The basics of network technologies and high-speed data transfer are a manual. Basic data transfer technologies to access the Internet

Effective use of IP is impossible without the use of network technologies. Computing network is a combination workstations(for example, on the basis of personal computers) related to each other data transmission channelsfor which they circulate messages.Network operations are governed by a set of rules and agreements - network protocolwhich determines the technique of equipment required for collaboration, signals, message formats, methods for detecting and correcting errors, network interface operation algorithms, etc.

Local networks allow you to effectively use system resources such as databases, peripherals of type laser printers, high-speed drives on large-volume magnetic disks, etc., and use email.

Global networks appeared when a protocol was created, allowing to connect local networks. Usually, this event is associated with a pair of interconnected protocols - TCP / IP Control Protocol / IP (TRANSMISSION. Control Protocol/ Internet Protocol), which on January 1, 1983, was tied to a unified system of the ARPANET network and the US defense network network. Thus was created "network of networks" - the Internet. Another important event in the history of the Internet was the creation of a distributed hypertext information system WWW (from English, World Wide Web. - "The World Wide Web"). It was made possible by developing a set of rules and requirements that facilitate writing software for workstations and servers. And finally, the third important event in the Internet history was the development of special programs that facilitate the search for information and processing text documents, images and sounds.

The Internet consists of computers that are its permanent nodes (they got a name hostfrom English. host.- owner) I. terminalswhich are connected to the host. The hosts are connected to each other on the Internet protocol, and any personal computer can be used as a terminal, running on it special emulator program.Such a program allows him to "pretend" to the terminal, that is, to perceive the commands and send the same response signals as the real terminal. In order to solve the problem of accounting for millions of PEVM connected to a single network, the Internet uses unique codes - the number and name that is assigned to each computer. As part of the name, the names of countries are used (Russia - RU, United Kingdom - UK, France - FR), and in the USA - Types of organizations (commercial - som, EDU education system, network services - NET).

In order to connect to the network on the Internet protocol, it is necessary to negotiate with the provider organization (from English. provider. - Supplier), which will redirect information using the TCP / IP network protocol on the telephone lines to this computer through a special device - modem.Usually, the Internet providers when registering a new subscriber give it a specially written software package, which automatically installs the necessary network software on the subscriber's computer.

The Internet provides users with many different resources. From the point of view of using the Internet for the purposes of education, two are the most interest - the system of file archives and the WORLD WIDE WEB database (WWW, "World Wide Web"),

The file archive system becomes available using the FTP protocol { File Transfer. Protocol - file transfer protocol); This system of archives is called: FTP archives. FTP archives is a distributed depository of different data accumulated in 10-15 years. Any user can anonymously contact this repository and copy the materials you are interested in. FTP protocol commands define the data transmission channel parameters and the transmission process itself, as well as the nature of the file system. The FTP protocol allows users to copy files from one computer connected to another. Another means - the Telnet network access protocol allows you to connect to another terminal as well as connected by telephone with another subscriber, and to carry out joint work with it.

A feature of the distributed hypertext information system WWW is the use of hypertext links that make it possible to view materials in order of their choice by the user.

The foundation of www serve four cornerstone:

hypertext marking of HTML documents;

universal method of addressing URL;

hTTP hypertext posts delivery protocol;

universal Firewall CGI.

The standard storage object in the database is an HTML document that matches the usual text file. Customer requests serves a program called Http.-server.It implements the connection on the HTTP protocol { Hypertext. Transfer. Protocol - Hypertext transmission protocol), which is an add-in over TCP / IP - the standard Internet protocol. Completed information object that is displayed by the user client when accessing the information resource is pagewWW databases,

The location of each resource is determined uniformbath pointer resourceURL(from English. Uniform Resource. Locator). The standard URL consists of four parts: the transmission format (the type of access protocol), the host name on which the resource is located is the path to this file and the file name. Using the URL naming system, references in hypertext describe the location of the document. Communication with all network resources is carried out through the Unified CUI user interface (COMMON. User. Interface.). The main purpose of this tool is to ensure the uniform data flow between the server and the application program that runs under its control. Viewing the information resource is performed using special programs - browsers(from English. browse. - Read, briefly view).

The term "browser" refers not to all the resources of the Internet, but only to that part of them, which is called the "World Wide Web". Only here uses the HTTP protocol required to transmit documents written using the HTML language, and the browser is a program that recognizes HTML formatting codes of the transmitted document and displaying it on the computer screen as the author, in other words, the program has been conceived. Watching an HTML document.

To date, a large number of browse-ditch programs for the Internet has been developed. Among them are Netscape Navigator, MS Internet Explorel, Mosaic, Tango, Ariadna, Cello, Lynx.

Let us dwell on how viewers work (browsers).

Data processing in HTTP consists of four stages: Opening communication, sending a request message, sending response data and closing communication.

To open communication, the World Wide Web viewer is connected to the HTTP server (Web server) specified in the URL. After establishing a connection www-viewer sends a request message. It indicates the server which document is needed. After processing the request, the HTTP server transmits the requested data WWW server. All these actions are visible on the monitor screen - all this makes a browser. The user is visible only the basic function, which is indicating, that is, highlighting the hyperlink from the total text. This is achieved by changing the pattern of the mouse pointer: when the pointer falls on the hyperlink, it rotates from the "arrows" in the "pointing finger" - a hand with an elongated index finger. If you click the mouse button at this moment, the browser will "leave" to the address specified in the hyperlink.

The technology of the HTTP server is so simple and cheapers that there are no restrictions to create a WWW-like system inside a separate organization. Since only the presence of an internal local network with the TCR / IP protocol is necessary, you can create a small (compared to the global) hypertext "Cellus", such a technology for creating Internet-like local networks is called intranet.

Currently, on the Internet, it moves monthly more than 30 information therabity (this is approximately 30 million books for 700 pages each), and the number of users is, by different estimates, from 30 to 60 million people.

GOU VPO "Far Eastern State

university of Railway Transport"

Institute IIFO

Department: "Atis"

Abstract on discipline

Network technologies of high-speed data transmission systems

Subject: "Computer network W Lan.»

Performed: Hedgehogs D.A.

CT13-ICT (BT) OS-240

Checked: Karitan K.A.

Khabarovsk 2015

Introduction……………………………………………………………………….3

Wireless technology…………………………………………………..4

Safety…………………………………………………………………..6

Wireless Lan. ………………………………………………………………….. 7

Networking …………………………………………………………….. 8

………………………………………... 8

Conclusion……………………………………………………………………10

……………………………………....11

Introduction

It so happened that in our country the district Ethernet networks, tightening a couple in the apartment, received a greater prevalence. When at home just one computer, questions with the connection of the cable usually does not occur. But when a desire to climb on the Internet from a computer, laptop and PDA with the possibility of wireless connection, we think about how to correctly implement it. Divide one Internet channel on all households, multifunctional routers help us.

The need for creating a personal Wi-Fi network has a network of networks, probably any laptop or PDA. Of course, you can buy a point of access and organize wireless access through it. But much more convenient to have a device "everything in one", because the routers cope with this feature no worse access points. The main thing is to pay attention to, these are supported Wi-Fi standards. For in the past few years, the trend has emerged among manufacturers to produce devices with support for not yet existing standards. Of course, there is a certain benefit. We receive greater performance and freedom of Wi-Fi when using equipment from one manufacturer. However, since each of them implements innovations as he likes more (it is not yet adopted by the standard), we do not observe the compatibility of the equipment from different manufacturers.

