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System Processes and Performance with a Direct Connect Configuration

System Processes and Performance with a Direct Connect Configuration

This chapter describes basic system processes and the performance metrics that are captured as a result of these system processes in a Direct Connect configuration. You can better understand how the system is performing if you understand the symmetrical digital subscriber line (SDSL) and asymmetric digital subscriber line (ADSL) connection processes. This chapter provides details about network connection concepts and processes, including bit error rate and noise margin, the SDSL and ADSL connection processes, training parameters and counters, and how to monitor connection activity.

This chapter includes the following sections:

Bit Error Rate and Noise Margin

Bit error rate and noise margin are primary factors in achieving subscriber-designated parameters. SDSL and ADSL transceivers seek an upstream and downstream data rate that can be maintained as long as the amount of line noise does not cause a bit error rate (BER) in excess of 1 x 10-7. Line noise is a function of reach and disturbers. As reach or noise in the loop increases, upstream and downstream payload rates decrease. Also, the thinner the copper wire, the more susceptible it is to noise. Line noise is not constant, and a certain amount of line noise fluctuation does not significantly affect the trained rates. Line noise fluctuation is known as the noise margin. The noise margin must be supplied to the transceivers when you use the multiband method of training.

The SDSL Connection Process

SDSL transmission unit - central office (STU-C) modules are designed to operate within narrow parameters. These parameters use a relatively low 1 Mbps of upstream and 1 Mbps of downstream, and a fixed baud rate of 8 kbps with 16-point constellations. Such a reduction from the ADSL transmission unit- central office (ATU-C) 7 Mbps downstream and 1.5 Mbps upstream rates presents the end user, usually a single office/home office (SOHO) subscriber, with less cost and less transport capacity.

Configuring an STU-C module is similar to configuring an ATU-C module.

SDSL Upstream and Downstream Bit Rates

The STU-C module upstream and downstream rates are the same. They range from 144 kbps to 1168 kbps. The following seven rates are the fixed upstream and downstream rates for the STU-C module:

The baud rate is fixed at 8 kbps. You determine bit rates based on the number of carriers and the number of bits per carrier.

Note The STU-C module is supported by the Cisco 6130 system only.

STU-C Module Training Rates

If you are familiar with training ATU-C modules, you may notice the extended training time needed for STU-C modules. STU-C modules require at least 35 seconds to train and can take up to 3 minutes. This time frame contrasts with the 60 seconds or less that an ATU-C module needs to train.

STU-C Module Training Parameters

This section describes the trained line attributes such as receive signal quality, receiver gain, and transmit power where it applies to noise margins on the Cisco 6100 Series systems. Each of these trained line attributes displays in ViewRunner on the STU-C Module Properties dialog box Port Status tab.

As a Cisco 6100 Series system operator, you can change the noise margin (upstream and downstream) on an STU-C module for each subscriber line. Increasing this margin could cause a line that trained previously to fail to train. When you attempt to increase noise margins, ViewRunner issues a warning message that is similar to the following warning script:

Warning: Increasing noise margin could reduce the reach for a given data rate, or reduce the achievable data rate for a given reach. In some cases, it may prevent the line from training at all. Please consult product documentation for more information.

Figure 6-1 shows an STU-C Module Properties dialog box with a Service State of In Service. The various train parameters are identified in this dialog box. See the ViewRunner for Windows User Guide for more information on the fields represented in this dialog box.


Figure 6-1: STU-C Module Properties Dialog Box---In Service


The ADSL Connection Process

The Carrierless Amplitude and Phase Modulation (CAP) rate-adaptive DSL (RADSL) transceivers that are used in the Cisco ATU-Cs and ATU-Rs can train at several discrete settings within each of three baud rate ranges. Because the upstream and downstream data paths transmit in different frequencies, they train independently.

The transceivers in the Cisco Discrete Multi-Tone---Issue 2 (DMT-2) ATU-C modules train at one of two settings within the fixed baud rate. DMT-2 refers to the use of a single or discrete frequency. Both upstream and downstream are transmitted on the same frequency and trained in tandem.

Payload Transmission Rates

Payload data represents transmitted information that is useful to the customer, but may also include additional information such as user-requested network management and accounting information. Upstream and downstream payloads transmit in different frequency ranges; therefore, the two payload rates are established independently. Layer 2 protocol data units (PDUs) are encoded into Layer 1 (xDSL) transmission frequencies through baud rates (also known as symbol rates) and constellations. You can set different baud rates to achieve different payload rates.

