What is an ADSL modem. What are the XDSL modems vary. Data transfer rate
In recent years, the development of the telecommunication services market has led to a shortage of access capacitance of access channels to existing network providers. If at the corporate level, this problem is removed, the provision of high-speed data transmission channels, which alternative can offer subscribers on existing lines, instead of a switched compound, in the apartment sector and small business sector?
To date, the main way to interact the end users with private networks and public networks is access using a telephone line and modems, devices that ensure digital information transmission by subscriber analog telephone lines - the so-called Dialup connection. The speed of such a connection is small, the maximum speed can reach 56 kbps. This is still enough to access the Internet, however, the saturation of pages graphics and video, large amounts of email and documents, the possibility of exchanging users with multimedia information, has set the task of increasing the bandwidth of the existing subscriber line. The decision of this issue was the development of ADSL technology.
ADSL technology (ASYMMETRIC Digital Subscriber Line is an asymmetric digital subscriber line) is the most promising at present, at this stage of the development of subscriber lines. It is part of a general group of high-speed data transmission technologies combined by a general term DSL (Digital Subscriber Line-digital subscriber line).
The main advantage of this technology is that there is no need to lay the cable to the subscriber. Already laid telephone cables are used to which splitters are installed to split the signal to the "telephone" and "modem". Different channels are used for receiving and data transfer: the admissive has a significantly higher bandwidth.
The general name of DSL technologies appeared in 1989, when the idea of \u200b\u200busing analog-to-digital conversion appeared on the subscriber end of the line for the first time, which would improve the data transfer technology over a twisted pair of copper telephone wires. The ADSL technology was designed to ensure high-speed (can even be measured by megabit) by film-actuable video services (video participation, video games, etc.) and no less fast data transmission (Internet access, remote access to LAN and other networks). To date, DSL technology, presents:
- ADSL (Asymmetric Digital Subscriber Line - Asymmetric Digital Subscriber Line)
This technology is asymmetric, that is, the speed of data transfer from the network to the user is significantly higher than the data transfer rate from the user to the network. Such asymmetry, in combination with the state of the "constantly installed connection" (when it is eliminated by the need to dial the phone number every time and wait for the connection of the connection), makes the ADSL technology ideal for organizing access to the Internet, access to bubble networks (LAN), etc. When organizing such connections, users usually receive a much greater amount of information than transmitted. The ADSL technology provides the speed of the "descending" data flow ranging from 1,5 Mbps to 8 Mbps with the spots of the "ascending" data flow from 640 kb / s to 1,5 Mbps. ADSL allows you to transmit data at a speed of 1.54 Mbps per distance to 5.5 km on one twisted pair of wires. The transmission rate of the order of 6-8 MBIT / C can be achieved when transmitting data to a distance of no more than 3.5 km along the wires with a diameter of 0.5mm.
- R-ADSL (Rate-Adaptive Digital Subscriber Line-Digital Subscriber Line with Connection Speed \u200b\u200bAdaptation)
R-ADSL technology provides the same data transfer rate as ADSL technology, but it allows you to adapt the transfer rate to the length and state of the twisted pair of wires. Using r-ADSL technologies The connection on different telephone lines will have a different data transfer rate. Data transfer rate can be selected when synchronizing the line during connection or snagging from the station.
- G. Lite (adsl.lite)
It is a cheapest and easy-to-install ADSL version, which provides the speed of the "downward" data stream to 1.5 Mbit / s and the speed of the "ascending" data flow to 512kbps or 256 block / s in both directions.
- HDSL (High Bit-Rate Digital Subscriber Line-High Speed \u200b\u200bDigital Subscriber Line)
HDSL technology provides for the organization of a symmetric data line, that is, data rates from the user to the network and from the network to the user are equal. Due to the transfer rate (1.544Mbps for two pairs of wires and 2.048 Mbps in three pairs of wires), telecommunication companies use HDSL technology as an alternative to T1 / E1 lines. (T1 lines are used in North America and provide the data transfer rate of 1.544 MBIT / s, and the E1 lines are used in Europe and provide a data transfer rate of 2.048Mbps.) Although the distance to which the HDSL system transmits data (and this is about 3.5 - 4.5km), less than when using ADSL technology, for an inexpensive, but efficient, increasing the length of the HDSL line, telephone companies can establish special repeaters. The use of two or three twisted pairs of telephone wires to organize the HDSL line, makes this system the ideal solution for connecting remote PBX nodes, Internet servers, local networks, etc.
- SDSL (Single Line Digital Subscriber Line-Single Room Digital Subscriber Line)
As well as HDSL technology, SDSL technology provides symmetric data transmission with speeds corresponding to the T1 / E1 line speeds, but the SDSL technology has two important differences. First, only one twisted pair of wires is used, and secondly, the maximum transmission distance is limited to 3km. Within this distance, the SDSL technology provides, for example, the operation of the video conferencing system, when you need to maintain the same data streams in both directions.
- SHDSL (Simmetric High Speed \u200b\u200bDigital Subscriber Line - Symmetrical High Speed \u200b\u200bDigital Subscriber Line
Most modern type DSL technology, is aimed primarily to ensure guaranteed quality Maintenance, that is, at a given speed and data range, it is not worse than 10 -7 errors even in the most unfavorable noise conditions.
This standard is the development of HDSL, since it allows you to transmit a single pair of digital stream. SHDSL technology has several important advantages compared to HDSL. First of all, these are the best characteristics (with respect to the limit length of the line and stock price) by applying a more efficient code, pre-coding mechanism, more advanced correction methods and improved interface parameters. This technology is spectrally compatible with other DSL technologies. Since the new system uses a more efficient linear code compared to HDSL, then at any speed, the SHDSL signal takes a narrower frequency band than the corresponding HDSL signal corresponding to the same velocity. Therefore, created by the SHDSL system, interference for other DSL systems have less power compared to HDSL interference. Spectacular SHDSL signal density has such a form that it turns out to be spectrally compatible with ADSL signals. As a result, compared with a single-page version of HDSL, SHDSL allows you to increase the transmission rate at 35-45% with the same range or increase the range by 15-20% at the same speed.
- IDSL (ISDN Digital Subscriber Line - IDSN digital subscriber line)
IDSL technology provides completely duplex data transmission at speeds up to 144 kbps. Unlike ADSL, IDSL features are limited only to data transmission. Despite the fact that IDSL as well as ISDN uses 2B1Q modulation, there are a number of differences between them. Unlike ISDN, the IDSL line is a noncommuted line that does not lead to an increase in the load on the commuting equipment of the provider. Also, the IDSL line is "permanently enabled" (like any line, organized using DSL technology), while ISDN requires a connection to install.
- VDSL (Very High Bit-Rate Digital Subscriber Line - ultrahigh-speed digital subscriber line)
VDSL technology is the most "fast" XDSL technology. It provides the transfer rate of the "descending" flow of flow within from 133 to 52 Mbps, and the rate of data transfer of the "ascending" flow ranging from 1.5 to 2.3 Mbps, with one twisted pair of telephone wires. In symmetrical mode, speeds are maintained to 26 Mbps. The VDSL technology can be considered as an economically effective alternative to laying the fiber-optic cable to the end user. However, the maximum data transmission distance for this technology ranges from 300 meters to 1300 meters. That is, either the length of the subscriber line should not exceed this value, or the optical fiber cable must be listed closer to the user (for example, headed by a building in which there are many potential users). VDSL technology can be used with the same objectives as ADSL; In addition, it can be used to transmit high definition television signals (HDTV), video on request, etc. Technology is not standardized, different equipment manufacturers are different speeds of speeds.
So what is ADSL? First of all, ADSL is a technology that allows you to turn the tween pair of telephone wires to the high-speed data transmission path. The ADSL line connects access equipment to the DSLAM (DSL Access Multiplexor) and the client modem, which are connected to each end of the twisted pair of the telephone cable (see Figure 1). At the same time, three information channels are organized - "downstream data transfer stream," ascending "data transfer stream and a channel of a regular telephone (POTS) (see Figure 2). The telephone channel is highlighted using the filter separator - Splitter, and directs it to the usual A telephone set. This scheme allows you to talk on the phone simultaneously with the transfer of information and use the telephone connection in the event of an ADSL hardware malfunction. A constructive telephone separator is a frequency filter that can be integrated into the ADSL modem and be an independent device.
Fig. one 
Fig. 2.
ADSL is an asymmetric technology. The speed of the "downward" data flow (i.e., the data that is transmitted towards the end user) is higher than the speed of the "ascending" data stream (in turn transmitted from the user towards the network). Immediately it should be said that you should not look for a reason for concern. The data transfer rate from the user (more "slow" data sending) is still significantly higher than when using an analog modem. Such asymmetry is introduced artificially, the modern range of network services involves a very minor transmission rate from the subscriber. For example, to obtain video in MPEG-1 format, a bandwidth is required 1.5 Mbps. For service information transmitted from the subscriber (exchange of teams, service traffic) is quite enough 64-128 kbps. According to statistics, incoming traffic several times, and sometimes an order of magnitude exceeds outgoing. Such speed ratio causes optimal performance.
To compress a large amount of information transmitted by twisted pair of telephone wires, the ADSL technology uses digital signal processing and specially created algorithms, advanced analog filters and analog-digital converters. Long length telephone lines can weaken the transmitted high-frequency signal (for example, at a frequency of 1 MHz, which is the usual transmission rate for ADSL) by up to 90DB. This causes the analog ADSL modem systems to work with a fairly heavy load, which allows you to have a large dynamic range and low noise levels. At first glance, the ADSL system is quite simple - the high-speed data transmission channels are created using the usual telephone cable. But, if you understand the ADSL in detail, it can be understood that this system refers to the achievements of modern technology.
ADSL technology uses a method of separating the bandwidth of the copper telephone line into several frequency bands (also called carriers). This allows you to simultaneously transmit multiple signals over the same line. Exactly the same principle underlies cable television when each user has a special converter, a decoding signal and allows you to see a football match or a fascinating film on the TV screen. When using ADSL, different carriers simultaneously transfer various parts of the data transmitted. This process is known as Frequency Division Multiplexing - FDM Frequency (Figure 3).
Fig. 3.
With FDM, one range is allocated to transmit the "ascending" data stream, and the other range for the "downward" data stream. The information "downward" stream is divided into several information channels - DMT (Discrete Multi-Tone), each of which is transmitted on its carrier frequency using QAM. QAM is a modulation method - Quadrature Amplitude modulation, called quadrature amplitude modulation (CAM). It is used to transmit digital signals and provides a discrete change in the state of the carrier segment simultaneously in phase and amplitude. Usually, DMT splits the band from 4 kHz to 1.1 MHz on 256 channels, each 4 kHz wide. This method, by definition, solves the range of block separation between voice and data (it simply does not use), but is more complicated in implementation than CAP (Carrierless Amplitude and Phase modulation) - amplitude-phase modulation without transferring carrier. DMT is approved in the ANSI T1.413 standard, as well as recommended as the basis of the Universal ADSL specification. In addition, echocompensation technology (Echo Cancellation) can be used, when using the "ascending" and "downward" bands overlap (see Figure 3) and are separated by means of local echompensation.
It is thus ADSL can provide, for example, simultaneously high-speed data transmission, video transmission and fax transmission. And all this without interrupting the usual telephone connection, which uses the same telephone line. Technology provides a redundancy of a specific frequency band for a regular telephone communication (or POTS-PLAIN OLD Telephone Service). It's amazing how quickly the telephone connection has become not only in the "simple" (Plain), but also in the "old" (old); It turned out something like a "old kind telephone connection". However, it should be given proper to developers of new technologies that still left the telephone subscribers a narrow strip of frequencies for live communication. In this case, the telephone conversation can be done simultaneously with high-speed data transmission, and not to choose one of two. Moreover, even if you turn off the electricity, the usual "old kind" telephone communication will still work and with the challenge of the electrician you have no problems. Ensuring such an opportunity was one of the sections of the original ADSL development plan.
One of the main advantages of ADSL over other high-speed data transmission technologies is the use of the most common twisted pairs of copper wires of telephone cables. It is quite obvious that there are much more such pairs of wires (and this is still weakly said) than, for example, cables laid specifically for cable modems. ADSL forms, if you can say so, "superimposed network".
ADSL is a high-speed data transfer technology, but how high-speed? Considering that the letter "A" in the name ADSL means "asymmetric" (asymmetric), it can be concluded that data transmission in one direction is faster than the other. Therefore, two data transfer rates should be considered: "Downward" stream (transmitting data from the network to your computer) and "ascending" stream (data transmission from your computer to the network).
Maximum receiving speed - DS (DOWN STREAM) and transmission - US (UP Stream) depends on many factors dependency on which we will try to consider later. In the classic version, ideally, the rate of reception and transmission depends and conditioned by DMT (Discrete Multi-Tone) by splitting the bandwidth from 4 kHz to 1.1 MHz on 256 channels, each 4 kHz wide. These channels, in turn, represent 8 digital flows T1, E1. For the transfer of Down Stream, 4 T1, E1 stream is used, the total maximum bandwidth of which is 6.144 MBIT / s - in the case of T1 or 8,192 MBIT / s in the case of E1. To transfer Up Stream, one stream T1 - 1.536 Mbps. The maximum maximum speeds are indicated without taking into account overhead, in the case of a classic ADSL. Each thread is supplied with error correction code (ECC) by introducing an additional bit.
