Adsl connection via telephone line. Internet connection Rostelecom using ADSL technology: an overview of tariffs. What is the difference between xDSL modems

Almost everyone needs internet access these days. Whether it's 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, in order to run 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 business everywhere. This is especially true for small towns, towns and villages. But what if such services are not provided, but the Internet is still needed?

There are different options, and one of the best is the use of twisted-pair subscriber telephone wires. Many will recall with horror a non-working phone while using the Internet. However, technology has come a long way. Today, xDSL technologies are the most widespread and effective. DSL stands for Digital Subscriber Line. This technology allows you to achieve a fairly high data transfer rate over copper pairs of telephone wires, while not occupying the phone. The fact is that the frequency range from 0 to 4 kHz is used for voice transmission, while signals with a frequency of up to 2.2 MHz can be transmitted over a copper telephone cable, and it is the section from 20 kHz to 2.2 MHz that uses xDSL technology . The speed and stability of such a connection is affected by the length of the cable, that is, the farther from your modem is the telephone exchange (or another modem in the case of a network), the lower the data transfer rate 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 xDSL connection, it is not necessary to change cables, which makes it theoretically possible to connect the Internet wherever there is a phone (depending on the availability of such a service from the provider).

The xDSL modem will act as the link between the phone cable and your devices (or router), but if you choose specific model You need to take into account a number of characteristics that are right for you.

What is the difference between xDSL modems

xDSL technologies

In the acronym xDSL, the "x" stands for the first letter of the DSL technology. xDSL technologies differ in signal transmission distance, data transfer rate, as well as the difference in the transfer rates of incoming and outgoing traffic.

ADSL technology is translated as asymmetric digital subscriber line. This means that the transmission speed of incoming and outgoing data is different. In this case, the data reception rate is 8 Mbps, and the transmission rate is 1.5 Mbps. In this case, the maximum distance from the telephone node (or another modem in the case of a network) is 6 km. But the maximum speed is possible only at a minimum distance from the node: the farther, the lower it is.

ADSL2 technology makes much better use of throughput wires. Its main difference is the ability to distribute information across multiple channels. That is, it uses, for example, an empty outgoing channel when the incoming is overloaded, and vice versa. Due to this, its data reception speed is 12 Mbps. The transmission speed remained the same as in ADSL. At the same time, the maximum distance from the telephone exchange (or other modem) is already 7 km.

ADSL2+ technology doubles the downstream speed by increasing the usable bandwidth to 2.2 MHz. Thus, the data reception rate is already equal to 24 Mbps, and the transmission rate is 2 Mbps. But such a speed is possible only at a distance of less than 3 km from the node - further it becomes similar to ADSL2 technology. ADSL2+ equipment has the advantage of being compatible with previous ADSL standards.

SHDSL technology is a standard for high-speed symmetrical data transmission. This means that the download and upload speeds are the same - 2.3 Mbps. At the same time, 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 rate, but is significantly limited by the distance from the node. It works in both asymmetric and symmetrical modes. In the first variant, the data reception speed reaches 52 Mbps, and the transmission speed - 2.3 Mbps. In symmetrical mode, speeds up to 26 Mbps are supported. However high speeds available at a distance of no more than 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 there are two copper pairs of wires, you can pay attention to SHDSL.

Annex Standards

Annex - a kind of ADSL standards for high-speed data transmission in conjunction with analog telephony (ordinary telephone).

The Annex A standard uses frequencies from 25 kHz to 138 kHz for data transmission, and from 200 kHz to 1.1 MHz for receiving data. This is a common standard for ADSL technology.

The Annex L standard extends the maximum communication distance to 7 km by increasing the 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 up to 3.5 Mbps. But in practice, the connection speed ranges from 1.3 to 2.5 Mbps. For an uninterrupted connection, this standard requires a telephone line without damage.

