and access, physical storage media, etc.

They are usually divided on a territorial basis into regional and global networks.

That's why regional networks sometimes called MAN (Metropolitan Area Network) networks. Regional ones include corporate networks (enterprise-scale networks), interconnecting LANs covering an area, usually representing one or more closely located buildings that are part of this corporation (enterprise). They form complex information systems (infosystems) with a distributed information architecture.

The corporate information system (CIS) includes the “Intranet”. This technology implies unity for the internal user and the external consumer, who can be the same person. He is an internal user for his organization, and an external consumer for a third-party company. The method is convenient for use when working with organizations with their branches, as well as in various corporations.

Wide Area Network(Wide Area Network, WAN) is a set of computers (host nodes) geographically remote from each other, interacting with each other using communication channels for data transfer and special software– network operating systems. Host computers are powerful multi-user computers computing systems(servers), as well as specialized computers that perform the functions of communication nodes. Users of personal computers become subscribers of such a network after connecting their computers to its main nodes.

Depending on the accepted control method networks are divided into: centralized, decentralized and mixed.

The Internet is a decentralized internet. The principle of its construction is to organize highways (high-speed telephone, radio, satellite and other communication lines) between central hub stations.

The growth of information systems connecting with each other to exchange information and solve other problems initiated the creation of international networks, and then the Internet. This contributed to the emergence of Internet technologies.

Modern network technologies provide the ability to work in deferred (offline) and interactive (online) modes, provide communication with any available information sources, allow for professionally oriented consulting and training, etc.

Online technologies include interactive types of services on the Internet: ISQ, Internet telephony, etc.

Offline technologies include: mailing lists, newsgroups, web forums, email, etc.

In information networks, control systems are called servers. The term “server” (eng. “server” - service processor, service node) is understood as a sufficiently powerful computing machine connected to the network, possessing certain public resources, and also, as a rule, the ability to combine a certain number of computers both locally and in global information networks. Network nodes with servers are called hosts(English “host” - owner). They usually become Internet providers.

Servers typically perform administrative functions on a network and are called system administrators. Their tasks include checking the functionality of the system (channels, computers, programs, etc.); identifying failures, unauthorized access and other violations in the network; restoring network functionality; accounting for network operation, preparing reports on its operation and providing users with information about network resources.

By purpose servers are divided into: file, communication, application, mail, etc. In addition, the networks use: database server (“Data Base Server”), print server, fax server, etc.

Computers connected to servers on a network are called workstations (PCs) or clients. The difference lies in the software used, which allows you to use computers on the network only as a server or as a PC. It is possible that any computer on the network can be a server in some conditions, and a “client” in others. A “client” is generally considered to be a less powerful computer whose resources are not shared on the network. A network formed from computers “servers” and “clients” and based on software that ensures their operation in such modes is called “ client-server”.

From an organizational point of view, there is a division of networks into three types: real, artificial and peer-to-peer.

Real networks include those in which computers are connected to each other according to a certain scheme using special devices - network adapters, and the presence of specialists is required to monitor and operate such networks. They are called “real network or Network With an Attitude” (NWA).

Artificial networks do not require a special network hard drive. Computers on these networks communicate with each other through serial or parallel ports without special network adapters. Sometimes this connection is called zero-modem or zero-slot network (English: “zero-slot network”), since none of the computer slots includes a network adapter. Such networks operate very slowly and, as a rule, allow simultaneous work with only two computers.

Peer-to-peer networks are organized according to the “peer-to-peer network” principle and are of an intermediate type between real and artificial. In such a network, depending on the need, each computer can be a server or a PC. For example, a PC with a printer connected to it can be used as a network print server, etc. The advantage of such networks is that they provide almost the same capabilities (services) as in real networks, while being much easier to install and maintain. In addition, there is no need to uniquely select servers, since any computer can be a server and a client at the same time.

Network construction structure(topology) is primarily determined by the way computers are connected to each other.