DMT-2 transceivers support upstream payload rates ranging from 864 kbps to 32 kbps, and downstream payload rates ranging from 8032 kbps to 32 kbps.

CAP RADSL transceivers support one baud rate to establish upstream payload rate (136 kilobaud) and three baud rates to establish downstream payload rate (340, 680, and 952 kilobaud). These baud rates enable CAP RADSL implementations to support downstream payload rates that range from 7168 kbps to 640 kbps, and upstream data rates that range from 1088 kbps to 91 kbps.

Modifying Noise Margins

You can modify the noise margins for a subscriber line. If you set a new noise margin, a line that was training successfully might not train after you set a new margin. ViewRunner alerts you to use caution when you change the margin.

Cisco recommends that you set the margin for 6 dB upstream and 3 dB downstream to provide optimal performance. The default values for noise margin are 0 upstream and 0 downstream.

As an example, if you train a unit that is provisioned with a 3 dB downstream margin and a 6 dB upstream margin against 24-ISDN near-end cross talk (NEXT) set to the 0dB reference level (-52.6 dBm), you can increase the noise to -49.6 dBm at the CPE and -46.6 dBm at the CO and still maintain a bit error rate that is less than 1 bit in error for every 10 million sent (10-7). Within each baud rate, transceivers use constellations to encode data into a frequency spectrum, and subsequently enable discrete payload options. This concept is described in the "CAP RADSL Upstream and Downstream Constellation Combinations" section, and the constellation combinations are listed in Table 6-1 and Table 6-2.

Cisco DMT-2 ATU-C module functionality supports several training options that measure and regulate subscriber traffic. You can configure these options on the Subscriber Properties DMT-2 dialog box. See the "Configuring Subscriber Properties for a DMT-2 ATU-C Module" section for more information about configuring this module.

DMT-2 Training Rates and Modes

DMT-2 transceivers support the following training rates:

The training mode that features the StandardTrain option supports Direct Connect lines only, specifically DMT-2 ATU-C modules. You use one setting for both the upstream and downstream rates. One option is available for the training mode, StandardTrain, which is the default.

The error message, "Reference Source Not Found," displays when ViewRunner finds a module that is incompatible with the baud rates you have set.

If you train a DMT-2 module that is provisioned with a 3 dB downstream margin and 6 dB upstream margin against 24-ISDN NEXT set to the 0 dB Reference level (-52.6 dBm), you will be able to turn the noise up to -49.6 dBm at the CPE and -46.6 dBm at the CO and still maintain a bit error rate that is less than 1 bit in error for every 10 million sent (10-7).

CAP RADSL Training Rates

CAP RADSL transceivers support the following training rates:

These baud rates enable CAP RADSL implementations to support the following rates:

Within each baud rate range, transceivers use constellations to encode data into a frequency spectrum, and subsequently enable the discrete payload options shown in Table 6-1 and Table 6-2.

Cisco's CAP RADSL implementation supports a number of ADSL training options that you can use to control subscriber traffic. See the following section, "CAP RADSL Upstream and Downstream Constellation Combinations" for an overview of the training process.

CAP RADSL Upstream and Downstream Constellation Combinations

The concept of constellation combinations refers to the way discrete subscriber line chip sets communicate with each other. Different constellations provide different levels of data transmission accuracy.

Valid CAP RADSL constellations include 256 UC, 256, 128, 64, 32, 16, 8, and 8 extended range. The 128, 32, 8, and 8 extended-range constellations are not supported with downstream baud rates of 952 and 680. Because of this, some upstream-downstream payload combinations cannot be achieved.

Table 6-1 lists the valid upstream and downstream constellation combinations.


