The BellSouth specific Westell 327W provides basic line statistics like Data Path, Line Attenuation, DSL Rate, Ethernet Stats, and Signal to Noise ratio. However, it does not have the ability to measure advanced statistics like Maximum Attainable Line Rate, ATM Rate, or Line Capacity.

Section 1 - Accessing the Line Statistics
Step 1
Open a browser session and enter "192.168.1.254" in the address field to access the Westell Interface.

Step 2
Click on Broadband DSL Line on the top menu. Click on Statistics on the right menu.

Step 3
Click on DSL on the right menu. The four most important statistics are Data Path, DSL Sync Rate,SN Margin (dB), and Line Attenuation (dB). Additional information on Data Path is available here. SN Margin (Signal to Noise Margin) should be 6 dB or more and Line Attenuation should be roughly 60 dB or less. See Section 3 below for more details.

Section 2 - Accessing the Event Logs

Step 4
Click on Broadband DSL Line on the top menu. Click on Log on the right menu. Select Connection and System from the Select a Log pull down.

Step 5
The log contains connection information and various statistics as shown.

Step 6
You can clear the current logs by clicking on Clear Log on the right menu. It is also reccommended that you print and/or save your logs for future troubleshooting by clicking on Printable/Savable Format on the right menu.

Section 3 - What do the numbers mean?
SN Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)
Relative strength of the DSL signal to Noise ratio. 6dB is the lowest dB manufactures specify for modem to be able to synch. In some instances interleaving can help raise the noise margin to an acceptable level. The higher the number the better for this measurement.
6dB or below is bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with no synch problems
20dB-28dB is excellent
29dB or above is outstanding

Line Attenuation
Measure of how much the signal has degraded between the DSLAM and the modem. Maximum signal loss recommendation is usually about 60dB. The lower the dB the better for this measurement.
20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

CRC Errors (Cyclic Redundancy Check)
CRC is a method of detecting errors in data transmission. A high CRC count in inself is not really cause for alarm. However, any increase in CRC errors after your initial connection is established is a problem and usually points to a physical issue somewhere between the modem and the DSLAM. Isolate your inside wiring as a cause by testing from the NID and troubleshoot from there.

TX Power
How much power modem (upstream) or DSLAM (downstream) is using. Maximum recommended is about 15dB. The lower the power the better for this measurement.

DSL Rate
Your provisioned ATM Rate (actual service rate). If this number is lower than actual provisioning rate you have a physical problem preventing full bandwidth.

Andy Houtz

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last modified: 2008-02-15 11:49:25