Data transfer via adsl. aDSL Technology Basics

    Testing Methodology for ADSL

    The testing methodology is intended to evaluate and visually display test results when problems arise when working on the Internet.
    You can read how to take a “screenshot” .

    We draw your attention to some features of working on the Internet:
    1) When the Subscriber connects to its Data Network, the Provider is not responsible for the quality of communication outside the subscriber's terminal device (if any) connected to the Provider's equipment.
    The provider guarantees Internet access speed only under the condition of a direct connection, i.e. The Provider's cable connects directly to a laptop or personal computer. You can read more about the Procedure for the provision of services.
    2) You can familiarize yourself with the division of areas of responsibility between the Provider and the Subscriber.
    3) When using ADSL technology, the data transfer speed is always less speed connections by at least 13-15%. This is a technological limitation, which we will discuss in more detail later. It does not depend on the provider or the modem used.
    IN ideal conditions with a connection speed of 12 Mbit/s you can count on maximum real speed~ 10 Mbit/s.
    Note! You can find out more about the factors affecting the data transfer speed when using ADSL technology.

    Attention! If you use Wi-Fi wireless networks to surf the Internet, it will be useful for you to read the information below.
    1. Sources of interference affecting the operation of wireless Wi-Fi networks may be the following:
    - material of walls and partitions in your apartment or office;
    - location of your neighbors' Wi-Fi points. For example, if your neighbor’s point is located near the wall adjacent to your apartment, and your point, in turn, is located near this wall, then the signals from both points will interrupt each other;
    - Wi-Fi module in your PC or other mobile device. A mobile device may not have the most modern module installed, which has a maximum speed limit;
    - simultaneous downloading from different devices, both inside your apartment and at neighboring points outside your apartment;
    - Bluetooth devices operating within the coverage area of ​​your Wi-Fi device;
    - various household appliances, which operates using the 2.4 GHz frequency range and operates within the coverage area of ​​your Wi-Fi device.
    You can find out more about possible sources of interference affecting the operation of wireless Wi-Fi networks.

    2. To speed up your work on the Internet and make it more stable, you need to:
    - configure the router to work with mobile devices. How to do this on a TP-Link router, see;
    - choose a freer channel;
    - select the optimal location of the Wi-Fi point;
    - purchase an external Wi-Fi adapter;
    - use a dual-antenna wireless access point operating in the 2.4 GHz band;
    - use a wireless access point operating in the 5 GHz band;
    - work via Ethernet cable.

    Learn more about ways to increase connection speed and bandwidth Wi-Fi can be found.

    Testing methodology

    Attention! If you are connected via additional equipment or use Wi-Fi wireless networks, you must first connect the Internet cable directly to your laptop or personal computer without additional devices, and then perform the speed testing method.

    To obtain adequate results during each of the test points, NO work on the Internet should be carried out!

    For Windows OS
    Download the archive. Unpack it to any folder on your computer. The file should appear in the same folder TEST.bat. We launch it and wait from 10 to 20 minutes (depending on the quality of the DSL connection).
    Attention! For Windows 7 and Windows 8, you must run the file as an administrator (right-click on TEST.bat and select “Run as Administrator”). When the BAT file has completed all the actions, you will see the following window.

    Press any key on the keyboard and the window will close. After that we go to Drive C and find text files there PING.txt, PATHPING.txt And CONFIG.txt . We attach these files to the results.

    For Mac OS X
    Download the archive. Unpack it to any folder on your computer. After unpacking, a file should appear in the same folder Test.app. We launch it and wait from 10 to 20 minutes. After completing the test, press any key on the keyboard - the window will close.
    Once testing is complete, three text files will appear on your desktop - CONFIG, PING, TRACEROUTE. We attach these files to the results.

  • We measure Internet speed.
    A) Let's go by link and press the button "Begin Test". We are waiting for the test to complete.

    When the test is completed, you will be presented with a window similar to this. Let's make it " screenshot” and attach it to the results.

    b) Download the file (size about 75 MB) from here: http://www.apple.com/itunes/download/
    We start downloading by clicking on the button "Download Now".
    During the download process we do "screenshot"
    Attention! To display the download speed in the browser, you need to go to the Downloads section by pressing the key combination Ctrl+J.