Table 6-1: CAP RADSL Upstream and Downstream Constellation Combinations
Upstream

Kilobaud

136

136

136

136

136

136

136

136

Constellation

256UC

256

128

64

32

16

8

8 er1

Kilobaud

Const

Payload

1088

952

816

680

544

408

272

91

952

256UC

7168

X

X

X

X

D o w n s t r e a m

952

256

6272

X

X

X

X

952

64

4480

X

X

X

X

952

16

2688

X

X

X

X

680

256UC

5120

X

X

X

X

680

256

4480

X

X

X

X

680

64

3200

X

X

X

X

680

16

1920

X

X

X

X

340

256UC

2560

X

X

X

X

X

X

X

X

340

256

2240

X

X

X

X

X

X

X

X

340

128

1920

X

X

X

X

X

X

X

X

340

64

1600

X

X

X

X

X

X

X

X

340

32

1280

X

X

X

X

X

X

X

X

340

16

960

X

X

X

X

X

X

X

X

340

8

640

X

X

X

X

X

X

X

X

136

256UC

1024

X

X

X

X

X

X

X

136

256

896

X

X

X

X

X

X

X

136

128

768

X

X

X

X

X

X

X

136

64

640

X

X

X

X

X

X

X

136

32

512

X

X

X

X

X

X

X

136

16

384

X

X

X

X

X

X

X

136

8

256

X

X

X

X

X

X

X

1er = extended range

Two entries in Table 6-1 represent the downstream rate for a payload of 4480 kbps:

The 680 kilobaud rate with a 256 constellation is the Cisco 6100 Series system and Cisco 675 default for achieving a payload rate of 4480 kbps. This rate combination supports a slightly better reach, according to 24-ISDN NEXT disturbers.

Table 6-1 also includes two entries in the downstream column for a payload of 1920 kbps:

The 340 kilobaud with a 128 constellation is the Cisco 6100 Series system and Cisco 675 default for achieving the payload rate of 1920 kbps. This rate combination is compatible with any of the upstream data rate selections. The 680 kilobaud option is limited to the 1088, 952, 680, or 408 kbps upstream payload.

CAP modules support 136-kilobaud training rates, which can be allowed or disallowed when the system controller module software supports this feature and the subscriber is locked.

If the system controller module supports per-subscriber provisionable 136 kilobaud or does not support ATUCPARMS, the Allow 136K Baud checkbox on the 6100 Properties dialog box Configuration tab is disabled. If the system controller module supports ATUCPARMS, but does not support per-subscriber 136 kilobaud, the toggle is enabled.

Table 6-2 lists valid rate combinations for upstream and downstream data.

.
Table 6-2: Valid Rate Combinations for Upstream and Downstream Data
Upstream Rate (kbps)
Downstream Rate (kbps) 1088 952 816 680 544 408 272 91

7168

X1

X

X

X

6272

X

X

X

X

5120

X

X

X

X

4480

X

X

X

X

3200

X

X

X

X

2688

X

X

X

X

2560

X

X

X

X

X

X

X

X

2240

X

X

X

X

X

X

X

X

1920

X

X

X

X

X

X

X

X

1600

X

X

X

X

X

X

X

X

1280

X

X

X

X

X

X

X

X

1024

X

X

X

X

X

X

X

960

X

X

X

X

X

X

X

X

896

X

X

X

X

X

X

X

768

X

X

X

X

X

X

X

640

X

X

X

X

X

X

X

X

512

X

X

X

X

X

X

X

384

X

X

X

X

X

X

X

256

X

X

X

X

X

X

X

1x = valid, empty cell = invalid

The actual training procedure is a function of transceiver-controlled parameter exchange and algorithms designed by Cisco to place parameters around valid data rate selections from Table 6-2.

ADSL Training Process

The following guidelines apply to the ADSL training sequence:

This setting means that control of the downstream data rate is relinquished to the ATU-C module; that is, the ATU-C module controls the upstream data rate setting by default.

By using the preceding guidelines, the ATU-C module has complete control over upstream and downstream data rate selection. You can select valid upstream and downstream data rate combinations on the GUI. ViewRunner communicates these rates to the ATU-C module. This process is accomplished as follows:
Figure 6-2: Subscriber Properties Dialog Box---Choosing Data Rates



Figure 6-3: Module Properties Dialog Box Module Configuration Tab Showing Data Rate Combination


ATU-C Module Training Parameters

This section describes the trained-line attributes: for receive signal quality, receiver gain, and transmit power, where applicable to noise margins on the Cisco 6100 Series systems. Each of these trained-line attributes displays in ViewRunner on the Module Properties dialog box Port Status tab.

You can modify the noise margin (upstream and downstream) on an ATU-C module for each subscriber line, but if you increase this margin, a line that trained previously could fail to train. When you attempt to increase noise margins, ViewRunner issues an alert that is similar to the following message:

Warning: Increasing noise margin could reduce the reach for a given data rate, or reduce the achievable data rate for a given reach. In some cases, it may prevent the line from training at all. Please consult product documentation for more information.

Figure 6-4 shows a Flexi Module Properties dialog box in which a session is in progress (Service State field reads In Service). The various training parameters are identified on this dialog box. (See the "Using the Subscriber Properties Dialog Box" section for more information on the fields represented in this dialog box.)