Now consider how the real data transfer is happening in the following example. Information IP packets generated in both local customer networks and personal computersDirectly connected to the Internet will enter the ADSL modem input in the frame of the Ethernet 802.3 standard. The subscriber modem splits and "places" the contents of Ethernet 802.3 frames into the ATM cells, provides the last address of the destination and transmits them to an ADSL modem output. That in accordance with the standard T1.413 "encapsulates" atm cells into the digital stream E1, T1, and then the traffic on the telephone line enters DSLAM. The DSL Multiplexor - DSLAM station is performed by the "Recovery" procedure of ATM cells from the T1.413 package format and directs them using the ATM Forum PVC (Permanent Circuit) protocol in the Main Access subsystem (ATM Network), which delivers ATM Cells According to the address specified in them, i.e., one of the service centers. When implementing the Internet access services, the cells arrive at the Internet provider router that performs the function of the terminal device in a constant virtual channel (PVC) between the subscriber terminal and the Internet provider node. The router produces the opposite (relative to the subscriber terminal) transformation: collects incoming cells atm and restores the source frame format Ethernet 802.3. When transmitting traffic from the service center to the subscriber, absolutely similar transformations are carried out, only in reverse order. In other words, a "transparent" Local Network of the Ethernet 802.3 protocol is created between the Ethernet port of the subscriber terminal and the virtual port of the router, and computers connected to the subscriber terminal are perceived by the Internet provider router as one of the devices. local network.
The general denominator when providing access services in the Internet is an IP network-level protocol. Therefore, the chain of protocol transformations carried out in the broadband access network can be represented as follows: client application - IP Pack - Ethernet Frame (IEEE 802.3) - ATM cells (RFC 1483) - modulated ADSL signal (T1.413) - ATM cells (RFC 1483) - Ethernet frame (IEEE 802.3) - IP Package - application on the Internet resource.
As already mentioned above, the stated speeds are possible only in the perfect version and without taking into account overhead. So in the E1 stream during data transmission, one channel (depends on the protocol used) is used to synchronize the stream. And in the end, the maximum speed taking into account the overhead costs will be the down stream - 7936kbit / sec. There are other factors that have a significant impact on the speed and stability of the connection. Such factors include: the length of the line (the bandwidth of the DSL line is inversely proportional to the length of the subscriber line) and the cross section of the wire. The characteristics of the line deteriorate with an increase in its length and decrease the cross section of the wire. Also on the data transfer rate affects the overall condition of the subscriber line, the presence of twists, cable taps. The most "harmful", factors that directly affect the ability to install the ADSL connection is the presence of Pupinovsky coils on the subscriber line, as well as a large number of taps. None of the DSL technologies can be used on lines having Pupinovsky coils. Ideally, when checking the line, not only to determine the presence of Pupinovsky coils, but also find the exact location of their installation (anyway, you will have to look for coils and remove them from the line). The Pupinovsk coil used in the analog telephone systems is a 66 or 88 mp inductor. Historically, Pupinovsky coils were used as a constructive element of a long (more than 5.5 km) of the subscriber line, which allows to improve the quality of the transmitted sound signals. Under the cable tap is usually understood as a cable site that is connected to the subscriber line, but is not included in the direct connection of the subscriber with the telephone station. The cable tap is usually connected to the main cable and forms branching in the form of the letter "Y". It often happens that the cable removal goes to the subscriber, and the main cable goes on (while this pair of cable should be open at the end). However, for the suitability of a specific subscriber line to use the DSL technology, not how much the fact of the connection is affected as the length of the cable removal itself. Until a certain length (about 400 meters), cable taps do not significantly affect XDSL. In addition, cable cancellations affect different XDSL technologies. For example, HDSL technology allows cable removal to 1,800 meters. As for ADSL, cable taps do not prevent the very fact of organizing high-speed data transmission over the copper subscriber line, but can narrow the bandwidth and, accordingly, reduce the transfer rate.
In the pluses of a high-frequency signal that gives the possibility of digital data transmission, there are its consumption, namely exposure to the effects of external factors (various fittings from third-party electromagnetic devices), as well as physical phenomena in the line during transmission. An increase in the capacitive characteristics of the channel, the emergence of standing waves and reflections, insulating characteristics of the line. All of these factors lead to an extraneous noise on line, and a faster signal attenuation and, as a consequence, to reduce the data transfer rate and reduce the length of the data line suitable for data transmission. Some characteristics of the ADSL line, which can be directly judged by the quality of the telephone line can give an ADSL modem itself. In almost all models of modern ADSL modem, contains information about the quality of the connection. Most often, Status-\u003e Modem Status tab. Approximate content (may vary depending on the modem model and manufacturer) the following:
Modem Status.
Connection Status Connected.
US RATE (KBPS) 511
DS RATE (KBPS) 2042
US MARGIN 26.
DS MARGIN 31.
Trained Modulation ADSL_2Plus
LOS ERRORS 0.
DS Line Attenuation 30
US Line Attenuation 19
PEAK CELL RATE 1205 CELLS PER SEC
CRC RX FAST 0
CRC TX Fast 0
CRC RX Interleaved 0
CRC TX Interleaved 0
Path Mode Interleaved.
DSL statistics
Near End F4 Loop Back Count 0
Near End F5 Loop Back Count 0
Let's explain some of them:
Connection Status Connected - Connection Status
US RATE (KBPS) 511 - Outgoing Flow Speed \u200b\u200bUp Stream
DS RATE (KBPS) 2042 - Downstream Downstream Speed
US MARGIN 26 - noise level of outgoing connection in DB
DS MARGIN 31 - noise noise level in DB
Los Errors 0 -
DS Line Attenuation 30 - Signal attenuation in a downlink in DB
US Line Attenuation 19 - Signal attenuation in the outgoing connection in DB
CRC RX Fast 0 - Non-non-error. There are also FEC (adjusted) and HEC - errors
CRC TX Fast 0 - Non-non-error. There are also FEC (adjusted) and HEC - errors
CRC RX Interleaved 0 - Number of non-errors. There are also FEC (adjusted) and HEC - errors
CRC TX Interleaved 0 - Number of uncorrected errors. There are also FEC (adjusted) and HEC - errors
Path Mode Interleaved - Error Correction Mode Enabled (Path Mode Fast - Disabled)
According to these values, it can be judged, as well as control yourself, about the status of the line. Values:
Margin - SN Margin or Signal to Noise Ratio). The noise noise level depends on the set of different wet factors, the number and length of the taps, the synchronism of the line, the "sprawling-beybiness" of the cable, the presence of twists, the quality of physical connections. In this case, a decreased signal of an outgoing ADSL stream (UPStream) is completely absence and, as a result, the loss of ADSL modem synchronization
Line Attenuation is the attenuation value (the more distance from Dslama, the greater the attenuation value. The greater the frequency of the signal, and consequently the connection speed is the greater the attenuation value).
AdSL technology
In recent years, the growth in information transfer has led to the fact that there is a shortage of bandwidth of access channels to existing networks. If at the corporate levels this problem is partially solved (renting high-speed transmission channels), then in the apartment sector, and in the small business sector these problems exist.
To date, the main way to interact the terminal users with private networks and network networks is access using a telephone line and modems, devices that provide digital information on subscriber analog telephone lines. The speed of such a connection is small, the maximum speed can reach 56 kbps. This is still enough to access the Internet, however, the saturation of pages of graphics and video, large amounts of email and documents will again raise the question of the ways to further increase the bandwidth.
The most promising is the ASYMMETRIC DIGITAL Subscriber Line. This is a new modem technology that turns standard subscriber telephone analog lines in high-speed access line. ADSL technology allows you to transfer information to the subscriber at a speed of up to 6 Mbps. IN reverse direction Used speed up to 640 kbps. This is due to the fact that the entire modern spectrum of network services involves a very small transmission rate from the subscriber. For example, to obtain video foilms in MPEG-1 format, a bandwidth is 1.5 Mbps. For service information transferred from the subscriber, 64-128 kbit / s is quite enough (Fig. 1).
Principles of organization ADSL services
The ADSL service (Fig. 1) is organized using the ADSL modem, and the ADSL modem racks called DSL Access Module. Almost all DSLAM is equipped with an Ethernet 10Base-T port. This allows us to use conventional hubs, switches and routers on access nodes.
A number of manufacturers began to supply DSLAM interfaces atm, which allows you to directly connect them to the ATM-switch-switches of geographically distributed networks. Also, a number of manufacturers create custom modems that are an ADSL modem, but for software are ATM adapters.
On the site between the ADSL modem and DSLAM, three streams function: high-speed flow to the subscriber, a bidirectional service and speech channel in the standard CT channel frequency range (0.3-3.4 kHz). Frequency dividers ( Pots Splitter.) Allocate the telephone stream, and send it to a regular telephone. This scheme allows you to talk on the phone simultaneously with the transfer of information and use the telephone connection in the event of a malfunction of the ADSL equipment. A constructive telephone separator is a frequency filter, which can be both integrated into the ADSL modem and be an independent device.
According to Theorem Shannon, It is impossible using modems to reach speeds above 33.6 kbps. In ADSL technology, digital information is transmitted outside the frequency range of the standard Channel Channel. This will lead to the fact that the filters installed on the telephone station will cut the frequency above 4 kHz, so it is necessary at each telephone station to install access equipment to geographically distributed networks (switch or router).
The transfer to the subscriber is carried out at speeds from 1.5 to 6.1 Mbps, the speed of the service channel ranges from 15 to 640 kbps. Each channel can be divided into several logical low-speed channels.
Speeds provided by ADSL modem multiple speeds of digital channels T1, E1. In the minimum configuration, the transmission is carried out at a speed of 1.5 or 2.0 Mbps. In principle, today there are devices transmitting data at a rate of up to 8 Mbps, but in the standards this speed is not defined.
ADSL modems speed depending on channel numbers
| Basic speed | Number of channels | Speed |
|---|---|---|
| 1.536 Mbps | 1 | 1.536 Mbps |
| 1.536 Mbps | 2 | 3,072 Mbps |
| 1.536 Mbps | 3 | 4,608 Mbps |
| 1.536 Mbps | 4 | 6,144 Mbps |
| 2,048 Mbps | 1 | 2,048 Mbps |
| 2,048 Mbps | 2 | 4,096 Mbps |
| 2,048 Mbps | 3 | 6,144 Mbps |
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 decrease the cross section of the wire. The table shows several options for the dependence of the speed of the line parameters.
The ADSL modem is a device built on the basis of a digital signal processor (CSP or DSP), similar to that used in conventional modems (Fig. 2). IN general, All the 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 range of data transmission signal lies in the range of 4 kHz to 1 MHz. The physical parameters of most lines do not allow to transmit data with a frequency of more than 1 MHz. Unfortunately, not all existing telephone lines (especially high length) have even characteristics, therefore you have to reduce the bandwidth, which entails a decrease in the transmission rate.
Two methods are used to create these threads: a method with frequency separation of channels and an echo compensation method.
Fig. 3. Flow split circuits in the band line pass band
The frequency separation method is that each of the streams highlights its frequency bandwidth. The high-speed flow can be separated by one or lower streams. The transfer of these threads is carried out by the method " "(DMT).
The echo method of compensation is that high-speed and service flow ranges are superimposed on each other. The separation of streams is carried out using a differential system built into the modem. This method is used in the work of modern modems v.32 and v.34. High-speed flow can be separated by one or lower-speed flows of transmission of these threads carried out by the method " discrete multi-end modulation"(DMT).
When transmitting multiple streams, each of them is separated into blocks. Each unit is supplied with error correction code (ECC).
Related technologies
There are a number of related technologies, some of which are intended for terminal users, others for transit transmission of high-speed flows. The principle of operation is similar to ADSL. The general name of such XDSL technologies.
High Data-Rate Digital Subscriber Line (HDSL)
HDSL is a technology that provides transmission at a speed of 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 the dedicated channels E1, T1. Requires a four-wire subscriber line.
Single-Line Digital Subscriber Line (SDSL)
Similar to HDSL, it is characterized in that it is enough to organize a line of a two-wire subscriber 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 to 1.5 km. The technology is quite expensive, and does not find a wide application.
Rate Adaptive Digital Subscriber Line (Radsl)
ADSL technology has one essential disadvantage. It does not allow to change the speed depending on the quality of the line. In such modem, the selection of speed, 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)
The ADSL technology has a number of minor disadvantages that impede the widespread technology introduction on subscriber access networks. This is the complexity of installing ADSL devices; They require a serious configuration to a specific subscriber line (as a rule, with the participation of the company's technical staff-operator), have a relatively large value.
Not so long ago, there were reports of creating a new version of ADSL technology, which is designed to eliminate these disadvantages. It is called Universal ADSL (UADSL), or DSL Lite. True, using this technology, the data is transmitted at lower speeds than in ADSL (with the length of the subscriber line up to 3.5 km, the speed is 1.5 Mbps towards the subscriber and 384 kbps - in the opposite direction; at length The subscriber line up to 5.5 km is provided by 640 kbps towards the subscriber and 196 Kbps - in the opposite). However, these devices are easier to install; In addition, there is a frequency separator in their composition, so it does not have to be installed separately. Essentially, it is enough just to connect the UADSL modem to the phone socket, as well as the usual modem.
The cost of such devices does not exceed the cost of the usual modem, so it is worth expecting that it is this technology that will find a wide application in the hardware access equipment.
Standards
US National Institute of Standards (ANSI), the Working Group T1E1.4 recently approved the standard for ADSL with a transfer rate to 6.1 Mbps (ANSI standard T1.413). ETSI completed this standard requirements for Europe. T1.413 Determines the unified terminal interface from the operator. The second version of this standard developed by the T1E1.4 group expanded the standard in which identified: a multiplexed interface from the operator; Configuration and network management protocols.
