I found some very informative and usefull information from this first link below on how ADSl connections work as such, I have often noticed many users on this site query about certain aspects of their connection such as attenuation and SNR so I just though I would create this topic in regards as a response, I certainly hope this helps.
http://www.kitz.co.uk/adsl/linestats.htmThis second link directs you to a tool that is used to calculate the maximum speed you can possible achieve on your DSL line by using the attenuation db as a reference. Let the fun times ensue
http://www.kitz.co.uk/adsl/max_speed_calc.php