Although what is monitored and the exact name may be different depending on manufacturer, the overall information is pretty much 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:

SN Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)
Relative strength of the DSL signal to Noise ratio. 6dB is generally the lowest dB manufactures specify in order for the modem to be able to synch. In some instances interleaving can help raise the noise margin to an acceptable level. Generally speaking, as overall bandwidth increases, your signal to noise ratio decreases. So a customer that upgrades from 1.5 to 6.0 service will typically see a corresponding decrease in the signal to noise ratio. 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. One of the biggest factors affecting line attenuation is distance from the DSLAM. Generally speaking, bigger distances mean higher attenuation. 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

said by gfaith :

today I was upgraded to 6.0 Mbps and my SNR fell to 11.5-16.0 and Atten increased to 40.5.

said by gfaith :

I would agree Doc, but the facts are it did increase wish I had saved a few screen shots.

said by Doctor Olds :

Test out at the NID then to see how much your inside wiring may be degrading the signal.

said by Doctor Olds :

Here you go, it has been posted in this Forum multiple times.

said by propflux01 :

I did not give my SNR/ATT to the tech, only my diagnostics page, a simple page informing of a pass/fail for hook up, and the modem log which only contained mac address and log of how many times connect/disconnect, So I fail to see how he figured the SNR I was getting at my modem vs what hs was gettign outside, while never entering my house.

said by gfaith :

After running Cat5 homerun. My Atten. went back down to 38.5db as expected and I can live with both it and the SNR. No doubt I had problems in my house wiring. My speeds are typically around 5600 down and 300 up. Workable for sure.