DHCP server

DHCP stands for Dynamic Host Configuration Protocol. DHCP server is a program that allows you to automatic tuning local computers for networking. It gives clients 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 enter the IP, which will make it easier to work on the network. However, it should be noted that for devices such as network printers, and for a constant remote access to a computer using special programs a static rather than a dynamic IP would be desirable, as constantly changing IP would 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 the computer via a USB port. It receives power from the computer. The advantages of such modems are low cost and ease of use. The disadvantages include compatibility not with all computers, the need for regular reinstallation of drivers, and work with only one device.

An ADSL modem connected to the device via an Ethernet port will work more stable. But for use with multiple devices, it must have a router function or Wi-Fi technology.

Setup and management

Modems are most often configured and managed using three technologies: Web interface, Telnet, and SNMP.

The web interface is a feature that allows configuration and control through a computer browser. This option will be enough for home use of the modem.

Telnet is a network protocol for remote access to a computer using a command interpreter. With it, you can configure the modem from devices that are not connected to it. This is useful for small chains of modems at home and in the office.

SNMP is a standard Internet protocol for managing devices on IP networks based on the TCP/IP architecture (means for exchanging information between networked devices). Using the SNMP protocol, network device management software can access information stored on managed devices. Due to this, it is most often used in the construction of office networks.

Criterias of choice

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

Recall 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.

We have distributed xDSL modems based on user needs.

To connect to the Internet using xDSL technology of one device it will be enough to purchase an inexpensive USB modem that supports the appropriate technology (for example, ADSL2 + or VDSL).

To create an Internet network at home or in a small office it is better to pay attention to xDSL modems connected via an Ethernet port. The choice of technology again depends on the capabilities of the telephone network.

To create a large office network with a chain of modems at distances up to 3 km choose among xDSL modems with the latest xDSL standards, symmetrical data transfer and support for the SNMP protocol.

What is ADSL?

Asymmetric Digital Subscriber Line is a technology that allows you to implement high-speed data transmission over a telephone line (ordinary copper telephone wire).

At the same time, there are significant differences from voice-frequency telephone modems - the transmission is organized at a higher frequency than that of an analog telephone signal. The result: you have threads that are independent of each other and can carry on conversations while being on the Web in parallel. ADSL is currently capable of providing up to 24 Mbps of downstream data and up to 1 Mbps of outgoing data, but this is under ideal conditions, a small distance from the station and underground cable laying, etc. For the most part, the connection speed depends on the technical capabilities of the provider and on average reaches 6-8 Mbps.

In the case of ADSL, you simply connect to a telephone jack through a special device that performs frequency separation - this is a splitter, a modem and telephone are connected to it, and the device gets output directly to your telephone line.

Which modem to choose?

Currently available are ADSL modems with Ethernet and USB interfaces, and a wireless device with Wi-Fi interface. The choice depends on your needs - the difference here is in the connection features and in the capabilities provided: modems that connect as network devices offer more of them than USB counterparts. For example, to connect one computer to the Network, a simple model is quite enough, and if there are two or more of them, then you need to pay attention to devices with a router function - the modem will in any case have an Ethernet or Wi-Fi interface.

You can find options from Ethernet models with and without a built-in switch (in this case, you will need to use an additional switch when connecting several computers). If you need increased security, then you can look at models with Firewall functions, anti-virus scanning, the ability to work with virtual private network and other "usefulness".

If you use signaling on the same line, in addition to telephony and Internet DSL, you will need a modem that supports ANNEX B operation mode, it can be either a separate modem model or a built-in switching capability (ANNEX A - ANNEX B).

How to connect?

An important detail: if there are phones connected in parallel in the apartment, and you cannot connect them through a splitter (they are located in other rooms), then each incoming call will cause a lot of headaches, which are associated with constant disconnections. To avoid this, it is necessary for each of the devices to buy an additional device, a microfilter, and connect them through it. One of the sides of the splitter has two inputs (Phone and DSL), a telephone cord from the modem is connected to the DSL input, and a telephone set is connected to the Phone. A splitter is a frequency separator, or, to put it simply, it allows you to surf the Internet and talk on the phone without any interference.