A little digit
Distances for Short Range modems depend on the diameter of the copper pair:
1. Telindus Crocus HDSL 2048KB / S:
| Wire Diameter (MM) | 2-Pair Version (KM) | 3-Pair Version (KM) |
|---|---|---|
| 0.4 | 3.6 | 4.0 |
| 0.5 | 5.0 | 5.5 |
| 0.6 | 7.1 | 7.8 |
| 0.8 | 8.9 | 9.9 |
| 1.0 | 12.5 | 13.9 |
2. Telindus Crocus SDSL:
| Wire Diameter. | 384 Kbit / s | 768 kbit / s | 1152 kbit / s |
|---|---|---|---|
| 0.4 mm. | 5.0 km. | 4.3 km. | 3.6 km. |
| 0.5 mm. | 6.9 km. | 6.0 km. | 5.0 km. |
| 0.6 mm. | 9.8 km. | 8.4 km. | 7.1 km. |
| 0.8 mm. | 12.4 Km. | 10.6 km. | 8.9 km. |
| 1.0 mm. | 17.3 km. | 14.9 km. | 12.5 km. |
| 1.2 mm. | 19.3 Km. | 16.6 km. | 13.9 km. |
3. Telindus Crocus HS (144KB / S):
| Wire Diameter (MM) | distance (KM) |
|---|---|
| 0.4 | 6.9 |
| 0.5 | 9.5 |
| 0.6 | 13.5 |
| 0.8 | 17.5 |
| 1.0 | 26.0 |
Supplement1
The article is well written, everything is true, but there are some comments regarding the introduction of ADSL in real life. Unfortunately, on ordinary Russian communication lines ADSL can only be used in the order of the experiment, and there is no speech about industrial operation. For ADSL, the line requires a twisted pair (and not noodles), and shielded, and if it is a multi-point cable, then in compliance with the direction and step of the oblast.
It is possible to argue (S.Zh.), noting that noodles goes only on the plot from the cross in the house to the apartment, it does not submit it to the vitua couple, both technical and economic difficulties. At the site, the cross-telephone station uses multi-party cables, where each pair is twisted.
It seems to be convincingly, did you try to disassemble the phone cable? Remove the isolation meter from an import cable and from domestic. Imported-blossoms to twisted couples that are not broken if they even lose them, and the domestic almost immediately turns into a broom and requires a fair workmanship to cut it without additional devices. The replacement of the noodle also does not seem to look scary, but after all the noodles will not cost here, it will be necessary to replace the CRT (distribution telephone box), especially if it is plastic (remember how the LAN is bred) and it costs it in each subsidence and often not one. The direction of the observant in domestic multi-park cables is not observed (disassemble our 50 pair cable or 100 pairwise), because no one thought that such cables will be used to transfer wide high-frequency signals, respectively, about protecting against transitional interference, too, no one wondered. In the capitalists, perhaps, this blessing also occurred by chance, because there is competition and that the products bought, it must be even not compliant, but the parameters recommended by all kinds of comedians (because these commissions are not given to their bread) and on the territory of one district (or Even quarters) two or more telephone service provider can work. As always, thanks to competition, high-quality goods and services are obtained.
For E1, a twisted pair is used with two screens isolated from each other by a long cable and with a regulated number of cable spans, otherwise it does not have to talk about any kilometer and about stable communication.
This is true, but in my opinion (s.zh.) DSL technology will rather find their applied not in industry, but in the apartment sector.
Yeah, that's what I can add (I.Sh.), a couple of years ago, this technology was offered to Rostelek for the reconstruction of short highways, and the main cable is not a home wiring for such a cable and 64 Mbps to skip and built this upgrades under the station scheme Cable station. Well, Rostelecom did not agree to use these technologies, because expensive. I doubt that now the equipment fell so much that it stands like an Ezernets hub? And if I'm wrong, then someone wants to warm up the hands at the modernization of cable lines and the introduction of new techniques.
Well, now I will imagine that 2-6 Mbps started in the telephone cable, and it does not possess the corresponding parameters (often the intermane isolation is underestimated - well, it was impelled to the poor fellowship, you were heard probably cods and space negotiations in the tube), as a result, pressing . I think that these tips will be a consequence of combinatorial frequencies, and a very wide spectrum that will create such interference with television receivers, which may begin a real war. So in practice, not everything is smooth, unfortunately.
That is why, personally, I think (s.zh.), which is much more relevant to introduce UADSL With low speeds (up to 640 kbps). All the indicated effects in this technology will be expressed in a much lesser extent.
I think (I.Sh.), that anyway, the price of such an introduction will be too high at this stage to seriously think about it. So, here more problemsWhat seems at first glance and in any case a more serious approach is required.
But my information (S.Zh.): providers, in particular, grew, do not share your views on the technical plan problems and can provide ADSL equipment. Installing the modem, setup, connection, costs about $ 2,500. It provides speeds of up to 640 kbps. The monthly subscription fee is about $ 300.
ADSL modems are now standing around $ 800-1500. UADSL modems must cost about $ 250-500, which is more acceptable.
As soon as the access equipment for data transmission networks will be installed on each telephone node, such a type of service will increase significantly, and the introduction of such access equipment is directly related to the implementation of ATM.
Supplement2.
In the article, Stanislav Zhuravlev is well referred to the 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, HDSL technologies were developed by the research division of Bell's research division specifically for use in the existing copper wire infrastructure, which even in USA is distinguished by old age and is built on a regular copper telephone pair, and not on shielded twisted.
Secondly, "noodles" is really not suitable for HDSL lines, but "noodles" is used on a plot from the distribution box to a 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 com), do not allow the use of HDSL devices, this is a pupinization and assembly of wires of various sections. Line pupinization is the introduction of the inductive component in the line in order to reduce the attenuation of the signal, but in Russia such lines are almost not used. The second problem occurs quite often, but if the station part of the equipment is located on the nearest PBX to you, then the likelihood of a similar problem is small, in any case this problem can be solved with a local telephone node. However, if you need a direct channel, for example, to connect two local networks, it is not a problem. In Moscow, there is a sufficiently large number of direct channels of copper working on a distance of 5-7 km and resistance to 1-1.5 com.
The wide distribution of HDSL technologies in Russia is contained, first of all, not the insufficient number of telephone pairs with acceptable parameters (as long as the number of installed lines in Moscow is calculated with tens or hundreds), and the cost of equipment, $ 2000-3000 for a set of station and subscriber parts, connection price and the cost of the dedicated channel (see for curiosity from any of the providers as much as the synchronous channel 64k the price channel is unpleasant). The speed of the already installed lines usually ranges within 64-512. HDSL lines operating at speeds more than 2MBIT on copper I did not meet at all and I think in the near future their appearance is unlikely. This is explained by the fact that the cost of 2Mbps the flow is so much so much that it can allow him to be either very large commercial firms, or telecommunication companies themselves, who are dealing with providing, and such a criterion is very important as a probability of error on the channel. The smallest probability of error ensures optical fiber, the stability of which will be in any case several orders of magnitude higher than the HDSL line.
The most rainbow perspectives seem to me have the equipment calculated at 64-512k, especially created in accordance with the standard UDSL, which must be accepted by the end of this year. Manufacturers promise the price of a subscriber UDSL modem no more than $ 300-400. If the provision of XDSL services will be interested in large telecommunications companies (the ideal MGTS: -)))), which will be able to place the station sets of equipment on a large number of phone nodes at their expense, we will have a sharp increase in the number of HDSL lines used in the near future.
ADSL is a technology of asymmetric Internet access. It is an asymmetric system by its structure and allows you to work with compounds at a speed of up to 8 Mbps. ADSL technology, the transmission rate of which is calculated up to 1 Mbps, operates on average at a distance of more than 5 km. Today we will look at what kind of connection type and how it works.
History of appearance
Before answering the question: "ADSL - what is it?", We bring to your attention some historical data. For the first time, the creation was spoken at the end of the 80s, when even the Internet in its modern guise was only the main task in 1989 there was an improvement and upgrades of data transmission technology over copper telephone wires. Analog-to-digital conversion was created mainly to quickly transmit information between different interactive services, video games, video files, as well as to obtain instant remote access to LAN and other network systems.
Modern ADSL technology: work principle
The network is based on a subscriber's digital line, which provides internet access channels. But the telephone lines use an analog signal to transmit voice messages. ADSL connection is designed to convert an analog signal into digital and transmit it directly to the computer. At the same time, in contrast to the already outdated Dial-UP modems, the ADSL database devices do not block the telephone line and allow you to use digital and analog signals at the same time.
The essence of the technology (asymmetry) is that the subscriber receives a huge amount of data - incoming traffic, and transfers the minimum of information - downstream traffic. As an incoming, different kind of content is meant: video and media files, applications, objects. The downward refers only important technical information - various commands and requests, emails and other secondary elements. Asymmetry is that the speed from the network to the subscriber is at times higher than the speed of the user.
The most important advantage that the ADSL-technology possesses is its budget and economy. The fact is that the same copper amounts in them are used to work the system, of course, significantly exceeds the number of similar elements in cable modems. But at the same time, no upgrades of switching equipment and complex reconstruction should be performed. ADSL connects quickly, and modern modem types are intuitive in management and configuration.
What equipment is used for this connection?
In order for the technology to work, special types of modems are used, differing in their structure, design, connection type:
- PCI modems (internal computer devices).
- External modem with USB connection type.
- Devices with an Ethernet view interface.
- with Ethernet scheme.
- Profile types of modems (for security enterprises, private telephone lines).
- Router with internal Wi-Fi access points.
Additional equipment: splitters and microfilters
We must not forget that to connect such a gadget as an ADSL modem, splitters and microfilters will be required. Separate devices in accordance with the design of the telephone cable. In that situation, when the cable is made (or can be carried out) to dilute the channel modem and telephone channel, splitter is used. In another case, the purchase of a microfilter, which is installed on each telephone present in the room.
The main task of the splitter is the separation of frequencies - voice (0.3-3.4 kHz) and used directly by the modem themselves (25 kHz-1.5 MHz). It is in this way that the simultaneous efficiency of the modem and the phone is ensured, which do not interfere with each other and do not create interference. Splitters are compact and not cause unnecessary inconvenience. The miniature box is equipped with three connectors and has a small weight.
ADSL - What is it? High Speed \u200b\u200bInternet Connection Stages
- Select provider. Use this technology to currently offers each provider. Different types and tariffs depend on the region, as well as on the technical capabilities of the company, the coverage area of \u200b\u200bwhich can be limited.
- Buying equipment. Currently, it is not necessary to buy a modem, splitters and microfilters. When making a contract for connecting the provider proposes to take the necessary equipment for rent, including the ADSL modem. In the future, when dividating the document, the equipment returns back. The client pays exclusively for the Internet connection. Modern Internet ADSL - What is it? This is a fast, cheap and high-quality connection method.
- Account activation. For each client, the provider reserves an account whose activation can take up to 12 days. However, in most cases, with normal network coverage, the procedure does not require more than a few hours. The provider checks the phone number on the ability to connect ADSL. If the access zones of technology is not enough, then high-speed Internet will not work.
- Setup equipment. At this stage, connecting devices to a telephone line, installation of splitters and microfilters, installation of modem drivers to a computer, as well as setting the network parameters of the modem in the Internet browser.
pros
What are the advantages of ADSL technology? Here are some of them:
- High ADSL allows without of great difficulty Transfer of files of any volume without a long wait. The technology is constantly improving, and speeds grow, significantly expanding the possibilities of the subscriber.
- Wireless connection. To use the ADSL system, you do not need to stretch the cable to the subscriber and set a large number of equipment. Reliability, quality and functionality of the network increases.
- No interference on the telephone line. The ADSL router operates in independent mode and does not create any problems for the phone. You can call and travel via virtual space can be completely free.
- Permanent access to the Internet ADSL. What it is? This means that during operation, the network will not give failures. Technology does not require reconnect. The user gets access to the Internet constantly and can be online on the clock.
- Reliability and stability. To date, ADSL is the most reliable type of Internet connection.
- Profitability. The cost of connecting ADSL and the installation of the modem with the router is minimal and will not hit the family budget.
disadvantages
- Lack of protection against cross-tip. If several dozen clients are connected to one channel, it is not necessary to count on high speed. The more subscribers on one ADSL, the lower the data transfer.
- ADSL technology deficiencies though has, but they are few. This also includes the minimum speed from the subscriber. The ADSL asymmetry has an obvious minus - from the subscriber the transfer of files will be long and inconvenient. But the technology is intended primarily to quickly access the Internet, for surfing. In addition, information transmitted from the subscriber takes a minimum of space and does not require a large resource.
Speed \u200b\u200band factors affecting it
ADSL is a high-speed Internet technology, but the universal value and the formula does not exist. For each individual subscriber, the speed is individual and is determined by a set of factors. Including some of them may affect the reliability and quality of equipment. Therefore, to install modems and routers best professionals.
The main reason for the low speed ADSL connection is the quality of the subscriber line. We are talking about the presence of cable taps, their condition, the diameter of the wires and length. The attenuation of the signal is a direct consequence of an increase in the length of the subscriber line, and it is possible to reduce the interference by expanding the diameter of the wire. The standard ADSL channel length does not exceed 5 km - the optimal range for high-speed data transmission.
Speed \u200b\u200bcharacteristics
If you compare with other Internet connection technologies, ADSL greatly wins the speed. Analog modem will give a maximum of up to 56 kbps, while the ADSL at the dawn of its appearance already allowed to transfer information at a speed of up to 144 kbps.
