Annex M is a facility on ADSL2+ that requires the ISP to activate it.
It is also the last thing you could possibly want - it would be a disaster for you. Its purpose is to increase the upstream maximum speed from 1.3Mbps to 2.5Mbps.
On ADSL2+ the upstream frequencies are below the downstream ones. What Annex M does is double the number of frequencies allocated to upstream, taking those frequencies from the bottom end of the downstream.
The effect is that unless the downstream connection speed is above 16Mbps on Annex A, then you lose at least 2.5Mbps downstream speed, but at that level of downstream attenuation the upstream attenuation is also high and the increase above 1.3Mbps simply doesn't happen. Lose-Lose!
At 24MBps downstream on Annex A then the strength of the top-end downstream frequencies is enough to compensate fully for the loss of the bottom end ones. and the attenuation each way is obviously much lower. So the full upstream increase is obtained. Win-Win!
In between those two extremes there is a sliding scale of downstream loss against upstream gain.
Your line just isn't suitable.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
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