Now we need to turn on the modem itself and look at it. The lights should come on and flash. The main indicator is the DSL light, which should be on without blinking after the modem is restarted. If the light is on correctly, then you can connect the modem to a laptop or computer using an Ethernet RJ45 network cable. It happens that the light flashes quickly or simply does not light up. You can solve the problem by checking the quality of the cable connection and the connection diagram or by calling the provider. Move on. The lights are on as they should. When you turn on the computer, connect the modem to the output of the network board, which is slightly wider than the telephone.

When you create a new Internet connection, you just need to set up your modem.
Depending on the configuration of your local network, the modem can be configured in the so-called bridge (bridge) mode.
Choosing an ADSL modem and setting it up is a very simple task if an agreement has been concluded with a provider from which you received a login and password, as well as a notification that the line was connected to the Internet.

The Internet has become a part of everyday life modern man. You can count on your fingers the areas of activity that the World Wide Web has not yet reached.

There are several ways to connect to it. One of the most common is the use of a telephone line. The most accessible for the home will be an ADSL connection.

The leading position in the telecommunications market is occupied by Rostelecom. It is the leader in the number of subscribers using the Internet through home phone from Rostelecom.

ADSL is a technology for connecting to the Internet via a telephone line from Rostelecom, which is being turned into a high-speed network access line. A modem is used here to receive and transmit data. In this case, the reception speed significantly exceeds the information transfer rate. This is the so-called asynchronous technology.

Another useful property is the ability to simultaneously use wired telephone and go online. This is achieved by installing a splitter. A splitter is a device that divides a telephone line into two channels - a regular telephone signal and a high-frequency one.

Important! Connection using this technology is considered the most beneficial for home use. For its implementation, the subscriber's telephone line is sufficient. Plus, it is less expensive than using fiber optic cable.

Connection diagram and necessary equipment

To connect you will need:

• telephone line;
• ADSL modem or router - wired or wireless;
• splitter - included with the modem.

ADSL modem can be purchased independently, rented or bought in installments from Rostelecom. It can be a regular modem or router. They differ in that only one device is connected to the first, and several to the second. The modem can be wired or wireless. For example, if you purchase wifi router ohm "D-Link DSL-2640", you will be able to connect several devices to the Network via a wireless Wi-Fi channel. There are two ways to buy a Wi-Fi router from Rostelecom - buy for 1890 rubles or take it in installments for 99 rubles. per month.

Important! The connection technology is quite simple. A splitter is connected to the outlet so that the wire enters the Line jack. In the remaining two jacks Phone and Modem, respectively, you need to connect a phone and a modem. This completes the physical connection phase. Next, you need to set up your computer.

Choice of tariff plan

The company operates throughout our country. The main tariff plans in all regions have a similar name, but the contents of these packages can vary greatly. Each region has a speed limit, which depends on the quality of telephone lines. The prices for the services provided can also differ significantly. In all regions, Rostelecom has three main tariff plans and, as a rule, one of them is promotional.

At the moment, the following Rostelecom Internet tariffs are relevant:

• "ADSL" - along with the tariff, the subscriber can get an elite tank at online game World of Tanks. Speed ​​up to 20 megabytes per second, cost 850 rubles. per month;
• « Home Internet ADSL+TV"- the user, in addition to accessing the Network, will be able to use digital television. The number of television channels is 122. The speed is up to 20 megabytes per second, the cost is 1050 rubles. per month;
• « Home Internet ADSL» is the cheapest. There are no bonuses and add-ons here, but it has the lowest subscription fee. Speed ​​up to 20 megabytes per second, cost 300 rubles. per month.

Customers can also take advantage of two additional promotions:

• « Maximum benefit"- speed 10 megabytes per second, cost 240 rubles. per month;
• « Two Internet» - speed of 10 megabytes per second, plus tariff plan for mobile phones"Supersimka M", cost 240 rubles. per month.

To use home Internet using ADSL technology, just go to the official website of Rostelecom, in the appropriate section, and leave a request there. After that, an operator will contact you, with whom you can discuss all the details and ask questions of interest.

