What are the basic principles of building the Internet. Structure and basic principles of building the Internet. What is the Internet in a modern interpretation

Ministry of Education and Science of the Republic of Kazakhstan

Kazakh-American Free University

Department of Business

ABSTRACT

on the topic: “Principles of building global networks”

Completed by: Pomolova N.A.

2nd year student,

Faculty of Management
Checked by: Chettykbaev R.K.

Ust-Kamenogorsk, 2010

Content

INTRODUCTION……………………………………………………………….3
1. GLOBAL COMPUTER NETWORKS…………………………………3
1.1 Principles of construction and functions of global computer networks……3
1.2 Communication equipment of global networks……………………..5
1.3 Network technologies. Global Circuit Switched Networks…………8
1.3.1 Wide-area networks with packet switching……………………………......9
2. INTERNET.……………………………………………………… …......10
2.1 Creation and development of the Internet…………………………………………….. 10
2.2 Methods of accessing the Internet………………………………… …………………...12
2.3 Addressing on the Internet……………………………………………………………... .15
2.4 TCP/IP protocol family…………………………………………………….…..16
2.5 Email……………………………………………………….....22
CONCLUSION…………………………………………………… ……………. 23
BIBLIOGRAPHICAL LIST…………………………………………..23

Introduction

Modern human society lives in a period characterized by an unprecedented increase in the volume information flows. This applies to both the economy and the social sphere. Market relations place increased demands on timeliness, reliability, and completeness of information. Application of modern electronic computers makes it possible to shift labor-intensive operations to automatic or automated devices that can operate at speeds millions of times faster than human processing speed. The use of computers leads to a radical restructuring of production technology in almost all industries, commercial and financial-credit activities and, as a consequence, to increased productivity and improved working conditions for people. That is why a modern specialist must have theoretical knowledge in the field of computer science and practical skills in using computer technology, communications technology and other management tools. The expansion of local computer networks and the extension of communication lines has led to the need to create global networks, which include local, regional networks and individual PCs. To connect PCs and networks in the global network, special communication lines are used: fiber-antique, telephone, satellite, etc. The transmission speed in such lines depends on the quality of all components. The most common data transmission channel is telephone lines. Computer networks, also called computer networks or data networks, are the logical result of the evolution of two of the most important scientific and technical branches of modern civilization - computer and telecommunication technologies. On the one hand, networks are special case distributed computing systems in which a group of computers coordinately perform a set of interrelated tasks, exchanging data in automatic mode. On the other hand, computer networks can be considered as a means of transmitting information over long distances, for which they use methods of encoding and multiplexing data, which have been developed in various telecommunication systems.
The unification of a large number of local computer networks ultimately led to the creation of a worldwide computer network - the Internet.

1 GLOBAL COMPUTER NETWORKS
1.1 Principles of construction and functions of global computer networks
The emergence of a need to connect computers located at great distances from each other gave rise to a solution to a simpler problem - access to a computer from terminals located many hundreds, or even thousands of kilometers away from it. The terminals were connected to computers through telephone networks using modems. Such networks allowed numerous users to receive remote access to the shared resources of several powerful supercomputers. Then systems appeared in which, along with remote terminal-to-computer connections, remote computer-to-computer connections were also implemented. Computers have the ability to exchange data automatically, which, in fact, is the basic mechanism of any computer network. Based on this mechanism, the first networks implemented file sharing, database synchronization, Email and other now traditional network services.
Thus, chronologically, the first to appear were global networks (Wide Area Networks, WAN), that is, networks that unite geographically dispersed computers, possibly located in different cities and countries. It was during the construction of global networks that many of the basic ideas and concepts of modern computer networks were first proposed and developed. Such, for example, as multi-level construction of communication protocols, packet switching technology, routing of packets in composite networks.
Global computer networks have inherited a lot from other, much older and more widespread global networks - telephone networks. The main result of the creation of the first global computer networks was the abandonment of the principle of circuit switching, which had been successfully used in telephone networks for many decades. A compound channel with a constant speed allocated for the entire duration of a communication session could not be effectively used by pulsating computer data traffic, in which periods of intense exchange alternate with long pauses. Field experiments and mathematical modeling have shown that pulsating and largely delay-insensitive computer traffic is transmitted much more efficiently by networks that use the principle of packet switching, when the data is divided into small portions - packets that independently move through the network by embedding the end node address in the header package. Since laying high-quality communication lines over long distances is very expensive, the first global networks often used existing communication channels that were originally intended for completely different purposes. For example, for many years, global networks were built on voice-frequency telephone channels capable of carrying only one conversation in analog form at a time. Because the transmission speed of discrete computer data over such channels was very low (tens of kilobits per second), the range of services provided in wide area networks of this type was usually limited to file transfers, mainly in the background, and e-mail. In addition to low speed, such channels have another drawback - they introduce significant distortion into the transmitted signals. Therefore, the protocols of global networks built using low-quality communication channels are characterized by complex procedures for monitoring and data recovery. A typical example of such networks is X.25 networks, developed in the early 1970s, when low-speed analog circuits leased from telephone companies were the predominant type of circuits connecting computers and wide area network switches. The progress of global computer networks was largely determined by the progress telephone networks. Since the late 60s, telephone networks have increasingly used digital voice transmission, which led to the emergence of high-speed digital channels connecting PBXs and allowing the simultaneous transmission of tens and hundreds of conversations. A special Plesiochronous Digital Hierarchy (PDH) technology has been developed, designed to create so-called primary, or backbone, networks. Such networks do not provide services to end users; they are the foundation on which high-speed point-to-point digital channels are built, connecting the equipment of another (so-called overlay) network, which is already working for the end user. PDH, which supports speeds up to 140 Mbps, was originally an internal technology of telephone companies. However, over time, these companies began to lease part of their PDH circuits to enterprises, which used them to create their own telephone and wide area computer networks. The technology of synchronous digital hierarchy (SDH), which appeared in the late 80s, expanded the range of speeds of digital channels to 10 Gbit/s, and the technology of spectral multiplexing (Dense Wave Division Multiplexing, DWDM) - to hundreds of gigabits and even several terabits per year. give me a sec. By now, global networks have caught up with local networks in terms of variety and quality of services, which for a long time were leaders in this regard, although they were born much later.

1.2 WAN communications equipment
A typical example of the structure of a global computer network is shown in (Fig. 1). The following designations are used here: S (switch) - switches, K - computers, R (router) - routers, MUX (multiplexor) - multiplexer, UNI (User-Network Interface) - user-network interface and NNI (Network-Network Interface) - network-network interface. In addition, the office PBX is indicated by the abbreviation PBX, and small black squares indicate DCE devices, which will be discussed below.
Rice. 1 Example of a global network structure
The network is built on the basis of non-switched (dedicated) communication channels that connect global network switches to each other. Switches are also called packet switching centers (PSC), that is, they are packet switches, which in different global network technologies may have other names - frames, cells. As in local network technologies, there is no fundamental difference between these data units, however, some technologies have traditional names, which also often reflect the specifics of packet processing. For example, a frame relay frame is rarely called a packet because it is not encapsulated in a frame or packet for more than low level and is processed by the link layer protocol.
Switches are installed in those geographic locations where branching or merging of end-subscriber data streams or trunk links carrying data from many subscribers is required. Network subscribers are generally connected to switches using dedicated communication channels. These communication channels have lower bandwidth than the backbone links that connect the switches, otherwise the network would not be able to cope with the data flows of its many users. To connect end users, it is possible to use switched channels, that is, telephone network channels, although in this case the quality of transport services usually deteriorates. Fundamentally, replacing a dedicated channel with a switched one does not change anything, but additional delays, failures and channel breaks are introduced due to the fault of the circuit-switched network, which in this case becomes an intermediate link between the user and the packet-switched network. In addition, in analogue telephone networks the channel is usually of low quality due to the high noise level. The use of switched channels on switch-to-switch backbone connections is also possible, but for the same reasons it is highly undesirable. The end nodes of a WAN are more diverse than the end nodes of a LAN. Figure 1 shows the main types of global network end nodes: individual computers. All these devices generate data for transmission on the global network, therefore they are DTE (Data Terminal Equipment) devices for it. The local network separated from the global network by a router or remote bridge (which is not shown in the figure), so for the global network it is represented by a single DTE device - the router or bridge port. When transmitting data through the global network bridges And routers, work in accordance with the same logic as when connecting local networks. Bridges, which in this case are called remote bridges, build a table of MAC addresses based on the traffic passing through them, and based on the data from this table they make a decision - to transmit frames to remote network or not. useful. Routers make a decision based on the network number of a packet of some network layer protocol (for example, IP or IPX) and, if the packet needs to be forwarded to the next router over a global network, for example, frame relay, they pack it into a frame of this network and provide it with the corresponding hardware address of the next router and sent to the global network.
Voice-data multiplexers are designed to combine computer and voice traffic within one territorial network. Since the global network in question transmits data in the form of packets, voice-data multiplexers operating on a network of this type pack voice information into frames or packets of the territorial network and transmit them to the nearest switch in the same way as any end node of the global network , that is, a bridge or router. If the WAN supports traffic prioritization, the multiplexer assigns the highest priority to voice traffic frames so that the switches process and forward them first. The receiving node at the other end of the WAN must also be a voice-to-data multiplexer that must understand what type of data is in the packet—voice measurements or computer data packets—and sort that data into its outputs. Voice data is sent to the office PBX, and computer data is sent through the router to the local network.
Since the end nodes of the global network must transmit data over a communication channel of a certain standard, each DTE type device must be equipped with a DCE (Data Circuit terminating Equipment) type device that provides the necessary protocol physical level of this channel. Depending on the type of channel, DCEs of three main types are used for communication with global network channels: modems for working over dedicated and switched analog channels, DSU/CSU devices for working over digital dedicated channels of TDM technology networks, and terminal adapters (TA) for working over digital ISDN network channels. DTE and DCE devices are collectively called equipment located on the territory of the global network subscriber - Customer Premises Equipment, CPE. Therefore, in the global network it is usually strictly described and standardized user-network interface(User-to-Network Interface, UNI). This is necessary so that users can easily connect to the network using communications equipment from any manufacturer that complies with the UNI standard for this technology (for example, X.25). Protocols for interaction between switches within a global network, called Network-to-Network Interface (NNI), are not always standardized. It is believed that an organization creating a global network should have freedom of action to independently decide how internal network nodes should interact with each other. In this regard, the internal interface, if standardized, is called “network-to-network” rather than “switch-to-switch”, emphasizing the fact that it should be used mainly when interacting between two territorial networks of different operators

