[Sephiroth]

Originally Posted by jem

Honestly, I really, really wouldn’t bother about it.

DOCSIS, is a ‘sort-of’ self-adjusting system, that’s how it was designed to work. It constantly makes adjustments based on changing conditions to keep the connection stable. You state that the connection is stable, so it’s doing its job.

Changing conditions? Well maybe someone else on the same network segment has a slightly dodgy connection which sometimes introduces noise/interference into the system? Maybe your area is a bit oversubscribed and at peak times struggles to cope with everyone? Your modem will adjust to compensate.

As long as your connection is stable and your speeds are roughly what you are paying for (incidentally VM doesn’t guarantee upload speeds, for reasons..), then don’t worry about it.

Technically the higher the QAM value, the more data can be sent in a certain time. This is more efficient for both you and VM. But if the local circumstances don't permit it, then the hub will drop the QAM value to ensure stability.

Jem has it right. They don't guarantee the upstream for the reason that it is noise prone; when that happens speed is reduced - more technically the potholes between data blocks are widened so that more of the noise will go there and not corrupting the data.