Figure 6-4: Flexi Module Properties Dialog Box---In Service


Receive-Signal Quality

The receive-signal quality is a measure of the signal quality for the upstream channel (from the ATU-R, in the case of the Cisco 675). This value is represented in decibels.

Signal Quality Overview

You can use the signal quality value to estimate the BER or signal-to-noise ratio (SNR) margin for the received data. The signal quality value takes into account the total signal-to-interference ratio (SIR), where the interference includes background noise, cross-talk, residual intersymbol interference, residual echo from the neighboring upstream or downstream data, and distortion.

A perspective of observed signal quality is described in the following paragraph. Stating explicit valid signal-quality ranges for a given loop reach is not, however, particularly valuable. The number and variety of interferers and wiring (outside-plant and in-home) creates many different scenarios. Therefore, specific data is not always helpful if, for example, you are trying to institute a corrective action by moving a wire pair to a different binder group as a remedy.

For 7 kft loops, a receive-signal quality of 37 to 44 dB is fairly common, with average interference and a 6 dB noise margin setting. For 10 kft loops, a signal quality range of 32 to 35 dB is common. As loop length increases, the signal quality decreases. Long loops (12 to 15 kft) or loops that have bridge taps could have a signal quality in the low 30s of the decibel range. Very long loops (over 15 kft) can even train with a signal quality as low as 20 dB at the decibels margin. If you reduce the noise margin to zero, even longer loops can train with a signal quality as low as 12 dB.

Future RADSL Development

One of the benefits of RADSL is that it figures out the values for optimal performance. RADSL helps you configure a device to operate at a specific speed or to dynamically select the highest practical operating speed. The values are presented in Table 6-1 primarily as an indicator that the trained loop is exhibiting expected characteristics, rather than for troubleshooting purposes.

In a subsequent Cisco 6100 Series system and ViewRunner release, layer 1 performance statistics will be added, which will be more valuable from a historical review perspective for loops that are experiencing problems. For a given training session, if RADSL is unable to overcome loop characteristics in a way that even the lowest upstream and downstream data rates are not supportable, these layer 1 attributes will not be displayed.

Signal Quality and Data Rate Interaction

Data rates are a function of signal quality, rather than signal quality being a function of data rates. For a given requested upstream and downstream data rate combination that you choose in ViewRunner, if the transceivers are unable to maintain the data rates to a 10-7 BER (with a 6 dB noise margin insertion), the transceivers seek the next lowest data rate combination where the BER can be preserved.

Beginning with Cisco 6100 Series Release 2.2.1, the node supports selectable noise margins. The Cisco 6100 Series supports a hard-coded 3 dB downstream and 6 dB upstream noise margin setting. This setting is valuable if, for example, a subscriber requests 7.168 Mbps x 1.088 Mbps, but loop quality is insufficient to hold the BER to less than or equal to 10-7.

In this example, the subscriber's RADSL train could settle to 6.272 Mbps x 1.088 Mbps. Therefore, interference could be causing the downstream channel to have just enough noise to prevent the 7.168 Mbps data rate from being achieved with the 6 dB margin setting. If you reduce to 3 dB the noise margin that the transceivers must take into account for determining the best data rates to lock onto, you might be able to provide the full 7 x 1 service.

Receiver Gain

Receiver gain is a measure of loop attenuation over the entire DSL frequency spectrum. The ATU-C or STU-C module uses an algorithm to boost receiver gain so that attenuation can be corrected for proper support of a given receive data rate.

The ATU-C or STU-C module algorithm attempts to keep gain to a minimum to prevent NEXT. However, if loop conditions warrant, the algorithm must boost gain enough to ensure that the required minimum signal level is received.

CAP modules support 136 kilobaud training rates, which you can allow or disallow when the system controller module software supports this feature and the subscriber is locked. If the system controller module supports per-subscriber provisionable 136 kilobaud or does not support ATUCPARMS, the Allow 136 K Baud checkbox on the 6100 Properties dialog box Configuration tab is disabled. If the system controller module supports ATUCPARMS, but does not support per-subscriber 136 kilobaud, the toggle is enabled.

The following factors tend to boost receiver gain and are associated with loop impairment:

Table 6-3 lists documented reach and receiver gains.


Table 6-3: Reach and Receiver Gain
Reach (kft) Receiver Gain (dB)

16

42

14.5

39

11

27

9

21

8.7

19

Transmit Power

Transmit power is a measure of the downstream power spectral density (PSD) mask. T1E1/97-104R2a states that the PSD for the downstream channel should have an upper limit of -40 dBm/Hz in the nominal passband region with no variation exceeding -37 dBm/Hz.