ADSL technology

In recent years, the growth in the volume of information transfer has led to the fact that there is a shortage of bandwidth for access channels to existing networks. If at corporate levels this problem is partially solved (by renting high-speed transmission channels), then in the residential sector and in the small business sector these problems exist.

Today, the main way for end users to interact with private and public networks is access using a telephone line and modems, devices that transmit digital information over subscriber analog telephone lines. The speed of such a connection is low, the maximum speed can reach 56 Kbps. This is still enough to access the Internet, however, the pages are saturated with graphics and videos, large volumes Email and papers in the near future will again raise the question of ways to further increase capacity.

The most promising at present is the ADSL (Asymmetric Digital Subscriber Line) technology. This is a new modem technology that turns standard analog subscriber telephone lines into high-speed access lines. ADSL technology allows you to transfer information to the subscriber at a speed of up to 6 Mbps. In the opposite direction, speeds up to 640 Kbps are used. This is due to the fact that the entire modern range of network services involves a very low transmission speed from the subscriber. For example, MPEG-1 video requires 1.5 Mbps of bandwidth. For service information transmitted from the subscriber, 64-128 Kbps is quite enough (Fig. 1).

ADSL service organization principles

The ADSL service (Figure 1) is established using an ADSL modem and an ADSL modem rack called the DSL Access Module. Almost all DSLAMs are equipped with a 10Base-T Ethernet port. This allows the use of conventional hubs, switches and routers on access nodes.

A number of manufacturers have begun to provide DSLAMs with ATM interfaces, allowing them to be directly connected to WAN ATM switches. Also, a number of manufacturers create custom modems, which are an ADSL modem, but for software are ATM adapters.

Three streams function in the section between the ADSL modem and the DSLAM: a high-speed stream to the subscriber, a bidirectional service and voice channel in the standard frequency range of the PM channel (0.3-3.4 kHz). Frequency separators ( POTS Splitter) allocate a telephone stream, and direct it to a conventional telephone set. Such a scheme allows you to talk on the phone simultaneously with the transfer of information and use telephone communications in the event of a malfunction of the ADSL equipment. Structurally, the telephone splitter is a frequency filter that can be either integrated into an ADSL modem or be an independent device.

According to the theorem Shannon, it is impossible to achieve speeds above 33.6 Kbps using modems. In ADSL technology, digital information is transmitted outside the frequency range of a standard PM channel. This will cause the filters installed at the telephone exchange to cut off the frequency above 4 kHz, so it is necessary to install WAN access equipment (switch or router) at each telephone exchange.

Transmission to the subscriber is carried out at speeds from 1.5 to 6.1 Mbps, the speed of the service channel is from 15 to 640 Kbps. Each channel may be divided into multiple logical low rate channels.

Speeds provided by ADSL modems are multiples of speeds of T1, E1 digital channels. In the minimum configuration, transmission is carried out at a speed of 1.5 or 2.0 Mbps. In principle, today there are devices that transmit data at speeds up to 8 Mbps, but this speed is not defined in the standards.

Speed ​​of ADSL modems depending on the number of channels

The maximum possible line speed depends on a number of factors, including the length of the line and the thickness of the telephone cable. The characteristics of the line deteriorate with an increase in its length and a decrease in the cross section of the wire. The table shows several options for the dependence of speed on line parameters.

An ADSL modem is a device built on the basis of a digital signal processor (DSP or DSP), similar to that used in conventional modems (Fig. 2). In the general case, the entire bandwidth of the line is divided into two sections. The first section is intended for voice transmission, and is in the range of 0.3-3.4 kHz. The signal range for data transmission is between 4 kHz and 1 MHz. The physical parameters of most lines do not allow data to be transmitted at a frequency above 1 MHz. Unfortunately, not all existing telephone lines (especially long ones) even have such characteristics, so it is necessary to reduce the bandwidth, which entails a decrease in the transmission speed.

