Significant difference between IP profile and measured attainable VDSL speeds

[#1]

Hi,
I'm on FTTC
My upload and downloads are rock solid - however they arr rock solid at 50Mbps down and 18Mbps up whenever I test them (to within 1Mbps, measured from a wired connection with no other network use)
This is fine if it is what the line can support - but is lower than I was expecting. The BT line check says my line profile is currently 76Mbps
How can I find out whether the speeds I am seeing are simply what the line can support (in which case fine), or down to a misconfiguration that can be tweaked?
The fact that my speeds are so consistent (albeit lower than expected) makes me a bit suspicious that there may be some kind of artificial limit in place, but my suspicions could be misplaced!

[#2]

Hi dbrb2,
Would you be able to PM me your account username please and I'll take a look at things for you.

[#3]

Thanks for the PM.
I've checked your line and your modem is connecting to your FTTC Cabinet at full speeds (80/20). Your Speed Profiles are all up to date and look fine to me.
If you're seeing slowdowns, would you be able to do Speed Tests whilst connected via a direct PPPoE connection?
http://community.plus.net/library/broadband/fibre-help-how-to-set-up-a-pppoe-dialler-in-vistawindows...

[#4]

Cheers I'll try that
Can you see what speeds the modem is actually synching at, or is that not possible on the VDSL service?

[#5]

Yep - I can see what you're in 'Sync' at, so the speeds that your Modem is connecting at your property at from the Fibre Cabinet, which is the full 80/20.

[#6]

Ah OK
I won't be able to check the PPoE immediately, but will try in the next day or so
When I do this, I won't be able to keep it like that for long. What would you like tested to acertain if there is a problem or not?
I know there can be variability in speedtest results - is there one which you would advise for testing? Anything else worth checking at the
same time?

[#7]

If you could connect via PPPoE directly to the Modem and just run a Speed Test at http://speedtest.btwholesale.com including 'Further Diagnostics'. Once you've done that, if you could pop us a screenshot of the results on here, you can then reconnect everything back the way it is again - I'm hoping it shouldn't take much longer than 10-15 mins.