    With) Upload the file large size(about 2.3 GB) from here:
    ftp://ftp.freebsd.org/pub/FreeBSD. During the download process we do "screenshot" Your download manager or browser and attach it to the testing results.
    Attention! There is no need to download the entire file! It’s enough to wait a minute or two until a stable speed is established, then do 2-3 “ screenshot"with an interval of 20-30 seconds and stop the download.

    d) Download the file using a torrent client. For correct speed testing, it is necessary to exclude local retrackers. You can see how to do this.
    Attention! It is necessary to test the connection speed when downloading 3-4 files at the same time, for which the number of uploaders is more than 100. During the download process, do “ screenshot» Your torrent client and attach it to the test results.

  • We measure speed from internal resources. For this Minsk subscribers come in next link .

    On the website click on "Change Server".

    In the search bar we write "Atlant Telecom" and select it as a server.

    Then press the button "GO".
    We are waiting for testing to be completed.

    As a result, a window with the results should appear.

    We take a screenshot and attach it to the overall results.

    Regional subscribers go to the following links and download the file:
    - link for Brest;
    - link for Vitebsk;
    - link for Grodno;
    - link for Gomel;
    - link for Mogilev.
    During the download process, we take a “screenshot” of your download manager or browser (except Internet Explorer) and attach it to the testing results.

  • Download the program and install it (for D-link brand modems - program).

    Zyxmon- free Windows program for managing and monitoring the status of Zyxel routers.

    Unpack the zip folder using some archiver. For example, WinRAR or WinZIP. Run the executable file " ZyxMon" A program window will open. Click on the button " Settings"(circled in red).

    The following window will appear. Filling out the fields Router IP And Router password. Click " OK».

  • After pressing " OK"we will return to the Main window of the program. We activate the connection with the modem. To do this, press the button " Telnet Router Connections" (circled in pink), while the indicators " Telnet connection status" And " PPPoE session status"will have to change color from red to green.

    Description of bookmarks:
    Telnet: Modem connection status and PPPoE status.
    Log: Modem text log;
    SyslogD: Messages received from the Syslg Daemon modem;
    SNMP: RealTime channel filling statistics;
    DynDNS: Dynamic DNS status (not used);
    Line: Data required for testing the line: noise margin , attenuation . To receive data you need to press the “ Get ”.

    Let's do " screenshot” of the obtained result and attach it to the test results.

    • We check at what speed the modem receives/sends data.

    a) telnet.
    Let's go to command line: Start -> Run -> cmd -> Ok . In the window that appears, write the command telnet (for example, telnet 192.168.1.1) and press the key "Enter". On next step a password request will pop up "Password" , enter the password (by default - 1234 ) and press the key "Enter".
    From the main menu of the modem go to the menu 24.1 - System Maintenance - Status . To do this, press on the keyboard 24 - “Enter”, 1- “Enter”. Let's take screenshots of this window:


    Explanations for the fields of interest to us in this menu:
    Tx B/s - transfer speed in Bytes per second;
    Rx B/s [Reception speed, Bytes/s] - reception speed in Bytes in seconds;
    Up Time [Connection time] - duration of connection between the modem and the provider;
    My WAN IP (from ISP) [my IP address on the global network (from the provider)] - the IP address received by the modem from the provider;
    Line Status [Line status] - current xDSL line status: Up - up, Down - not up;
    Upstream Speed [Outgoing speed] - transmission speed of outgoing traffic in Kbps;
    Downstream Speed [Incoming speed] - transmission speed of incoming traffic in Kbit/s;
    CPU Load [CPU load] - percentage of modem CPU load.

    b) For modems ZyXel 660R, ZyXel 660R-T1, ZyXel 660RU-T1, ZyXel 660HT1, ZyXel 660HW-T1 via WEB interface.

    192.168.1.1 and press the key "Enter". 1234 and press the button "Login". "Ignore"
    In the main menu of the modem, select "System Status". In the window that opens, find the button "Show Statistics" and press it. Let's do " screenshots» last window:
    - first: during downloading from the Internet;
    - second: during downloading from internal resources.
    We name the files accordingly and attach them to the results.

    c) For modems ZyXel 660R-T2, ZyXel 660RU-T2, ZyXel 660HT-2, ZyXel 660HW-T2.

    Type in the address bar of your Internet browser (Chrome, Mozilla Firefox, etc.) the address 192.168.1.1 and press the key "Enter". Next, a window will appear asking for a password. We register 1234 and press the button "Login". A window will appear in which you are advised to change the password for logging into the modem. Press the button "Ignore"
    In the main menu of the modem, click "Status", and in the window that opens, click the link "Packet Statistics".
    As a result, a statistics window will open, do it “ screenshot»:
    - first: during downloading from the Internet;
    - second: during downloading from internal resources.
    We name the files accordingly and attach them to the results.

    d) For D-Link 2500/2540/2600/2640U v.2 modems

    Type 192.168.1.1 in the address bar of your Internet browser (Chrome, Mozilla Firefox, etc.) and press the " Enter " Next, a window will appear asking for a user and password. We register the user - admin and password - admin , press the button " Ok ».
    Next we go to the menu Device Info -> Statistics -> WAN
    As a result, a window will open, do it “ screenshot»:
    - first: during downloading from the Internet;
    - second: during downloading from internal resources.