ADSL technology, the maximum speed of which is also determined by the characteristics of the modem and can reach 2048 Mbps, optimizes the process of transmitting information. Digital lines significantly increase the ability of the user, withdrawing it beyond restrictions, even if there are several connected computers, mobile phones, tablets and other gadgets.
Prospects of technology
The capabilities and resources of ADSL technology are still far from being exhausted. Even ADSL2 and ADSL2 + standards, introduced in the mid-2000, still retain their relevance and opportunity. This is essentially the only technology that can provide wide Internet access without failures and software problems, therefore is a competitor for many other methods of connecting to the Internet.
The minimum technical equipment is complemented by modern modem species. Manufacturers annually release new devices designed for continuous operation without the need for service and service. In addition, the ADSL speed is constantly growing and is not limited to megabit. The connection becomes relevant for both at home and for a whole office company with several dozens of computer clients.
Conclusion
So, we found out what ADSL-technology is, what is its essence and principle of work. As you can see, this is one of those technologies that practically does not give failures when working (even if several dozens of users are connected to the network). At the same time, it does not require constant reconnection and speed limit.
& NBSP & NBSP Digital Channel Access using XDSL technology - Ability to receive high speeds Data transfer with relatively low cost of equipment using a regular telephone network. Conventional telephone cables become high-speed digital channels, and the data transfer rate depends only on the quality and length of the line connecting the user and the provider.
In the XDSL abbreviation, the x "symbol is used to designate the first character in the name of a specific technology, and the DSL denotes a digital subscriber line (Digital Subscriber Line).
The existing types of HDSL technologies differ mainly on the modulation form and data transfer rate used, which can reach 52 Mbps per second for VDSL technology (on a good communication line and up to 1.5 km). To date, ADSL technology is most common (ASYMMETRIC Digital Subscriber Line - asymmetric digital subscriber line). For data transfer, a regular telephone pair is used, but at the same time three information channels are organized - "downstream) with a exchange rate of up to 8 Mbps," ascending "data transfer stream (Upstream) with a exchange rate of up to 1.5 Mbps sec. and a regular telephone channel (POTS - Plain Old Telephone Service). With that, the telephone channel is highlighted using filters, which ensures that your phone will ensure that ADSL is malfunction. As a result, you get round-the-clock access to the Internet while maintaining the normal operation of a regular phone. ASML technology is simply expressed in the low cost of the equipment used and a significant difference in the data rate "to you" and "from you". Further development of ADSL technology led to the emergence of its modifications of different data transmission (ADSL2, ADSL2 +)
& NBSP & NBSP Connecting to the Internet Provider is performed using an ADSL modem. By the method of connecting to a computer, the modem can be divided into USB and Ethernet - modems. The same modem can have both USB and Ethernet port (several ports). USB modems are usually cheaper, but assume the possibility of using only in the bridge mode (bridge). In this mode, the modem works similarly to Dial-UP modems. Instead of a standard remote connection, a PPPoE connection is used (point-point via Ethernet). USB - modems in pure form are practically not available.
& NBSP & NBSP is more commonly connected to a computer via Ethernet, which assumes the presence of a network card in it. With this connection, it is possible to use a modem both in the mode of the bridge and in the router mode. Modern ADSL - modem, practically, is a specialized computer, with its software that performs not only Routing (Routing) and broadcasting network addresses (Network Address Translation or NAT), but also support for controlling the device via HTTP and (or) Telnet protocols, services Domain Name Resolution (DNS), Dynamic Configuration of Nodes (DHCP), Firewall (Firewall), TFTP server, etc. Naturally, all these internal functions are available if the modem works in router mode. Below is an example of a simple domestic network connection scheme to the Internet using the ZyXEL P660RU2 modem in the router mode.
The ZyXEL P660RU modem has only 1 Ethernet port, so you use a switch (Switch) to connect multiple computers. If a modem has several ports, the number of which is enough to connect your computers, the switch is not needed. The modem has an IP address equal to 192.168.1.1 on the LAN interface. Client computers have addresses 192.168.1.2, 192.168.1.3, and 192.168.1.33. Network mask - 255.255.255.0. The modem is used in the router mode with NAT. DHCP is not used, TCP / IP client computers are performed manually.
If there is no Internet access Try:
1.
Check if there is a physical connection to the equipment of the provider. Almost all modems have the display panel on which the ADSL-line state is displayed. The status indicator is usually signed as "ADSL", "DSL", "LINK", "CD", etc.
In the case of the normal functioning of your modem equipment, the data line and provider equipment, the mentioned indicator should be lit on the modem display pane. If this is not, try to do the following:
2.
If there is an indication of the operational state of the ADSL line, but there is no access to the Internet, the absence of a PPPoE connection to the provider may be possible. In the bridge mode (bridge or bridge), such a connection is performed by means of the operating system. In the router mode - modem software. Depending on the modem model, the display panel can be a connection activity LED, designated as "Internet", "PPP", "PPPoE", "WAN", and the like. The reason for the lack of connection can be an incorrect username and / or password to connect to the provider network. If they are correct, it is possible to exhaust the balance of the personal account, or your account is blocked by the provider for some other reasons. Contact technical support.
3.
If the ADSL and PPPoE connection line is normal, but there is no access to the Internet, try the following:
iPConfig / All.
As a result, we get:
NVIDIANFORCENETADAPER - Ethernet adapter:
DNS suffix of this connection. . :
Description. . . . . . . . . . . . : NVIDIA NFORCE Networking Controller
Physical adress. . . . . . . . . : 00-18-F3-EF-60-DC
DHCP is enabled. . . . . . . . . . . : not
IP address. . . . . . . . . . . . : 192.168.1.33
Subnet mask. . . . . . . . . . : 255.255.255.0.
Main gate. . . . . . . . . . : 192.168.1.1
DNS servers. . . . . . . . . . . : 192.168.1.1
& NBSP & NBSP The "IP address" string is an IP address of the computer, the "subnet mask" - a mask that coincides with the router's mask (standard 255.255.255.0). The "Main Gateway" line should be the IP address of your modem. In the "DNS servers" string, the addresses of the DNS servers or the IP address of the modem, if its DNS server is used to resolve names. A combination of these addresses is possible. If you have a suspicion about the performance of the DNS server provider, try manually change their addresses in TCP / IP settings, addresses
208.67.222.222 or 208.67.220.220 - OpenDNS servers
8.8.8.8.8 or 8.8.4.4 - Google Servers
It is better to choose a Google Server Combination and OpenDNS Server.
& NBSP & NBSP One of the main tools for diagnosing network problems is the node availability command ping.exe. and route trace command to the selected node tracert.exe.. When using these commands in the firewall, the ICMP protocol must be allowed, and even better, during the diagnosing problems, the firewall is disabled.
Brief help using Ping.exe can be obtained by a team:
ping /? Examples:
ping Yandex.ru. - Check availability of the yandex.ru node
ping 192.168.1.1 - Check the availability of our router.
When performing Ping without specifying the keys, a 4-fold setting of ICMP messages (echo request) is performed by a node specified on the command prompt, and receiving an answer to response time analysis (echo-response). The query and response field contains a repetitive string of the symbols of the Latin alphabet (from A to W). By default, the data length in Windows is 32 bytes. Example of the result of the execution of "Ping Yandex.ru":
Exchange packages with yandex.ru 32 bytes:
Answer from 77.88.21.11: Number byte \u003d 32 Time \u003d 5ms TTL \u003d 57
Answer from 77.88.21.11: number byte \u003d 32 Time \u003d 2ms TTL \u003d 57
Answer from 77.88.21.11: number byte \u003d 32 Time \u003d 1ms TTL \u003d 57
Ping statistics for 77.88.21.11:
Packages: Posted \u003d 4, obtained \u003d 4, lost \u003d 0 (0% loss),
Approximate transmission and reception time:
The smallest \u003d 1ms, the largest \u003d 5ms, average \u003d 2ms
& NBSP & NBSP Ping Statistics gives a complete sharing picture between your computer and a pingown node. The TTL field in echo response depends on the implementation of the IP protocol of the corresponding node (simplified, can be considered from the type and version of the operating system). It must be borne in mind that some nodes are configured in such a way that it does not respond to Ping (Microsoft.com, for example)
More examples of using ping.exe:
ping -t Yandex.ru. - Perform Ping before pressing the Ctrl-C or Ctrl-Break combination
ping -n 1000 -L 500 192.168.1.1- Perform ping 1000 times using messages, 500 bytes long.
ping -A -N 1 -R 9 yandex.ru - Run Ping 1 time (key -N 1), to identify the address by name (key -a), issue a route for the first 9 transitions (-R 9)
& NBSP & NBSP Key Use -r.To some extent, it allows you to get a route trace similar to the tracert.exe command, but the maximum number of transitions may be 9, which is usually not enough. Therefore, it is advisable to use tracert.exe.
tracert Google.com. - Route trace to Google.com
Result:
Route tracing to google.com with a maximum number of jumps 30:
1 1 MS 2 498 MS 444 MS 302 MS PPP83-237-220-1.PPPOE.mtu-net.ru
3 * * * .
4 282 MS * * A197-CRS-1-BE1-53.msk.stream-internet.net
5,518 MS 344 MS 382 MS SS-CRS-1-BE5.MSK.Stream-internet.net
6 462 MS 440 MS 335 MS M9-CR01-PO3.MSK.Stream-internet.net
7 323 MS 389 MS 339 MS BOR-CR01-PO4.SPB.Stream-internet.net
8 475 MS 302 MS 420 MS ANC-CR01-PO3.FF.Stream-internet.net
9 334 MS 408 MS 348 MS 74.125.50.57
10 451 MS 368 MS 524 MS 209.85.255.178
11 329 MS 542 MS 451 MS 209.85.250.140
12 616 MS 480 MS 645 MS 209.85.248.81
13 656 MS 549 MS 422 MS 216.239.43.192
14 378 MS 560 MS 534 MS 216.239.43.113
15 511 MS 566 MS 546 MS 209.85.251.9
16 543 MS 682 MS 523 MS 72.14.232.213
17 468 MS 557 MS 486 MS 209.85.253.141
18 593 MS 589 MS 575 MS YX-IN-F100.Google.com
Tracing completed.
& NBSP & NBSP Let's remind you like it works. When developing an IP protocol, to achieve nodes whose addresses do not belong to the current network, the routing is provided for transmitting IP packets between different networks. When you execute the "Tracert Google.com" command, google.com (74.125.45.100) is first defined, which does not belong to the address range of your local network specified by the IP address of the network card and the subnet mask (192.168.1.0-192.168 .1.255). Such a package will be sent to the router, whose address is set as the default gateway. In the trace results you see it first (192.168.1.1). Then (simplistic of course) works the same algorithm - if the google.com node is not reaches locally, it is determined that the packet must be sent through which router, and send it.
& NBSP & NBSP In the trace results, the above for reaching the Google.com node, 18 transitions needed. And now imagine that on the node number 10 (209.85.255.178) to achieve the google.com node, the route is wrong not to the node number 11, but for example, to the node number 5. The result of such an error would be the looping and perpetual circulation of the package between nodes 5 and 10. In order for such a situation, the IP protocol developers prudently entered the TTL field ("Lifetime" - Time to Live) in the IP packet header ("Life time" - Time to Live), which takes values \u200b\u200bfrom 0 to 255. Actually This field is not related to time, but is a counter of the number of possible transitions when transmitting the router packet. Each router, receiving a package, deducts from this field 1 and checks the value of the TTL counter. If the value has become equal to zero, this package is discarded and an ICMP message is sent to the sender ("Time Exceeded" - value 11 in the ICMP header).
& NBSP & NBSP When executing the tracert.exe command, first executes the ICMP package with the TTL field 1
And the first router in the chain (your modem) reset the TTL and reports an exception of the lifetime. This sequence is repeated three times, so in the string of the result by tracert.exe, after the transition number, the three response time values \u200b\u200bare displayed:
1 & NBSP & NBSP 1 MS & NBSP & NBSP 1 - Transition number (1 - first router, i.e. your modem)
1 MS 192.168.1.1 - its address (or name)
& NBSP & NBSP then the procedure is repeated, but TTL is set to equal 2
- Your router will reduce it to 1 and will send the following in the chain - i.e. Provider router. That after subtraction 1 will reset the TTL and inform about exceeding the lifetime. And so on until the specified node (google.com) is reached or a malfunction will not be detected that does not allow to deliver the package to the recipient.
& NBSP & NBSP In the trace results, there may be records of nodes in the form of stars (node \u200b\u200bnumber 3 in example) - this is not a sign of a malfunction and most likely, it says that the settings of this node prohibit the ICMP protocol for security reasons (Fighting DDOS - attacks)
& NBSP & NBSP The Ping command mentioned above has the key -I.. It allows you to set the TTL value for the echo request, i.e. Implement the same route tracing when performing ping -I. With a sequential increase of -i from one.
Ping -i 1 yandex.ru
Ping -i 2 yandex.ru
...
& NBSP & NBSP In the TRACERT.EXE command line parameters, it is sometimes more convenient to specify the node name, but any real non-private IP address. For example, commands:
Ping Yandex.ru.
TRACERT YANDEX.RU.