Usually wireless networking technologies are grouped into three types, differing on the scale of their radio system, but they are successfully used in business.

WLAN (Wireless Local Networks) - Radius Up to 100 m. With their help, wireless access to group resources in the building, campus university, etc. Usually such networks are used to continue wired corporate local networks. In small WLAN companies can completely replace wired connections. The main standard for WLAN - 802.11.

Wireless technology

Wireless technology - a subclass of information technologies, serve to transfer information to the distance between two or more points, without demanding communication with their wires. Infrared radiation, radio wave, optical or laser radiation can be used to transmit information. Currently, there are many wireless technologies, most frequently known users for their marketing names, such as Wi-Fi, WiMAX, Bluetooth. Each technology has certain characteristics that determine its scope.

There are various approaches to the classification of wireless technologies.

By range:

Wireless Personal Networks (WPAN - Wireless Personal Area Networks). Examples of technology - Bluetooth.

Wireless Local Area Networks (WLAN - Wireless Local Area Networks). Examples of technologies - Wi-Fi.

Wireless Networks of the City (WMAN - Wireless Metropolitan Area Networks). Examples of technologies - WiMAX.

Wireless global networks (WWAN - Wireless Wide Area Network). Examples of technologies - CSD, GPRS, EDGE, EV-DO, HSPA ....... on topology:

- "Point-to-point".

- "Point-Multiple" ....... on the scope:

Corporate (departmental) Wireless networks - created by companies for their own needs.

Operator wireless networks - created by telecom operators for compensated service provision.

Wireless computer networks

. The wireless computer network is a technology that allows you to create computing networks that are fully relevant to standards for conventional wired networks (for example, Ethernet), without using cable wiring. As a carrier of information in such networks, radio waves of the microwave range are performing.

Application

There are two main directions for applying wireless computer networks:

Work in a closed volume (office, exhibition hall, etc.);

The connection of remote local networks (or remote local network segments).

To organize a wireless network in a closed space, transmitters with omnidirectional antennas are used. The IEEE 802.11 standard defines two network operation modes - AD-HOC and client server. Ad-Hoc mode (otherwise called "point-to-point") is a simple network in which the connection between stations (clients) is set directly without using a special access point. In the client-server mode, the wireless network consists of at least from one access point connected to a wired network, and some set of wireless client stations. Since in most networks it is necessary to provide access to file servers, printers and other devices connected to the wired local network, the client-server mode is most often used. Without an additional antenna, a stable connection for IEEE 802.11b equipment is achieved on average in the following distances: open space - 500 m, a room separated by partitions from non-metallic material - 100 m, an office from several rooms - 30 m. It should be borne in mind that through Walls with a large content of metal reinforcement (in reinforced concrete buildings are carrying walls) Radio waves of a range of 2.4 GHz sometimes can not be held at all, therefore in rooms separated by a similar wall, you will have to put your access points.

To connect remote local networks (or remote segments of the local network), equipment with directional antennas is used, which makes it possible to increase the range of up to 20 km (and using special amplifiers and a high altitude of antennas accommodation - up to 50 km). Moreover, Wi-Fi devices can be used as such equipment, you only need to add special antennas to them (of course, if it is allowed by the design). Complexes for combining local networks on topology are divided into a "point point" and "star". With the "Point-to-point" topology (AD-HOC mode in IEEE 802.11), a radio station is organized between two remote network segments. With the topology "Star" one of the stations is central and interacts with other remote stations. At the same time, the central station has an omnidirectional antenna, and other remote stations are unidirectional antennas. The use of an omnidirectional antenna in the central station limits the range by a distance of approximately 7 km. Therefore, if you want to connect the local network segments, remote from each other for a distance of more than 7 km, you have to connect them according to the point-to-point principle. At the same time, a wireless network is organized with a ring or other, more complex topology.

The power emitted by the transmitter of the access point or client station operating according to the IEEE 802.11 standard does not exceed 0.1 W, but many manufacturers of wireless access points limit the power only by programmatically, and it is enough just to raise power up to 0.2-0.5 W . For comparison, the power emitted by a mobile phone is an order of magnitude more (at the time of the call - up to 2 W). Since, unlike a mobile phone, network elements are located far from the head, as a whole, we can assume that wireless computer networks are safer in terms of health than mobile phones. If the wireless network is used to combine the local network segments remote over long distances, antennas are usually placed outside the room and at high height.

Safety

The products for wireless networks that meet the IEEE 802.11 standard offer four levels of security tools: physical, service set identifier (SSID - Service Set Identifier), an access control identifier (MAC ID - Media Access CONTROL ID) and encryption. DSSS technology for data transmission in the frequency range of 2.4 GHz over the past 50 years has been widely used in military communication to improve wireless safety. As part of the DSSS circuit, the flow of data requested "unfolds" through the 20 MHz width channel as part of the ISM range using the Complemenient Code Keying, CCK key). To decode received data, the recipient must set the correct frequency channel and use the same CCK scheme. Thus, the DSSS database technology provides the first defense line from unwanted access to the transmitted data. In addition, DSSS is a "quiet" interface, so that almost all overhearding devices will filter it as "white noise". The SSID identifier allows you to distinguish between individual wireless networks that can act in the same place or area. It is a unique network name, included in the header of data packets and IEEE 802.11 control. Wireless clients and access points use it to filter and take only those queries that relate to their SSID. Thus, the user will not be able to refer to the access point, unless it is provided to the correct SSID.

Wireless Lan.

...... Wireless Lan (Eng. Wireless Local Area Network; WLAN) - Wireless LAN. With this method of building networks, data transmission is carried out through the radio; Combining devices to the network occurs without the use of cable connections. The most common ways to build are Wi-Fi and WiMAX.

Wi-Fi and WiMAX

WiMAX and Wi-Fi comparisons are far from uncommon - terms consonant, the name of the standards on which these technologies are based similar are based (standards are developed by IEEE, both begin with "802."), as well as both technologies use a wireless connection and are used to connect to the Internet. (data exchange channel). But despite this, these technologies are aimed at solving completely different tasks.

WiMAX is a long-range system that coats the space kilometers that usually uses licensed frequency spectra (although the use of unlicensed frequencies is possible to provide a connection with the Internet-to-point point to the end user. Different standards of the 802.16 family provide different types of access, from mobile (similar to data transfer from mobile phones) to a fixed (alternative to wired access at which the user's wireless equipment is tied to the location).

Wi-Fi is a shorter action system, usually covering tens of meters, which uses unlicensed frequency bands to provide access to the network. Usually Wi-Fi is used by users to access their own local network, which may not be connected to the Internet. If WiMAX can be compared with a mobile connection, then Wi-Fi is rather similar to a stationary cordless phone.

WiMAX and Wi-Fi have a completely different QUALITY OF SERVICE (QoS) mechanism. WiMAX uses a mechanism based on establishing a connection between the base station and the user device. Each compound is based on a special planning algorithm that can guarantee the QoS parameter for each compound. Wi-Fi, in turn, uses the QoS mechanism similar to what is used in Ethernet in which the packages receive a different priority. This approach does not guarantee the same QoS for each compound.