In general, there are “bus” (parallel connection of computers to one communication line), star (radial, i.e. when all PCs are connected to the server), ring and mixed compounds computers on the network. Mixed includes both the simultaneous use of the above connection methods and the hierarchical, multiconnected (in this case, each computer is connected to all others in the network) connection of computers into a network.

From point of view number of computers used on the network can be divided into small (up to 10 PCs), medium (up to 30 PCs) and large (more than 30 PCs).

By type of means used Information transmission networks can be wired (cable), wireless (radio and satellite) and combined.

An important aspect network technology is the choice method of transmitting messages over a network. Three transmission methods are known and used: priority access transmission method, shuttle polling method and token packet method. There are options for using mixed types of data transfer.

Priority access transmission method. A request to transfer information is received from the sending computer. He is given a channel for temporary use. All other computers on the network are waiting for the end of the transfer session.

Shuttle survey method. An information packet circulates in the network with an empty interval and sequentially polls all computers for the need to transmit information. If there is such a need, the moving interval picks up an information packet that can be transmitted and transfers it to the addressee.

Token packet method. This method is similar to container shipping, when a message prepared for transmission is “converted” (converted) into packets with an address and waits for an opportunity with a transporter, which in this case is a marked time interval. This interval can only be used by one computer.

By data transfer methods there are networks with:

1) data transmission via dedicated communication channels;
2) channel switching;
3) message switching;
4) switching of message packets.

Network protocols
To be able to create and effectively operate any network, it is necessary to standardize the methods of working in it. For this purpose, network protocols are developed and used.

The transmission and reception of messages in any computer networks is carried out using special data exchange protocols, which represent a set of semantic and syntactic rules that determine the behavior of functional blocks in the network.

On the low Data exchange between PCs is carried out by sending message packets. Mid-level protocols NetBIOS, IPX/SPX, TCP/IP usually act as a transport, allowing computers on a network to communicate with each other. High level protocols provide file redirection and maintenance of file servers by transmitting message packets using middle-level protocols.

On the Internet, data is sent in packets using the IP protocol.

Internet Protocol (IP) is an internetworking protocol. It provides delivery of network packets with information and machine-to-machine communications. The protocol controls the addressing of packets, sending them along different routes between network nodes, and allows different networks to be connected.

The concept " information network"(as opposed to the concept of "telecommunications network") is more capacious and reflects the diversity of information processes performed on the network when end systems interact through a telecommunications network. The telecommunications network, therefore, as part of the information network performs the functions transport system, through which flows of user and service information generated by information processes are moved.

In general, under information network How physical object should be understood a set of geographically dispersed end systems united by a telecommunications network, through which the interaction of application processes activated in the end systems and their collective access to network resources is ensured.

All intellectual work in the information network, as we see (see Fig. 3), is performed on the periphery, i.e. in the end systems of the network, and the telecommunications network, although it occupies a central position, is only a connecting component. an information network, in essence, is smart add-on over the telecommunications network through which users(Users) are provided with mechanisms for processing information, effectively searching for it anywhere on the network and at any time, as well as the ability to accumulate and store it.

So, the concept of “information network” in our case indicates a shift in the focus of attention when studying or researching an information and communication network towards information processes that arise in the network during the interaction of end systems through a telecommunication network. The description of this interaction demonstrates the complexity of building a communication architecture in a network (communication architecture is discussed in detail later in the lecture course).

Information processes online can be divided into two groups. The first of these includes application processes (ApplicationProcesses). They occupy a dominant position in the network. Application processes are initiated when user programs called applications(Applications). All other processes in the network (determining formats for presenting information for transmission over the network, establishing data transfer modes, promotion routes, etc.) are auxiliary and are intended to serve application processes. They form a group of so-called interaction processes (InterworkingProcesses). Application and interaction processes are supported network operating systems(SOS).

