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Although what is monitored and the exact name may be different depending on manufacturer, the overall information is the same. Below are some of the common terms and measurements used to judge line quality. Remember these are not hard numbers but simply a generalization of line statistics:
Attainable Line Rate (AKA Synch Rate)
This is the maximum rate at which your modem can connect to the DSLAM if there was no service provisioning limiting the bandwidth. Anything over 2,000Kbps is considered good. The higher the number the better.
Used Line Rate
Your Used ATM Rate (actual service rate) plus bandwidth to cover the overhead and provisioning of the service.
Fast Used ATM Rate
Actual bandwidth at which your service has been provisioned. The actual number can vary a little depending how you are physically serviced. If there is a number here that also means your connection is "fastpathed".
Interleaved Used ATM Rate
Actual bandwidth at which your service has been provisioned. The actual number can vary a little depending how you are physically serviced. If there is a number here that also means your connection is "interleaved".
Relative Capacity (AKA Line Capacity)
Percentage of your overall available bandwidth used to obtain your service ATM rate. For example; if your max line synch rate was 5888Kbps and you were provisioned on a 1472Kbps service you would be using 25% capacity. 1472/5888=25% capacity. The lower the relative capacity the better, but you can still get maximum speeds (although a less stable connection) even with a very high relative capacity. In other words you could be synching at 1472Kbps with 98% relative capacity and achieve maximum speeds, but you may experience more disconnects.
Noise 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.
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.
How much power modem (upstream) or DSLAM (downstream) is using. Maximum recommended is about 15dB. The lower the power the better for this measurement.
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