1.3 Network technologies. Circuit-switched wide area networks
Wide Area Networks (WAN), which refer to territorial computer networks, are designed, like local networks, to provide services, but to a much larger number of users located over a large area.
Switching methods: There are three fundamentally different switching schemes in wide area networks:

circuit switching
message switching
packet switching

Circuit switching in global networks – a process that, on demand, connects two or more data stations and maintains exclusive use of the data channel until disconnection occurs. Circuit switching involves the formation of a continuous composite physical channel from individual channel sections connected in series for direct data transfer between nodes. Individual channels are connected to each other by special equipment - switches, which can establish connections between any end nodes of the network.
Message switching in global networks– the process of sending data, including reception, storage, selection of the original direction and further transmission of messages without violating their integrity. Used in cases where an immediate response to a message is not expected. Messages are transmitted between transit computers on the network with temporary buffering on the disks of each computer.
Messages are data that are united by semantic content, have a specific structure and are suitable for processing, forwarding or use.
Message sources can be voice, images, text, data. To transmit sound, the telephone is traditionally used, images are transmitted by television, text is transmitted by the telegraph (teletype), and data is transmitted by computer networks. Establishing a connection between the sender and the recipient with the ability to exchange messages without noticeable time delays characterizes the online operating mode. If there are significant delays in storing information in intermediate nodes, we have an offline mode.

1.3.1 Wide-area packet-switched networks
Packet switching in wide area networks– this is the switching of messages presented in the form of addressed packets, when the data transmission channel is occupied only during the transmission of the packet and, upon its completion, is freed for the transmission of other packets. Network switches, which act as gateways and routers, receive packets from end nodes and, based on address information, transmit them to each other, and ultimately to destination stations. In global networks, the following types of switching are used to transmit information:
- channel switching (used when transmitting audio information over regular telephone lines;
- message switching (used mainly for transmitting email, teleconferences, electronic news);
- packet switching (for data transmission, currently also used for transmitting audio and video information)
The advantage of circuit switching networks is ease of implementation (formation of a continuous composite physical channel), and the disadvantage is low channel utilization, high cost of data transmission, increased time expectations of other users. When switching messages, data (message) is transmitted after the channel is released until it reaches the recipient. Each server receives, verifies, assembles, routes, and transmits messages.

2. INTERNET
2.1 Creation and development of the Internet

Structure and basic principles of building the Internet:

Internet– a worldwide information computer network, which is an association of many regional computer networks and computers that exchange information with each other through public telecommunications channels.
Information on the Internet is stored on servers. Servers have their own addresses and are controlled by specialized programs. They allow you to forward mail and files, search databases, and perform other tasks. The exchange of information between network servers is carried out via high-speed communication channels (dedicated telephone lines, fiber optic and satellite communication channels). Individual users' access to Internet information resources is usually carried out through a provider.
Provider- network service provider – a person or organization providing services for connecting to computer networks. The provider is an organization that has a modem pool for connecting to clients and accessing the World Wide Web.
The main cells of the global network are local area networks. If a local network is directly connected to a global network, then every workstation on this network can be connected to it. There are also computers that are directly connected to the global network. They are called host computers (host - master). A host is any computer that is a permanent part of the Internet, i.e. connected via the Internet protocol to another host, which in turn is connected to another, and so on.
Ri With. 2 Structure of the global Internet network

To connect communication lines to computers, special electronic devices are used, which are called network cards, network adapters (modems).
Almost all Internet services are built on the client-server principle. All information on the Internet is stored on servers. Information exchange between servers is carried out via high-speed communication channels or highways. Servers connected by high-speed highways make up the basic part of the Internet. Individual users connect to the network through the computers of local Internet service providers, Internet Service Providers (ISPs), which have a permanent connection to the Internet. A regional provider connects to a larger national provider that has nodes in various cities of the country. Networks of national providers are combined into networks of transnational providers or first-tier providers. United networks of first-tier providers make up the global Internet network. The transfer of information to the Internet is ensured by the fact that each computer on the network has a unique address (IP address), and network protocols provide interaction between different types of computers running different operating systems. The Internet primarily uses the TCP/IP family of network protocols (stack). At the data link and physical layers, the TCP/IP stack supports Ethernet, FDDI, and other technologies. The basis of the TCP/IP protocol family is the network layer, represented by the IP protocol, as well as various routing protocols. This layer facilitates the movement of packets in the network and controls their routing. The packet size, transmission parameters, and integrity control are carried out at the TCP transport layer.
The application layer integrates all the services that the system provides to the user. The main application protocols include: telnet remote access protocol, FTP file transfer protocol, HTTP hypertext transfer protocol, email protocols: SMTP, POP, IMAP, MIME.
2.2 Internet access methods
The following methods of accessing the Internet are currently known:

1. Dial-Up (when the user’s computer connects to the provider’s server using a telephone) – dial-up access over an analog telephone network, data transfer speed up to 56 Kbps;
2. DSL (Digital Subscriber Line) - a family of digital subscriber lines designed to organize access over an analog telephone network using a cable modem. This technology (ADSL, VDSL, HDSL, ISDL, SDSL, SHDSL, RADSL, collectively called xDSL) provides high-speed connections up to 50 Mbit/s (actual speed up to 2 Mbit/s). The main advantage of xDSL technologies is the ability to significantly increase the speed of data transmission over telephone wires without upgrading the subscriber telephone line. The user gains access to the Internet while maintaining normal telephone communication;
3. ISDN - dial-up access over a digital telephone network. The main feature of using ISDN is the high speed of information transfer, compared to Dial-Up access. The data transfer rate is 64 Kbit/s when using one and 128 Kbit/s when using two communication channels;
4. Internet access via dedicated lines (analog and digital). Leased line access is a method of connecting to the Internet when the user’s computer is connected to the provider’s server using a cable (twisted pair) and this connection is permanent, i.e. non-switched, and this is the main difference from regular telephone communication.
5. Internet access via local network (Fast Ethernet). Connection is made using network card(10/100 Mbit/s) with data transfer speeds of up to 1 Gbit/s on the backbone sections and 100 Mbit/s for the end user. To connect the user's computer to the Internet, a separate cable (twisted pair) is supplied to the apartment, while the telephone line is free.
6. Satellite Internet access or satellite Internet (DirecPC, Europe Online). There are two types of satellite Internet access - asymmetric and symmetric:
- Data exchange between the user’s computer and the satellite is two-way;
- Requests from the user are transmitted to the server of the satellite operator through any available terrestrial connection, and the server transmits data to the user from the satellite. Maximum data reception speed up to 52.5 Mbit/s
7. Internet access using cable television network channels, data reception speed from 2 to 56 Mb/sec. Cable Internet (“coax at a home”). Currently, two data transmission architectures are known: symmetric and asymmetric architectures. In addition, there are two connection methods: a) a cable modem is installed separately in each user’s apartment; b) the cable modem is installed in a house where several Internet service users live.
8. Last mile wireless technologies:

WiFi
WiMax
RadioEthernet
MMDS
LMDS
Mobile GPRS – Internet

WiFi (Wireless Fidelity - accurate data transmission without wires) is a technology for broadband access to the Internet. The information transfer speed for the end subscriber can reach 54 Mbit/s. Their range of action does not exceed 50 - 70 meters. Wireless access points are used within an apartment or in public places in large cities.
WiMAX (Worldwide Interoperability for Microwave Access), similar to WiFi - broadband Internet access technology. WiMAX, unlike traditional radio access technologies, also operates on a reflected signal, outside the line of sight of the base station. Currently, WiMAX partially satisfies the conditions of 4G networks based on packet data transfer protocols. The 4G family includes technologies that allow data transmission over cellular networks at speeds above 100 Mbit/s. and improved voice quality. MMDS (Multichannel Multipoint Distribution System). These systems are capable of serving an area within a radius of 50-60 km, while direct visibility of the operator’s transmitter is not necessary. The average guaranteed data transfer rate is 500 Kbps - 1 Mbps, but up to 56 Mbps per channel can be provided. LMDS (Local Multipoint Distribution System) is a standard for cellular networks for wireless information transmission for fixed subscribers. The system is built on a cellular principle, one base station allows you to cover an area with a radius of several kilometers (up to 10 km) and connect several thousand subscribers. The BSs themselves are connected to each other by high-speed terrestrial communication channels or radio channels (RadioEthernet). Data transfer speed up to 45 Mbit/s. Mobile GPRS – Internet. To use the Mobile Internet service using GPRS technology, you must have a telephone with a built-in GPRS modem and a computer. GPRS technology provides data transfer speeds of up to 114 Kbps. When using GPRS technology, it is not the time of connection to the Internet that is charged, but the total volume of information transmitted and received. You will be able to view HTML pages, download files, work with email and any other Internet resources. GPRS technology is an improvement on the basic GSM networks or packet switching protocol for GSM networks. EDGE is a continuation of the development of GSM/GPRS networks. EDGE technology (enhanced GPRS or EGPRS) provides higher data transfer speeds compared to GPRS (speeds up to 200 Kbps). EDGE (2.5 G) is the first step towards 3G technology.
Mobile CDMA - Internet. The CDMA standard network is a fixed and mobile connection, as well as high-speed Mobile Internet. To use the Mobile Internet service using CDMA technology, you must have a telephone with a built-in CDMA modem or a CDMA modem and a computer. CDMA technology provides data transfer rates of up to 153 Kbps or up to 2400 Kbps - using EV-DO Revision 0 technology. Currently, CDMA technology provides third generation mobile communication services. 3G mobile communication technologies (third generation) - a set of services that provides both high-speed mobile access to the Internet and organizes video telephony and mobile television. Third generation mobile communications are based on packet data transmission. Third generation 3G networks operate in the range of about 2 GHz, transmitting data at speeds of up to 14 Mbit/s. .
9. Currently, Home PNA (HPNA) and HomePlug technologies are used for the “last meters” of Internet access. Internet access via dedicated Home PNA or HPNA lines (telephone lines) and access via a 220-volt household electrical network. Typically, Internet access via Home PNA and HomePlug leased lines is combined with access methods such as DSL, WiFi, and others, i.e. For the “last meters” of access, technologies are used. The HomePlug 1.0 standard access to the Internet through a household electrical network supports transmission speeds of up to 14 Mbit/s. the maximum length between nodes is up to 300 m. The Renesas company has released a modem in the form of a plug for data transmission over electrical networks. PLC (Power Line Communication) technology allows you to transmit data over high-voltage power lines, without additional communication lines. The computer is connected to the electrical network and accesses the Internet through the same outlet. To connect to home network no additional cables required. You can connect various equipment to your home network: computers, phones, security alarms, refrigerators, etc.