Two methods are used to create these streams: the frequency division method and the echo cancellation method.

Rice. 3 Stream separation schemes in the frequency band of a telephone line

The frequency division method consists in the fact that each of the streams is allocated its own frequency bandwidth. The high speed stream may be split into one or more low speed streams. These streams are transmitted using the " "(DMT).

The echo cancellation method is that the ranges of the high-speed and service streams are superimposed on each other. The streams are separated using a differential system built into the modem. This method is used in modern V.32 and V.34 modems. The high-speed stream can be divided into one or more low-speed streams. These streams are transmitted using the " discrete multitone modulation"(DMT).

When transmitting multiple streams, each of them is divided into blocks. Each block is provided with an error correction code (ECC).

Related technologies

There are a number of related technologies, some for end-users, others for high-speed backhaul. The principle of their operation is similar to ADSL. The common name for such technologies is xDSL.

High Data-Rate Digital Subscriber Line (HDSL)

HDSL is a technology that provides transmission at 1.536 or 2.048 Mbps in both directions. The length of the line can reach 3.7 km. Oriented as a cheaper alternative to dedicated channels E1, T1. Requires a 4-wire subscriber line.

Single-Line Digital Subscriber Line (SDSL)

It is similar to HDSL, differs in that a two-wire subscriber line is enough to organize a line. The length of the line can reach 3 km.

Very High Data-Rate Digital Subscriber Line (VDSL)

Similar to HDSL, speed up to 56 Mbps. Distance up to 1.5 km. The technology is very expensive and is not widely used.

Rate Adaptive Digital Subscriber Line (RADSL)

ADSL technology has one significant drawback. It does not allow you to change the speed depending on the quality of the line. In such modems, the choice of speed, a multiple of 1.5 or 2 Mbps, is made using software. Equipment built on the basis of RADSL technology allows you to automatically reduce the speed depending on the quality of the line.

Universal ADSL (UADSL)

ADSL technology has a number of minor drawbacks that prevent the wide implementation of the technology on subscriber access networks. This is the complexity of installing ADSL devices; they require serious tuning to a specific subscriber line (as a rule, with the participation of a technical employee of the company - network operator), have a relatively high cost.

Not so long ago there were reports of the creation new version ADSL technology, which is designed to eliminate these shortcomings. It is called Universal ADSL (UADSL), or DSL Lite. True, when using this technology, data is transmitted over more low speeds than in ADSL (with a subscriber line length of up to 3.5 km, the speed is 1.5 Mbps in the direction to the subscriber and 384 kbps in the opposite direction; with a subscriber line length of up to 5.5 km, 640 kbps are provided towards the subscriber and 196 kbit/s in the opposite direction). However, these devices are easier to install; in addition, they include a frequency separator, so it does not have to be installed separately. Essentially, just plugging a UADSL modem into a telephone jack is as simple as plugging in a regular modem.

The cost of such devices does not exceed the cost of a conventional modem, so we should expect that this particular technology will find wide application in end user access equipment.

Standards

The American National Standards Institute (ANSI) Working Group T1E1.4 recently approved a standard for ADSL up to 6.1 Mbps (ANSI Standard T1.413). ETSI has supplemented this standard with requirements for Europe. T1.413 defines a single terminal interface from the operator side. The second version of this standard, being developed by the T1E1.4 group, expanded the standard in which it defined: a multiplexed interface on the operator side; configuration protocols and network management.

Some numbers

Distances for short range modems depend on the diameter of the copper pair:

1. Telindus Crocus HDSL 2048Kb/s:

2. Telindus Crocus SDSL:

3. Telindus Crocus HS (144Kb/s):

Addition1

The article is well written, everything is correct, however there are some comments regarding the implementation of ADSL in real life. Unfortunately, ADSL can only be used on ordinary Russian communication lines on an experimental basis, so far there is no talk of commercial operation. An ADSL line requires a TWISTED pair (and not a noodle) and shielded, and if it is a multi-pair cable, then in compliance with the direction and pitch of the twist.