They can end with the message that it is not possible to resolve the name Yandex.ru (unknown node yandex.ru). The reason for this may be like the inoperability of the DNS server used (servers), the wrong address, the stopped service "DNS client", the wrong firewall settings, the incishes of the pickled virus, etc. And maybe I. lack of Internet access. You can use the team:
TRACERT 77.77.77.77
IP address 77.77.77.77
A whatever actually existing node is taken. The main thing is that it was correct, not reserved for local networks ("white") IP address. If the trace results for it will show the available nodes after the 2nd transition (after your modem and the provider router) - then with a lot of probability, it can be assumed that there is access to the provider's network, and it is necessary to deal with name resolution.
A few more signs:
If after Ping or Tracert on the team:
ARP -A.
You will see that an IP and hardware (Mac) address of the router is present in the ARP cache, then there is a tract between the client machine and the router (modem), the Ethernet and IP protocols work.
If the track is completed before your modem, but the ARP cache has the above entry, then ICMP protocol is blocked by the ICMP protocol for your computer or router firewall.
If the track is completed after your modem, the problem is on the plot between you and the provider.
If the tracing gives the availability of nodes after the provider's network, it is most likely that problems in the settings on the client computer.
So far, on this topic, everything is planned to be continued.
& NBSP & NBSP Here I gathered some useful things that can help users "Stream", and not only "Stream".
& NBSP & NBSP within Standard unlimited tariffsThe user gets access to the Internet using ADSL technology (ADSL2 +). The IP address is real but dynamic. Traffic filtering is used - TCP ports 21, 23, 25, 69, 80, 135-139, 40, 80, 135-139, 445, 8080, 254, 255, 161 UDP - 69, 135-139, 161. This is done to ensure the security of Widows systems, prevent spam -The appliance and protection of subscriber equipment. In other words, Windows network resources are not available on the client side, standard HTTP-FTP-, TFTP-, SMTP-servers. Sometimes the dynamic address and filtering of traffic creates some problems whose solution (free) is proposed below.
We solve the problem of a dynamic IP address.
& NBSP & NBSP Go to the site dyndns.com. To work with an existing or new account, use a button "SIGN IN" (in the upper right side of the page).
Create your account - click "CREATE ACCOUNT". When registering, select Free Account. The registration form varies periodically, but the entry of the desired username, password and your e-mail is mandatory. On the recorded e-mail comes a letter with a reference to confirm. I confirm and enter the site. Click the button "MY SERVICES" On the left side of the screen and then select the item in the menu "HOST SERVICES"
Zhmem. "Add New HostName" and fill out the form where you specify the desired name of the computer, the desired domain and IP addressNo matter what, if only valid, for example, proposed by the most form, your current address. Click the button "CREATE HOST". If the selected name is not employed by anyone, "HostName" will be created.
& NBSP & NBSP now stays download and install a special client program Dyndns Updater.
Go to the section "Support" - subsection "Update Clients"
& NBSP & NBSP download the client under our operating system. When installing in Windows (dynupsetup.exe), you will be asked to install a DyndNS client as a service. This will allow it to start until the user logs. Otherwise, when you first start, after installation, the client is registered in the autoload, and will be performed after the user logs in. I do not like unnecessary services on the computer and the installation as a service did not use.
& NBSP & NBSP You will need to enter the username and password received when registering on Dyndns.com. After that, you will see a list of your HostName names created in Dyndns.com. Mark the names, the update for which will be performed by the client. Number of names is limited to free account, which will find information on the site. The program is very simple, basic settings - on the tab Advanced:
& NBSP & NBSP Some of the modern ADSL modems have a built-in DYNDNS client. The setting is usually very simple, - fill in the username and password received when registering on dyndns.com and the name of your HOST. Example for ZyXEL P660RU2
& NBSP & NBSP Using the Dyndns Modem Customer is sometimes very helpful. The computer can be remotely turned off and include as described in the example "Wake On LAN technology" section "Network", as well as deploy to it the servers you need, connect to its desktop and manage it, being anywhere, would be access to the Internet.
We solve the transition to ADSL2 +.
& NBSP & NBSP A slight retreat. At the end of 2008, quite attractive tariffs with ADSL2 + technology have appeared in Stream. In addition, since March 2009, existing tariffs have changed, except for the tariffs of the ADSL2 + line. The difference in payment in my unlimited tariff "Stream 6 Hit" (transfer rate 6144/768 KB / s) and "Stream 10 Hit 2+" (speed 10240/896 KB / s) amounted to 70 rubles. My zyxel P660 RU2 modem supports ADSL2 +, so there should be no problems with the transition to a new tariff - I switched. Like many other subscribers Stream. There was a lot of problems with the transition to ADSL2 on many thematic forums, the people spit on Stream, many change the provider, in short, everything turned out to be at all not easy. At first, I also blocked slightly, because in the ADSL2 + mode, the modem could have been at half an hour to establish a connection, and in the case when it was able to be the outgoing flow rate (Upstream) could be 9 kb / s instead of 896 kb / s. Sometimes, however, it reached 500 kb / s, but it rarely happened, and, as it may, such a speed is very far from declared for this tariff. True, the speed of the downstream (DOWNSTREAM) was almost always appropriate tariff plan. As it turned out, other subscribers could be the opposite, the speed of Upstream is normal, and downstream is no. There were cases when it was impossible to perform an ADSL connection for hours. A few days later everything earned everything, but not long. Then I noticed that the speed fell, it became the same as on my previous tariff. I watch the state of the modem - it is - the speed of 6144/768 and DSL MODE - G.DMT, i.e. I get my old "Stream 6 Hit", although I see my current tariff in the personal account - "Stream 10 Hit2"
& NBSP & NBSP Of course, all this does not please. Even with me (I use Streaming about 5 years) there was a desire to change the provider. But in the end, cooled and decided to wait, the case for streaming is new, there are lining. Tehnar himself, I understand. After about a month, he called the technical support of Stream and asked to turn on ADSL2 +. After 20 minutes, the connection was disappeared, then recovered, and the old picture returned - no speed on the outgoing stream. From messages on the forums, I concluded - "run" on the technical support and engineers of Strima - an ungrateful occupation and, I would say that harmful to my own nervous system. And then - the technology for them is new, the spent standard solutions do not work, and the transition to ADSL2 + apparently has been performed too hastily and without proper events as testing settings, checking on different modem models, personnel training, etc.
& NBSP & NBSP It can be assumed that the ADSL modems supporting ADSL2 mode are supplied mainly with a configuration that has been established to work in the usual ADSL. Also, it can be assumed that if you adjust the modem settings to the provider's equipment settings, (DSLAM -DIGITAL Subscriber Line Access Multiplexer is a digital subscriber line access multiplexer), then everything will earn steadily at the required speed. In my case it turned out.
& NBSP & NBSP To change the modem settings, connect to it using telnet.exe:
telnet 192.168.1.1
The modem will ask for a password
Password:
We enter the administrator password
To view the acting modem settings, enter the command:
SYS VIEW AUTOEXEC.NET.
The modem will display the contents of the file AUTOEXEC.NET
SYS ERRTL 0.
SYS TRCL LEVEL 5
SYS TRCL TYPE 1180
SYS TRCP CR 64 96
SYS TRCL SW OFF
SYS TRCP SW OFF
IP TCP MSS 512
IP TCP Limit 2
IP TCP IRTT 65000
IP TCP Window 2
IP TCP Ceiling 6000
IP Rip Activate
IP Rip Merge ON
PPP IPCP COMPRESS OFF
SYS WDOG SW ON
IP ICMP Discovery Enif0 Off
Bridge Mode 1.
SYS Quick Enable
WAN ADSL RATE OFF
Ether Driver QROUTE 2
WAN DMT DB TLB E
For ADSL settings, teams from the group are important. wAN.. The "WAN DMT ..." command refers to the settings of the usual ADSL, and for the ADSL2 it should be viewed "Wan DMT2 ..."
I did not find a clear description of the command "WAN DMT2 DB ..." I did not find it, but it suggested that it is using the selected profile of the optimal modem settings under the DSLAM provider. Possible settings for a specific modem can be obtained by a team:
Wan DMT2 DB DISP
For P660Ru2 we have the result:
& nbsp.
db_sel \u003d ff db_final_sel \u003d 4
NBSP & NBSP & NBSP PRE & NBSP & NBSP & NBSP AFTER & NBSP & NBSP & NBSP After & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP
0 & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP
1 & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp CTLM Database
2 & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp GSPN Database
3 & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP BCM Database
4 & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp & nbsp IFNEON Database
5 & \u200b\u200bNBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP & NBSP TI Database
& nbsp.
Total - 5 options, 0 - not used, 1-5 can be tried.
(Abbreviated, equipment manufacturers - 1 \u003d CTLM \u003d Centillium, 2 \u003d GSPN \u003d GlobeSpan, 3 \u003d BCM \u003d Broadcom, 4 \u003d ifneon \u003d infineon)
Team to download option settings:
WAN DMT2 DB TLB X - where x from 1 to 5
We serve:
WAN DMT2 DB TLB 1
Reset line
Wan Adsl Reset.
After setting the connection, see the condition of the channel:
Wan Adsl Chandata.
You will see the connection data:
DSL Standard: ADSL2 + MODE -Reply ADSL2 +.
Near-End Bit Rate: 10240 Kbps
- speed to you.
Far-End Bit Rate: 1020 kbps - speed from you.
& NBSP & NBSP When you decide what option you have the most stable job, you need to record this command in the modem, so as not to enter it each time after turning off. To do this, enter the command:
SYS edit autoexec.net
We see a message:
Edit CMD: Q (UIT) X (Save & Exit) i (NSERT AFTER) D (Elete) R (EPLACE) N (EXT)
This is a tip of editing commands:
q - exit without saving results;
x - output with preservation;
i - insert the string after the derived;
R - replace the current line;
n - display the following line. You can simply press ENTER;
& NBSP & NBSP & NBSP & NBSP Now Click ENTER until lines appear
WAN DMT DB TLB E
- Zhmem. R.without clicking after it ENTER
- We recruit the command for the selected option:
WAN DMT2 DB TLB 3 - for option 3
- Press ENTER and press "X" to save and exit editing.
Result You can check the SYS View Autoexec.net command
SYS VIEW AUTOEXEC.NET.
SYS ERRTL 0.
SYS TRCL LEVEL 5
SYS TRCL TYPE 1180
SYS TRCP CR 64 96
SYS TRCL SW OFF
SYS TRCP SW OFF
IP TCP MSS 512
IP TCP Limit 2
IP TCP IRTT 65000
IP TCP Window 2
IP TCP Ceiling 6000
IP Rip Activate
IP Rip Merge ON
PPP IPCP COMPRESS OFF
SYS WDOG SW ON
IP ICMP Discovery Enif0 Off
Bridge Mode 1.
SYS Quick Enable
WAN ADSL RATE OFF
Ether Driver QROUTE 2
WAN DMT2 DB TLB 3
With the right job in the ADSL2 + mode on the Tariff "Stream 10 Hit2" the state of the modem should be like this:
Just in case, some teams for P660RU2:
The list of commands of each level can be obtained by entering a question mark or an invalid command:
WAN - will give a list of the subcommand for WAN, WAN ADSL - for the WAN AdSL level. For "Wan DMT:" There is no tip in the firmware of this modem. You can dial commands not fully-"Wan ADSL CHANDATA" and "W ADSL C" - identical. However, there is information that in some modems there is no reduction everywhere, but the diagnosis is no, therefore, it is better to use the abbreviated options for commands, or enjoy controlling their triggering.
Perhaps someone will help include the OLR (Online Reconfiguration) mode, which allows you to change the configuration without breaking the connection. It must be supported by the provider's equipment.
WAN DMT2 SET OLR X
Where
x \u003d 0 - OLR off
x \u003d 1 - OLR included
X \u003d 2 - SRA (Streamless Rate Adaptation) Disabled.
X \u003d 3 - SRA is included, adaptation to an existing line is possible.
& NBSP & NBSP To assess the quality of the line uses the "WAN ADSL Linedata" command:
Line status for outgoing flow (long-end):
Wan Adsl Linedata Far
Noise Margin Upstream: 11 DB - With a value below 7 DB, an unstable connection was observed and a low Upstream speed (although according to the information from the ZyXEL website, 6 DB is 6 DB)
Output Power DownStream: 0 db
Attenuation Upstream: 2 DB
Tone 0- 31: 00 00 00 35 68 9A BB BC CC DD DD DC CC CB BA A9
TONE 32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
TONE 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
TONE 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
TONE 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
TONE 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Condition of the line for stream to you (Middle End):
WAN ADSL LINEDATA NEAR
Noise Margin DownStream: 21 DB
- For my line in the range of 20-24 dB
Output Power Upstream: 10 db
Attenuation DownStream: 0 DB
TONE 0- 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Tone 32- 63: 00 00 00 00 00 01 00 11 42 45 53 55 55 47 65 57
Tone 64- 95: 55 57 75 57 58 55 76 68 34 53 55 48 77 65 77 75
Tone 96-127: 55 65 45 57 65 77 74 44 76 76 57 77 55 88 55 97
Tone 128-159: 79 94 76 75 78 48 49 75 76 59 56 88 44 57 85 45
Tone 160-191: 55 55 73 58 76 53 45 53 55 67 45 54 57 76 55 55
TONE 192-223: 56 64 56 66 55 54 46 35 56 25 14 31 53 02 54 35
Tone 224-255: 15 54 33 02 31 04 15 00 11 01 30 55 41 33 14 46
Tone 256-287: 64 34 31 56 63 65 67 56 55 47 67 67 55 46 78 79
Tone 288-319: 69 58 89 99 79 76 97 98 79 76 98 79 89 87 79 74
Tone 320-351: 76 88 89 99 99 9A 89 49 98 49 77 A9 4A 99 A9 98
Tone 352-383: 6A 8A 86 86 A9 89 97 A9 97 98 9A A9 99 99 79 79
Tone 384-415: 88 97 88 46 88 94 99 74 88 98 87 87 88 59 99 98
Tone 416-447: 88 88 88 48 99 87 98 88 98 98 88 87 84 98 89 48
Tone 448-479: 86 48 47 98 68 88 88 88 88 88 89 98 88 88 48 88
Tone 480-511: 88 86 88 98 87 40 68 87 88 89 44 48 68 AA A8 80
& NBSP & NBSP Noise Margin Downstream (Noise immunity when receiving data) - is used as a criterion for estimating the line status and determines the minimum limit at which the signal level is higher than noise level. It is believed if the ADSL modem is hardly synchronized with DSLAM, then reduce the limit of noise immunity on the switch.