2.3 Addressing on the Internet
The main protocol of the Internet is the TCP/IP network protocol. Each computer on a TCP/IP network (connected to the Internet) has its own unique IP address or IP number. Internet addresses can be represented either by a sequence of numbers or by a name constructed according to certain rules. Computers use digital addresses when sending information, while users use primarily names when accessing the Internet.
Digital addresses on the Internet consist of four numbers, each of which does not exceed two hundred and fifty-six. When writing, numbers are separated by dots, for example: 195.63.77.21. This numbering method makes it possible to have more than four billion computers on the network. For an individual computer or local network that connects to the Internet for the first time, a special organization that administers domain names assigns IP numbers. Initially, IP numbers were used on the Internet, but when the number of computers on the network became more than 1000, a method of connecting names and IP numbers was adopted, which was called a Domain Name Server (DNS). The DNS server maintains a list of local network and computer names and their corresponding IP numbers. The Internet uses the so-called domain name system. Each level in such a system is called a domain. A typical domain name consists of several parts, arranged in a certain order and separated by periods. On the Internet, the domain name system uses the principle of sequential qualifications, just like in regular postal addresses - country, city, street and house to which the letter should be delivered.
The domain-based address generation system ensures that there is no other computer on the entire Internet with the same address. The Internet address system accepts domains represented by geographic regions. for example: Ukraine – ua; France - fr; Canada - sa; USA - us; Russia - ru. There are also domains divided by thematic criteria, for example:
Educational institutions – edu; Government agencies – gov; Commercial organizations - com.
Recently, new zones have been added, for example: biz, info, in, .cn and so on. When working on the Internet, it is not domain names that are used, but universal resource locators called URLs (Universal Resource Locator). A URL is the address of any resource (document, file) on the Internet; it indicates which protocol should be used to access it, which program should be run on the server, and which specific file should be accessed on the server.

2.4 TCP/IP protocol family
TCP/IP stack routing information exchange protocols
All routing information exchange protocols of the TCP/IP stack belong to the class of adaptive protocols, which in turn are divided into two groups, each of which is associated with one of the following types of algorithms:

distance vector algorithm (DVA),
Link State Algorithms (LSA).

In distance vector algorithms, each router periodically and broadcasts over the network a vector of distances from itself to all networks known to it. Distance usually refers to the number of intermediate routers that a packet must pass through before reaching the corresponding network. Another metric can be used that takes into account not only the number of transfer points, but also the time it takes for packets to travel through communications between neighboring routers. Having received a vector from a neighboring router, each router adds to it information about other networks known to it, which it learned about directly (if they are connected to its ports) or from similar advertisements from other routers, and then again broadcasts the new vector value throughout the network. Ultimately, each router learns information about the networks available on the Internet and the distance to them through neighboring routers.
The most common protocol based on the distance vector algorithm is the RIP protocol. Link-state algorithms provide each router with information sufficient to construct an accurate graph of the network's links. All routers operate based on the same graphs, which makes the routing process more resilient to configuration changes. Broadcasting is used here only when the state of links changes, which does not happen very often in reliable networks. In order to understand the state of the communication lines connected to its ports, the router periodically exchanges short packets with its closest neighbors. This traffic is also broadcast, but it circulates only between neighbors and therefore does not clog the network as much. The link-state protocol in the TCP/IP stack is OSPF.
Distance Vector Protocol RIP
The RIP (Routing Information Protocol) is one of the oldest protocols for exchanging routing information, but it is still extremely common in computer networks. In addition to the RIP version for TCP/IP networks, there is also a RIP version for Novell IPX/SPX networks. In this protocol, all networks have numbers (the way the number is formed depends on the network layer protocol used in the network), and all routers have identifiers. The RIP protocol makes extensive use of the concept of "distance vector". A distance vector is a set of pairs of numbers, which are the numbers of networks and the distances to them in hops. Distance vectors are iteratively propagated by routers throughout the network, and after a few steps, each router has information about the networks it can reach and the distances to them. If the connection with any network is lost, the router notes this fact by assigning the maximum possible value to the element of the vector corresponding to the distance to this network, which has a special meaning - “no connection.” This value in the RIP protocol is the number 16.
etc.................

Target: become familiar with the structure and basic principles of operation of the World Wide Web, with basic Internet protocols and the addressing system.

Architecture and operating principles of the Internet

Global networks, reaching millions of people, have completely changed the process of dissemination and perception of information.

Wide Area Network (WAN)– these are networks designed to connect individual computers and local networks located at a considerable distance (hundreds and thousands of kilometers) from each other. Global networks connect users located around the world using a wide variety of communication channels.

Modern Internet- a very complex and high-tech system that allows the user to communicate with people located anywhere in the world, quickly and comfortably find any necessary information, publish for public information the data that he would like to communicate to the whole world.

In reality, the Internet is not just a network, it is a structure that unites ordinary networks. The Internet is a “network of networks.”

To describe today's Internet, it is useful to use a strict definition.

In his book « TheMatrix:ComputerNetworksandConferencingSystemsWorldwide » John Quarterman describes the Internet as “a metanetwork consisting of many networks that operate according to the TCP/IP family of protocols, connected through gateways and using a single address space and name space”.

There is no single point of subscription or registration on the Internet; instead, you contact a service provider who gives you access to the network through a local computer. Consequences of such decentralization in terms of accessibility network resources are also very significant. The data transmission environment on the Internet cannot be considered only as a web of wires or fiber optic lines. Digitized data is sent via routers , which connect networks and, using complex algorithms, select the best routes for information flows (Fig. 1).

Unlike local networks, which have their own high-speed information transmission channels, global (as well as regional and, as a rule, corporate ) the network includes a communication subnetwork (otherwise: a territorial communication network, an information transmission system), to which local networks, individual components and terminals (means for entering and displaying information) are connected (Fig. 2).

The communication subnetwork consists of information transmission channels and communication nodes, which are designed to transmit data over the network, select the optimal route for transmitting information, switch packets and implement a number of other functions using a computer (one or more) and the corresponding software available in the communication node. The computers on which client users work are called workstations , and computers that are sources of network resources provided to users are called servers . This network structure is called nodal .

Fig.1 Scheme of interaction on the Internet

Internet is a global information system that:

· logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP);

· capable of supporting communications using the Transmission Control Protocol family - TCP/IP or its subsequent extensions/successors and/or other IP-compatible protocols;

· provides, uses, or makes available, on a public or private basis, high-level services built on top of the communications and other related infrastructure described herein.

Internet infrastructure(Fig.2):

1.backbone level (system of connected high-speed telecommunication servers).

2.level of networks and access points (large telecommunications networks) connected to the backbone.

3.level of regional and other networks.

4.ISP – Internet providers.

5.users.

To technical resources on the Internet include computer nodes, routers, gateways, communication channels, etc.

Fig.2 Internet infrastructure

The network architecture is based on multi-level message transmission principle . The message is generated usingthe highest level of the model ISO/OSI .. Then (when transmitting) it is afterThe message consistently passes through all levels of the system down to the lowest level, where it is transmitted via a communication channel to the recipient. As each one passesfrom the levels of the system the message is transformed, divided into relatively short parts that are equipped with additionalwith headers that provide similar levels of informationnor on the destination node. At this node, the message passes from the lower level to the upper level, stripping itself of headers. As a result, the recipient receives the message in its original form.

In territorial networks data exchange management realizedcovered by protocols top level models ISO/OSI . Regardless internal design of each specific top protocollevel, they are characterized by the presence of common functions: initialization of communication, transmission and reception of data, completion of exchange. Every protothe count has the means to identify any workstation on the networkby name, network address, or both. Activization of information exchange between interacting nodesis found after the destination node has been identified by the initiating nodedata exchange. The originating station installs one of the Methods for organizing data exchange: datagram method or method communication sessions. The protocol provides a means to receive/transmitchi messages by addressee and source. In this case, usually overlayingThere are restrictions on the length of messages.

TCP/IP- internetworking technology

The most common exchange control protocoldata is the TCP/IP protocol. The main difference between the network Internet from other networks lies precisely in its TCP/IP protocols, coveringcontaining a whole family of protocols for interaction between computersterami network. TCP/IP is an internetworking technology Internet technology. Therefore r a global network that connects manyvariety of networks with technologyTCP/IP, called Internet.

TCP/IP protocol is a family of software-implementedhigher-level protocols that do not work with hardware devicesjerking. Technically, the TCP/IP protocol consists of two parts - IP and TCP.

Protocol IP ( Internet Protocol - internetwork protocol) is the main protocol of the family, it implements the distribution of information formations in IP -network and is executed at the third (network) level of the mode whether ISO/OSI. IP protocol provides datagram delivery to the packageComrade, its main task is packet routing. He is not responsible for the reliability of information delivery, for its integrity, for the preservationchanging the order of the packet flow. Networks that use the protocol IP, called IP -networks. They work mainly analogue channels (i.e., to connect a computer to the network you need IP-mo dem) and are packet switched networks. The package is called hereyes datagram.

High level protocol TCP ( Transmission Control Protocol- transmission control protocol) works at the transport layer andpartially - at the session level. This is a protocol with the establishment of lological connection between sender and recipient. He is promisedprints a session connection between two nodes with guaranteed delivery of information, monitors the integrity of the transmission information received, preserves the order of the packet flow.