    We diagnose the DSL channel connection.
    To do this we go: Start -> Run -> cmd -> Ok.
    In the window that appears, write the commands one by one (after each press the key "Enter" ):
    netsh("Enter")
    ras("Enter")
    set tracing ppp enable (“Enter”)
    exit("Enter")
    Next, go to the Windows folder (usually c: Windows) and create a folder there tracing . If it writes to you that such a folder already exists, do not be alarmed. We go into it (example path: c:Windowstracing) and copy the ppp.txt file from there with the results of the commands we entered earlier. We attach this file to the results of the method.

    Analyzing the DSL channel on the modem.

    a) For modems ZyXel 660R, ZyXel 660RT1, ZyXel 660RU1, ZyXel 660HT1, ZyXel 660HW-T1
    We go to the modem configurator, as shown in step 6-a, go to the menu - modem command line. We write the commands one by one (after each press the key "Enter" ):
    wan adsl chandata ("Enter")
    wan adsl opmode (“Enter”)
    wan adsl linedata far (“Enter”)
    wan adsl linedata near (“Enter”)
    wan adsl perf (“Enter”)
    wan hwsar disp (“Enter”)
    Let's do " screenshots» the results obtained. First of all, the state of the 1st (physical) level is analyzed. This information is retrieved using the commands “xdsl state”, “wan adsl linedata far”, “wan adsl linedata near”. Link for information: http://zyxel.ru/kb/1543.
    The main parameters for monitoring are “SNR margin value”, “Loop attenuation” for 782 and 791, and “noise margin downstream”, “attenuation downstream” - for 642, 650, 650, 660. Both values ​​are measured on the receiving channel of the transceiver. The first universally characterizes the noise immunity margin of the line. A level of 6 db roughly corresponds to an error rate of 10E-6 and is the threshold for reliable communication. This parameter clearly depends on the speed, i.e. the higher the speed, the smaller the margin. It is also worth noting that the measured values ​​at each line end device may differ. This indicates that the source of interference is located closer to one end of the line.
    Attenuation downstream is the attenuation of the signal in the line and clearly depends on the active resistance of the wire. The effect of noise on communication quality and maximum speed is higher than that of attenuation. You need to do this several times at different times of the day. The results should be attached to the results of the method.

    b) For modems ZyXel 660RT2, ZyXel 660RU2, ZyXel 660HT2, ZyXel 660HW-T2, ZyXel 660RT3, ZyXel 660RU3, ZyXel 660HT3
    When entering the modem settings via telnet (as shown in point 6-a), you will immediately be taken to the modem command line, where you need to enter the commands indicated above.

    c) For ZyXel 700 series modems (782 and 791)
    In a similar way, go to the modem configurator (see point 6-a) and go to the menu 24.8 - Command Interpreter Mode.
     We write the commands one by one (after each press the key "Enter" ):
    xdsl cnt disp ("Enter")
    wan hwsar disp (“Enter”)
    xdsl state ("Enter")
    Let's do " screenshots» obtained results and attach them to the test results.

    d) For D-Link 2500/2540/2600/2640U v.2 modems
    We go to the modem configurator, as shown in point 6-d, go to the menu Device Info -> Statistics -> ADSL .
    Take a screenshot and attach it to the results.

    We save all the results of the testing methodology in one archive and send them to your email address technical support [email protected] indicating client data (personal account number/organization name, contact phone number/address email) for feedback.

These days, almost everyone needs access to the Internet. Be it work, entertainment, communication - the global network has entered our lives everywhere. To provide Internet access at home or in the office, you need a modem that will allow you to connect all the necessary devices to the network. In large cities, providers offer fiber optic and fiber coaxial systems that allow you to get a fast and stable connection. However, to install such cables, it is necessary that the number of users allows filling the entire bandwidth of the cable - otherwise it is simply not profitable. Therefore, the possibility of such a connection is not provided by businesses everywhere. This is especially true for small cities, towns and villages. What to do if such services are not provided, but you still need the Internet?