Caution Cisco advises you to set the transmit power to -40 dBm/Hz. To avoid data transmission errors, do not change the PSD from -40 dBm/Hz downstream and -38 dBm/Hz downstream.

Each network provider chooses the maximum transmit power. As power increases, you can extend reach for a given data rate. At the same time, however, the boosted signal can disturb other services.

Although not currently displayed on the ViewRunner GUI, T1E1/97-104R2a also specifies that the PSD for the upstream channel must have an upper limit of -38 dBm/Hz nominal with no variation exceeding -35 dBm/Hz.

Beginning with Cisco 6100 Series Release 2.1.1, you can control transmit power. Controlling transmit power is helpful when the network provider wants to boost or reduce the power of a given loop.

The ATU-R transceiver determines its transmit power during the training process as it tries to fulfill the upstream data rate request. The ATU-R transceiver tries to support the requested data rate at the lowest possible transmit power to minimize NEXT in the Cisco 6100 Series system.

Understanding Performance Train Counters

The Cisco 6100 Series system includes the following train counters for capturing system performance statistics in a Direct Connect configuration:

ViewRunner uses counters to display individual subscriber and CAP ATU-C, DMT-2 ATU-C, and STU-C modem port statistics.

After the Cisco 6100/6130 establishes the connection, the training sequence begins that is described in the "ADSL Training Process" section.

If the CAP ATU-C, DMT-2 ATU-C, STU-C, and ATU-R modems train, a successful train counter increments for these modems. If the xTU-C modem and ATU-R modem fail to train, a failed train counter increments for the xTU-C modem. You can view train counter statistics on the Performance Management dialog box. For more information about this topic, see the "Using the Performance Management Dialog Box" section.

Getting Information about Subscriber Line Performance

The following sections describe how to get information about subscriber line performance from the Performance Management dialog box.

Using the Performance Management Dialog Box

To check the performance of an xTU-C module in a dedicated configuration, right-click the chassis to access the Chassis menu and choose 6100 Performance. The Performance Management dialog box for an xTU-C module opens, shown in Figure 6-5. The Performance Management dialog box has two top-level tabs, the xTUC tab and the Cell Counts tab.


Figure 6-5: Performance Management Dialog Box---xTUC Tab


Table 6-4 describes the columns on the Performance Management dialog box xTUC tab.


Table 6-4: Performance Management Columns
Column Description

Port

Lists the chassis, slot, and port number of the ATU-C or STU-C module.

Type1

Names the type of module---ATU-C (CAP or DMT-2) or STU-C module (2B1Q).

Successful Trains

Lists the number of times the associated module has trained successfully.

Failed Trains

Displays the number of times the associated module has failed to train successfully.

Line Statistics

Displays at the bottom of the dialog box to present a running count of the following statistics:

  • Line ports

  • Successful trains

  • Failed trains

  • Nontimer failed trains

  • ATU-C ports failing to train

1Type header occurs for STU-C modules only

If a module fails to train, you may have provisioned it incorrectly. See "Provisioning Subscribers for a Direct Connect Configuration," for more information on provisioning.

Viewing Training Data Graphically

To view a graphical representation of the training data for a DMT-2 ATU-C or CAP ATU-C module, follow these steps:

Step 1 Click the Successful Trains or Failed Trains column for the port whose training statistics you want to see.

Doing this opens a Training Data dialog box, shown in Figure 6-6.


Figure 6-6: Training Data Dialog Box---Bit Allocation Tab


Step 2 Click the Bit Allocation tab to view an x-y graph of bit allocation for upstream and downstream training rates.

Step 3 Click the SNR tab to view an x-y graph of the signal-to-noise ratio for upstream and downstream training rates.

Step 4 Click the Rcvr tab to view an x-y graph of the receiver gain rates for upstream and downstream training rates.

Step 5 Click Refresh to get the most recent data.

Step 6 Click Close to close the dialog box.

The range of the training statistics that display should be equal to what is specified in the MIB.

Using the Cell Counts Tab

When you click the Cell Counts tab, two new tabs appear, the PVC tab and the ATM tab. You can get cell or packet count data by using these tabs, which are described in the following sections.

Checking PVC Performance Management

To check the PVC performance status for a subscriber line, follow these steps:

Step 1 Click the Cell Counts tab and then click the PVC tab on the Performance Management dialog box.

