FTTC VDSL: Yesterday 72Mbps Down, today only 9 Mbps. Speed dropped by 63Mbps

[#1]

OK. This is strange...
Before connecting BT modem:
1. SpeedTest using Fritz!Box (FB) (before test with BT modem) - 😧 10Mbps, U:19
With BT modem and Win8.1 setup for DSL:
2. SpeedTest using BT modem and Win8 PC DSL setup - 😧 70Mbps: U: 16
Restored Fritz!Box. FB wasn't rebooted at any of these steps. Just plugged back DSL cable to FB:
3. SpeedTest using FB (after test with BT modem) - 😧 70, U: 16
Af if BT's modem kick started speed increase...  

[#2]

If you've got your Fritz!Box connected now, I think it'd be a good idea to monitor the connection for a few days to ensure the speeds don't drop as they appear to have done.

[#3]

Thank you Chris. Will keep an eye on the speed. If pattern repeats - it will happen overnight and I should know by tomorrow morning.

[#4]

Quote from: Jaggies

Could this not perhaps be a late Delta Report, dropping the Current Line Speed to ADSL levels? Check here: https://portal.plus.net/my.html?action=data_transfer_speed (log-in required).

PT Data Transfer Speed
Telephone number:
0207XXXXXXX
Phone exchange:
ALBERT DOCK
Estimated line speed:
74Mb (Download speed could vary depending on line conditions. Estimates are the maximum speeds that your phone line can support. These speeds are dependent on the package you choose.) - Checked on 2014-05-10 17:25:38
Current line speed:
74.4 Mb

[#5]

Quote from: tomcemerka

Af if BT's modem kick started speed increase...

The act of disconnecting the DSL cable will have necessitated a resynch.  You might well have got the same result by disconnecting and reconnecting to the FB, or indeed rebooting it.

[#6]

I rebooted FB yesterday twice, but without any change. Sync speed was high, but SpeedTest was still reporting only ~10 Down
adie:quote

[#7]

Daft question here...
...is there any possibility that the LAN side (PC to router - either end) got slugged to 10Mbps?
If the FB was reporting a high synch rate, the only things which can slug the data transfer rates are...
1. PN profile
2. Exchange congestion
3. Line profile
4. LAN speed (wired or wifi)
Any retransmission required over any part or sub-part of the end to end link.

[#8]

I tested using Laptop with 1Gbps LAN port connected over LAN cable directly to FB Router LAN port. Windows reported 1Gbps Link speed.
Will keep an eye on the line to see whether download speed stays in 60-70Mbps or will it drop again to 10Mbps.
adie:quote