Figure 3. Information network

Information network end systems

Information network end systems can be classified as:

terminal systems(TerminalSystem) – computers of end users of the network;

hosting systems(HostSystem) – computers on which information and software resources of the network are located;

servers ( Servers ) – computers that can provide network services. For example, managing access to information resources and shared devices, registering users and monitoring their access rights to the network, servicing calls, etc. Servers, depending on the capabilities of their operating systems, can operate both in host mode (information servers) and in network communication device mode;

administrative systems(ManagementSystem) – computers and devices that provide operational management applications for the network and its individual parts.

NOTE. Since computers act as end systems of an information network, it is also called a “computer network.” The telecommunications network is classified as a “data transmission network” (the previously used classification according to the type of information transmitted).

Information network- a set of geographically dispersed end systems and a telecommunications network connecting them, providing access to application processes of any of these systems to all network resources and their sharing.

User(User) - a consumer of information who has gained access to the information network (individuals, legal entities (firms, organizations, enterprises)).

Application process(Application Process) is process in a network end system that performs information processing for a specific communications service or application. Thus, a user, when organizing a request for the provision of a particular service, activates a certain application process.

End systems information network:

· terminal systems (Terminal System), providing access to the network and its resources;

· workers systems (Server, Host System), providing network services (controlling access to files, programs, network devices, servicing calls, etc.);

· administrative systems (Management System), implementing management of the network and its individual parts.

Information network resources:

Informational resources- information and knowledge accumulated in all areas of science, culture and social life, as well as entertainment industry products. They are systematized in network data banks with which network users interact. These resources determine the consumer value of the information network and must not only be constantly created and expanded, but also updated on time. Outdated data should be dumped into archives. Using the network provides the opportunity to receive up-to-date information exactly when it is needed.

Data processing and storage resources- this is the performance of network computer processors and the amount of memory of storage devices, as well as the time during which they are used.

Software Resources- software involved in providing services and applications to users, as well as programs for related functions. The latter include: issuing invoices, accounting for payment for services, navigation, searching for information on the network, servicing electronic mailboxes, organizing a bridge for teleconferences, converting the formats of transmitted information messages, cryptographic protection of information (encoding and encryption), authentication (electronic signature of documents certifying them authenticity).

Communication Resources– these are resources involved in transporting information and redistributing flows in communication nodes. These include the capacity of communication lines, the switching capabilities of nodes, as well as the time they are occupied during user interaction with the network. They classified according to the type of telecommunication networks:

· resources of the public switched telephone network (PSTN),

· packet switching data network resources,

· mobile network resources,

· terrestrial broadcast network resources,

· resources of the integrated service digital network (ISDN), etc.

All listed information network resources shared , i.e. can be used simultaneously by several application processes.

Severability can be either actual or simulated.

The basic component, the core of the information network, is telecommunications network(TN - Telecommunication Network), which is totality technical means, ensuring the transmission and distribution of information flows during the interaction of remote objects.

Deleted objects:

terminal systems of information networks

· separate local and territorial networks.

Telecommunication networks are usually assessed side by side indicators, reflecting in general the possibility and efficiency of transporting information in them.

Opportunity transfer of information in a telecommunications network is related to the degree of its performance in time, i.e., performing specified functions

· in the prescribed amount

at the required quality level

· during a certain period of network operation or at an arbitrary point in time.

Performance networks is related to concepts reliability And survivability.

Reliability- the ability to provide communication while maintaining the values of established quality indicators over time V given conditions operation. (Internal influencing factors– random failures of technical equipment caused by aging processes, manufacturing technology defects or maintenance personnel errors).

Indicators reliability, for example:

· ratio of network uptime to total operating time,

number of possible independent ways of transmitting an information message between a pair of points,

· probability of failure-free communication, etc.

Vitality - ability to maintain full or partial functionality during action reasons, hiding offline and leading to destruction or significant damage to some of its elements (points and communication lines). Possible reasons:

· spontaneous

§ earthquake, landslides, river floods, etc.

· intentional. to deliberate

§ enemy nuclear missile strikes, sabotage actions, terrorism, unscrupulous competition, etc.