There are different options, and one of the best is to use twisted pair telephone wires. Many will remember with horror a phone not working while using the Internet. However, technology has long gone far ahead. Today, xDSL technologies are the most common and effective. DSL stands for digital subscriber line. This technology allows you to achieve fairly high data transfer speeds over copper pairs of telephone wires, without occupying the phone. The fact is that voice transmission uses a frequency range from 0 to 4 kHz, while copper telephone cable can transmit signals with a frequency of up to 2.2 MHz, and it is the section from 20 kHz to 2.2 MHz that xDSL technology uses . The speed and stability of such a connection is affected by the length of the cable, that is, the farther the telephone node (or another modem in the case of creating a network) is located from your modem, the lower the data transfer speed will be. The stability of the network is due to the fact that the data flow goes from the user directly to the node, its speed is not affected by other users. Important factor: to provide an xDSL connection, there is no need to replace cables, which makes it theoretically possible to connect to the Internet wherever there is a telephone (depending on the availability of such a service from the provider).

An xDSL modem will be the link between your phone cable and your devices (or router), but when choosing a specific model, you need to consider a number of characteristics that are right for you.

What are the differences between xDSL modems?

xDSL technologies

In the acronym xDSL, the “x” represents the first letter of DSL technology. xDSL technologies differ in signal transmission distance, data transmission speed, and also in the difference in transmission speeds of incoming and outgoing traffic.

ADSL technology translates to asymmetric digital subscriber line. This means that the transfer speed of incoming and outgoing data is different. In this case, the data reception speed is 8 Mbit/s, and the transmission speed is 1.5 Mbit/s. In this case, the maximum distance from the telephone exchange (or another modem in the case of creating a network) is 6 km. But the maximum speed is possible only at a minimum distance from the node: the further away, the lower it is.

ADSL2 technology makes much better use of wire bandwidth. Its main difference is the ability to distribute information over several channels. That is, it uses, for example, an empty outgoing channel when the incoming channel is overloaded, and vice versa. Thanks to this, its data reception speed is 12 Mbit/s. The transmission speed remains the same as in ADSL. In this case, the maximum distance from a telephone exchange (or other modem) is already 7 km.

ADSL2+ technology doubles the speed of the incoming data stream by increasing the usable frequency range to 2.2 MHz. Thus, the data reception speed is already 24 Mbit/s, and the transmission speed is 2 Mbit/s. But such a speed is only possible at a distance of less than 3 km from the node - then it becomes similar to ADSL2 technology. The advantage of ADSL2+ equipment is that it is compatible with previous ADSL standards.

SHDSL technology is a standard for high-speed symmetric data transmission. This means that the reception and upload speeds are the same - 2.3 Mbit/s. Moreover, this technology can work with two copper pairs - then the speed doubles. The maximum distance from the telephone exchange (or other modem) is 7.5 km.

VDSL technology has the maximum data transfer speed, but is significantly limited by the distance from the node. It works in both asymmetric and symmetric modes. In the first option, the data reception speed reaches 52 Mbit/s, and the transmission speed – 2.3 Mbit/s. In symmetric mode, speeds up to 26 Mbps are supported. However, high speeds are available up to 1.3 km from the node.

When choosing an xDSL modem, you need to focus on the distance to the telephone exchange (or other modem). If it is small, you can safely focus on VDSL, but if the node is far away, you should choose ADSL2+. If you have two copper pairs of wires, you can also pay attention to SHDSL.

Annex Standards

Annex is a type of ADSL standards for transmitting high-speed data in conjunction with analog telephony (regular telephone).

The Annex A standard uses frequencies from 25 kHz to 138 kHz to transmit data, and from 200 kHz to 1.1 MHz to receive data. This is the usual standard for ADSL technology.

The Annex L standard allows you to increase the maximum communication distance to 7 km thanks to increased power at low frequencies. But not all providers use this standard due to interference.

The Annex M standard allows you to increase the speed of the outgoing stream to 3.5 Mbit/s. But in practice, connection speeds range from 1.3 to 2.5 Mbit/s. For an uninterrupted connection, this standard requires an undamaged telephone line.

DHCP server


The abbreviation DHCP stands for Dynamic Host Configuration Protocol. A DHCP server is a program that allows you to automatically configure local computers to work on a network. It provides clients with IP addresses (unique identifiers of a device connected to a local network or the Internet), as well as additional parameters necessary for working on the network. This will allow you not to manually register an IP, which will make your work on the network easier. However, it must be taken into account that for devices such as network printers and for constant remote access to a computer using special programs, a statistical rather than a dynamic IP will be desirable, since constantly changing the IP will cause difficulties.