For computers, the TCP/IP protocol is the same as the rulestalk for people. It is accepted as an official standard on the web Internet , i.e. network technology TCP/IP has become the de facto technologygy of the World Wide Web.

A key part of the protocol is a packet routing scheme based on unique network addresses. Internet. Each work tea station, part of a local or global network, hasThere is a unique address that includes two parts identifyingnetwork address and station address within the network. This scheme allows give messages both within this network and to external networks.

ADDRESSING ON THE INTERNET

Basic Internet protocols

The operation of the Internet is based on the use of families of communication protocols TCP/IP (TransmissionControlProtocol/ InternetProtocol). TCP/IP is used for data transmission both on the Internet and on many local networks.

The name TCP/IP defines a family of network data transfer protocols. Protocol is a set of rules that all companies must adhere to to ensure the compatibility of the hardware and software they produce. These rules ensure that the hardware and software produced are compatible. In addition, TCP / IP is a guarantee that your personal computer will be able to communicate via the Internet with any computer in the world that also works with TCP / IP. As long as certain standards are met for the operation of the entire system, it does not matter who the software or hardware manufacturer is. Ideology open systems involves the use of standard hardware and software. TCP/IP is an open protocol and all specific information is published and can be freely used.

The various services included in TCP/IP and the functions of this protocol family can be classified according to the type of tasks they perform. We will only mention the main protocols, since their total number amounts to more than a dozen:

· transport protocols- manage data transfer between two machines :

· TCP/ IP(Transmission Control Protocol),

· UDP(User Datagram Protocol);

· routing protocols- process data addressing, ensure the actual transfer of data and determine the best path for the packet to travel :

· IP(Internet Protocol),

· ICMP(Internet Control Message Protocol),

· R.I.P.(Routing Information Protocol)

· and others;

· network address support protocols- process data addressing, provide machine identification with a unique number and name :

· DNS(Domain Name System),

· ARP(Address Resolution Protocol)

· and others;

· application service protocols are programs that a user (or computer) uses to access various services :

· FTP(File Transfer Protocol),

· TELNET,

· HTTP(HyperText Transfer Protocol)

· NNTP(NetNewsTransfer Protocol)

·and others

This includes transferring files between computers, remote terminal access to the system, transfer of hypermedia information, etc.;

· gateway protocols help transmit routing messages and network status information over the network, as well as process data for local networks :

· E.G.P.(Exterior Gateway Protocol),

· GGP(Gateway-to-Gateway Protocol),

· IGP(Interior Gateway Protocol);

· other protocols– used to transmit email messages when working with directories and files remote computer and so on :

· SMTP(Simple Mail Transfer Protocol),

· NFS(Network File System).

IP-addressing

Now let's take a closer look at the concept of IP address.

Every computer on the Internet (including any PC when it establishes a session connection with an ISP over a telephone line) has a unique address called IP-address.

An IP address is 32 bits long and consists of four 8-bit parts, named according to network terminology octets (octets) . This means that each part of the IP address can have a value between 0 and 255. The four parts are combined into a notation in which each eight-bit value is separated by a period. When it comes to network address, this usually means an IP address.

If all 32 bits of an IP address were used, there would be over four billion possible addresses - more than enough for the future expansion of the Internet. However, some bit combinations are reserved for special purposes, which reduces the number of potential addresses. In addition, the 8-bit quads are grouped in special ways depending on the type of network, so that the actual number of addresses is even smaller.

With the concept IP addresses are a closely related concept hosta (host) . Some simply equate the concept of a host with the concept of a computer connected to the Internet. In principle, this is true, but in general under host refers to any device that uses the TCP/IP protocol to communicate with other equipment. That is, in addition to computers, these can be special network devices - routers, hubs and others. These devices also have their own unique I P addresses, just like the computers of users’ network nodes.

Any IP-the address consists of two parts: network addresses(network identifier, Network ID) and host addresses(host identifier, Host ID) on this network. Thanks to this structure, the IP addresses of computers in different networks may have the same numbers. But since the network addresses are different, these computers are uniquely identified and cannot be confused with each other.

IP addresses are allocated depending on the size of the organization and the type of its activities. If this is a small organization, then most likely there are few computers (and, therefore, IP addresses) on its network. In contrast, a large corporation may have thousands (or even more) of computers organized into many interconnected local networks. For maximum flexibility IP-addresses are divided into classes: A, B and C. There are also classes D And E, but they are used for specific service purposes.

So, three classes of IP addresses allow them to be distributed depending on the size of the organization's network. Since 32 bits is the legal full size of an IP address, the classes break the four 8-bit parts of the address into a network address and a host address depending on the class.

Class network addressA determined by the first octet of the IP address (counted from left to right). The value of the first octet, which is in the range 1-126, is reserved for giant multinational corporations and the largest providers. Thus, in Class A there may be only 126 large companies in the world, each of which may contain almost 17 million computers.

ClassBuses The first 2 octets as the network address, the value of the first octet can range from 128-191. Each Class B network can have about 65 thousand computers, and the largest universities and other large organizations have such networks.

Respectively, in classC The first three octets are already allocated for the network address, and the value of the first octet can be in the range 192-223. These are the most common networks, their number can exceed more than two million, and the number of computers (hosts) in each network can be up to 254. It should be noted that “gaps” in the permissible values ​​of the first octet between classes of networks appear due to the fact that one or several bits are reserved at the beginning of the IP address to identify the class.

If any An IP address is symbolically designated as a set of octets w .x .y .z, then the structure for networks of various classes can be presented in Table 1.

Whenever a message is sent to any host on the Internet, the IP address is used to indicate the sender and recipient addresses. Of course, users do not have to remember all IP addresses themselves, since there is a special service TCP/IP, called Domain Name System

Table 1. Structure of IP addresses in networks of various classes

Network class	First octet value (W)	Network number octets	Host number octets	Number of possible networks	Number of hosts in such networks
	1-126		x.y.z	128(2 7)	16777214(2 24)
	128-191	w.x	y.z	16384(2 14)	65536(2 16)
	192-223	w.x.y		2097151(2 21)	254(2 8)

The concept of a subnet mask

To separate the network ID from the host ID, a special 32-bit number called a subnet mask is used. Purely outwardly, a subnet mask is exactly the same set of four octets, separated by dots, like any IP address. Table 2 shows the default subnet mask values ​​for class A, B, C networks.

Table 2. Subnet mask value (default)

Network class	Mask value in bits (binary representation)	Mask value in decimal form
	11111111 00000000 00000000 00000000	255.0.0.0
	11111111 11111111 00000000 00000000	255.255.0,0
	11111111 11111111 1111111100000000	255,255.255.0

The mask is also used to logically divide large IP networks into a number of smaller subnets. Let's imagine, for example, that at the Siberian Federal University, which has a class B network, there are 10 faculties and 200 computers (hosts) are installed in each of them. By using a subnet mask of 255.255.0.0, this network can be divided into 254 separate subnets with up to 254 hosts each.

The default subnet mask values ​​are not the only possible ones. For example, a system administrator on a particular IP network might use a different subnet mask value to highlight just some of the bits in the host ID octet.

How to registerIP-the network of your organization?

In fact, end users have nothing to do with this task, which falls on the shoulders of system administrator this organization. In turn, he is assisted in this by Internet providers, usually taking upon themselves all registration procedures in the relevant international organization called InterNIC (NetworkInformationCenter). For example, Siberian Federal University wants to receive an Internet email address containing the string sfu -kras .ru. This identifier, which includes the company name, allows the sender of the email to identify the recipient's company.

To obtain one of these unique identifiers, called a domain name, a company or ISP sends a request to the authority that controls Internet connections - InterNIC. If InterNIC (or the body authorized by it for such registration in a given country) approves the company name, then it is added to the Internet database. Domain names must be unique to prevent errors. The concept of a domain and its role in addressing messages sent over the Internet will be discussed below. Additional information You can learn about the work of InterNIC by visiting the Internet page http://rs.internic.ru.

DOMAIN NAME SYSTEM

Domain names

In addition to IP addresses, the so-called Domain host name . Just like an IP address, it is a name is unique for each computer (host) connected to the Internet - only here words are used instead of digital address values.

In this case, the concept domain means a collection of Internet hosts united according to some characteristic (for example, by territorial, when we are talking about the domain of the state).

Of course, the use of a domain host name was introduced only to make it easier for users to remember the names of the computers they need. The computers themselves, for obvious reasons, do not need such a service and make do with IP addresses. But just imagine that instead of such sonorous names as, www. microsoft. com or www. ibm. com you would have to remember the sets of numbers - 207.46.19.190 or 129.42.60.216 respectively.

If we talk about the rules for composing domain names, then there are no such strict restrictions on the number of components of the name and their meanings as in the case of IP addresses. For example, if in KhTI - Branch of Siberian Federal University there is a host with the name khti, included in the domain of the Republic of Khakassia khakassia, and that, in turn, is part of the Russian domain ru, then the domain name of such a computer will be khti. khakassia. ru. In general, the number of components of a domain name can be different and contain one or more parts, for example, rage. mp3. apple. sda. org or www. ru .

Most often, a company’s domain name consists of three components, the first part is the host name, the second is the company’s domain name, and the last is the country’s domain name or the name of one of seven special domains indicating the affiliation of the host with an organization of a certain activity profile (see Table 1 ). So, if your company is called "KomLinc", then most often the company's Web server will be named www.komlinc.ru (if it is a Russian company), or, for example, www.komlinc.com, if you asked the provider to register you mainly international domain of commercial organizations.

The last part of the domain name is called the top-level domain identifier (for example, . ru or . com). There are seven top-level domains established by InterNIC.

Table1. International top level domains

domain name	Domain host ownership
ARPA	Great-great... grandmother of the Internet, ARPANet network (obsolete)
COM	Commercial organizations (firms, companies, banks, etc.)
GOV	Government agencies and organizations
EDU	Educational institutions
MIL	Military institutions
NET	"Network" organizations that manage the Internet or are part of its structure
ORG	Organizations that do not belong to any of the listed categories

Historically, these seven default top-level domains denote the fact that a host (belonging to them) is geographically located in the United States. Therefore, the international committee InterNIC, along with the above top-level domains, allows the use of domains (special combinations of characters) to identify other countries in which the organization that owns this host is located.