Output Power Downstream (Data Output Power) - Shows output power when receiving data at the time synchronization of the DSLAM modem.
Attenuation Downstream (Attenuation when receiving data) - shows attenuation when receiving data at the time of synchronization of the modem with DSLAM (this parameter must be
Cisco 827-4V and Stream.
& NBSP & NBSP
Connect the console cable when the devices are turned off. To exchange with the console port in HyperTerminal, use the parameters:
Speed \u200b\u200b- 9600 bits / s
Data bits - 8
Parity - no
Stop bits - 1
Hardware flow control.
& NBSP & NBSP After turning on the modem in the terminal window, you will see messages about the start of the download. After 30-60 seconds, press Ctrl-Break, the download must stop and you will see the ROM monitor invitation:
rOMMON 1\u003e
Now you need to change the value of the modem configuration register so that when loading Cisco IOS is not used, the configuration stored in the modem (startup-config) with a password unknown to us:
rOMMON 1\u003e CONFREG 0x2142
The 0x2142 value is bypassing the STARTUP-CONFIG processing. Restart Cisco Reload (or Reset) command. After the boot, a message will appear to select a configuration dialogue:
Would You Like to Enter The Initial Configuration Dialog? :
Respond - No.
After that, a standard invitation to enter commands (Router\u003e) appears. To enter the privileged mode, use the command
Router\u003e Enable
Invitation Router\u003e Changes on Router #
Now you can copy the saved configuration as the current (running-config):
Router # sopy Startup-Config Running-Config
We change the password to a new one, for which we set configuration in the terminal:
Router # Configure Terminal
The invitation will change, reflecting the level on which you are - Router # is switched on Router (Config) #. To return to the previous level, use the EXIT command.
We enter a new password:
Router (Config) # Enable Secret
This is a new password for the privileged mode. To access Telnet, you also need to set a new password other than the previous one:
Router (Config) # Line VTy 0 4
Router (Config Line) # Password
Route # (Config Line) # EXIT
Now we have a previously saved configuration, with new passwords as the current configuration (RUNNING-CONFIG). But in this configuration, all network interfaces are stopped (Administrative DOWN). Therefore, for each of the interfaces used, you need to execute the NO Shutdown command. List of interfaces can be obtained by team:
Router # Show IP Interface Brief
For each interface from the received list, perform no shutdown. Example for Ethernet0:
Router (Config) # Interface Ethernet0
Router (Config IF) # no shutdown
Router (Config-If) # EXIT
Router (Config)
After starting all interfaces, you need to return the standard configuration register value to download Startup-Config:
Router (Config) # Config-Register 0x2102
Router (Config) # EXIT
Now we have the current configuration (running-config) is fully ready for operation. It remains to copy it to Cisco NVRAM memory to process when starting the device (startup-config):
Router (Config) Copy Running-Config Startup-Config
& NBSP & NBSP To save and download the configuration, it is convenient to use the Cisco TFTP Server "Cisco TFTP Server", which can be taken from the Cisco site or install it (by default the installation is performed in the "Program Files \\ Cisco Systems \\ Cisco TFTP Server" directory) and run.
To save the current configuration to the MyConfig.txt file on the server from IP 192.168.0.10:
Copy Running-Config TFTP: //192.168.0.10/Myconfig.txt
To save the start configuration to the MyConfig1.txt file:
Copy Startup-Config TFTP: //192.168.0.10/Myconfig1.txt
To download as the current configuration of the MyConfig.txt file:
Copy TFTP: //192.168.0.10/Myconfig.txt Running-Config
To download as the start configuration of the MyConfig1.txt file:
Copy TFTP: //192.168.0.10/Myconfig1.txt Startup-Config
& NBSP & NBSP Below is the contents of the configuration file for stream:
!
Version 12.1.
No Service Pad.
Service TimeStamps Debug Uptime
Service TimeStamps Log Uptime
NO Service Password-Encryption
! HostName Stream-GW
! Logging Rate-Limit Console 10 Except Errors
Enable Secret TRXOXVO9BH8.
Enable Password Password.
! Clock Timezone MSK 3
IP Subnet-Zero
no ip finger
IP Name-Server 212.188.4.10
IP Name-Server 195.34.32.116
!
NO IP DHCP-Client Network-Discovery
VPDN Enable
No Vpdn Logging
! VPDN-GROUP PPPOE
Request-Dialin.
Protocol PPPoe
!
!
!
!
Interface Ethernet0.
IP Address 192.168.1.1 255.255.255.0
IP Nat Inside
NO IP MROUTE-CACHE
No CDP Enable
!
Interface ATM0.
no ip address
NO IP MROUTE-CACHE
NO ATM ILMI-KEEPALIVE
PVC 1/50
Encapsulation aal5snap
Protocol PPPoe
PPPoe-Client Dial-Pool-Number 1
!
bundle-enable
DSL Operating-Mode Auto
!
Interface Dialer1
MTU 1492.
IP Address Negotiated.
IP Nat Outside
Encapsulation PPP.
IP TCP Adjust-MSS 1452
DIALER POOL 1.
DIALER-GROUP 1
No CDP Enable
PPP Chap Hostname. [Email Protected]
PPP CHAP PASSWORD XXXXXXX
!
IP Classless
IP Route 0.0.0.0 0.0.0.0 DIALER1
NO IP HTTP Server
!
ip nat inside source list 101 interface Dialer1 overload
Access-List 101 Permit Ip Any Any
DIALER-LIST 1 PROTOCOL IP LIST 101
No CDP Run.
!
Line Con 0
Transport Input None
StopBits 1.
Line VTY 0 4
Password Password.
Login.
!
Scheduler Max-Task-Time 5000
SNTP Server 192.43.244.18
End.
& NBSP & NBSP Create in the catalog Program Files \\ Cisco Systems \\ Cisco TFTP Server A text file with this content, and copy it to Running Config, change the access password in privileged mode (Enable Secret) and the password for Telnet (Enable Password). If necessary, you can change the address for the Ethernet, VPI and VCI interface for your provider, if you do not stream (PVC 1/50 - for stream). And you need to enter your username and password to connect to the network stream.
PPP Chap Hostname. [Email Protected] - Username
PPP CHAP PASSWORD XXXXXXX - Password
These edits could be made in the created file before copying to Running-Config. After you make sure that this configuration works, save it to startup-config.
Introduction to the development of the Internet to ensure full-fledged work in it required all the large and large access speeds - if first the Internet was predominantly text, then in the past few years there were already popularity services related to the transmission of sound and video modifications in real time, and even the volume of typical Pages, thanks to colorful graphics and flash animations, rose from units and tens of kilobytes to hundreds of kilobytes, and sometimes several megabytes.
However, if there was no problems with high-speed access to a network of large organizations, then the provision of home access was always resting at the same thing - the so-called "last mile". This term in telephony traditionally denotes the cable laid from a certain node (for example, a telephone station) to the subscriber, that is, the end user. The problem was that the cost of laying such a cable is usually from a few hundred to several thousand dollars, and, obviously, in the case of connecting the home user, it completely falls on its shoulders, making an individual high-speed connection to the network is exorbitantly expensive.
For this reason, an existing infrastructure has traditionally been used to access the Internet, that is, a regular telephone network. Indeed, because in the modern city, the phone already exists in almost every apartment, in other words, if you use the telephone line also to access the Internet, the cost of the cable laying will be zero, and the client will have to pay only the cost of final equipment, that is, the modem.
However, in the city telephone network, initially intended for voice transmission, the frequency band is forcibly limited at about 4 kHz - this is more than enough for the usual tasks of the phone, the larger frequency range would only complicate the work of the telephone network (heard only worsened due to the appearance High-frequency interference and increasing mutual fittings between adjacent lines). This limitation is, of course, the signals transmitted to the modem transmitted, not allowing high data transmission rates - during the long-term development of modems managed to reach only 33.6 kbps speed.
Above the diagram shows a slightly primitive situation - in practice, all how large providers are connected to the telephone network on digital channels; However, the 4-kilohert filter from the user side still does not disappear anyway.
The situation was slightly improved only with the advent of the V.90 standard, which made it possible to bring the transmission rate from the provider to the client to 56 kbps, but even such a speed was not always achieved - first, if between the provider and its client in the telephone network was produced more than one signal conversion from the analog form into digital (in modern telephone networks the signal between the PBX is transmitted in digital form), then the V.90 protocol did not work at all; Secondly, it turned out to be very sensitive to the quality of the line - not on all lines where V.34 worked stably, it was possible to get high-quality work V.90. And, again, a further increase in the speed in the existing telephone network was impossible (the theoretical limit is 64 kbps., However, in practice, the speed is consciously limited to reduce mutual interference between adjacent lines).
As usual modems stopped satisfying the needs of users, all sorts of alternative options began to appear, which do not use the telephone network, but somehow solve the problem of high cost of gasket " last mile". Two technologies received the greatest distribution - radio access and satellite access.
The first technology was installed instead of the wired "last mile" of the radio channel - one transceiver was located directly from the client, the second - on the station located nearby, which was already connected to the trunk channel, for example, fiber optic. Alas, but this decision was again quite expensive and not universal - the antennas had to be placed in the direct visibility of each other, so each base station Could serve only a relatively small number of customers, which adversely affected the cost of connection and further work.
The second technology is also familiar to many satellite Internet. Since the transmitting satellite antenna is very and very expensive, a hybrid system was developed to connect home users, in which the downward flow of data (from the provider to the user) was transferred through the satellite and was taken by the usual inexpensive parabolic antenna, completely similar to those used in satellite television reception systems, And the upward flow (from the user to the provider) was transmitted through the familiar telephone network using a regular modem. Alas, but such a system did not solve most of the problems - the user still for work on the Internet was forced to occupy a telephone line, and the transfer rate from it left to desire the best, which was impossible, for example, holding bilateral teleconferences. Yes, and with one-sided translation of the video signal, problems could arise - the transmission of the signal through the satellite spent quite noticeable delays.
Thus, none of the wireless (or partially wireless, as in the case of satellite Internet), the technologies could not conquer popularity, at least remotely comparable to the popularity of the usual switching access through the city telephone network. Wired technologies continued to restart the cost of laying the "last mile" ...
The exit from this deadlock turned out to be quite obvious. After all, the bandwidth bandwidth limits the equipment installed on the PBX itself, while the client goes to the PBX itself, the most common copper cable is capable of transmitting significantly higher frequencies than some three kiloherts ... In this way, DSL idea was born (Digital Subscribers Line) - Set one modem, as before, by the user, connecting it to a regular telephone line, and another modem (more precisely, DSLAM - DSL Access Multiplexer) - Not the provider, but on the same PBX to which the telephone line connects user, and turn it on before PBX itself. As a result, there was actually a simple piece of wire between the modems, without any inherent telephone network restrictions. Of course, due to the need to install the equipment on each PBX The costs of building and maintaining the network were noticeably higher than in the case of classical dial-up access, when all the modem providers were installed on one PBX, however, compared with the cost of other ways to provide high-speed Internet access, DSL technology was not just cheap, but highly cheap.
Perhaps the only serious competitor for DSL was a technology that uses another existing infrastructure - cable television networks. Technically, their use was more than justified - after all, they are originally designed to transmit high-frequency (dozens and hundreds of megahertz), however, the practically prevalence of cable television is much lower than telephone networks, which has led to a greater DSL popularity.
ADSL technology (asymmetric DSL) is a DSL version in which the available channel bandwidth is distributed between downlink and asymmetrically - for the absolute majority of users, the downstream traffic is much more substantial than the upward, so the provision of most of the bandwidth is quite natural for it.
As I have already noted above, the usual telephone network (in English-language literature it is usually denoted by the Abbreviation Pots, Plane Old Telephone System) uses the frequency band of 0 ... 4 kHz. In order not to interfere with the use of the telephone network for its intended purpose, in the ADSL, the lower limit of the frequency range is at the level of 26 kHz, that is, outside not only the frequency range of phones, but even outside the possibilities of human hearing. The upper limit, based on the requirements for the data transfer speed and the capabilities of the telephone cable, is 1.1 MHz. This bandwidth is divided into two parts - frequencies from 26 kHz to 138 kHz is assigned to upward data flow, and frequencies from 138 kHz to 1.1 MHz - downward.
Such a frequency separation provides ADSL another advantage over dialed access - if a regular modem takes a telephone line, making it impossible to simultaneously use the phone and Internet access, then the ADSL modem does not interfere with the work of the phone - you can calmly talk on it without disconnecting from Internet, and at the same time you will not feel any inconvenience. Of course, situations are possible, when either the high-frequency ADSL-modem signal adversely affects the electronics of the modern phone (on old phones with disk diabetes, it is obviously not able to influence - to influence there almost nothing), or the phone due to any features His scheme engineering makes a foreign high-frequency noise into the line or strongly changes its response in the field of high frequencies; To combat this telephone network directly in the subscriber's apartment, a low frequency filter is set, transmitting only a low-frequency component of the signal to normal phones and eliminating the possible effect of phones on line. I note that the usual analog modem connected through the filter continues to work as if nothing has happened, since it does not need any signals over the limits of 4 kHz maximum filter.