USB ports

Today, there are two options for organizing an Internet connection using ADSL technology: via a USB port and via an Ethernet port.
An external USB ADSL modem is connected to a computer via a USB port. It receives power from the computer. The advantages of such modems: low cost and ease of use. The disadvantages include not being compatible with all computers, the need to regularly reinstall drivers, and working with only one device.
An ADSL modem connected to the device via an Ethernet port will work more stable. But to be used with multiple devices, it must have a router function or Wi-Fi technology.

Setup and management


Configuring and managing modems is most often carried out using three technologies: Web interface, Telnet and SNMP.
The web interface is a function that allows configuration and management via a computer browser. This option will be sufficient for home use of the modem.

Telnet is a network protocol for remotely accessing a computer using a command interpreter. With its help, you can configure the modem from devices not connected to it. This is useful for small modem circuits at home and in the office.

SNMP is a standard Internet protocol for managing devices on IP networks operating on the TCP/IP architecture (a means for exchanging information between devices connected to a network). Using the SNMP protocol software to manage network devices, it can access information stored on managed devices. Due to this, it is most often used when building office networks.

Selection criteria

xDSL modems differ in a number of characteristics, the most important of which are the maximum distance from the telephone exchange, the speed of data reception and transmission, the presence of symmetric or asymmetric transmission. Understanding under what conditions and how exactly the modem will be used, you can choose the device that is right for you.

Let us remind you that when choosing an xDSL modem, it is important to know the characteristics of the telephone network: the length of the cable to the telephone exchange, the number of copper pairs of the cable and its quality, the offers and capabilities of the provider. It is important that there is no interference on the line, which is caused by the intersection of cable pairs or its poor quality.

ADSL(Asymmetric Digital Subscriber Line) is one of the high-speed data transmission technologies known as DSL (Digital Subscriber Line) technologies, collectively referred to as xDSL. Other DSL technologies include HDSL (High data rate Digital Subscriber Line), VDSL (Very high data rate Digital Subscriber Line) and others.

The general name for DSL technologies arose in 1989, when the idea of ​​using analog-to-digital conversion at the subscriber end of the line first appeared, which would improve the technology of data transmission over twisted pair copper telephone wires. ADSL technology was developed to provide high-speed (one might even say megabit) access to interactive video services (video on demand, video games, etc.) and equally fast data transmission (Internet access, remote access to LAN and other networks).

ADSL technology - so what is it?

First of all, ADSL is a technology that allows you to turn twisted pair telephone wires into a high-speed data transmission path. ADSL line connects two ADSL modem, which are connected to each end of the twisted pair telephone cable (see Figure 1). In this case, three information channel— downstream, upstream, and POTS (see Figure 2). The telephone communication channel is allocated using filters, which ensures that your phone will work even if the ADSL connection fails.


Figure 1


Figure 2


ADSL is an asymmetric technology - the speed of the “downstream” data flow (that is, the data that is transmitted towards the end user) is higher than the speed of the “upstream” data flow (in turn, transmitted from the user to the network). It should be said right away that there is no cause for concern here. The data transfer rate from the user (the "slower" direction of data transfer) is still significantly higher than using an analog modem. In fact, it is also significantly higher than ISDN (Integrated Services Digital Network).

To compress large amounts of information transmitted over twisted pair telephone wires, ADSL technology uses digital signal processing and specially created algorithms, advanced analog filters and analog-to-digital converters. Long distance telephone lines can attenuate the transmitted high frequency signal (for example, at 1 MHz, which is the typical transmission rate for ADSL) by up to 90 dB. This forces analog ADSL modem systems to operate under a fairly heavy load to allow for high dynamic range and low noise levels. At first glance, the ADSL system is quite simple - high-speed data transmission channels are created over a regular telephone cable. But, if you understand in detail how ADSL works, you can understand that this system belongs to the achievements of modern technology.

ADSL technology uses a method of dividing the bandwidth of a copper telephone line into several frequency bands (also called carriers). This allows multiple signals to be transmitted simultaneously on one line. Exactly the same principle underlies cable television, when each user has a special converter that decodes the signal and allows them to see a football match or an exciting film on the TV screen. When using ADSL, different carriers simultaneously carry different parts of the transmitted data. This process is known as Frequency Division Multiplexing (FDM) (see Figure 3). In FDM, one band is allocated for the upstream data stream and another band for the downstream data stream. The downstream range is in turn divided into one or more high-speed channels and one or more low-speed data channels. The upstream range is also divided into one or more low-speed data links. In addition, echo cancellation technology can be used, in which the ranges of the “upstream” and “downstream” streams overlap (see Figure 3) and are separated by means of local echo cancellation.