You can object (S.Zh.), noting that the noodles go only in the area from the cross in the house to the apartment, its replacement with a twisted pair does not present both technical and economic difficulties. In the cross-telephone station section, multi-pair cables are used, where each pair is twisted.

It seems to be convincing BUT have you tried to disassemble the telephone cable? Remove the insulation meter from the imported cable and from the domestic one. The imported one will dissolve into twisted pairs that will not fall apart even if they are pulled, and the domestic one almost immediately turns into a broom and a fair amount of skill is required to cut it without additional devices. Replacing noodles also doesn’t seem to be scary, but noodles won’t do here, you will need to replace the KRT (telephone distribution box), especially if it is plastic (remember how LANs are divorced) and it costs in each entrance and often not one at a time. The direction of the lay in domestic multi-pair cables is not respected (disassemble for example our 50-pair cable or 100-pair cable), because no one thought that such cables would be used to transmit wide-spectrum high-frequency signals, and, accordingly, no one also spoke about protection against crosstalk. thought. For the capitalists, perhaps, this benefit also arose by chance, because there is competition and in order for products to be bought, it must meet not even the obligatory, but the parameters recommended by all sorts of commissions (because these commissions do not eat their bread for nothing) and on the territory of one district (or even blocks) there may be two or more telephone service providers. Vooschem, as always, thanks to competition, quality goods and services are obtained.

For E1, a twisted pair is used with as many as two screens isolated from each other along the length of the cable and with a regulated number of cable spans, otherwise there is no need to talk about any mileage and stable communication.

This is true, but in my opinion (S.Zh.) DSL technology is more likely to find its application not in industry, but in the residential sector.

Yeah, that’s what I can add (I.Sh.), a couple of years ago this technology was offered to ROSTELECOM for the reconstruction of short trunk lines, and the main cable is not your home wiring for such a cable, you can skip 64 Mbps and this upgrade was built according to the station- cable station. Well, ROSTELECOM did not agree to use these technologies, because it is expensive. I doubt that now the equipment has fallen in price so much that it costs like an Ethernet hub? And if I'm wrong, then someone wants to warm their hands a lot on the modernization of cable lines and the introduction of new technology.

Well, now let's imagine that 2-6 Mbit is loaded into the telephone cable, but it (the cable) does not have the appropriate parameters (often the inter-wire insulation is underestimated - well, they wet the poor fellow, they probably heard cod and space conversations in the receiver), as a result, pickups will come out . I think that these pickups will be the result of combinatorial frequencies, and a very wide spectrum, which will interfere with television receivers so much that a real war can begin. So in practice, not everything goes smoothly, unfortunately.

That is why, personally, I think (S.Zh.) that the introduction of UADSL with low speeds (up to 640 Kbps). All these effects in this technology will be expressed to a much lesser extent.

I think (I.Sh.) that anyway, the price of such an implementation will be too high at this stage to seriously think about it. So, there are more problems than it seems at first glance, and in any case, a more serious approach is required.

And here is my information (S.Zh.): providers, in particular Rosnet, do not share your views on technical problems and can provide ADSL equipment. Installing a modem, setting up, connecting, costs about $2,500. At the same time, speeds up to 640 Kbps are provided. The monthly subscription fee is about $300.

ADSL modems now cost around $800-1500. UADSL modems should cost around $250-500, which is more acceptable.

As soon as each telephone node has installed data network access equipment, this type of service will become much cheaper, and the introduction of such access equipment is directly related to the introduction of ATM.

Addition2

In the article, Stanislav Zhuravlev sets out well theoretical aspect, but does not affect the specifics of the application of this technology in Russia. In the first addition, some gaps are eliminated, but there are several inaccuracies:

First, xDSL technologies were developed by Bell's research division specifically for use on the existing copper wire infrastructure, which, even in the USA, is old and built on a conventional copper telephone pair, rather than a shielded twisted one.