Survivability indicators:

· the probability that a limited amount of information can be transmitted between any pair (a given pair) of network points after exposure to damaging factors;

· the minimum number of points, lines (or both) of the network, the failure of which leads to a disconnected network for an arbitrary pair of points;

· the average number of points that remain connected when several communication lines are damaged simultaneously.

Bandwidth. In cases where the network cannot service (implement) the imposed load, it makes sense to talk about the volume of realized load in the network.

The amount of realized load is determined by the capacity of the communication network. In some cases, throughput can be quantified. For example, you can estimate the maximum information flow that can be passed between a certain pair of points (source-sink), or determine the capacity of the network section that is the bottleneck when dividing the network between the source and sink into two parts.

Bandwidth assessment is largely related to parameters quality of service , since the implementation of the presented load in the network must be carried out with the specified quality parameters.

Quality of service We will understand it as a set of characteristics that determine the degree of satisfaction of the network user:

· network operational characteristics (information transfer speed, probability of errors, etc.),

indicators of ease of use of services,

· completeness of services (these indicators are usually assessed in points), etc.

Profitability and cost. A telecommunications network is profitable if the costs of organizing it and ensuring its operation are repaid by the economic effect provided by the services provided to users through it. The main economic characteristics of the communication network are reduced costs(social costs), which are determined by the cost of the network, the cost of its operation and management.

Fixed and variable expenses.

Explicit and implicit costs.

A network is a collection of objects formed by data transmission and processing devices. The International Organization for Standardization has defined a computer network as the serial bit-oriented transfer of information between interconnected independent devices.

Networks are usually privately run by the user and occupy a certain territory and are divided on a territorial basis into:

Local area networks (LAN) or Local Area Network (LAN), located in one or more nearby buildings. LANs are usually located within an organization (corporation, institution), which is why they are called corporate.

Distributed computer networks, global or Wide Area Network (WAN), located in different buildings, cities and countries, which can be territorial, mixed and global. Depending on this, global networks come in four main types: city, regional, national and transnational. Examples of distributed networks of a very large scale include: Internet, EUNET, Relcom, FIDO.

In general, the network includes the following elements:

Network computers (equipped with a network adapter);

Communication channels (cable, satellite, telephone, digital, fiber optic, radio channels, etc.);

Various types of signal converters;

Network hardware.

There are two concepts of network: communication network and information network (Fig. 1.1).

The communication network is designed to transmit data, and it also performs tasks related to data conversion. Communication networks vary in the type of physical connection used.

An information network is designed to store information and consists of information systems. A group of information networks can be built on the basis of a communication network.

An information system should be understood as a system that is a supplier or consumer of information.

Rice. 1.1. Information and communication networks

A computer network consists of information systems and communication channels.

An information system should be understood as an object capable of storing, processing or transmitting information. The information system includes: computers, programs, users and other components intended for the process of processing and transmitting data. In the future, the information system designed to solve user problems will be called a workstation (client). A workstation on a network differs from a regular personal computer (PC) in the presence of a network card (network adapter), a data transmission channel and network software.

A communication channel refers to the path or medium through which signals are transmitted. The means of transmitting signals is called a subscriber, or physical, channel.

Communication channels (data links) are created along communication lines using network equipment and physical communications. Physical communications are built on the basis of twisted pairs, coaxial cables, optical channels or airwaves. Logical channels are established between interacting information systems through physical channels of the communication network and switching nodes.

A logical channel is a path for transmitting data from one system to another. A logical channel is routed through one or more physical channels. A logical channel can be characterized as a route laid through physical channels and switching nodes.

Information on the network is transmitted in blocks of data according to exchange procedures between objects. These procedures are called data transfer protocols.

A protocol is a set of rules that establish the format and procedures for exchanging information between two or more devices.

Network load is characterized by a parameter called traffic. Traffic is the flow of messages on a data network. It is understood as a quantitative measurement at selected points of the network of the number of passing data blocks and their length, expressed in bits per second.