So, top level domains are divided into organizational(see table 1) and territorial. There are two-letter designations for all countries of the world: . ru- for Russia (the domain is still in use . su, uniting hosts on the territory of the republics of the former USSR), .sa- for Canada, . uk- for Great Britain, etc. They are usually used in place of one of the seven identifiers listed in Table 1 above.

Territorial top level domains:

. ru (Russia) - Russia;

Su (Soviet Union ) - countries of the former USSR, now a number of CIS countries;

UK (United Kingdom ) - Great Britain;

Ua (Ukraine) - Ukraine;

Bg (Bulgaria) - Bulgaria;

Hu (Hungary) - Hungary;

De (Dutchland ) - Germany, etc.

A complete list of all domain names of states can be found on various servers on the Internet.

Not all companies outside the US have country IDs. To some extent, whether you use a country identifier or one of the seven US identifiers depends on when the company's domain name was registered. Thus, companies that connected to the Internet quite a long time ago (when the number of registered organizations was relatively small) were given a three-letter identifier. Some corporations operating outside the US but registering a domain name through a US company choose whether to use the host country identifier. Today in Russia you can get a domain identifier . com, for which you should discuss this issue with your Internet provider.

HowworkserversDNS

Now let's talk about how domain names are converted into computer-readable IP addresses.

Is doing this DomainNameSystem(DNS, Domain Name System) a service provided by TCP/IP that helps in addressing messages. It is thanks to the work of DNS that you can not remember the IP address, but use a much simpler domain address. The DNS system translates a computer's symbolic domain name into an IP address by finding an entry in distributed database data (stored on thousands of computers) corresponding to this domain name. It is also worth noting that DNS servers in Russian-language computer literature are often called "name servers".

Root zone name servers

Although there are thousands of name servers in the world, at the top of the entire DNS system are nine servers called root zone servers ( root zone servers ) . Root zone servers are named a. root_ server. net, b. root_ server. net and so on until i. root_ server. net. The first one is a. root_ server. net- acts as the primary Internet name server, controlled from the InterNIC information center, which registers all domains included in several domains top level. The remaining name servers are secondary to it, but they all store copies of the same files. Thanks to this, any of the root zone servers can replace and back up the others.

These computers contain information about the host computers of the name servers serving seven top-level domains: .com, .edu, .mil, .gov, .net, .org, and special.arpa (Fig. 1). Any of these nine servers carries the same top-level file as .uk (UK), .de (Germany), .jp (Japan) and so on.

Rice. 1. Hierarchical structure of Internet domain names

The root zone files contain all host names and IP -name server addresses for each subdomain included in the top-level domain. In other words, each root server has information about all top-level domains, and also knows the name of the host computer and IP -the address of at least one name server serving each of the secondary domains included in any top-level domain. For domains of foreign countries, the database stores information on name servers for each country. For example, in a certain domaincompany. comroot zone files for a domain contain nameserver information for any address ending incompany. com.

In addition to the root zone nameservers, there are local name servers , installed in lower level domains. The local name server caches a list of host computers that it has recently searched for. This eliminates the need to constantly access the system DNS with queries about frequently used host computers. Additionally, local name servers are iterative, and the root zone servers are recursive. This means that the local name server will repeat the process of requesting information about other name servers until it receives a response.

Root servers Internet , located at the top of the structure DNS , on the contrary, only provide pointers to the next level domains. Get to the end of the chain and get the required IP -address is the task of the local name server. To solve it, he must go down the hierarchical structure, sequentially asking local servers names are pointers to its lower levels.

1. Principles of building the Internet

The Federal Networking Council's definition of the Internet states: “The Internet is a global information system, the parts of which are logically interconnected through a unique address space based on the Internet Protocol (IP) or its subsequent extensions, capable of communicate using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite, its subsequent extensions, or other IP-compatible protocols, and publicly or privately providing, using, or making available a high-level communications service.” In other words, the Internet can be defined as an interconnection of networks based on a single communication protocol - TCP/IP.

The main and most common Internet access device for the end user is a computer. The computer can be located in any place that has modern means of communication.

Internet access, which is provided by organizations called Internet Service Providers, can be obtained by the user through a modem or the organization's local network. The ISP has one or more connections to the backbones or large networks that form the Internet's main bloodstream. In this case, a dial-up connection or a leased line connection is offered. In any case, there must be a line of communication of some kind.

The boundaries of the Internet are quite blurry. Any computer connected to it can already be considered part of it, and even more so this applies to the local network of an enterprise with Internet access. Web servers on which they are located informational resources, can be located in any part of the Internet (at the provider, in the local network of the enterprise). The main condition: they must be connected to the Internet so that Internet users can access their services. The services can be email, FTP, WWW and others. The information component of the services comes from a wide variety of sources. This could be data, photographs, sound clips, videos: everything that users strive for and achieve through an Internet connection.

The main difference between the Internet and other networks lies precisely in its TCP/IP protocols, which cover a whole family of protocols for interaction between network computers. TCP/IP is an Internet technology. The TCP/IP protocol consists of two parts - IP and TCP.

The IP protocol (Internet Protocol) implements the dissemination of information in an IP network. It provides packet delivery, its main task is packet routing.

The high-level TCP protocol (Transmission Control Protocol) is a protocol that establishes a logical connection between the sender and the recipient. It provides session communication between two nodes with guaranteed delivery of information, monitors the integrity of transmitted information, and maintains the order of the packet flow.

Being the basic protocol, TCP/IP has undeniable advantages: openness, scalability, versatility and ease of use, but this family of protocols also has disadvantages: the problem of information security, the disorder of packet transmission and the inability to track the route of their progress, the amount of address space.

To identify computers (host nodes) connected to the Internet and internetwork routing of packets, each computer is assigned a unique four-byte address (IP address). An IP address entry consists of four segments separated by dots. Each segment is a decimal number ranging from 0 to 255, which corresponds to one byte.

IP addresses are the main type of address used to transmit packets between networks. An IP packet contains two addresses - a sender and a recipient. Both addresses are static, i.e. do not change throughout the entire packet path.

In order to make access to all Internet resources as simple and transparent as possible, the Internet has a DNS domain name system. It is designed to ensure that any resource, in addition to a unique IP address, has an easy to remember domain name.

The Domain Name Service is designed to match IP addresses with a machine's domain name, and vice versa. The domain name of any resource consists of the following main parts: the name of the machine name, the proper domain name and the zone name.

For example, www.rbk.ru (this domain name says that the resource is located in the geographical domain ru, has its own name rbc and the functional name www, that is, it performs the functions of a WWW server).

The names of zones can be divided into “organizational” and “geographical”. The following organizational zones are registered in first-level domains: com - commercial; edu - educational; gov - government; mil - military; net - organizations that ensure the operation of the network; org - non-profit organizations.

Each country (state) has its own geographic domain of two letters. Here are the domains of some of the countries: ca - Canada (Canada); fi - Finland (Finland); fr - France (France); jp - Japan (Japan); ru - Russia (Russia); ua - Ukraine (Ukraine); uk - United Kingdom (England).

A number of specialized organizations are involved in the process of registering and maintaining domain names.

2. Internet services

internet payment security marketing

Internet services are systems that provide services to Internet users. These include: e-mail, WWW, newsgroups, mailing lists, FTP, IRC, as well as other products that use the Internet as a medium for transmitting information.

The services provided by the Internet can be divided into two main categories.

1. Deferred (off-line) - the main feature of this group is the presence of a temporary break between the request and receipt of information.

2. Direct (on-line) - characterized by the fact that information upon request is returned immediately. If the recipient of information is required to immediately respond to it, then such a service is interactive.

Email

The very first and most widespread Internet service is electronic mail (e-mail). This service provides lazy reading services. The user sends a message, and the recipient receives it on his computer after a certain period of time.

The email can be digitally signed and encrypted. The transfer speed is on average several minutes. The main advantages of e-mail are simplicity, low cost and versatility. Disadvantages of e-mail include weak protection of messages (possibility of access by third parties).

Teleconferences

Teleconferencing is the second most common Internet service that provides deferred services.

The newsgroup service consists of many thematic newsgroups (newsgroups) supported by news servers. A news server is a computer that can contain thousands of news groups on a wide variety of topics. Each news server that receives a new message broadcasts it to all nodes with which it exchanges news. A newsgroup is a collection of messages on a specific topic. News is divided into hierarchically organized thematic groups, and the name of each group consists of the names of sub-levels. For example, the comp.sys.linux.setup conference belongs to the “computers” group, the “operating systems” subgroup, more specifically, the Linux system, namely its installation.

There are both global hierarchies and hierarchies that are local to an organization, country, or network.

Access to news groups is carried out through the subscription procedure, which consists of indicating the coordinates of the news server and selecting news groups of interest to the user.

Many people can participate in a teleconference topic, regardless of where they are physically located. Usually, special people, so-called moderators, keep order in conferences.

The idea of ​​a mailing list is to combine the addresses of many people - mailing list subscribers - under one email address. When a letter is sent to this address, all subscribers receive the message this list mailings.

Depending on the number of subscribers, the mailing list is maintained on the server by programs of varying complexity.

Chats

The word chat (from English chat) refers to Internet services that allow text discussions to be held in real time. What distinguishes them from the traditional form of conversation is that they are conducted in text form - by typing on a keyboard. The most popular open standard underlying chat is IRC (Internet Relay Chat).

Internet pagers

An intermediate position between e-mail and chats in terms of dynamism and interactivity of communication is occupied by Internet pagers or instant messaging services. Internet messengers are gradually becoming one of the most popular means of communication on the Internet and will soon be able to reach e-mail in terms of breadth of use. Instant messaging services allow you to communicate in real time, combining the benefits of email and telephone. Part of the exchange process in such systems can be text dialogue, graphics transmission, voice and video communication, and file exchange. Examples of such programs are ICQ, MSN, AOL Instant Messenger and others like them.

FTP (file transfer protocol) is a file transfer protocol, but when considering FTP as an Internet service, we mean not just a protocol, but a service for accessing files in file archives. One of the reasons for its relatively high popularity is explained by the huge amount of information accumulated in FTP archives over decades of operation. computer systems. Another reason is the ease of accessing, navigating and transferring files via FTP.