Due to the cheapness and simplicity of installation, Wi-Fi is often used to provide customers with rapid access to the Internet by various organizations. For example, in some cafes, hotels, railway stations and airports, you can detect a free Wi-Fi access point.

Networking

...... Standard IEEE 802.11 operates at two lower levels of the ISO / OSI model: physical and channel. In other words, the use of Wi-Fi equipment is as simple as Ethernet: TCP / IP protocol is superimposed on top of the protocol describing the transmission of information on the communication channel. The extension of IEEE 802.11b does not affect the channel level and makes changes to IEEE 802.11 only at the physical level.

In the wireless LAN there are two types of equipment: a client (usually this is a computer equipped with a wireless network card, but there may be a different device) and an access point that serves as a bridge between wireless and wired networks. Access point contains a transceiver, a wired network interface, as well as a built-in microcomputer and data processing software.

Types and varieties of connections

AD-HOC connection (point-point).

All computers are equipped with wireless cards (clients) and are connected directly to each other by radio channel to operating according to the 802.11b standard and providing the exchange rate of 11 Mbps, which is quite enough for normal operation.

Infrastructure connection.

All computers are equipped with wireless cards and connect to access point. Which, in turn, has the ability to connect to a wired network. This model is used when you need to connect more than two computers. The server with a point of access can perform the role of the router and independently distribute the Internet channel.

Access point, using a router and modem.

Access point is included in the router, router - in the modem (these devices can be combined into two or even one). Now on each computer in the Wi-Fi zone, in which there is a Wi-Fi adapter, the Internet will work.

Connection bridge.

Computers are combined into a wired network. Each group of networks are connected to access points, which are connected to each other by radio channel. This mode is intended for combining two or more wired networks. Connecting wireless customers to an access point operating in the bridge mode is not possible.

Repeater.

Access point simply expands the range of another access point running in the infrastructure mode.

Conclusion

Wireless Local Area Networks (WLAN - Wireless LAN) can be used in the office for connecting mobile employees (laptops, wearable terminals) in places of accumulation of users - airports, business centers, hotels, etc.

Mobile Internet and mobile local networks are opened by corporate and home users new areas of use of pocket PCs, laptops. At the same time, the prices of Wi-Fi wireless equipment are constantly reduced and its range is expanding. Wi-Fi is also suitable for people who are needed to move around the room, for example, in a warehouse or in the store. In this case, for accounting (shipment, reception, etc.) of goods, wearable terminals are used, which are constantly connected to the corporate network via Wi-Fi protocol, and all changes are immediately reflected in the central database. WLAN is applicable and in the organization of temporary networks, when long and unprofitably put the wires, and then dismantle them.

Another use option is in historical buildings where the wire laying is impossible or prohibited. Sometimes I do not want to spoil the appearance of the premises with wires or boxes for their gasket. In addition, the Wi-Fi protocol is also suitable for domestic use, wherever it is inconvenient to stroke the wires.

List of used literature

Tutorial for universities / ed. Professor V.P. Shuvalov

2017 G.

Circulation 500 copies.

Format 60x90 / 16 (145x215 mm)

Execution: in a soft cover

ISBN. 978-5-9912-0536-8

BBK 32.884

UDC 621.396.2

Griff Um.
Recommended by UMO on education in infocommunication technologies and communication systems as a textbook for students of higher educational institutions, students in the direction of preparation 11.03.02 and 11.04.02 - "Infocommunication technologies and communication systems" of qualifications (degrees) "Bachelor" and "Master "

annotation

In compact form, issues of building infocommunication networks providing high-speed data transmission are presented. The sections that are necessary to understand how can be transmitted not only with high speed, but also with other indicators characterizing the quality of the services provided. A description of the protocols of various levels of the reference model of interaction of open systems, technology of transport networks are given. Considered issues of data transfer in wireless communications networks and modern approaches that ensure the transfer of large information arrays for acceptable time segments. The attention is paid to the increasing popularity of technology-configurable networks.

For students learning towards the preparation of bachelors "Infocommunication technologies and communication systems (degree)" Bachelor "and" Master ". The book can be used to improve the qualifications of telecommunication workers.

Introduction

References for the introduction

Chapter 1. Basic concepts and definitions
1.1. Information, message, signal
1.2. Information transfer rate
1.3. Physical data environment
1.4. Methods for converting signals
1.5. Multiple access methods
1.6. Telecommunication networks
1.7. Organization of work on standardization in the field of data transfer
1.8. Reference model of interaction of open systems
1.9. Control questions
1.10. Bibliography

Chapter 2. Providing service quality indicators
2.1. Quality of service. General provisions
2.2. Ensuring the transfer of data
2.3. Providing structural reliability indicators
2.4. QoS routing
2.5. Control questions
2.6. Bibliography

Chapter 3. Local Networks
3.1. LAN protocols
3.1.1. Ethernet technology (IEEE 802.3)
3.1.2. TECKEN RING TECHNOLOGY (IEEE 802.5)
3.1.3. FDDI technology
3.1.4. Fast Ethernet (IEEE 802.3U)
3.1.5. 100VG-Anylan technology
3.1.6. High Speed \u200b\u200bGigabit Ethernet Technology
3.2. Technical means that ensure the functioning of high-speed data networks
3.2.1. Hubs
3.2.2. Bridges
3.2.3. Switches
3.2.4. Protocol STP.
3.2.5. Routers
3.2.6. Gateways
3.2.7. Virtual Local Network (Virtual Local Area Network, VLAN)
3.3. Control questions
3.4. Bibliography

Chapter 4. Channel Level Protocols
4.1. The main tasks of the channel level, the protocol functions 137
4.2. Byte-oriented protocols
4.3. Bit-oriented Protocols
4.3.1. HDLC channel level protocol (High-Level Data Link Control)
4.3.2. Slip Protocol (Serial Line Internet Protocol). 151.
4.3.3. PPP Protocol (Point-to-Point Protocol - Double-Resizing Protocol)
4.4. Control questions
4.5. Bibliography

Chapter 5. Network and Transport Protocols
5.1. IP protocol
5.2. IPv6 protocol
5.3. RUP Routing Protocol
5.4. Internal OSPF Routing Protocol
5.5. BGP-4 Protocol
5.6. Resource Reservation Protocol - RSVP
5.7. RTP Transmission Protocol (Real-Time Transport Protocol)
5.8. DHCP Protocol (Dynamic Host Configuration Protocol)
5.9. LDAP protocol
5.10. ARP, RARP protocols
5.11. TCP Protocol (TRANSMISSION CONTROL PROTOCOL)
5.12. UDP Protocol (User Datagram Protocol)
5.13. Control questions
5.14. Bibliography

Chapter 6. Transport IP Networks
6.1. ATM technology
6.2. Synchronous Digital Hierarchy (SDH)
6.3. Multi-protocol tag tag
6.4. Optical transport hierarchy
6.5. Ethernet model and hierarchy for transport networks
6.6. Control questions
6.7. Bibliography