The access method has a significant impact on the network characteristics. An access method is a way of determining which workstation can next use the communication channel and how to control access to the communication channel (cable).

In a network, all workstations are physically connected to each other by communication channels according to a certain structure called topology. Topology is a description of the physical connections in a network, indicating which workstations can communicate with each other. The type of topology determines the performance, operability and reliability of workstations, as well as the time it takes to access the file server. Depending on the network topology, one or another access method is used.

The composition of the main elements in a network depends on its architecture. Architecture is a concept that defines the interconnection, structure, and functionality of workstations in a network. It provides for the logical, functional and physical organization of the hardware and software of the network. The architecture determines the principles of construction and operation of the hardware and software of network elements.

There are mainly three types of architectures: terminal-host architecture, client-server architecture and peer-to-peer architecture.

Modern networks can be classified according to various signs: by remoteness of computers, topology, purpose, list of services provided, management principles (centralized and decentralized), switching methods, access methods, types of transmission media, data transfer rates, etc.

1.1. Purpose and classification of computer networks

Modern production requires high speeds of information processing, convenient forms of its storage and transmission. It is also necessary to have dynamic ways to access information, ways to search for data in given time intervals; implement complex mathematical and logical data processing. Command and control of troops requires the participation of fairly large teams in this process. Such teams can be located in different locations. To solve management problems, the speed and convenience of information exchange, as well as the possibility of close interaction between everyone involved in the process of developing management decisions, become important and relevant.

In the era of centralized use of computers with batch information processing, users preferred to purchase computers on which almost all classes of their problems could be solved in inverse proportion to their number, and this led to inefficient use of computer computing power at significant material costs. One cannot ignore the fact that access to computer resources was difficult due to the existing policy of centralizing computing resources in one place.

The principle of centralized data processing (Fig. 1) did not meet high requirements for the reliability of the processing process, hampered the development of systems and could not provide the necessary time parameters for interactive data processing in multi-user mode. A short-term failure of a centralized computer led to fatal consequences for the system as a whole, since it was necessary to duplicate the functions of the central computer, significantly increasing the costs of creating and operating data processing systems.

Central computer

Terminal Terminal Terminal Terminal

Rice. 1. Centralized data processing system

The emergence of small computers, microcomputers and personal computers required a new approach to the organization of data processing systems and the creation of new information technologies. A logical, justified requirement arose for the transition from the use of individual computers in centralized data processing systems to distributed data processing (Fig. 2).

Computer 1 Computer 2

Terminal Terminal Terminal Terminal

Rice. 2. Distributed data processing system

Distributed Data Processing - data processing performed on independent but interconnected computers representing a distributed system.

To implement distributed data processing, multi-machine associations were created, the structure of which is being developed in one of the following areas;

multi-machine computing systems (MCC);

computer (computer) networks.

Multi-machine computing complex - a group of computers installed nearby, united using special interface means and jointly performing a single computing process.

Under process a certain sequence of actions to solve a problem, determined by the program, is understood.

Multi-machine computing systems can be:

local provided installation of computers in one room that do not require special equipment and communication channels for interconnection;

remote, if some computers of the complex are installed at a considerable distance from the central computer and telephone communication channels are used for data transmission.

Computer (computer) network - a set of computers and terminals connected via communication channels into a single system that meets the requirements of distributed data processing.

The main differences between a computer network and a multi-machine computing complex:

1.Dimension. The composition of an intermediary complex can usually include two, maximum three computers, located mainly in one room. A computer network can consist of tens or even hundreds of computers located at a distance from several meters to thousands of kilometers.

2. Division of functions between computers. If in a multi-machine complex the functions of data processing, data transmission and system control can be used in one computer, then in computer networks these functions are distributed between different computers.

3. The need to solve the problem of message routing in the network. A message from one computer to another in the network can be transmitted along different routes depending on the state of the communication channels connecting the computers to each other.