FTP is a direct access service that requires a full Internet connection.

World Wide Web

WWW (World Wide Web) is a direct access service that requires a full Internet connection and allows you to interact interactively with information presented on websites. This is the most modern and convenient Internet service. It is based on the principle of hypertext and is capable of presenting information using all possible multimedia resources: video, audio, graphics, text, etc. Interaction is carried out on a client-server principle using the Hyper Text Transfer Protocol (HTTP). Using the HTTP protocol, the WWW service allows you to exchange documents in the hypertext markup language format - HTML (Hyper Text Markup Language), which ensures the proper display of document content in user browsers.

The principle of hypertext underlying the WWW is that each element of an HTML document can be a link to another document or part of it. WWW links can point not only to documents specific to the WWW service, but also to other services and information resources on the Internet. Thus, WWW software tools are universal for various services Internet, and the WWW information system itself performs an integrating function in relation to them.

It must be emphasized that the Internet and WWW are not identical concepts. A narrow definition of the Internet represents it as an interconnection of computer networks based on the TCP/IP protocol family, in the space of which it becomes possible to operate higher-level protocols, including the Hypertext Transfer Protocol (HTTP) - the World Wide Web protocol, a hypertext service for accessing remote information. In addition to the World Wide Web, other protocols at this layer (called the application layer) include email (POP3, SMTP, IMAP), real-time communication (IRC), and newsgroups (NNTP).

New Internet services

IN separate group It is possible to highlight Internet services that today are not as widespread as those described earlier and do not have uniform standards recognized by all. They are also based on the use of the Internet as a medium for transmitting information. In particular, this group includes:

· software for conducting video and audio conferences via the Internet;

· systems for broadcasting multimedia information.

Information retrieval services

A special group are Internet services that are supported by one of its member groups and are included in this category due to the global nature of the information retrieval services they provide. Searching for information is one of the key problems of the Internet today, since the number of web pages presented on it today is estimated at more than several hundred million. The following are the main tools for searching information on the Internet:

· Search engines (spiders, crawlers). The main function of search engines is to study the Internet in order to collect data about the websites existing on it and, at the user’s request, provide information about the web pages that most fully satisfy the entered query.

· Catalogs. They represent a hierarchically organized thematic structure into which, unlike search engines, information is entered at the initiative of users. The added page is strictly linked to the categories accepted in the catalog.

· Meta search tools. Meta search tools allow you to streamline the process by running multiple search tools simultaneously. This method significantly improves speed, but does not allow you to take advantage of the complex query capabilities offered by most modern systems search.

3. Methods for ensuring security on the Internet

One of the most important conditions The widespread use of the Internet has been and remains to ensure an adequate level of security for all transactions conducted through it.

The concept of information security can be defined as a state of information resistance to accidental or intentional influences. Since the Network is completely open to external access, the role of these methods is very important. The great importance of the safety factor is also noted by numerous studies conducted on the Internet.

Cryptography, the science of ensuring data security, is designed to solve security problems. Cryptography and systems built on its basis are designed to solve the following problems.

· Confidentiality. Information must be protected from unauthorized access both during storage and transmission. Provided with encryption.

· Authentication. The sender must be uniquely identified. Provided with an electronic digital signature and certificate.

· Integrity. Information must be protected from unauthorized changes, both during storage and transmission. Provided with an electronic digital signature.

In accordance with these tasks, the main methods of ensuring security are encryption, digital signature and certificates.

Encryption

Encryption technologies convert plain text into a form that cannot be read without a special encryption key.

Any encryption system works according to a specific methodology, including one or more encryption algorithms (mathematical formulas), the keys used by these algorithms, and a key management system.

The security of these types of systems depends on the confidentiality of the key used in the encryption algorithm, rather than on the confidentiality of the algorithm itself, which can be publicly available and therefore well verified.

Digital signature

Encrypting data transmitted over the Internet helps protect it from unauthorized persons. However for complete safety there must be confidence that the second participant in the transaction is the person for whom he claims to be. In e-commerce, the electronic equivalent of a traditional signature is used - a digital signature. As with encryption, electronic signature technology uses either a private key (in which case both parties to the transaction use the same key) or a public key (requiring a pair of keys - a public and a private one).

A digital signature allows you to verify the authenticity of the sender’s identity: it is based on the use of the personal key of the message author and provides the highest level of information security.

Certificates

An electronic certificate is a digital document that associates a public key with a specific user or application. To certify an electronic certificate, an electronic digital signature of a trusted center - CA (Certification Center) is used. Based on the functions that the CA performs, it is the main component of the entire public key infrastructure (PKI - Public Key Infrastructure). Using the CA's public key, each user can verify the validity of the electronic certificate issued by the CA and use its contents.

4. Internet payment systems

An online payment system is a system for making payments between financial, commercial organizations and users in the process of buying/selling goods and services via the Internet. It is the payment system that allows you to turn an order processing service or an electronic storefront into a full-fledged store with all the standard attributes: by selecting a product or service on the seller’s website, the buyer can make a payment without leaving the computer.

Payment in the e-commerce system can be made if a number of conditions are met:

Maintaining confidentiality. When making payments via the Internet, the buyer wants his data to be known only to organizations that have the legal right to do so.

Maintaining the integrity of information. Purchase information cannot be changed by anyone.

Carrying out the authentication procedure. Buyers and sellers must be confident that all parties involved in a transaction are who they say they are.

Availability of a seller's risk guarantee. The magnitude of the risks associated with product refusals and buyer dishonesty must be agreed upon with the payment system service provider and other organizations included in the trade chain through special agreements.

Minimizing transaction fees. Transaction processing fees for ordering and paying for goods are included in their price, so reducing the transaction price increases competitiveness. It is important to note that the transaction must be paid in any case, even if the buyer refuses the goods.

All specified conditions must be implemented in payment system Internet.

Classification of payment systems

Credit systems

These include online bank account management systems offered by various banks, as well as credit card systems.

Internet banking

Internet banking is a remote method of providing banking services clients.

In the first case, the bank supplies the client with its specialized software and connects it to its internal system.

In the second case, the application software is a special Internet application that functions only during a dialogue session between the client and the bank. In this case, the client can access his bank account, by logging into the bank’s server on the Internet from any computer, having previously entered your password and PIN code. To increase security in such systems, they use various ways protection economic information from unauthorized access.

Use of plastic cards

The most important feature of all plastic cards is that they store a certain set of information used in various application programs. In the field of money circulation, plastic cards are one of the progressive means of organizing non-cash payments. A plastic card is a means of managing an account transferred by the bank to the account owner for temporary use.

Barcode cards use a barcode as an identifying element.

Cards with a magnetic stripe are by far the most common. The magnetic stripe is located on the back of the card and consists of three tracks. Of these, the first two are designed to store identification data, and the third can be used to record information (for example, the current value of the debit card limit).

In smart cards or memory cards, the storage medium is a microcircuit. Memory cards are divided into two types: with fully accessible and protected memory. In the first type of cards there are no restrictions on reading and writing data. Secure memory cards have an identification data area and one or more application areas.

The identification area of ​​the cards allows only one entry during personalization, and in the future it is only available for reading. Access to application areas is regulated and carried out upon presentation of the appropriate key.

A special case of memory cards are counter cards, in which the value stored in memory can only change by a fixed amount.

Microprocessor cards are essentially microcomputers and contain all the associated major hardware components. At the same time, some of the data can be accessed only by the card’s internal programs, which, together with built-in cryptographic tools, makes the microprocessor card a highly secure instrument that can be used in financial applications.

In addition to the types of plastic cards described above used in financial applications, there are a number of cards based on other data storage mechanisms. Such cards (optical, induction, etc.) are used in medical systems, security systems, etc.

Debit systems

Online debit payment schemes are structured similarly to their traditional counterparts: check and cash schemes. The scheme involves two independent parties: the issuer (the entity that manages the payment system) and the users. The issuer issues certain electronic units that represent means of payment.

System users perform two main functions. They make and accept payments online using issued electronic units.

When using electronic monetary obligations, information of independent financial value is transferred between the parties to the transaction. This information can be immediately verified for authenticity and solvency by the party accepting the payment or issuing these obligations, and immediately used for the next payment or transferred to other, non-electronic means of payment.

Electronic checks

Electronic checks are analogous to regular paper checks. There are two main differences here. Firstly, in the virtual version, the signature is electronic. Secondly, the checks themselves are issued electronically.

Making payments consists of several stages:

The payer issues electronic check, signs electronic signature and forwards it to the recipient. For greater reliability and security, the checking account number can be encrypted public key jar.

The check is presented for payment to the payment system. Next, the electronic signature is verified.

If the authenticity of the electronic signature is confirmed, the product is delivered or the service is provided. Money is transferred from the payer's account to the recipient's account.

The Russian system that uses the functioning scheme of electronic checks is CyberPlat.

Electronic money

Electronic money completely simulates real money. At the same time, the issuing organization produces their electronic analogues. Next, they are purchased by users, who use them to pay for purchases, and then the seller redeems them from the issuer. When issued, each monetary unit is certified by an electronic signature, which is verified by the issuing structure before redemption.

Main difference electronic money from real ones is that they represent electronic monetary obligations of the party that issued them, but from a legal point of view they cannot be real money. The term “money” used shows that electronic money largely inherits the properties of real cash, the main one of which is anonymity.

Both banks and non-banking organizations can issue electronic cash. In Russia this is PayCash, WebMoney.

5. Problems and prospects for the development of Internet marketing

At the moment, several payment instruments and the technological solutions that support them are actually working. The choice of adequate payment instruments, which is a key issue for the development of the online payments market, should be determined by a number of criteria, including: ease of use, reliability and speed of the transaction, security and low cost of the instrument and its support for all payment participants: buyers , sellers, banks. At one extreme of the spectrum of possible instruments are traditional payment cards, and at the other is digital cash. As for digital money, a number of factors hinder its spread. These include: anonymity of payments, the danger of uncontrolled emission, as well as the difficulty of auditing trading operations. Payment cards are a recognized payment instrument.

