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[renluop]

Please forgive me, should this have been aired before, but I am seeing max attainable less than actual sync both up and downstream. How can that be, please?

Any connection to invalid floating point errors possible?

[roswellgrey]

One scenario ...

Say your target SNR is 6, for example
Current SNR drops a bit below 6, maybe due to daytime/nightime fluctuation, or other reason.
So, Max Attainable drops a bit.
However, the modem hasn't resynced  - it is still holding onto sync (at less than target SNR) at a rate determined before the SNR drop
Hence, Max Attainable < Current Line Sync Rate.

[roseway]

The max attainable values and the floating point errors are completely unconnected. The max attainable speeds reported by DSLstats are exactly as reported by the modem. They are estimates made by the modem based on current stats and some assumptions. The max attainable values can be lower than the actual speeds if, for example, noise conditions have worsened since the latest resync and the SNRM is now significantly less that 6 dB. Or it could be that the modem is simply getting it wrong.

[renluop]

Thank you all for polite replies to what must be annoying questions.

[skyeci]

Its possible if you get a resync when max attainable is lower you could see a reduction in your ds sync. Mine did this only 2 weeks ago. Max attainable was 4 mb less than the sync, then had a power cut and ds sync dropped back. Has not recovered the loss.
How much is your ds max attainable lower than the sync?

[ktz392837]

Please forgive me, should this have been aired before, but I am seeing max attainable less than actual sync both up and downstream. How can that be, please?

Any connection to invalid floating point errors possible?

Could also be crosstalk.  Each customer who gets fttc on the same cabinet you are using could have an impact of your sync speed as this additional user causes interference (aka crosstalk).  This means your attainable speed will go down due to this interference.  It will get to the point where the DLM will intervene and force a reconnection and you will sync back up at 6db but will the lower speed to correspond to this.

This is how the technology works and when you see people discussing vectoring this is the technology that should reduce the impact of crosstalk on lines.

If you are the first line to be connected to the cabinet you can probably expect 30-40% reduction in speed over time depending on your distance from cabinet and how many of your neighbours get fibre.

[renluop]

Actually I am still ADSL (2+); exchange by road ~3 km and I sync just under 8K with 3dB margin.
FTTC wise we are about 800 m from cabinet.