Understanding what speed I should get on my DSL

Untill a week ago my connection was established at 8100Kbps. During off peak times I would get 10 second burst speeds of around 13000Kbps, so I decided to email my ISP (Torch Communications/Karoo) and ask them to upgrade my connection.

I explained what the characteristics of my connection and without hesitation the upgraded the line to a 11700Kbps IP Profile. It stayed at this for two days straight without any problems at all.

But today it seems to have dropped to 10231 kbps. I recently passed the BSCI CCNP unit and covered ADSL technologies. It is my understanding that a DSLAM will negotiate a connection to a given SNR specified by an IP profile and will decrease connection speeds to attempt to meet it.

The specs on my connection yesterday was:

ADSL Link Downstream Upstream
Connection Speed 11723 kbps 1028 kbps
Line Attenuation 45.6 db 20.3 db
Noise Margin 7.3 db 12.4 db

And today:

ADSL Link Downstream Upstream
Connection Speed 10231 kbps 1023 kbps
Line Attenuation 40.5 db 21.9 db
Noise Margin 6.1 db 11.6 db

looking at these stats its looks like the DSLAM has lowered my connection speed to stable the connection, but what I don't understand is why it has done this becuase the stats yesterday look fine to me.

Can anybody shed any light on why my connection speed has been dropped and if I can call my ISP again to get it pumped with digital steroids again.

All help greatly appreciated