Chapter 7. Wireless High Speed \u200b\u200bData Transmission Technologies
7.1. Wi-Fi Technology (Wireless Fidelity)
7.2. WiMAX technology (WorldWide Interoperability For Microwave Access)
7.3. Transition from WiMAX to LTE technology (LongterMevolution)
7.4. State and perspectives of high-speed wireless networks
7.5. Control questions
7.6. Bibliography

Chapter 8. Instead of imprisonment: Some considerations on the topic "What should be done to ensure the transfer of data at high speed in IP networks"
8.1. Traditional data transfer with guaranteed delivery. Problems
8.2. Alternative data transfer protocols with guaranteed delivery
8.3. Algorithm for overload control
8.4. High speed data transfer conditions
8.5. Implicit data to ensure high-speed data transfer
8.6. Bibliography

Appendix 1. Software-configurable networks
P.1. General.
P. OpenFlow and OpenFlow switch protocol
P.3. NFV network virtualization
P.4. Standardization PKS.
P.5. SDN in Russia
P.6. Bibliography

Terms and Definitions

High-speed connection is divided into 2 types:

Wired connection

These include - telephone wire, coaxial cable, twisted pair, fiber optic cable.

Wireless connection

Basic data transfer technologies to access the Internet

Wired compound technology:

• 1 DVB.
• 2 xDSL
• 3 docsis
• 4 Ethernet
• 5 FTTX
• 6 Dial-Up
• 7 isdn.
• 8 PLC
• 9 PON

UMTS / WCDMA (HSDPA; HSUPA; HSPA; HSPA +)

Satellite Internet

DVB (eng. Digital Video Broadcasting - Digital Video Broadcasting) - Family of Digital Television Standards Developed by the International DVB Project Consortium.

The standards developed by the DVB Project consortium are divided into applications. Each group has an abbreviated name with a DVB prefix, for example, DVB-H is a standard for mobile television.

DVB standards encompass all levels of interaction model of OSI open systems with different degrees of detail for various ways to transfer a digital signal: ground (ethereal and mobile), satellite, cable television (both classical and IPTV). At higher levels of OSI, conditional access systems are standardized, ways to organize information for transmission in IP media, various metadata.

hDSL (Eng. Digital Subscriber Line, Digital Subscriber Line) - Family of Technologies to significantly increase the bandwidth of the subscriber line of the public telephone network by using effective linear codes and adaptive methods for correcting line distortion based on modern achievements of microelectronics and digital signal processing methods.

In the abbreviation XDSL, the X symbol is used to designate the first character in the title of the specific technology, and the DSL denotes the DSL digital subscriber line (Eng. Digital Subscriber Line - digital subscriber line; there is also another name option - Digital Subscriber Loop - Digital Subscriber plume). HDSL technology allows you to transmit data with speeds, significantly exceeding those speeds that are also available to the best analog and digital modem. These technologies support voice transmission, high-speed data transmission and video signals, while creating significant advantages for both subscribers and providers. Many HDSL technologies allow combining high-speed data transmission and voice transmission on the same copper pair. The existing types of HDSL technologies differ mainly according to the modulation form and data rate used.

The main types of XDSL includes ADSL, HDSL, IDSL, MSDSL, PDSL, RADSL, SDSL, SHDSL, UADSL, VDSL. All these technologies provide high-speed digital access via the subscriber telephone line. Some XDSL technologies are original developments, others are simply theoretical models, while the third has already become widespread standards. The main differences in these technologies are modulation methods used to encode data.

Wide access to XDSL has a number of advantages compared to ISDN technology. The user receives integrated service of two networks - telephone and computer. But for the user, the availability of two networks is inconspicuous, it is only clear for it that it can simultaneously use the usual telephone and connected to the Internet computer. The speed of computer access at the same time exceeds the capabilities of the ISDN PRI network interface with a significantly lower cost determined by the low cost of IP network infrastructure.

Data Over Cable Service Interface Specifications (DOCSIS) - standard data transmission standard for a coaxial (television) cable. This standard provides for data transfer to the subscriber over a cable television network with a maximum speed of up to 42 Mbps and receiving data from the subscriber at a speed of up to 10.24 Mbps. It is designed to change the earlier solutions based on the branded data transfer protocols and modulation methods that are incompatible with each other, and must guarantee the compatibility of the equipment of various manufacturers.

DOCSIS 1.1 additionally provides for the presence of special mechanisms that improve support for IP telephony, reduce speech transmission (for example, mechanisms for fragmentation and assembling large packets, organizing virtual channels and tasks of priorities).

Docsis has direct support for IP protocol with non-fixed long packets, unlike DVR-RC, which uses ATM Cell Transport to transmit IP packets (that is, the IP package is first translated into ATM format, which is then transmitted via cable; on the other side The reverse process is performed).

Ethernet (from the English. Ether - "Ether" and English. Network - "Network, Chain") - a family of packet data technology for computer networks. Ethernet standards define wired connections and electrical signals at the physical level, frame format and medium access control protocols - on channel level of the OSI model. Ethernet is mainly described by the 802.3 IEEE standards.

The name "Ethernet" (literally "ether network" or "network environment") reflects the initial principle of operation of this technology: everything transmitted by one node is simultaneously accepted by all the others (that is, there is some kind of similarity with broadcasting). Currently, there is almost always a connection through switches (Switch), so that the frames sent by one node reach only to the addressee (the exception is transmitted to the broadcast address) - it increases the speed and safety of the network.

When designing an Ethernet standard, it has been provided that each network card (as well as the built-in network interface) must have a unique six-scale number (MAC address), stitched in it in the manufacture. This number is used to identify the sender and the recipient of the frame, and it is assumed that when the new computer appears in the network (or another device capable of working on the network), the network administrator does not have to configure the MAC address.

The uniqueness of MAC addresses is achieved by the fact that each manufacturer receives a range of sixteen million (224) addresses in the Coordinating IEEE Registration Authority Committee, and as the dedicated addresses expedited can request a new range. Therefore, by three senior bytes of MAC addresses, you can determine the manufacturer. There are tables that allow you to determine the manufacturer by the MAC address; In particular, they are included in Arpalert programs.

The MAC address is read once from the ROM when initializing a network card, in the future, all frames are generated by the operating system. All modern operating systems allow it to change it. For Windows, starting at least with Windows 98, it changed in the registry. Some network card drivers allowed to change it in the settings, but the shift works absolutely for any cards.

Some time ago, when network card drivers did not give the ability to change their MAC address, and alternative features were not too known, some Internet providers used it to identify the machine on the network when traffic. Programs from Microsoft Office, starting with the Office 97 version, recorded the MAC address of the network card to the editable document as a component of a unique GUID identifier.

Quick Ethernet varieties: Gigabit Ethernet (Gigabit Ethernet, 1 Gbit / s), 2.5- and 5-gigabit variants NBASE-T, MGBase-T, 10-Gigabit Ethernet (10G Ethernet, 10 Gb / s), 40-gigabit and 100 gigabit Ethernet.

About Terabit Ethernet (so simplisticly called Ethernet technology with a transmission rate of 1 Tbit / s) became known in 2008 from the application of the creator of Ethernet Bob Metcalph at one of the conferences dedicated to fiber optic communications, which suggested that the technology will be developed by 2015, the truth without expressing any confidence at the same time, because for this it will have to solve a lot of problems. However, in his opinion, the key technology that can serve further traffic growth will be one of the DWDM developed in the previous decade.