Secondly, "noodles" are really not suitable for xDSL lines, but "noodles" are used in the area from the telephone distribution box to the subscriber socket, which is usually about 5-15 meters. In fact, there are two limitations that, with a given line resistance (usually 1-1.5 kOhm), do not allow the use of xDSL devices, these are loading and assembly from wires of various sizes. Line loading is the introduction of an inductive component into the line in order to reduce signal attenuation, but in Russia such lines are almost never used. The second problem is quite common, but if the station part of the equipment is located at the nearest PBX to you, then the likelihood of such a problem is small, in any case, this problem can be solved with a local telephone exchange. However, if you need a direct channel, for example to connect two local networks, then this is not a problem. In Moscow, there are a fairly large number of direct channels operating on copper at a distance of 5-7 km and a resistance of 1-1.5 kOhm.

The wide distribution of xDSL technologies in Russia is constrained, first of all, not by an insufficient number of telephone pairs with acceptable parameters (while the number of installed lines in Moscow is estimated at tens or hundreds), but by the price of equipment, $ 2000-3000 for a set of station and subscriber parts, the price of connection and the cost of a dedicated channel (for the sake of curiosity, look at any of the providers how much a synchronous channel costs 64K channel, the prices will unpleasantly amaze you). The speed of already installed lines usually ranges from 64-512K. xDSL lines operating at a speed of more than 2Mbit over copper, I have not seen at all and I think their appearance is unlikely in the near future. This is explained by the fact that the cost of a 2Mbit stream is so high that either very large commercial firms or telecommunications companies that are themselves engaged in providing services can afford it, and such a criterion as the probability of an error on the channel is very important for them. The smallest error probability is provided by optical fiber, the stability of which will in any case be several orders of magnitude higher than xDSL lines.

It seems to me that the most promising prospects are for equipment designed for speeds of 64-512K, especially those created in accordance with the UDSL standard, which should be adopted before the end of this year. Manufacturers promise the price for a subscriber UDSL modem not more than $300-400. If large telecommunication companies become interested in providing xDSL services (ideal case of MGTS :--)), which will be able to place at their own expense station equipment sets on in large numbers telephone nodes, we expect a sharp increase in the number of used xDSL lines in the near future.

Hello Irina!
Basically, 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. Do not delve into the numbers, the main thing is the meaning.
Judging by the designation 1.55 M b/s, you have a speed of 1.55 Megabyte per second. The capital letter "M" says it all.
Movies online, depending on the format (I have in “ Additional materials” there is a link to my lesson on this topic, on films in particular) and quality, the size of an average quality online movie can be from 300 megabytes to 5000 megabytes.
Let's take something in the middle, for example, the size of a movie is 1000 megabytes.
How is watching a movie online?
When you enter the page for watching a movie, a player appears on your screen for viewing with the buttons “Pause”, “Playback”, “Stop”.
When you click "Play", the movie starts downloading to your computer.
As soon as a very small part of the movie, which the player is already capable of playing, is downloaded to your computer, the player (after a few seconds) starts showing you the movie.
And the rest of the movie continues to swing in the background.
It turns out that the whole movie has not yet been downloaded, and you are 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 hits the nerves.
But 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 1000 megabyte movie should be downloaded for
1000Mb / 1.55Mb/s = 645 seconds = 10 minutes
Judging by my observations, this is a fairly comfortable viewing of an average quality movie.
But!!!
Now a little fly in the ointment.
The reception speed of 1.55 Mb/s does not mean at all that the 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 movie.
3. Much depends on the workload of the channels through which you receive information.
4. A lot depends on how loaded your computer is directly - how many programs and processes are loaded and how much they “eat away” the memory and resources of the processor itself.
5. What is the quality of the movie you are watching - low, medium or high.
In general, we make discounts for factors on which we do not depend and it turns out (according to experience) somewhere around 20 - 40 minutes.
But, that's also acceptable. After all, the player has a “Pause” button.
And finally. The whole movie, in fact, is not downloaded to the computer. Parts only. Viewed parts are automatically deleted.
Regards, Oleg