The best I've been able to achieve is 11.7 Meg with a line attentuation of 22.0dB. 
That's poor. I synch at 1136 up / 17569 down, on attenuation as reported by my router (HomeHub 3) of 24dB. Mind you, my noise margin is currently at 2.1dB downstream, but the connection hangs on for grim death - synch has been up for over 40 days 
My Billion router tells me that my downstream data rate is 16386 kbps, but the actual speed is nowhere near that.
The SNRM downstream fluctuates - just checked it now at 4.1 dB, but earlier it was 5.9 dB. It has been as low as zero.
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Wagstaff
"Due to government cutbacks, the light at the end of the tunnel has been switched off."