Fiber to the x or fttx (eng. Fiber to the X - optical fiber to point X) is a common term for any broadband telecommunication network of data transmission using a fiber optic cable in its architecture as the last mile to provide all or parts of the subscriber line. The term is collective for several configurations of deploying fiber - ranging from FTTN (to the node) and ending with FTTD (to the desktop).

In strict definition, FTTX is only a physical data transfer, but in fact, the concept is covered by a large number of channel and network level technologies. With a wide strip of FTTX systems, the possibility of providing a large number of new services is inextricably linked.

Depending on the conditions of use, the telecommunications industry distinguishes several individual FTTX configurations:

FTTN (Fiber to the node) - fiber to the network node. Fiber opens in an outdoor communication cabinet, perhaps 1-2 km from the end user, with further copper laying - it can be XDSL or hybrid fiber-coaxial lines. FTTN is often an intermediate step to full FTTB and, as a rule, is used to deliver the extended TRIPLE Play Pack of telecommunications services.

Fiber To Curb / Fiber To the Kerb) - fiber to the neighborhood, quarter or group of houses. The option is quite similar to the FTTN, but the street cabinet or post closer to the client's premises and is, as a rule, within 300 meters - distances for broadband copper cables, similar to a wired Ethernet or communication on IEEE 1901 LPG or Wi-Fi wireless technology. Sometimes FTTC is ambiguously called FTTP (fiber-to-the-pole, optics to a pillar), which causes confusion with "Fiber To the Premises System" (optics to the room system).

Fiber to the Distribution Point - fiber to distribution point. It also looks like FTTC / FTTN, but one more step closer. The fiber opens a few meters from the end consumer border and the last cable connection takes place in the distribution box, called the distribution point, which allows subscribers close to gigabit velocity.

FTTP (Fiber To the Premises) - fiber to the room. This abbreviation summarizes the terms FTTH and FTTB or used in cases where the fiber is summarized where at the same time there are homes and small business.

FTTB (Fiber To the Building) - fiber comes to the border of a building, such as the foundation of an apartment building, a basement or a technical floor with the final connection of each residential premises using alternative methods in FTTN or FTTP configurations.

FTTH (Fiber to the home) - fiber to home, apartment or separate cottage. The cable is communicated to the border of the residential area, for example, a communication box on the housing wall. Next, the subscriber of the operator's services are provided by the PON and PPPoE technology through FTTH networks.

Fiber To The Desktop, Fiber To the Subscriber) - The optical connection comes to the main computer room into the terminal or the media converter near the client's desktop.

Fiber To The Telecom Enclosure, Fiber To The Zone) is a view of the cable system commonly used in the local network of enterprises when the optical connection is used from the server room to the workplace. These species are not included in the FTTX technology group, despite the similarity in the names.

Hardware Architecture and Connection Types

The simplest optical network architecture is straight fiber. With this method, each fiber in the cable from the premises of the telecom operator goes to one client. Such networks can provide excellent data transfer rate, but they are significantly more expensive due to the irrational use of fibers and equipment serving communication line.

Straight fibers are usually provided to large corporate clients or government agencies. The advantage is the possibility of using the 2nd network technologies, regardless of whether it is an active, passive or hybrid optical network.

In the other cases (mass connections of subscribers), each fiber coming from the telecom operator serves a variety of clients. It is called "total fiber" (eng. Shared Fiber). At the same time, optics are communicated as close as possible to the client, after which it is connected to the individual, reaching the end consumer with fiber. Such a connection is used both active and passive optical networks.

Depending on the method of building optical networks are divided into:

active optical networks - with operating active network equipment for amplifying and transmitting the signal;

passive optical networks - with splitters of optical signals;

hybrid optical networks - using active and passive components simultaneously.

Active optical network

Based on the transmission of the optical signal with network electrical equipment receiving, reinforcing and transmitting these signals. It can be a switch, a router, a media converter - as a rule, optical signals in the active optical network are converted into electrical and back. Each optical signal from the centralized equipment of the telecom operator only to the end user for which it is intended.

The signals incoming from the subscribers avoid conflicts in a single fiber, as electrical equipment provides buffering. As the first mile from the equipment operator equipment, active ETTH equipment is used, which includes optical network switches with optics, and an employee to distribute the signal to subscribers.

Similar networks are identical to computer networks Ethernet used in offices and educational institutions with the only exception that they are intended to connect houses and buildings to the central building of the telecom operator, and not to connect computers and printers in a limited space. Each distribution cabinet can serve up to 1000 subscribers, although it is usually limited to connecting 400-500 people.

Such nodal equipment provides switching of the second and third levels, as well as routing, unloading the main router of the telecom operator and providing data transfer to its server room. The IEEE 802.3ah standard allows Internet service providers to provide speeds of up to 100 Mbps and a complete duplex over a single-mode fiber optic cable (Eng. Single-Mode Optical Fiber) connected according to the FTTP scheme. Commercially available also become speeds of 1 Gb / s.

Remote access (eng. Dial-up - "Dialing, call") - a service that allows a computer using a modem and a common telephone network to connect to another computer (access server) to initialize the data transmission session (for example, for access On the Internet). Usually a Dial-UP "Ohm calls only Internet access on the home computer or remote modem access to the corporate network using the PPP two-point protocol (you can theoretically use and outdated SLIP protocol).

Telephone communication via modem does not require any additional infrastructure except the telephone network. Since telephone points are available throughout the world, such a connection remains useful for travelers. Connecting to the network using a modem on a conventional switchable telephone line - a single choice available for most rural or remote areas, where the production of broadband is impossible due to the low population density and requirements. Sometimes connecting to the network using a modem can also be an alternative to people with a limited budget, as it is often offered for free, although the broadband network is now more and more accessible at lower prices in most countries. However, in some countries, commutable access to the Internet remains basic due to the high cost of broadband access, and sometimes the lack of demand for the population. Dialing takes time to establish a connection (for a few seconds, depending on the location) and confirmation of the connection was made before the data transfer can be implemented.

The cost of accessing the Internet through dial-up access is often determined by the time spent by the user on the network, and not by the volume of traffic. A telephone line access is a non-permanent or temporary connection, because at the request of the user or ISP will sooner or later be broken. Internet service providers often establish a restriction on the duration of communication and disconnect the user after the expiration time, as a result, it is necessary to re-connect.

In modern modem connections, the maximum theoretical velocity is 56 kbps (using V.90 or V.92 protocols), although in practice the speed rarely exceeds 40--45 kbps, and in the overwhelming majority of cases holds at no more than 30 Kbit / s. Factors such as the noise in the telephone line and the quality of the modem itself plays a large role in the value of communication velocities. In some cases, in a particularly noisy line, speed can fall up to 15 kbps and less, for example in a hotel room, where the telephone line has many branches. The telephone connection through the modem is usually a high delay time, which comes to 400 milliseconds or more and which makes online games and video conferences is extremely difficult or completely impossible. The first first-person games (3D-Actions) are the most sensitive response time, making the game on the modem is impractical, but some games such as Star Wars Galaxies, The Sims, Warcraft 3, Guild Wars and Unreal Tournament, Ragnarok Online, The same is capable of functioning on a connection of 56 kbps.