65 nanometers is the next goal of the Zelenograd plant Angstrem-T, which will cost 300-350 million euros. The company has already submitted an application for a preferential loan for the modernization of production technologies to Vnesheconombank (VEB), Vedomosti reported this week with reference to the chairman of the board of directors of the plant, Leonid Reiman. Now Angstrem-T is preparing to launch a production line for microcircuits with a 90nm topology. Payments on the previous VEB loan, for which it was purchased, will begin in mid-2017.

Beijing crashes Wall Street

Key American indices marked the first days of the New Year with a record drop; billionaire George Soros has already warned that the world is facing a repeat of the 2008 crisis.

The first Russian consumer processor Baikal-T1, priced at $60, is being launched into mass production

The Baikal Electronics company promises to launch industrial production at the beginning of 2016 Russian processor Baikal-T1 costs about $60. The devices will be in demand if the government creates this demand, market participants say.

MTS and Ericsson will jointly develop and implement 5G in Russia

PJSC " Mobile TeleSystems"and Ericsson have entered into agreements on cooperation in the development and implementation of 5G technology in Russia. In pilot projects, including during the 2018 World Cup, MTS intends to test the developments of the Swedish vendor. At the beginning of next year, the operator will begin a dialogue with the Ministry of Telecom and Mass Communications on the formation technical requirements for the fifth generation of mobile communications.

Sergey Chemezov: Rostec is already one of the ten largest engineering corporations in the world

The head of Rostec, Sergei Chemezov, in an interview with RBC, answered pressing questions: about the Platon system, the problems and prospects of AVTOVAZ, the interests of the State Corporation in the pharmaceutical business, spoke about international cooperation in the context of sanctions pressure, import substitution, reorganization, development strategy and new opportunities in difficult times.

Rostec is “fencing itself” and encroaching on the laurels of Samsung and General Electric

The Supervisory Board of Rostec approved the “Development Strategy until 2025”. The main objectives are to increase the share of high-tech civilian products and catch up with General Electric and Samsung in key financial indicators.

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Ministry of Education and Science of the Republic of Kazakhstan

On the topic: “Basic principles of construction and structure of the Internet”

Completed by: student gr. MP 411

Kuznetsova E.A.

Taldykorgan

2014-2015 academic year year

1. Structure and basic principles of operation of the Internet

Target: become familiar with the structure and basic principles of operation of the World Wide Web, with basic Internet protocols and the addressing system.

2. Aarchitecture and principles of operation of the Internet

Global networks, reaching millions of people, have completely changed the process of dissemination and perception of information.

Wide Area Network (WAN)- these are networks designed to connect individual computers and local networks located at a considerable distance (hundreds and thousands of kilometers) from each other. Global networks connect users located around the world using a wide variety of communication channels.

Modern Internet-- a very complex and high-tech system that allows the user to communicate with people located anywhere in the world, quickly and comfortably find any necessary information, and publish for public information the data that he would like to communicate to the whole world.

In reality, the Internet is not just a network; it is a structure that connects ordinary networks. Internet--it is a “network of networks.”

To describe today's Internet, it is useful to use a strict definition.

In his book « The Matrix: Computer Networks and Conferencing Systems Worldwide» John Quarterman describes the Internet as “a metanetwork consisting of many networks that operate according to the TCP/IP family of protocols, connected through gateways and using a single address space and name space” .

There is no single point of subscription or registration on the Internet; instead, you contact a service provider who gives you access to the network through a local computer. The consequences of such decentralization in terms of the availability of network resources are also quite significant. The data transmission environment on the Internet cannot be considered only as a web of wires or fiber optic lines. Digitized data is sent via routers , which connect networks and, using complex algorithms, select the best routes for information flows (Fig. 1).

Unlike local networks, which have their own high-speed information transmission channels, global (as well as regional and, as a rule, corporate ) the network includes a communication subnetwork (otherwise: a territorial communication network, an information transmission system), to which local networks, individual components and terminals (means for entering and displaying information) are connected (Fig. 2).

The communication subnetwork consists of information transmission channels and communication nodes, which are designed to transmit data over the network, select the optimal route for transmitting information, switch packets and implement a number of other functions using a computer (one or more) and the corresponding software available in the communication node. The computers on which client users work are called workstations , and computers that are sources of network resources provided to users are called servers . This network structure is called nodal .

Fig.1 Scheme of interaction on the Internet

Internet is a global information system that:

· logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP);

· capable of supporting communications using the Transmission Control Protocol family - TCP/IP or its subsequent extensions/successors and/or other IP-compatible protocols;

· provides, uses, or makes available, on a public or private basis, high-level services built on top of the communications and other related infrastructure described herein.

Internet infrastructure(Fig.2):

1. backbone level (system of connected high-speed telecommunications servers).

2. level of networks and access points (large telecommunication networks) connected to the backbone.

3. level of regional and other networks.

4. ISP - Internet providers.

5. users.

To technical resources on the Internet include computer nodes, routers, gateways, communication channels, etc.

Fig.2 Internet infrastructure

The network architecture is based on multi-level message transmission principle . The message is generated at the highest level of the ISO/OSI model. Then (during transmission) it sequentially passes through all levels of the system to the lowest, where it is transmitted over the communication channel to the recipient. As it passes through each level of the system, the message is transformed, divided into relatively short parts, which are supplied with additional headers that provide information to similar levels at the recipient's node. At this node, the message passes from the lower level to the upper level, stripping itself of headers. As a result, the recipient receives the message in its original form.

In territorial networks data exchange management carried out by top-level protocols of the ISO/OSI model. Regardless of the internal design of each specific upper-level protocol, they are characterized by the presence of common functions: initialization of communication, transmission and reception of data, completion of exchange. Each protocol has a means of identifying any workstation on a network by name, network address, or both. Activation of information exchange between interacting nodes begins after identification of the destination node by the node initiating the data exchange. The initiating station sets one of the methods for organizing data exchange: datagram method or session method. The protocol provides a means for receiving/transmitting messages by the destination and the source. In this case, restrictions are usually imposed on the length of messages.

3. TC.P./ IP --internetworking technology

The most common communication control protocol is TCP/IP. The main difference between the networkInternetfromother networks lies precisely in its TCP/IP protocols, covering a whole family of protocols for interaction between network computers. TCP/IP is an internetworking technology, Internet technology. Therefore, a global network that combines many networks with technology TCP/IP, called Internet.

TCP/IP protocol is a family of software-implemented high-level protocols that do not work with hardware interrupts. Technically, the TCP/IP protocol consists of two parts - IP and TCP.

Protocol IP ( Internet Protocol --internetwork protocol) is the main protocol of the family, it implements the dissemination of information in the IP network and is executed at the third (network) level of the ISO/OSI model. The IP protocol provides datagram delivery of packets, its main task is packet routing. It is not responsible for the reliability of information delivery, for its integrity, or for maintaining the order of the packet flow. Networks that use the IP protocol are called IP networks. They operate primarily over analog channels (i.e., an IP modem is required to connect a computer to the network) and are packet-switched networks. The package here is called datagram.

High level protocol TCP ( Transmission Control Protocol -- transmission control protocol) works at the transport level and partially at the session level. This is a logical connection protocol between the sender and the recipient. It provides session communication between two nodes with guaranteed delivery of information, monitors the integrity of transmitted information, and maintains the order of the packet flow.

TCP/IP is for computers what conversation rules are for people. It has been adopted as an official standard on the Internet, i.e. TCP/IP network technology has become the de facto technology of the World Wide Web.

A key part of the protocol is a packet routing scheme based on unique Internet addresses. Each workstation that is part of a local or global network has a unique address, which includes two parts that define the network address and the address of the station within the network. This scheme allows messages to be transmitted both within a given network and to external networks.

4. Addressing on the Internet. Basic Internet protocols

The operation of the Internet is based on the use of families of communication protocols TCP/IP(TransmissionControlProtocol/ InternetProtocol). TCP/IP is used for data transmission both on the Internet and on many local networks.

The name TCP/IP defines a family of network data transfer protocols. Protocol is a set of rules that all companies must adhere to to ensure the compatibility of the hardware and software they produce. These rules ensure that the hardware and software produced are compatible. In addition, TCP/IP is a guarantee that your personal computer will be able to communicate via the Internet with any computer in the world that also works with TCP/IP. As long as certain standards are met for the operation of the entire system, it does not matter who the software or hardware manufacturer is. The open systems ideology involves the use of standard hardware and software. TCP/IP is an open protocol and all specific information is published and can be freely used.

The various services included in TCP/IP and the functions of this protocol family can be classified according to the type of tasks they perform. We will only mention the main protocols, since their total number numbers more than a dozen: Internet network architecture server

· transport protocols-- manage data transfer between two machines :

· TCP/IP(Transmission Control Protocol),

· UDP(User Datagram Protocol);

· routing protocols-- handle data addressing, ensure the actual transmission of data, and determine the best path for the packet to travel :

· IP(Internet Protocol),

· ICMP(Internet Control Message Protocol),

· R.I.P.(Routing Information Protocol)

· and others;

· network address support protocols-- process data addressing, provide machine identification with a unique number and name :

· DNS(Domain Name System),

· ARP(Address Resolution Protocol)

· and others;

· application service protocols-- these are programs that a user (or computer) uses to access various services :

· FTP(File Transfer Protocol),

· TELNET,

· HTTP(HyperText Transfer Protocol)

· NNTP(NetNewsTransfer Protocol)

· and others

This includes transferring files between computers, remote terminal access to the system, transfer of hypermedia information, etc.;

· gateway protocols help transmit routing messages and network status information over the network, as well as process data for local networks :

· E.G.P.(Exterior Gateway Protocol),

· GGP(Gateway-to-Gateway Protocol),

· IGP(Interior Gateway Protocol);

· other protocols- used for sending email messages, when working with directories and files on a remote computer, and so on :

· SMTP(Simple Mail Transfer Protocol),

· NFS(Network File System).

5. IPaddressing

Now let's take a closer look at the concept of an IP address.

Every computer on the Internet (including any PC when it establishes a session connection with an ISP over a telephone line) has a unique address called IP-address.

An IP address is 32 bits long and consists of four 8-bit parts, named according to network terminology octets (octets) . This means that each part of the IP address can have a value between 0 and 255. The four parts are combined into a notation in which each eight-bit value is separated by a period. When we talk about a network address, we usually mean an IP address.

