Modem Line Statistics

When using a TP-Link TD-8616 DSL modem with an IQrouter, this section of the overview page shows line statistics for your modem. If we detect a change in line quality a message will be shown alerting you to the problem with suggestions to improve performance.

The actual values shown inform you of the metrics relevant to the DSL connection and are as follows:

SNR Margin 

This describes the Signal to Noise Ratio margin for the indicated direction. The higher this value, the better.

An SNR below 10 results in unstable line results, with possibly frequent drops and re-syncs from the modem. Ideally, it is in the low teens and above. An SNR of less than 7 should result in a call to the ISP to have the line checked, as that will not stay up, and / or change capacity frequently.

Line Attenuation

This indicates how much signal loss, or attenuation is present on the line, the lower this number, the better.

Values in the 60's and above indicate a very long line back to the DSLAM and / or many bridge-taps that cause signal loss. Not much can be done about these, other than ensure the local wiring is pristine. See this article for more info.

Data Rate

Indicates the actual modem sync rate with the DSLAM. This is the raw connect rate is NOT the actual Internet throughput achievable by the line.

In DSL, there is around a 9% overhead for line-protocols, so a 10Mbps sync means at best a 9.1Mbps throughput, but due to other overheads, the actual throughput could be as much as 15% lower than the sync rate. And once traffic management is applied, it can be around 20% less than the sync rate. So a 12Mbps sync, may result in speedtests showing 7.5 to 8.5Mbps.