When the phone-based modem 56 kbps began to lose popularity, some Internet service providers, such as Netzero and Juno, began to use pre-compression to increase bandwidth and support the client base. For example, Netscape ISP uses a compression program that compresses images, text, and other objects before sending them through the telephone line. Compressing from the server works more efficiently than "continuous" compression, supported by v.44 modems. Usually, the text on websites is compacted to 5%, thus the bandwidth increases to approximately 1000 kbps, and the images are compressed with losses to 15-20%, which increases the bandwidth to ~ 350 kbps.

The disadvantage of this approach is the loss of quality: graphics acquires compression artifacts, but the speed increases sharply, and the user can manually choose and consider uncompressed images at any time. Providers using such an approach advertise it as "DSL speed on ordinary telephone lines" or simply "high-speed Dialup".

Replacing a broadband network

Starting with (approximately) 2000, broadband Internet access on DSL technology has replaced access through a regular modem in many parts of the world. Broadband typically proposes speed from 128 kbps and above for a smaller price than Dialup. All increasing content volume in areas such as video, entertainment portals, media, etc., no longer allows sites to work on Dialup modems. However, in a variety of areas, the dial-up access is still in demand, namely where high speed is not required. In part, this is due to the fact that in some regions, the laying of broadband networks is economically unprofitable or for one reason or another is impossible. Although there are wireless broadband access technologies, but due to the high cost of investments, low yield and poor quality of communication are difficult to organize the necessary infrastructure. Some communication operators providing Dialup responded to all increasing competition, lowering tariffs for values \u200b\u200bof 150 rubles per month and make Dialup an attractive choice for those who simply want to read emails or view news in text format.

ISDN (English Integrated Services Digital Network) is a digital network integration. Allows you to combine telephone services and data exchange services.

The main purpose of ISDN is the transfer of data at a speed of up to 64 kbps by a subscriber wired line and ensuring integrated telecommunication services (telephone, fax, etc.). The use of telephone wires for this purpose has two advantages: they already exist and can be used to supply power to terminal equipment.

The 64 Kbps selection of the standard is determined by the following considerations. With the frequency band of 4 kHz, according to the Kotelnikov Theorem, the sampling frequency should be not lower than 8 kHz. The minimum number of binary discharges to represent the results of the voice signal gating under the logarithmic conversion is 8. Thus, as a result of multiplying these numbers (8 kHz * 8 (the number of binary discharges) \u003d 64) and the value of the ISDN B channel value is 64 kb /from. The basic configuration of the channels has a form 2 h b + d \u003d 2 h 64 + 16 \u003d 144 kbps. In addition to B-channels and auxiliary D-channel, ISDN can also offer other channels with a greater bandwidth: H0 channel with a band 384 Kbps, H11 - 1536 Kbps and H12 - 1920 Kbps (real digital stream speeds ). For primary channels (1544 and 2048 kbps), the d-channel band may be 64 kbps.

Principle of operation

To combine ISDN networks of various types of traffic, TDM technology is used (English Time Division Multiplexing, time multiplexing). For each data type, a separate bar is released, called an elementary channel (or standard channel). For this band, a fixed, consistent share of bandwidth is guaranteed. The band isolation occurs after the call signal is supplied via a separate channel called the non-channel signaling.

The basic types of channels are defined in ISDN standards, from which various user interfaces are formed (Appendix 1).

In most cases, binary channels are used.

The interfaces are formed from the specified channel types, the following types were obtained.

Basic level interface (Basic Rate Interface, BRI) - provides for the communication of the subscriber's equipment and the ISDN station two B-channels and one D-channel. The base level interface is described by formula 2b + d. In the standard operation of the BRI operation, both B channels can be used simultaneously (for example, one for data transmission, another for voice transmission) or one of them. With simultaneous operation of the channels, they can provide a connection with different subscribers. The maximum data transfer rate for the BRI interface is 128kb / s. The D-channel is used only to transmit control information. In AO / Di mode (Always On / Dynamic ISDN), the 9.6 bar / c D-channel bar is used as a permanently enabled selected channel X.25, as a rule, connected to the Internet. If necessary, the band used to access the Internet is expanded by turning on one or two B-channels. This mode, although standardized (under the name x.31), did not find widespread. For incoming BRI connections, up to 7 addresses (numbers), which can be assigned by various ISDN devices separating one subscriber line. Additionally provides compatibility mode with conventional, analog subscriber devices - ISDN subscriber equipment, as a rule, allows connecting such devices and allows them to work transparent. An interesting side effect of such a "pseudo-analytade" mode of operation was the possibility of implementing a symmetric modem protocol X2 of the company US Robotics, which allowed the data transmission over the ISDN line in both directions at a speed of 56 kbps.

The most common type of signaling is Digital Subscriber System No. 1 (DSS1), also known as EURO-ISDN. Two trunk ports of BRI ports are used relative to the station or telephones - S / those and NT. S / Those mode - the port emulates the operation of the ISDN phone, NT mode - emulates the station. A separate addition is the use of an ISDN phone with additional power in this mode, since the standard not all ports (and HFC cards) are powered by an ISDN-loop (eng. Inline Power). Each of the two modes can be "point-multiple" (English Point-to-Multi-Point, PTMP) is also MSN (eng. Multiple Subscriber Number), or "Point-to-point" (English Point-to-Point, PTP). In the first mode, the MSN numbers are used to search for the destination destination on the loop, which, as a rule, coincide with the dedicated telephony provider with city numbers. The provider must inform MSN transmitted to them. Sometimes the provider uses the so-called "technical numbers" - intermediate MSN. In the second mode, BRI ports can be combined into a trunk - a conditional highway, which transmitted numbers can be used in multichannel mode.

ISDN-technology uses three main types of interface BRI: U, S and T.

U is one twisted pair, laid from the switch to the subscriber working in full or half-duplex. Only 1 device called a network end (eng. Network Termination, NT-1 or NT-2) can be connected to the U-interface.

S / T interface (S0). Two twisted pairs, transmission and reception are used. It can be compressed both in the RJ-45 and RJ-11 socket / cable. The interface socket of the interface can be connected by one cable (loop) on the tire principle to 8 ISDN devices - phones, modems, faxes called TE1 (Terminal Equipment 1). Each device listens to the bus requests and responds to the MSN attached to it. The principle of operation is largely similar to SCSI.

NT-1, NT-2 - Network Termination, Network Ending. Converts one pair U in one (NT-1) or two (NT-2) 2 paired S / T interface (with separate pairs for receiving and transmission). In essence, S and T are the same interfaces, the difference is that the s-interface can be powered for TE devices, such as phones, and T - no. Most NT-1 and NT-2 converters are able both, therefore, the interfaces are most often called S / T.

Primary level interface

• (PRIMARY RATE INTERFACE, PRI) - used to connect to broadband highways connecting local and central PBXs or network switches. The primary level interface combines:
• * For standard E1 (distributed in Europe) 30 B channels and one D-channel 30b + d. PRI elementary channels can be used both for data transmission and to transmit a digitized telephone signal.
• * For standard T1 (distributed in North America and Japan, as well as in DECT technology) 23 V-channel and one D-channel 23b + d.