If all 32 bits of an IP address were used, there would be over four billion possible addresses - more than enough for future expansion of the Internet. However, some bit combinations are reserved for special purposes, which reduces the number of potential addresses. Additionally, 8-bit quads are grouped in special ways depending on the network type, so the actual number of addresses is even smaller.

Closely related to the concept of an IP address is the concept hosta (host) . Some people simply equate the concept of a host with the concept of a computer connected to the Internet. In principle, this is true, but in general under host refers to any device that uses the TCP/IP protocol to communicate with other equipment. That is, in addition to computers, these can be special network devices-- routers, hubs and others. These devices also have their own unique IP addresses, just like the computers of the users' network nodes.

Any IP-the address consists of two parts: network addresses(network identifier, Network ID) and host addresses(host identifier, Host ID) on this network. Thanks to this structure, the IP addresses of computers on different networks can have the same numbers. But since the network addresses are different, these computers are uniquely identified and cannot be confused with each other.

IP addresses are allocated depending on the size of the organization and the type of its activities. If this is a small organization, then most likely there are few computers (and therefore IP addresses) on its network. In contrast, a large corporation may have thousands (or even more) of computers organized into many interconnected local networks. For maximum flexibility IP-addresses are divided into classes: A, B and C. There are also classes D And E, but they are used for specific service purposes.

So, three classes of IP addresses allow them to be distributed depending on the size of the organization's network. Since 32 bits is the legal full size of an IP address, the classes break the four 8-bit parts of the address into a network address and a host address depending on the class.

Class network addressA determined by the first octet of the IP address (counted from left to right). The value of the first octet, which is in the range 1-126, is reserved for giant multinational corporations and the largest providers. Thus, in Class A there may be only 126 large companies in the world, each of which may contain almost 17 million computers.

ClassBuses The first 2 octets as the network address, the value of the first octet can take a value within the range of 128--191. Each Class B network can have about 65 thousand computers, and the largest universities and other large organizations have such networks.

Respectively, in classC The first three octets are already allocated for the network address, and the value of the first octet can be in the range 192-223. These are the most common networks; their number can exceed more than two million, and the number of computers (hosts) in each network can be up to 254. It should be noted that “gaps” in the permissible values ​​of the first octet between classes of networks appear due to the fact that one or a few bits are reserved at the beginning of the IP address to identify the class.

If any IP address is symbolically designated as a set of octets w.x.y.z, then the structure for networks of various classes can be presented in Table 1.

Whenever a message is sent to any host on the Internet, the IP address is used to indicate the sender and recipient addresses. Of course, users do not have to remember all the IP addresses themselves, since there is a special TCP/IP service for this, called the Domain Name System.

Table 1. Structure of IP addresses in networks of various classes

6. The concept of a subnet mask

To separate the network ID from the host ID, a special 32-bit number called a subnet mask is used. Outwardly, the subnet mask is exactly the same set of four octets, separated by dots, like any IP address. Table 2 shows the default subnet mask values ​​for class A, B, C networks.

Table 2. Subnet mask value (default)

The mask is also used to logically divide large IP networks into a number of smaller subnets. Let's imagine, for example, that at the Siberian Federal University, which has a class B network, there are 10 faculties and 200 computers (hosts) are installed in each of them. By using a subnet mask of 255.255.0.0, this network can be divided into 254 separate subnets with up to 254 hosts each.

The default subnet mask values ​​are not the only possible ones. For example, a system administrator on a particular IP network might use a different subnet mask value to highlight just some of the bits in the host ID octet.

7. How to registerIP-the network of your organization

In fact, end users are not involved in this task, which falls on the shoulders of the system administrator of a given organization. In turn, Internet providers assist him in this, usually taking upon themselves all registration procedures in the relevant international organization called InterNIC(NetworkInformationCenter). For example, Siberian Federal University wants to receive an Internet email address containing the string sfu-kras.ru. This identifier, which includes the company name, allows the sender of the email to identify the recipient's company.

To obtain one of these unique identifiers, called a domain name, a company or ISP sends a request to the authority that controls the Internet connection -- InterNIC. If InterNIC (or the body authorized by it for such registration in a given country) approves the company name, then it is added to the Internet database. Domain names must be unique to prevent errors. The concept of a domain and its role in addressing messages sent over the Internet will be discussed below. Additional information about the work of InterNIC can be found by visiting Internet page http://rs.internic.ru.

8. Domain name system. Domain names

In addition to IP addresses, the so-called Domain host name . Just like an IP address, it is a name is unique for each computer (host) connected to the Internet - only here words are used instead of digital address values.

In this case, the concept domain means a collection of Internet hosts united according to some characteristic (for example, by territorial, when we are talking about the domain of the state).

Of course, the use of a domain host name was introduced only to make it easier for users to remember the names of the computers they need. The computers themselves, for obvious reasons, do not need such a service and make do with IP addresses. But just imagine that instead of such sonorous names as, www . microsoft . com or www . ibm . com you would have to memorize the sets of numbers -- 207.46.19.190 or 129.42.60.216 respectively.

If we talk about the rules for composing domain names, then there are no such strict restrictions on the number of components of the name and their meanings as in the case of IP addresses. For example, if in KhTI - Branch of Siberian Federal University there is a host with the name khti, included in the domain of the Republic of Khakassia khakassia, and that, in turn, is part of the Russian domain ru, then the domain name of such a computer will be khti. khakassia. ru. In general, the number of components of a domain name can be different and contain one or more parts, for example, rage. mp3. apple. sda. org or www . ru .

Most often, a company's domain name consists of three components, the first part is the host name, the second is the company's domain name, and the last is the country's domain name or the name of one of seven special domains that indicate the host's affiliation with an organization of a certain activity profile (see. Table 1). So, if your company is called “KomLinc”, then most often the company’s Web server will be named www.komlinc.ru (if it is a Russian company), or, for example, www.komlinc.com if you asked the provider to register you mainly international domain of commercial organizations.

The last part of the domain name is called the top-level domain identifier (for example, . ru or . com). There are seven top-level domains established by InterNIC.

Table1. International top-level domains

domain name	Domain host ownership
	Great-great... grandmother of the Internet, ARPANet (obsolete)
	Commercial organizations (firms, companies, banks, etc.)
	Government agencies and organizations
	Educational institutions
	Military institutions
	"Network" organizations that manage the Internet or are part of its structure
	Organizations that do not belong to any of the listed categories

Historically, these seven default top-level domains denote the fact that a host (belonging to them) is geographically located in the United States. Therefore, the international committee InterNIC, along with the above top-level domains, allows the use of domains (special combinations of characters) to identify other countries in which the organization that owns this host is located.

So, top level domains are divided into organizational(see table 1) and territorial. There are two-letter designations for all countries of the world: . ru-- for Russia (the domain is still in use . su, uniting hosts on the territory of the republics of the former USSR), .sa-- for Canada, . uk-- for Great Britain, etc. They are usually used in place of one of the seven identifiers listed in Table 1 above.

Territorial top level domains:

.ru (Russia)-- Russia;

Su (Soviet Union) - countries of the former USSR, now a number of CIS countries;

Uk (United Kingdom) -- Great Britain;

Ua (Ukraine) -- Ukraine;

Bg (Bulgaria) -- Bulgaria;

Hu (Hungary) - Hungary;

De (Deutchland) - Germany, etc.

A complete list of all domain names of states can be found on various servers on the Internet.

Not all companies outside the US have country IDs. To some extent, whether you use a country identifier or one of the seven US identifiers depends on when the company's domain name was registered. Thus, companies that connected to the Internet quite a long time ago (when the number of registered organizations was relatively small) were given a three-letter identifier. Some corporations operating outside the US but registering a domain name through a US company choose whether to use the host country identifier. Today in Russia you can get a domain identifier . com, for which you should discuss this issue with your Internet provider.

9. HowworkserversDNS

Now let's talk about how domain names are converted into computer-readable IP addresses.

Is doing this DomainNameSystem (DNS, Domain Name System) a service provided by TCP/IP that helps in addressing messages. It is thanks to the work of DNS that you can not remember the IP address, but use a much simpler domain address. The DNS system translates a computer's symbolic domain name into an IP address by finding an entry in a distributed database (stored on thousands of computers) that matches that domain name. It is also worth noting that DNS servers in Russian-language computer literature are often called "name servers".

10. Root zone name servers

Although there are thousands of name servers in the world, at the top of the entire DNS system are nine servers called root zone servers ( root zone servers ) . Root zone servers are named a. root_ server. net, b. root_ server. net and so on until i. root_ server. net. The first one is a. root_ server. net-- acts as the primary Internet name server, managed from the InterNIC information center, which registers all domains that are part of several top-level domains. The remaining name servers are secondary to it, but they all store copies of the same files. Thanks to this, any of the root zone servers can replace and back up the others.

These computers contain information about the host computers of the name servers serving seven top-level domains: .com, .edu, .mil, .gov, .net, .org and special.arpa (Fig. 1). Any of these nine servers carries the same top-level file as .uk (UK), .de (Germany), .jp (Japan) and so on.

Rice. 1. Hierarchical structure of Internet domain names

The root zone files contain all the host names and name server IP addresses for each subdomain that is part of the top-level domain. In other words, each root server has information about all the top-level domains, and also knows the host name and IP address of at least one name server serving each of the secondary domains included in any top-level domain. For domains of foreign countries, the database stores information on name servers for each country. For example, in a certain domain company. com root zone files for a domain contain nameserver information for any address ending in company. com.

In addition to the root zone nameservers, there are local name servers , installed in lower level domains. The local name server caches a list of host computers that it has recently searched for. This eliminates the need to constantly query the DNS system for frequently used host computers. Additionally, local name servers are iterative, and root zone servers - recursive. This means that the local name server will repeat the process of requesting information about other name servers until it receives a response.

In contrast, Internet root servers, located at the top of the DNS structure, only provide pointers to the next level of domains. Getting to the end of the chain and getting the required IP address is the task of the local name server. To solve it, he must go down the hierarchical structure, sequentially asking local name servers for pointers to its lower levels.

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