ot, explanations of the various adsl modes and what they mean

[Gregory Nowak]

Hi all.

I've been looking all over the web, as well as in the linux adsl howto
for an explanation of the various adsl modes, and the differences
between them, but I couldn't find anything about that. I could find a
listing of the different adsl modes used, but I'm interested in what
they all mean, and the differences between them.

Specifically, on the diagnostics page for my adsl modem, sometimes it
says "ADSL Mode: T1-413", and other times it says "ADSL Mode:
GDMT". Why would the dsl modem sometimes switch from mode to mode,
what is the difference between them, and is one better then the other?
Also, under the down/up stream sections it says something like:
"Capacity Occupation:  20 %__________
       Noise Margin: 27.51 dB______________
       Attenuation: 32.62 dB_______________
       Output Power: 19.73 dBm".

Does the capacity occupation refer to how much of the phone line's
capacity is currently being used for the signal? Is the noise margin
the amount of extra noise on the line, and the attenuation the modem's
way of compensating for the extra noise?

If anyone knows of a site which can provide these answers for people
that aren't just satisfied with the fact that their internet
connection works, but want to know all the tech stuff, or if someone
has the knowledge to provide an explanation of the above, your input
would be appreciated by me.
Thanks.

Greg


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