Generally speaking, the filters are customized to divide on microfilters and splitters. Under the first, filters are understood as followed directly before telephones - between the telephone socket and the actual wire going to the phone (I will note that there are also conventional analog modems under the phones, under the second - filters included in the telephone entry in the apartment and separating it Two parts are ADSL and ordinary telephone. As you can see, the difference only at the installation site, on the device, both microfilters and splitters are exactly the same, so there is no point in emphasis on this attention.
Of course, the capabilities of the cable are not limitless - with an increase in its length increases resistance, while ADSL equipment allows you to work with a cable resistance of no more than 1500 ohms. Based on this, it is not difficult to determine the limits of the ADSL work - if a cable is laid from your apartment to the PBX with a length of more than 5.2 km, the ADSL-modem has the full right not to earn at all. If the cable length is exactly 5.2 km, then it should earn it, but speeds above 128 kbps. Not guaranteed. The ideal conditions are the length of the cable not more than 1.8 km - while the ADSL modem can develop the maximum speed constituting 8 Mbps. From the provider to the user and 1.2 Mbps. from user to the provider. Of course, these are these indicative numbers - in each specific case, they depend on the section of the cable used in the telephone line and its state (the presence of connectors and "twists", all sorts of external interference and so on), however, the practice shows that 1 Mbps speed. It is quite real for any urban telephone line as reasonable quality. Again, I note that the value for ADSL has only the quality of the wire from your apartment to PBX - everything that costs the most direct impact on regular switched access, but has nothing to do with ADSL. And even in your area there is a decade-step PBX building in the fifties of the last century, you can only talk on the phone only a cry, and the usual modem refuses to connect to the speed provider above 9,600 bits / s. - If the ADSL equipment is possible on your PBX, you have all the chances of accessing Internet at a speed of several megabits per second.
The above described the most common, basic ADSL version, also known as G.DMT and Full Rate ADSL names. However, there is another option, "lightweight", known as G.Lite or Universal ADSL. Unlike G.DMT, the band of the used frequencies used is strongly trimmed in it and, accordingly, the maximum connection speed is only 1.5 Mbps. "Down" and 512 kbps. "up". The advantages of G.Lite two - first, this standard allows you to some cheap equipment, secondly, it is less demanding about the quality of the lines and in most cases does not require the filter installation, allowing the user to simply connect the modem to the phone outlet, without any either interference with the telephone wire wiring through the house (thanks to this G.Lite is sometimes also called "Plug-N-Play ADSL"). However, the ADSL modem is already fully supporting both G.Lite and G.DMT, you can buy less than $ 50, and not in all conditions when installing even G.Lite can do without a filter - it all depends exclusively from The phones you use and the quality wiring of the telephone cable for your apartment, so the benefit from using G.Lite is not so high.
Other DSL technology
In addition to ADSL, there are several more data transfer technologies based on DSL with other characteristics and requirements. First, the DSL abbreviation itself means not only the entire set of technologies, but also a specific, providing speed of 160 kbps. (Strictly speaking, the data transfer rate is 144 kbps. - Two so-called B-channels with a speed of 64 kbps. and one D-channel at a speed of 16 kbps; the remaining 16 kbps. are The overhead costs of the protocol) at a distance of 6 km in one pair. The "classic" DSL uses the frequency band from 0 to 80 kHz (in some implementations - up to 120 kHz), and therefore incompatible with a regular phone. However, nothing prevents the use of one of the B-channels to transmit a digitized voice (the benefit of the "telephone" range 0 ... 4 kHz with a bit of 8 bits gives a data stream just 64 kbps.), Moreover, DSL is often used For the organization of two independent telephone lines (since all b-channels are two) on one pair of wire.In the sixties, AT & T Bell Labs engineers. Created the first voice digitization system for telephone networks with subsequent multiplexing twenty-four voice data streams (64 kbps each) in a single data channel operating at a speed of 1.544 MBIT / s. This system has been named T1 (its European analogue, in which already thirty voice channels have been combined, was called E1 and worked at a speed of 2.048 Mbps.) And used to transmit a bandwidth of 1.5 MHz with a maximum at a frequency of 750 kHz. The maximum data range was about 1 km from the central station to the first repeater and about 2 km between subsequent repeaters, but this technology is unsuitable for connecting private users did not do so much the need for repeater, how much too much level of the vehicle created, which did not allow it to be organized in one A stranded cable (which, in fact, comes from each residential building to the nearest PBX) more than one channel T1 / E1. Moreover, the mutual films are so high that in general it is not possible to run another channel T1 / E1 even in a nearby cable, so the network of large telephone and telecommunication companies remained the use of T1 / E1 channels.
To eliminate this disadvantage, the HDSL standard (High Data Rate DSL) was developed, which actually represents an improved T1 / E1 transmission technology along a twisted pair. HDSL uses the frequency band with a width of only 80 ... 240 kHz (depending on the specific implementation), allows you to easily place several lines in one cable, and also runs at distances up to 4 km without any repeaters. The most serious drawback of HDSL is that to achieve a speed of 1.544 Mbps. (T1) He needs two pairs of wires at once, for the speed of 2048 Mbps. - Already three pairs that again complicated the installation of HDSL for private users, usually having only one telephone line in the house. However, this HDSL was the first DSL standard, overlapping a threshold of 1 Mb / s.
Improved HDSL version called SDSL (Single Line DSL), used to transmit all the same T1 / E1 streams with only one telephone pair, while providing speeds up to 1.544 / 2.048 Mbps at a distance of about 3 km from the PBX. In addition, the lower limit of the signal band in the SDSL lies above 4 kHz, so nothing prevents using the SDSL modem on the same line and the usual phone.
I note that all these technologies are symmetrical, that is, they provide the same data transfer rates in both directions. This greatly satisfies the needs of telephone companies, however, for home users who, as a rule, the amount of information received is at least an order of magnitude more transmitted, more profitable to use asymmetric channels, giving most of the bandwidth of the downward flow of data, which was done in the above described above ADSL.
And finally, another standard created after ADSL is VDSL, Very High Data Rate DSL. Data transfer speed in VDSL can reach 51.84 Mbps. - But for this you have to pay a reduced distance of a sustainable connection, which at such a speed is only about 300 m. In fact, VDSL is very good for use with a small one - less than 2 km - distance from PBX, but, since, according to statistics, the average distance from PBX to subscribers is about 5 km, then for widespread use, the more "long-range" ADSL is suitable better.
In conclusion of this section, I will give a table with the basic characteristics (speed and range) of modern technology transfer technologies over a copper pair:
Introduction to ATM technology
As a transport protocol, the ATM technology (asynchronous transfer mode, asynchronous transmission mode), which has gained great popularity in recent years, has been used with ADSL-connections, which has gained highly popular due to flexibility, high efficiency and at the same time - comparative ease of implementation.Initially, ATM technology was developed as an efficient transport mechanism for the needs of a rapidly developing telecommunications market. In fact, you can select two extreme options for organizing data networks - channel switching network (Circuit Switching) and packeting packets network (Packet Switching). The first technology perfectly illustrates all familiar telephone network - for all the time you conversation, you are provided with your own physical data channel (that is, voices) with some bandwidth. On the one hand, it guarantees you that for your channel needs enough under any conditions - after all, you take it and only you; But, on the other hand, when you do in a conversation pause - the channel is actually idle, therefore, on average, its bandwidth is used relatively little. I note that such an explosive nature of traffic is typical for the absolute majority of multimedia data networks, and for many others too.
In the second version - on the packet switching network, the same channel is provided to several clients. On the client end of this channel there is a multiplexing equipment that accepts data packets from clients, builds them in the queue and sequentially transmitting this queue according to the existing channel. Such an approach provides high channel use efficiency - it practically does not idle, but, on the other hand, it cannot provide you with a guaranteed delay time - if there is a large package from another client before your package in the queue, then sending your package for a while necessary to transfer the previous one. And since the size of the package standing in the queue can be the most different - then the delay is not only great, but also unpredictable, which leads to the actual inability to transmit multimedia streams in real time over channels with switching packets (for example, video conferencing or even a normal voice).
ATM technology is a gold middle between channel switches and packages. First of all, an ATM introduces the concept of a cell - a fixed-length package. In the modern standard, the cell length is 53 bytes, of which 5 bytes are accounted for to the address and 48 bytes - in itself to the transmitted information. The packages who came from the client are divided into the so-called ATM adaptation level on cells, each cell is supplied with address information and is queued. It would seem, here we come to the same problem as with switching of packages - to unpredictable delays due to the queue; However, the fixed cell size, and also so small, in ATM it was not chosen by chance - cells containing 48-byte pieces of packages of different users are mixed in line, so delays are so small that in the absolute majority of cases can be neglected. In addition, ATM introduced the concept of service quality (QoS, Quality of Service) - cells can have a different priority: for example, cells in which the video stream is transmitted will be priority higher than the cells in which the data is transmitted non-critical to the delay time. This technology is absolutely similar to the implementation of multitasking in modern computers - in fact, only one process is performed at each time, but the switching time between the processes is so little that, from the point of view of a person, they are all performed simultaneously.
ATM adaptation levels (AAL - ATM Adaptation LEVEL) are only five, depending on the type of service. In total, in ATM, it is customary to allocate three levels - physical (this is directly the data transfer environment, that is, in our case, ADSL; in general, ATM technology is not tied to any particular transmission medium, therefore it makes it easy to combine heterogeneous networks), level ATM (it is engaged in direct transmission and reception of cells) and the adaptation level described above, which adapts the top-level protocols to the ATM cells.
The ATM technology also uses the concept of a virtual connection. Unlike technologies that operate in physical communication channels, in ATM binding to such (that is, specifying the address of the package recipient) is carried out only at the connection setup phase. After that, there is a virtual channel, unambiguously indicated by two numbers - Virtual Path Identifier, VPI and Virtual Channel (Virtifier, VCI). Such a solution allows, firstly, to reduce the size of the cell header and, accordingly, the time of its processing, without pointing out in it the full address of the recipient, and, secondly, it is easy to build multi-connected networks (networks in which all nodes are connected in pairwise friend with A friend), thereby getting rid of transit nodes, only bringing additional delays in data transmission. For each virtual path, you can create multiple virtual channels, which allows, for example, when you run a video conferencing on one channel, the image is transmitted, otherwise - sound, and in the third - other related information.
Data transfer protocols
From the point of view of the provider, using ATM on top of ADSL on the "last mile" allows it to create a homogeneous network - as I noted above, ATM is not tied to any particular physical transmission medium, as well as any specific speed, so the entire network provider , including external communication channels, can be built on the basis of ATM, which markedly facilitates its operation. But from the user's point of view, not everything is so simple - the absolute majority of existing software is not designed for direct work with ATM, so the use of ATM "in pure form" requires a serious update.Incapsulation of protocols in this case is extremely simple: applications work directly with ATM, nothing superfluous (below on all similar tables Blue color marked "Native" protocols ATM and the physical level of ADSL, yellow - "auxiliary" protocols providing compatibility with software, those or other services and the like, and orange - stages of encapsulation of these protocols in ATM):
The most common way to solve the software adaptation problem is the encapsulation of the ethernet ethernet frames in the ATM cell (Ethernet Over ATM technology, or, abbreviated, EOA, is described in detail in RFC 1483 documents and more new RFC 2684). Encapsulation is performed on the fifth adaptation level ATM (AAL-5) directly ADSL-modem - respectively, on the client computer only requires the presence of a conventional network card supporting it, which is a de facto standard for any modern system.
As you can see, the encapsulation scheme is noticeably more complicated - now applications work with TCP / IP to them, then TCP / IP packets are transported by Ethernet, and in the Ethernet frame modem is converted to ATM cells (and back) in accordance with RFC 2684:
To ensure user authorization, dynamic issuing IP addresses and similar tasks over the Ethernet network, another protocol is often launched - PPPoE (PPP Over Ethernet), well-known to many home network users and being analogous to any owner of the PPP protocol modem (Point-to-Point Protocol).
In the simplest case, the ADSL modem works in the so-called bridge (Bridge) mode, converting the ATM cells to the Ethernet frames and back and passing these frames to the user's computer, where it is already installed - if necessary - software for implementing PPPoE (in Microsoft Windows XP It, for example, is in the standard delivery). However, there are both modems that can run the PPPoe session independently and log in to the provider.
Ethernet Over ATM technology is good from the point of view of simplicity of connecting and the cost of user equipment (enough modem that can work in bridge mode - and this is the cheapest modem variety), however, the efficiency of transporting large Ethernet packets by splitting into 53-byte ATM cells is relatively Light. It is largely compensated for high (compared to conventional modems) the speed of the ADSL connection, but still somewhat makes it difficult to organize video conferencing (and in general the transmission of multimedia traffic in real time).
However, once for user authorization, we traditionally use the PPP protocol, the fact that it interfers encapsulate PPP packets in the ATM cells, thereby getting rid of the intermediate layer in the form of the Ethernet described in the first version "Ah? This method was called PPP Over ATM (PPPOA) and Described in detail in the RFC 2364 document. On the one hand, when using PPPOA, there is no need for double encapsulation (Ethernet OVER ATM, and then PPP Over Ethernet), and on the other hand, all the advantages of the PPP protocol are saved: a convenient user authorization mechanism, IP dynamic algorithms -press and so on. Of course, this option means that an ADSL modem must be installed on the client computer, which does not perform any transformations, and the PPPOA software client, or the modem should be able to independently support the PPPOA session, transmitting the received data to the client computer , for example, by Ethernet network (I will note that there is no speech on the encapsulation of data ).