Figure 3

This is how ADSL can provide, for example, simultaneous high-speed data transmission, video transmission and fax transmission. And all this without interrupting regular telephone communication, which uses the same telephone line. The technology involves reserving a certain frequency band for regular telephone communications (or POTS - Plain Old Telephone Service). It's amazing how quickly telephone communication turned not only into “simple” (Plain), but also into “old” (Old); it turned out something like “good old telephone communication”. However, we should pay tribute to the developers of new technologies, who still left telephone subscribers a narrow band of frequencies for live communication. In this case, a telephone conversation can be carried out simultaneously with high-speed data transfer, rather than choosing one of the two. Moreover, even if your electricity is cut off, the usual “good old” telephone connection will still work and you will not have any problems calling an electrician. Providing this capability was part of the original ADSL development plan. This feature alone gives ADSL a significant advantage over ISDN.

One of the main advantages of ADSL over other high-speed data transmission technologies is the use of ordinary twisted pair copper telephone cables. It is quite obvious that there are much more such pairs of wires (and this is an understatement) than, for example, cables laid specifically for cable modems. ADSL forms, so to speak, an “overlay network”. At the same time, expensive and time-consuming upgrades of switching equipment (as is necessary for ISDN) are not required.

ADSL connection speed

ADSL is a high-speed data technology, but how high-speed? Considering that the letter “A” in the name ADSL stands for “asymmetric”, we can conclude that data transfer in one direction is faster than in the other. Therefore, there are two data transfer rates to consider: "downstream" (transferring data from the network to your computer) and "upstream" (transferring data from your computer to the network).

Factors affecting the data transfer speed are the condition of the subscriber line (i.e., the diameter of the wires, the presence of cable outlets, etc.) and its length. Signal attenuation in a line increases with increasing line length and signal frequency, and decreases with increasing wire diameter. In fact, the functional limit for ADSL is a subscriber line 3.5 - 5.5 km long with a wire thickness of 0.5 mm. Currently, ADSL provides downstream speeds ranging from 1.5 Mbit/s to 8 Mbit/s and upstream speeds from 640 Kbit/s to 1.5 Mbit/s. The general development trend of this technology promises an increase in data transfer speeds in the future, especially in the “downstream” direction.

In order to evaluate the data transfer speed provided by ADSL technology, it is necessary to compare it with the speed that may be available to users using other technologies. Analog modems allow you to transfer data at speeds from 14.4 to 56 Kbps. ISDN provides a data rate of 64 Kbps per channel (user typically has access to two channels for a total of 128 Kbps). Various DSL technologies give the user the ability to transmit data at speeds of 144 Kbps (IDSL), 1.544 and 2.048 Mbps (HDSL), downstream 1.5 - 8 Mbps and upstream 640 - 1500 Kbps s (ADSL), “downstream” stream 13 - 52 Mbit/s and “upstream” stream 1.5 - 2.3 Mbit/s (VDSL). Cable modems have data transfer rates from 500 Kbps to 10 Mbps (note that the bandwidth of cable modems is divided among all users simultaneously accessing a given line, so the number of concurrent users has a significant impact on actual speed data transmission of each of them). Digital lines E1 and E3 have data transfer rates of 2.048 Mbit/s and 34 Mbit/s, respectively.

When using ADSL technology, the bandwidth of the line through which the end user is connected to the backbone network always belongs to that user entirely. Do you need an ADSL line? It's up to you to decide, but for you to accept the right decision, let's look at some of the benefits of ADSL.

First of all, the data transfer speed. The numbers were stated two paragraphs above. Moreover, these numbers are not the limit. The new ADSL 2 standard implements speeds of 10 Mbit/s downstream and 1 Mbit/s upstream with a range of up to 3 km, and ADSL 2+ technology, the standard of which should be approved in 2003, includes downstream speeds. streams of 20, 30 and 40 Mbit/s (on 2,3 and 4 pairs, respectively).

Internet via ADSL

In order to connect to Internet via ADSL, no need to dial the phone number. ADSL creates a broadband data transmission channel using an already existing telephone line. After installing ADSL modems, you get a permanent connection. A high-speed data link is always ready to go – whenever you need it.