Doing this opens the Cell Counts PVC tab, shown in Figure 6-8.


Figure 6-7: Performance Management Dialog Box Cell Counts---PVC Tab


Step 2 View the following subscriber line settings on the All PVCs group box:

Step 3 To monitor the PVC performance of a specific subscriber line, highlight that subscriber line and click Add.

Doing this moves that subscriber ID to the Monitor List. Under the Monitor List group box columns, you can monitor subscriber-side and network-side channel transmissions to identify bottlenecks. The Monitor List group box columns contains the following subscriber line information:

Step 4 To delete a subscriber from the Monitor List group box, highlight the Subscriber ID and click Delete.

Checking ATM Performance

To check the port status for subscribers who are using ATM, click the Cell Counts tab and then click the ATM tab on the Performance Management dialog box of an xTU-C module. Doing this opens the Cell Counts ATM tab, shown in Figure 6-8.


Figure 6-8: Performance Management Dialog Box Cell Counts---ATM Tab


Table 6-5 describes the fields on the Cell Count ATM tab.


Table 6-5: Performance Management Cell Count ATM Tab Fields
Field Description

Port Index

Displays the chassis slot number for the port whose performance management you are accessing.

Rx Cell Count

Displays the number of cells being received.

Tx Cell Count

Displays the number of cells being transmitted.

Header Control Errors

Displays the number of errors accumulated in the header control.

Section Bit Interleave Parity

Displays interleave parity counts by section bits.

DS3 Far End Block Error

Displays far end block errors from the DS3.

Plcp1 Far End Block Error

Displays far end block errors from the Plcp.

Plcp Frame Error

Displays frame errors that have occurred in the Plcp.

DS3 Frame Error

Displays frame errors that have occurred in the DS3.

DS3 Parity Error

Displays parity errors in the DS3.

Bipolar Violations

Displays counts of bipolar violations.

1Plcp = physical layer convergence protocol.

Current Connection Activity

You can view current connection activity displays on the following dialog boxes:

These two connection displays are described in the following sections.

Module Properties Dialog Box Port Status Tab

For modules (flexi and STU-C) in a dedicated configuration, the Module Properties dialog box Port Status tab (Figure 6-9 and Figure 6-10) displays state information.


Figure 6-9: Flexi Module Properties Dialog Box Port Status Tab



Figure 6-10: STU-C Module Properties Dialog Box Port Status Tab


Active Connections Dialog Box

The Active Connections dialog box lists data about all of the currently active connections in the Cisco 6100 Series system. To open the Active Connections dialog box, right-click the chassis and choose Active Connections from the menu. Figure 6-11 and Figure 6-12 present the Active Connections dialog box first in the far-left position, then scrolling right for the last illustration.


Figure 6-11: Active Connections Dialog Box---Left Side



Figure 6-12: Active Connections Dialog Box---Right Side


You can use the logical, service-oriented navigation to go directly to an entity by clicking any blue hyperlink in the Active Connections dialog box.

Table 6-6 describes the columns on the Active Connections dialog box.


Table 6-6: Active Connections Columns
Column Description

Subscriber ID

Displays the identifier by which the subscriber is known.

ATU-C or STU-C Port

Displays the chassis, slot number, and port number to which the line port is connected.

Modem Status

Indicates whether the modem is trained or training.

Actual Up

Displays the actual upstream train rate at which the subscriber is training. This rate can never be higher than the value of the Provisioned Up column.

Actual Down

Displays the actual downstream train rate at which the subscriber is training. This rate can never be higher than the value of the Provisioned Down column.

Rx SNR

Signal-to-noise ratio for the ADSL upstream (receive side) data channel.

Provisioned Up

Displays the upstream rate set by the CO, the maximum upstream rate at which the subscriber can train.

Provisioned Down

Displays the downstream rate set by the CO, the maximum downstream rate at which the subscriber can train.

Provisioned Down Margin

Displays the downstream noise margin that the operator provisions.

Provisioned Up Margin

Displays the upstream noise margin that the operator provisions.

Actual Down Margin

Displays the downstream noise margin that is actually occurring within the margin that you have provisioned for the subscriber.

Actual Up Margin

Displays the upstream noise margin that is actually occurring within the margin that you have provisioned for the subscriber.

The Active Connections dialog box includes fields for provisioned upstream and downstream bit rates, actual trained upstream and downstream bit rates, and the received signal-to-noise ratio.


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Posted: Thu Feb 17 08:29:24 PST 2000
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