ISDN network architecture

The ISDN network consists of the following components:

network terminal devices (NT, eng. Network Terminal Devices)

linear Terminal Devices (LT, English Line Terminal Equipment)

terminal Adapters (TA, Eng. Terminal Adapters)

subscriber terminals

Subscriber terminals provide users with access to network services. There are two types of terminals: TE1 (specialized ISDN terminals), TE2 (non-specialized terminals). TE1 provides direct connection to the ISDN, TE2 network requires the use of terminal adapters (TA).

Interesting Facts

Of the more than 230 basic functions of ISDN, only a very small part of them is actually used (in demand by the consumer).

PLC - (Power Line Communication) - Communication built on power lines.

Communication via PLC is a term describing several different systems to use power lines (LEP) to transmit voice information or data. The network can transmit voice and data by overlapping an analog signal over a standard alternating current with a frequency of 50 Hz or 60 Hz. PLC includes BPL (Broadband Over Power Lines - broadband transmission through power lines), providing data transmission at speeds up to 500 Mbps, and NPL (eng. Narrowband Over Power Lines - narrowband transmission through power lines) with significantly smaller data transmission speeds up to 1 Mbps.

PLC technology is based on the use of power grid for high-speed information metabolism. Experiments on the transfer of data on the electrical network was carried out quite a long time, but low transmission rate and weak noise immunity were the most narrow place of this technology. The appearance of more powerful DSP processors (digital signal processors) made it possible to use more complex modulation methods, such as OFDM modulation, which made it possible to significantly move forward in the implementation of the PLC technology.

In 2000, several major leaders in the telecommunications market were united in HomePlug Powerline Alliance in order to jointly conduct research and practical testing, as well as the adoption of a single standard for transmitting data on power systems. The Powerline prototype is Intellon's PowerPacket technology, based on the creation of a single HOMEPLUG1.0 standard (accepted by the HomePlug Alliance June 26, 2001), which determines the data transfer rate up to 14 MB / s.

However, at the moment, the HOMEPLUG AV standard has raised the data transfer rate to 500 Mbps.

Technical Basics of PLC Technology

The basis of POWERLINE technology is the use of a frequency separation of a signal at which a high-speed data stream is separated by several relatively low-speed flows, each of which is transmitted on a separate subcarrier frequency with their subsequent combination into one signal. Really in PowerLine technology uses 1536 subcarriers with the allocation of 84 best in the range of 2--34 MHz.

When transmitting signals for the household electrical power grid, large attenuation may occur in the transmitting function at certain frequencies, which can lead to data loss. The PowerLine technology provides a special solution to this problem - dynamic signaling signal (Dynamically Turning Off and On Data-Carrying Signals). The essence of this method is that the device performs constant monitoring of the transmission channel in order to detect the spectrum section with an exception of a certain threshold attenuation value. In case of detection of this fact, the use of these frequencies is terminated until the normal attenuation value is restored, and the data is transmitted at other frequencies.

There is also a problem of the occurrence of pulse interference (up to 1 microsecond), the sources of which may be halogen lamps, as well as the inclusion and turning off of powerful household electrical appliances equipped with electric motors.

Application PLC technology to connect to the Internet

Currently, the overwhelming majority of end connections are carried out by laying a cable from a high-speed line to an apartment or user office. This is the cheapest and reliable solution, but if the cable laying is not possible, you can use the system electrical electrical communications system available in each building. In this case, any electrical outlet in the building can be an Internet access point. The user requires only the presence of a PowerLine-modem to communicate with a similar device installed, as a rule, in a switchboard and connected to a high-speed channel. The PLC can be a good solution of the "last mile" in the cottage villages and in low-rise buildings, due to the fact that traditional wires are several times more expensive PLC.

PON (Abbr. From English. Passive Optical Network, Passive Optical Network) - Technology of Passive Optical Networks.

The PON access network is based on a tree-like fiber-cable architecture with passive optical splitters on nodes, represents an economical way to ensure broadband information transmission. In this case, the PON architecture has the necessary efficiency of increasing network nodes and bandwidth, depending on the present and future needs of subscribers.

The first steps in PON technology were undertaken in 1995, when a group of 7 companies (British Telecom, France Telecom, Deutsche Telecom, NTT, KPN, Telefonica and Telecom Italia) created a consortium to implement the idea of \u200b\u200bmultiple access by one fiber.

Standards

APON (ATM Passive Optical Network).

BPON (Broadband PON)

GPON (Gigabit Pon)

EPON or GEPON (Ethernet PON)

10Gepon (10 Gigabit Ethernet PON)

Development of PON standards

NGPON 2 standards are the specifications of the further development of GPON and EPON technologies. Today, the role of the NGPON 2 standard claims at least three technologies:

"Pure" (Pure) WDM PON

Hybrid (TDM / WDM) TWDM PON

UDWDM (Ultra Dense WDM) PON

The main idea of \u200b\u200bthe PON architecture (the principle of operation) is the use of only one receiving module in the OLT (eng. Optical Line Terminal) to transmit information by a multitude of ONT subscriber devices (Optical Network Terminal in ITU-T terminology), also called OPTICAL Network Unit In the IEEE terminology and reception of information from them.

The number of subscriber nodes connected to one OLT selection module may be so large as the power budget and the maximum speed of the receiving instrument. To transfer the flow of information from OLT to ONT - direct (downward) flow, as a rule, a wavelength of 1490 nm is used. On the contrary, data streams from different subscriber nodes to the central node sharing the forming reverse (ascending) stream are transmitted at a wavelength of 1310 nm. A wavelength of 1550 nm is used to transmit a television signal. The OLT and ONT built-in WDM multiplexers separating outgoing and incoming threads.

Direct flow

The direct stream at the optical signals level is broadcast. Each subscriber node ONT, reading the address fields, highlights from this common stream, part of the information only to it. In fact, we are dealing with a distributed demultiplexer.

Reverse flow

All subscriber nodes ONT are transmitted in the reverse stream on the same wavelength, using the TDMA Time Division Multiple Access, multiple access concept. To exclude the ability to cross the signals from different ONTs, for each of them, its individual data transmission schedule is set to the delay correction associated with the removal of this ONT from the OLT. This task is solved by the TDMA protocol.

Topology access networks

There are four main topologies for building optical access networks:

"ring";

"Point-to-point";

"Tree with active nodes";

"Tree with passive nodes."

Advantages of PON technology

lack of intermediate active nodes;

saving optical receptionists in the central node;

saving fibers;

P2MP tree topology allows you to optimize the placement of optical splitters, based on the real location of the subscribers, the cost of gasket OK and the operation of the cable network.

The disadvantages of the PON network technology can be attributed:

the increased complexity of PON technology;

no reservation in the simplest tree topology.

Wireless technology:

Satellite Internet

Wi-Fi is a Wi-Fi Alliance brand for wireless networks based on IEEE 802.11. Under the Wi-Fi abbreviation (from the English phrase of Wireless Fidelity, which can be literally translated as "Wireless Quality" or "Wireless Accuracy") Currently develops a whole family of transmission standards for transmitting digital data streams on radio channels.