There is also another method - the transfer of IP packets over the ATM network (IP OVER ATM, or, abbreviated, IPOA), described in RFC 2225 (former RFC 1577). Recently, this option encapsulation is becoming increasingly popular.
Plus, there are two possible modes for each of the encapsulation types - LLC (Logical Link Control) and VC-MUX (Virtual Channel Based Multiplexing). I will not stop in detail in this article, I will not note in this article, I will only note that the choice of a specific regime, as well as the protocol itself among those presented above, depends on your ADSL provider.
In this way, it can be concluded that from a theoretical point of view, the choice of specific protocols is a compromise between the complexity of setting up and the efficiency of work on one side and the support of the available hardware and software - on the other.
Custom equipment
From the user's point of view, all ADSL modems can be divided into four groups - internal PCI modems, external modems with USB interface, external Ethernet interface modem and external routers (routers) with Ethernet interface.Internal ADSL modems compared to externalities have the same advantages and disadvantages as the classic modems. On the one hand, they do not take place on the table, do not require a separate power supply and significantly reduce the number of wires, but, on the other hand, it is necessary to open the system unit (which is not always possible if the unit is under warranty and sealed), and Also, they cannot work without drivers, and therefore, as a rule, only for MS Windows users (as in the case of classic PCI modems, for alternative driver systems, there are far from ever, and the quality usually leaves much to be desired). The modem setting is carried out using a special utility supplied with the drivers.
PCI ADSL MODEM MICRONET SP3300C
Exactly the same functionality as internal modems provide external USB modems. They have only two connectors - a USB and a connector for connecting a telephone line and, as a rule, two indicators - one LED indicates that the modem is on, and the other is that an ADSL connection is installed. Like PCI modems, they can only work in bridge mode - even if PPPoE support is declared for the modem, then in practice it will mean simply the presence of a client's own PPPoe in its driver. Again, the modem requires the driver, and for configuration - a special utility, so that users of systems other than MS Windows are worth a minimum to first find out the availability and quality of the drivers for their OS, and even better - pay attention to the modems with the interface Ethernet.
USB ADSL Modem Billion BIPAC-7000
More universal ADSL modem with Ethernet interface - to work with them from the operating system, only support for the TCP / IP protocol and any network card with 10Baset interface ("twisted pair") to which the modem is connected. Configuring the modem also does not require any special drivers or utilities - it is made from any browser (the modem has its own HTTP server and a web-interface for configuration), and many modem support and connect to Telnet for supporters of the command line. There are also double-standard modems, with both interfaces - both USB and Ethernet (for example, Efficient Networks SpeedStream 5100 has only USB interface, and SpeedStream 5200 is already both USB and Ethernet).
Ethernet ADSL modem Zyxel Prestige 645m
Generally speaking, theoretically, such a modem can be connected even directly to a hub or a switch on which a homemade local network is organized, but there is practically in this, as a rule, there is no point - these modems do not support network addresses (NAT, Network Address Translation), Neither any authorization methods (PPPoE or PPPOA), they can only perform the functions of the converter between the ATM and Ethernet interfaces. Thus, their main advantage over USB modems is the presence of an interface supported by all modern OS and, accordingly, in the absence of need for any specific drivers.
As is known, the most common way to connect homemade (yes, however, not only domestic) Internet networks in conditions when the provider provides only one IP address is to use network address broadcast (NAT). In this case, computers inside the network are so-called private IP addresses (often they are also called "gray") - these addresses can be used by any wishing, but only within the local network, they do not have any meaning in the global network. Obviously, for this reason, computers with private IP addresses can only be available from the local network in which they are located - beyond its limits, such a addressing loses any meaning; Therefore, to ensure access to the Internet, a server is installed that has two addresses at once - "gray", corresponding to the local network, and "white", available outside for everyone. If the server from the local network receives a package that comes out - the server replaces the "gray" address of the sender to its own "white" address and sends further, at the same time commemorating, from which "gray" address this package came to when from the Internet The answer to it will come to send this response to the sender of the source package. This mechanism is called the broadcast of network addresses and provides the most transparent and easier dependent on the applications used and operating systems. The method of connecting local networks to the Internet.
A variety of ADSL modems that have built-in NAT support is called ADSL routers. In addition to the NAT itself, most of the ADSL routers are also supported by PPPoE and PPPOA protocols (that is, if necessary, it is possible to independently log in from the provider, without installing the PPPOE client to the user computer), you can work with a DHCP server, automatically distributing IP addresses and the basic settings connected To them computers, and also have a DNS server and firewall. In other words, the ADSL router is able to easily replace a separate server, fully providing operation and access to the Internet small local network. Of course, for how a serious network of modem features is not enough - it does not count the traffic for each of the network computers, filtering URLs, the caching proxy server and much more, however, for a small home network, usually consisting of a maximum of three-four Computers (for example, one desktop computer and two laptops), such a modem is a practically perfect solution.
Ethernet / USB ADSL Router U.S. Robotics SureConnect 9003.
As the Ethernet ADSL-Modems considered above, the routers are connected via the Ethernet interface, and in this case the ability to connect them to a switch or a huba directly becomes much more tempting. Modems configuration is also carried out via a web interface using any browser, but many models support both protocols such as Telnet and SNMP. Often, Ethernet ADSL modems are simplified versions of ADSL routers, whose capabilities are limited to software - compare, for example, Zyxel Prestige 645M and 645R, or D-Link DSL-300G and DSL-500G.
ADSL routers and home users who have only one computer are very attractive. First, such a router due to the use of NAT allows you to extinguish your computer from the network, completely protecting it from worms like MSBLAST - the fact is that a computer that has a "gray" IP address cannot be direct access from the Internet, for The quality of the package recipient must be specified the "White" address, that is, the address of the router. The way to specify the router from the outside that this package must be intended for any of the local computers connected to it, in the general case does not exist - therefore all attempts of attacks will be on the router, to which they will not be able to cause the slightest harm at least because The OS standing on it has nothing to do with Windows. In addition, the ADSL router is a completely independent device, which is very convenient if you have several OS on your computer - for example, if you changed the password from the provider, it is enough to change it once in the router settings, and not edit PPPoe settings in each From systems. Yes, and the OS setting is reduced only to setting up a network interface to automatically receive an IP address and all related information from the router.
And finally, the highest category of ADSL modems - ADSL routers with built-in switches, Wi-Fi access points, print servers ... Such a router allows you to organize a small home network without using any additional equipment, which is not only very convenient, But it costs cheaper purchases of two or three separate devices. The same part of the device, which is responsible for ADSL and Internet access, is no different from that in ordinary ADSL routers.
ADSL-router D-Link DSL-604G + with Wi-Fi and 4-port Sweetch
In addition to the modem, you will also need splitter or microfilters - depending on how the telephone cable is laid in your apartment. If it is possible to make a separate discharge for the modem between entering the cable to the apartment and the first phone, it will be more profitable to purchase one splitter, but if there is no such possibility - the microfilters are required, one thing for each of the phones installed in the apartment.
ADSL-splitter
Development prospects
A year and a half ago, in the early 2003 year, ITU (International Telecommunication Union - International Telecommunication Commission, MCE) completed the development of two new standards - ADSL2 (ITU G.992.3 and G.992.4 - these two options differ in the same way As G.DMT and G.Lite - in the second is reduced both occupied frequency band and, appropriate, speed) and ADSL2 + (G.992.5), providing both an increase in the ADSL-compound bandwidth and new functionality.The ADSL2 standard is more aimed at an increase in functionality, and not speed - the latter increased only by 50 kbps. Compared to ADSL at the same length of the line (or, at the same speed, it became possible to lengthen the line by 200 meters). The noiselessness of the connection was noticeably increased in the presence of narrowband interference (for example, from radio stations of long and middle-racs), it was possible to change the overhead costs of the protocol - if earlier they were 32 kbps. Regardless of the connection speed, now at low speeds they can decrease to 4 kbps., which significantly increases the speed of transmitting user data. In addition, ADSL2 allows real-time to collect and process information about the status of the connection and quality of the line (last - even if the connection is not possible), which can be extremely useful to providers and telephone companies in diagnosing problems.
Energy consumption of ADSL2-transceivers has greatly decreased - if in the current ADSL they always work at full capacity, then two additional levels of energy saving appeared in ADSL2, called L2 and L3. ADSL2-transceiver operates at full power (level L0) only when transmitting a continuous data stream (for example, if the user downloads a large file), if a small break in data transmission occurs (for example, when the user just walks over the network, the data is downloaded very small portions. ), then the modem can automatically reduce the speed and move to the level L2 with more than twice the reduced power consumption compared to L0; The transitions between L2 and L0 occur almost instantly and without any loss of information, so for the user they are completely invisible. If the break in the data transmission is delayed, the modem can go to the "hibernation" to the L3 level, generally turning off the transceivers - however, to return from the L3 state to L0, it will be required for about three seconds. By the way, 3 seconds are the connection time of the connection and when the modem is first turned on, against more than ten seconds at the current ADSL modems.
Promotional analog modems are quite a long time for surely remember the appearance of the adaptive speed change (ASL) function in the V.32BIS protocol, which allows the modem to change the speed depending on the quality of the line "on the fly", that is, without reinstalling the connection (Retrein). Such technology appeared in ADSL2 called Seamless Rate Adaptation (SRA) - now DSL modems can change the speed without breaking the connection or any errors, that is, imperceptibly for the user. For example, if the medium-wave radio station interfere with the modem stops its broadcast at midnight - shortly after turning off its transmitter modem itself will raise the connection speed itself.
Undoubtedly, remember old-timers and appeared in Windows 98 and Windows NT 4.0 SP5. The ability to combine two analog modems in a couple - at that time it caused numerous disputes, it is possible that two modem on 56K each will give a total speed of 112K, or in reality an increase in Speed \u200b\u200bwill not be so significant. However, due to the lack of support for this innovation by the majority of providers, as well as, the main thing, the absence of most users of the second telephone line was rather general theoretic, rather than practical ... However, the ADSL2 appeared a similar possibility of combining modems in a pair (and Even more), and this option is implemented at the modem level, and not the operating system, which allows manufacturers to produce multi-channel modems (that is, single-circuit devices that are connected to several lines immediately), allowing you to double or even triple bandwidth. It is unlikely that they will interest private users, but may well be useful for organizations for which the rental of an excess telephone line does not represent a big problem.
Appeared in ADSL2 and the ability to create virtual channels, allowing you to make something similar to translate traffic to ATM - for example, to transfer a voice or video, you can select a low-delay channel, but a large percentage of errors, and for data transmission - channel with a small percentage of errors, but also A relatively large delay. On the basis of this technology, the so-called Channelized Voice Over DSL function (CVODSL) is also provided, which allows one or several 64 kilobite channels from the total data stream to transmit voice, as in a conventional telephone system. Thus, since the ADSL2-modem bandwidth is much higher than 64 kbps., You can organize several voice channels on one physical telephone line, and support them will be carried out at the physical level of DSL, as opposed to Voice Over IP (VoIP technologies. This technology is implemented at the IP network level, and therefore requires special equipment - that is, roughly speaking, computer) and even Voice Over ATM (VOATM, this technology is implemented by the second adaptation level AAL2 ATM).
After reading the previous paragraph, a thought arises by itself - and is it now needed by ADSL2 compatibility with regular phones, because now we can easily organize several digital telephone channels without any problems? And indeed, in ADSL2 modems it is possible to disable the compatibility mode, after which the modem expands the frequency range used to them in the direction of the low frequencies, due to which increases speed ascending flow data on 256 kbps / s. Of course, using simultaneously with the modem, the ordinary phone becomes impossible.
From the point of view of the home user, the most significant changes occurred in ADSL2 + - compared to ADSL2, the frequency band used for the downward flow of data is extended in half (in ADSL2 G.992.3 it extends from 140 kHz to 1.1 MHz, in ADSL2 + - from 140 kHz to 2.2 MHz), which made it possible to increase the speed of the downstream of up to 24 Mbps. True, it efficiently works only on lines of length of one and a half kilometers - with a further increase in the length of the line, the difference between ADSL2 and ADSL2 + is quickly reduced and already on line with a length of 2.5 km becomes zero.
In addition, ADSL2 + allows you to reduce the mutual fittings in the cable between adjacent lines due to the range of 0.14 ... 1.1 MHz for one line and 1.1 ... 2.2 MHz for another (with both lines get such The same speed as in ADSL2) - however, here again it is understood that the second line should not be longer than one and a half kilometers, otherwise make the modem on it only in the high-frequency band will not be possible.
Already existing hardware solutions allow both providers and users to migrate to ADSL2 and ADSL2 + - for example, in June of this year, TEXAS INSTRUMENTS presented the UNI-DSL platform (UDSL) supporting five standards at once - ADSL, ADSL2, ADSL2 +, VDSL And the ITU has not yet been approved by the ITU standard (its approval is expected during 2005, and, unlike the current VDSL, at long distances, it is not inferior to ADSL in speed, and there is a closer with it). Thus, the transition from ADSL to ADSL2 / 2 + will occur gradually, without any restructuring of the existing infrastructure, as the equipment is gradually upgraded by providers and users.
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