The line bandwidth belongs entirely to the user. Unlike cable modems, which allow the bandwidth to be shared among all users (which greatly affects the data transfer speed), ADSL technology allows only one user to use the line.

ADSL connection technology allows you to fully use line resources. Typical telephone communications use about one hundredth of the telephone line's bandwidth. ADSL technology eliminates this "disadvantage" and uses the remaining 99% for high-speed data transmission. In this case, different frequency bands are used for different functions. For telephone (voice) communications, the lowest frequency region of the entire line bandwidth is used (up to approximately 4 kHz), and the entire remaining band is used for high-speed data transmission.

The versatility of this system is not the least argument in its favor. Since different frequency channels of the subscriber line bandwidth are allocated for the operation of different functions, ADSL allows you to simultaneously transfer data and talk on the phone. You can make and answer calls, send and receive faxes, while at the same time being on the Internet or receiving data from the corporate LAN. All this over the same telephone line.

ADSL opens up completely new possibilities in those areas where it is necessary to transmit high-quality video signals in real time. These include, for example, video conferencing, distance learning and video on demand. ADSL technology allows providers to provide their users with services that are more than 100 times faster than the current fastest analog modem (56 Kbps) and more than 70 times faster than ISDN (128 Kbps) ).

ADSL technology allows telecommunications companies to provide a private, secure channel to facilitate the exchange of information between the user and the provider.

Internet connection via ADSL

We should not forget about costs. The technology for connecting to the Internet via ADSL is effective from an economic point of view, if only because it does not require the installation of special cables, but uses already existing two-wire copper telephone lines. That is, if you have a connected telephone at home or in the office, you do not need to lay additional wires to use ADSL. (Although there is a fly in the ointment. The company that provides you with regular telephone communication must also provide ADSL service.)

Not much equipment is needed to make an ADSL line work. ADSL modems are installed at both ends of the line: one on the user side (at home or in the office), and the other on the network side (at the Internet provider or at the telephone exchange). Moreover, the user does not have to buy his own modem, but it is enough to rent it from the provider. In addition, in order for the ADSL modem to work, the user must have a computer and an interface card, for example, Ethernet 10baseT.

As telephone companies gradually enter the untapped field of delivering video and multimedia data to the end user, ADSL technology continues to play a large role. Of course, after some time the broadband cable network will cover all potential users. But the success of these new systems will depend on how many users will be involved in the process of using new technologies now. By bringing movies and television, video catalogs and the Internet into homes and offices, ADSL makes the market viable and profitable for telephone companies and other service providers in a variety of industries.

04. 09.2017

Blog of Dmitry Vassiyarov.

What is ADSL - an old but current connection method

Hi all.

You can't live without the Internet now. Therefore, anyone to modern man worth knowing about different options its connections to choose the one that suits you. For these reasons, I will tell you about what ADSL is. What if you like this way of connecting to the World Wide Web? If not, you will simply be more knowledgeable about Internet technologies. In any case, after reading the article you will win ;).

Introduction to the xDSL family

In the mid-90s, a new family was born, and not just any simple one, but digital technologies that use a telephone line to connect to the Internet. It is called DSL, which means “digital subscriber line” (digital subscriber line). The abbreviation is usually preceded by an "x" to hide a specific member of that family.

There are quite a lot of them, but one of the most popular nowadays is Asymmetric. So our further conversation will be about ADSL. As the name implies, its feature is asymmetry. It's about about the uneven distribution of downstream and upstream traffic.

The speed of the second one is lower. Practice shows that the first digit is more important for users. Because the volume of incoming traffic always exceeds the amount of outgoing traffic.

ADSL physical design

To understand the essence of our conversation, you must understand what ADSL actually is. Connection to the network using this technology is performed through a telephone line and 2 modems (1 is located at the subscriber, the other at the provider).

There is usually an intermediary between the telephone cable socket and the user's modem - a splitter. It has 1 input for connecting a telephone line and 2 outputs - for the telephone itself and the modem. The splitter also eliminates communication interference and ensures the safety of devices from high-voltage pulses thanks to its inductors and electrical protection circuits on varistors.

By the way, there are modems that allow you to additionally connect one that distributes Wi-Fi.

A modem is no problem for your phone

Representatives of the “old school”, who remember how in the 1990-2000s they connected to the Internet via telephone using cards, do not rush to write off ADSL. For those who don’t remember this, let me explain: in those days you could either go online or talk on the phone - one of two things.

But in asymmetric technology this drawback is eliminated. The fact is that talking on the phone takes up a tiny percentage of the line's capabilities. Smart people figured out to use the rest of the channel to access the network so that one does not interfere with the other.