Any equipment that meets the IEEE 802.11 standard can be tested in Wi-Fi Alliance and obtain the appropriate certificate and the right of Wi-Fi logo.

Wi-Fi was created in 1996 in the CSiro radio astronomy laboratory (Commonwealth Organization) in Canberre, Australia. The creator of the wireless data exchange protocol is an engineer John about Sullivan (John O "Sullivan).

The IEEE 802.11n standard was approved on September 11, 2009. Its application allows you to increase the data transfer rate almost four times compared to 802.11g standards devices (the maximum speed of which is 54 Mbps), provided in the 802.11n mode with other 802.11n devices. Theoretically 802.11n is capable of providing data transfer rate to 600 Mbps. From 2011 to 2013, the IEEE 802.11ac standard was developed. Data transfer rate When using 802.11AC can reach multiple Gb / s. Most of the leading equipment manufacturers have already announced devices that support this standard.

On July 27, 2011, the Institute of Electrical Engineering and Electronics Engineers (IEEE) issued the official version of the IEEE 802.22 standard. Systems and devices that support this standard allow you to receive data at speeds up to 22 Mbps within a radius of 100 km from the nearest transmitter.

Principle of operation

Typically, the Wi-Fi network scheme contains at least one access point and at least one client. It is also possible to connect two customers in point-point mode (AD-HOC) when the access point is not used, and clients are connected via network adapters "directly". The access point transmits its SSID network identifier using special signal packets at a speed of 0.1 Mbps every 100 ms. Therefore, 0.1 Mbps is the smallest data transfer rate for Wi-Fi. Knowing the SSID network, the client can find out if connecting to this access point is possible. If you get into the zone, two access points with an identical SSID receiver can choose between them based on the signal level data. The Wi-Fi standard gives the client complete freedom when choosing criteria for the connection.

However, the standard does not describe all aspects of building wireless LAN Wi-Fi networks. Therefore, each equipment manufacturer solves this task in its own way, applying those approaches that he considers the best from one or another point of view. Therefore, it is necessary to classify how to build wireless local networks.

By the method of combining access points in a single system, you can allocate:

Autonomous access points (also called independent, decentralized, smart)

Access points running the controller (also called "lightweight", centralized)

Uncontrollable but not autonomous (controlled without controller)

By the method of organizing and managing radio channels, you can allocate wireless local networks:

With static radio channels

With dynamic (adaptive) settings of the radio channels

With a "layered" or multilayer structure of the radio channels

Benefits Wi-Fi

Allows you to deploy a network without cable laying, which can reduce the cost of deploying and / or network expansion. Places where the cable cannot be paved, for example, outdoors and in buildings with historical value can be serviced by wireless networks.

Allows you to access the network to mobile devices.

Wi-Fi devices are widespread on the market. Equipment compatibility is guaranteed thanks to the mandatory certification of equipment with Wi-Fi logo.

Mobility. You are no longer tied to one place and you can use the Internet in a comfortable setting for you.

Within the Wi-Fi zone on the Internet, there are several users from computers, laptops, phones, etc.

Radiation from Wi-Fi devices at the time of data transfer to the order (10 times) is less than that of the cell phone.

Discharge Wi-Fi

In the range of 2.4 GHz, there are many devices, such as devices that support Bluetooth, etc., and even microwave ovens, which worsens electromagnetic compatibility.

Equipment manufacturers are indicated by the speed on L1 (OSI), as a result of which the illusion is created that the equipment manufacturer highlights the speed, but in fact in Wi-Fi a very high service "overhead costs". It turns out that the data transfer rate on L2 (OSI) in the Wi-Fi network is always below the declared speed on L1 (OSI). The actual speed depends on the share of service traffic, which depends on the presence between the devices of physical obstacles (furniture, walls), the presence of interference from other wireless devices or electronic equipment, the location of the devices relative to each other, etc.

The frequency range and operational restrictions in different countries are not the same. In many European countries, two additional channels are allowed that are prohibited in the United States; In Japan, there is another channel at the top of the range, and other countries, such as Spain, prohibit the use of low-frequency channels. Moreover, some countries, such as Russia, Belarus and Italy, require registration of all Wi-Fi networks operating outdoors, or require registration of a Wi-Fi operator.

In Russia, wireless access points, as well as Wi-Fi adapters with EIM, exceeding 100 MW (20 dBm), are subject to mandatory registration.

The WEP encryption standard may be relatively easily hacked even with proper configuration (due to weak resistance of the algorithm). New devices support more advanced WPA and WPA2 data encryption protocols. The adoption of the IEEE 802.11 (WPA2) standard in June 2004 made it possible to use a safer communication scheme, which is available in new equipment. Both schemes require a more resistant password than those that are usually assigned to users. Many organizations use additional encryption (for example, VPN) to protect against invasion. At the moment, the main method of hacking WPA2 is a password selection, so it is recommended to use complex digital-letter passwords in order to complicate the password selection task as much as possible.

In point-to-point mode (AD-HOC), the standard prescribes only to realize the speed of 11 Mbps (802.11b). Encryption WPA (2) is not available, only the liquefied WEP.

Wi-Fi is suitable for using VoIP in corporate networks or in SOHO environment. The first samples of the equipment appeared in the early 2000s, but they came to the market only in 2005. Then companies like Zyxel, UT Starcomm, Samsung, Hitachi and many others, presented to the VoIP Wi-Fi phones on the "reasonable" prices. In 2005, ADSL ISP providers began to provide VoIP services to their customers (for example, Netherlands ISP XS4All). When calls with VoIP became very cheap, and often free, providers that can provide VoIP services have the opportunity to open a new market for VoIP services. GSM phones with integrated support for Wi-Fi and VoIP capabilities began to be output, and potentially they can replace wiring phones.

Currently, the direct comparison of Wi-Fi and cellular networks is inappropriate. The phones using only Wi-Fi have a very limited range of action, so the deployment of such networks is very expensive. However, the deployment of such networks may be the best solution for local use, for example, in corporate networks. However, devices supporting several standards may occupy a significant market share.

It is worth noting that in this particular place of covering both GSM and Wi-Fi, it is economically much more profitable to use Wi-Fi, talking through Internet telephony services. For example, the Skype client has long exist in versions for both smartphones and PDAs.

International projects

Another business model consists in connecting already available networks in new ones. The idea is that users will share their frequency range through personal wireless routers equipped with special software. For example, FON is a Spanish company established in November 2005. Now the community unites more than 2,000,000 users in Europe, Asia and America and is developing rapidly. Users are divided into three categories:

linus - allocate free internet access,

bills - selling your frequency range,

aliens - using access via Bills.

Thus, the system is similar to peerge services. Despite the fact that FON receives financial support from companies such as Google and Skype, only with time it will be clear whether this idea really will work.

Now this service has three main problems. The first is that to transition a project from the initial stage, more attention is required by the public and the media. It is also necessary to take into account the fact that providing access to your Internet channel to other persons may be limited to your contract with an Internet provider. Therefore, Internet providers will try to protect their interests. Also, most likely, sound recording companies will come against the free distribution of MP3s.

In Russia, the main number of access points of the FON community is located in the Moscow region.