For undemanding voice communications, the lowest frequency band is used, for the Internet - everything else. In particular, the phone uses the range 400 - 3500 Hz, incoming traffic - 26000 - 138000 Hz, outgoing traffic - from the last digit to 1.1 MHz.

Which line is suitable for the Internet?

Connecting to the network via ADSL is cost-effective. Since you don’t have to buy a modem, but rent it from a provider, and you don’t have to lay new cables. But this is only if the telephone company provides Internet service. In addition, not just any line will do the job. It must meet the following requirements:

  • loop resistance is no more than 1200 Ohms, and insulation resistance is no less than 40 Ohms;
  • loop capacity - maximum 300 nanofarads;
  • capacitive asymmetry - maximum 10 nF;
  • signal attenuation: good - 5-20 decibels, in the range from the last digit to 30 dB there are glitches, and at 31-40 dB synchronization may be lost;
  • noise level: from -65 dB to -55 dB - excellent, up to -35 dB - good, up to -21 dB there may be malfunctions, and if lower, the equipment will not work.

The quality of the cable also matters. It is best to use shielded twisted pair cable. Often the phone is connected via a single-pair distribution wire(TRP), especially in old buildings. Which, of course, is not suitable for new technologies.

Data transfer rate

The primary question when choosing a method to connect to the Internet is what is its speed? Compared to other modern types ADSL connections“smokes on the sidelines,” although it is considered high-speed. Compare for yourself.

The latest generation of this technology is 2++. Its maximum input speed is 48 Mbit/s, output speed is 3 Mbit/s. While the currently popular family can offer customers an incoming traffic speed of 5 Gbit/s, although 1 Gbit/s remains more affordable, and, nevertheless, this is much more than the ADSL maximum.

For these reasons, a leased line is in greater demand than modem technologies. However, ADSL is still showing its ability to compete. For example, in government agencies and other enterprises where landline phones are indispensable, it is convenient and profitable to use their lines for the Internet, because high speed in such a situation is not needed.

You are always welcome on my blog page.

Hello Irina!

In principle, you can watch movies online at any speed.

Another question is how much it will cost nerves and health at very low speeds.

I will give an example specifically for your reception speed in numbers. Don’t delve into the numbers, the main thing is the meaning.

Judging by the designation 1.55 M b/s, your speed is 1.55 Megabyte per second. capital letter"M" speaks about this.

Online films, depending on the format (in “Additional Materials” I have a link to my lesson on this topic, on films, in particular) and quality, the size of an online film of average quality can range from 300 Megabytes to 5000 Megabytes.

Let's take something average, for example the movie size is 1000 Megabytes.

How to watch a movie online?

When you go to the movie viewing page, a player appears on your screen for viewing with the “Pause”, “Play”, “Stop” buttons.

When you click “Play,” the movie begins downloading to your computer.

As soon as a very small part of the film, which the player is already capable of playing, is downloaded to your computer, the player (after a few seconds) begins to show you the film.

Moreover, the rest of the film continues to swing in the background.

It turns out that the movie hasn’t even downloaded yet, but you’re already watching it.

So the problem with low reception speeds is that while you are viewing the first downloaded part, the next one does not have time to download to your computer. Then the “Brakes” begin. What gets on your nerves.

But even in this case there is a way out. The truth takes some time. You put the player on “Pause” and do other things. After 5-10 minutes, turn on playback and watch the movie normally.

Now for your speeds.

Roughly speaking, a movie 1000 megabytes in size should be downloaded in

1000Mb / 1.55Mb/s = 645 seconds = 10 minutes

Judging by my observations, this is a fairly comfortable viewing of an average quality film.

Now a little bit of ointment in the ointment.

A reception speed of 1.55 Mb/s does not mean that a movie will be downloaded at that speed.

1. In addition to useful information (the film itself), there is a lot of service information in the communication channel.

2. A lot depends on the workload of the site from which you are watching the film.

3. A lot depends on the congestion of the channels through which you receive information.

4. A lot depends on how loaded your computer is - how many programs and processes are loaded and how much they “eat up” the memory and resources of the processor itself.

5. What quality of film are you watching - low, medium or high?

In general, we make discounts on factors on which we do not depend and it turns out (from experience) somewhere around 20 - 40 minutes.

But this is also acceptable. After all, there is a Pause button on the player.

And finally. The entire film, in fact, is not downloaded to the computer. Only parts. Viewed parts are automatically deleted.

Best regards, Oleg



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