Speed drop

[#1]

My fibre was installed a couple of months ago and apart from a couple of short lived speed drops my download speed has consistently been ~64Mbps which I have been very pleased with, especially as my estimated speed had been 53.
However over the last week download speed has been ~54Mbps despite nothing being changed. Given that I am getting what was promised I cannot complain but was just wondering what can cause a speed reduction like this.
This is for my wired set up and I use Speedtest.net for all testing (although figures are also confirmed by BT)

[#2]

It is possible given the time frame of couple of months that you are seeing the effect of cross talk in the cables.
As more and more people get connected to FTTC the presence of their VDSL signal in the multi-core cable alongside your feed will adversly affect your signal.
This is a known effect of the high frequencies used in FTTC and is why there is no definitive distance from cabinet vs speed graphs.
This is also why in general the estimates are lower than people initally find they get - the estimates allow for this effect over time.
Those connected first to a cab will see the greatest speed drop, while those connected after a period will see less as their connection starts with all the cross talk from the others on the cabinet present from the begining.

[#3]

Thanks for the quick response.
What you say makes sense and I'm not sure there are any practical effects in the drop in speed. Downloads seem to be as quick and streaming is fine.

[#4]

Run the BTw Performance test (ignore the red preamble except make sure no other programs are using the Internet) and at the end of the first run, click the Further Diagnostics button, enter just your Phone number and Run the Further Diagnostics Test. if you want to post the results just do a Copy and Paste of the results and post (no need to grab an image).
The figure to look for is the Downstream BT IP Profile x1.033 = sync speed on FTTC. So this is the figure to keep an eye on to assess what may be happening with your connection. If you see this changing a lot there may be a problem. Hopefully it will stay stable. If the recent drop was due to a passing problem, DLM will put your speed back up again in due course.

[#5]

Thanks Anotherone
These are the (wired) figures I obtained
1. Best Effort Test: -provides background information.
Download Speed
55.27 Mbps

0 Mbps 68.1 Mbps
Max Achievable Speed
Download speedachieved during the test was - 55.27 Mbps
For your connection, the acceptable range of speedsis 16 Mbps-68.1 Mbps .
Additional Information:
IP Profile for your line is - 68.1 Mbps
2. Upstream Test: -provides background information.
Upload Speed
15.59 Mbps

0 Mbps 20 Mbps
Max Achievable Speed
Upload speed achieved during the test was - 15.59Mbps
Additional Information:
Upstream Rate IP profile on your line is - 20 Mbps

We were unable to identify any performance problem with your service at this time.
It is possible that any problem you are currently, or had previously experienced may have been caused by traffic congestion on the Internet or by the server you were accessing responding slowly.
If you continue to encounter a problem with a specific server, please contact the administrator of that server in the first instance.
My reading of this is that I could expect up to 68Mbps downloads but at the moment I am getting 55. I'm not sure if I should be expecting to get the IP profile figures or not. I must admit to being a bit of a novice where all of this is concerned. Should I raise it as an issue with Plusnet?

[#6]

It's possible that if you had a resync that was very quick or whatever, you had no drop of PPP session, so the relevant BT servers haven't been updated with your current sync speed - the system relies on a new PPP session (or DHCP request).
Here's the solution - Log in to the Modem/Router, in the Internet box, click Disconnect to drop the PPP(oE) Internet session (this is not the sync), wait 30 seconds then click Connect. This should ensure the relevant servers are updated with the current sync speeds.
Then run the BTw Diagnostics speed test again and hopefully the profile will show correctly what it should be currently. Note that you will also change which Gateway you are on by establishing a new PPP session (usually).

[#7]

It's certainly had an effect A1 - but only lowered the Download  IP profile so that the download speed now matches the IP profile more closely. Is there any reason why this might happen?
Best Effort Test: -provides background information.
Download Speed
54.77 Mbps

0 Mbps 56.53 Mbps
Max Achievable Speed
Download speedachieved during the test was - 54.77 Mbps
For your connection, the acceptable range of speedsis 16 Mbps-56.53 Mbps .
Additional Information:
IP Profile for your line is - 56.53 Mbps
2. Upstream Test: -provides background information.
Upload Speed
15.87 Mbps

0 Mbps 20 Mbps
Max Achievable Speed
Upload speed achieved during the test was - 15.87Mbps
Additional Information:
Upstream Rate IP profile on your line is - 20 Mbps
The gateway changed (at least I think so) from ptw-ag03 to pte-ago4 (both at Telehouse West)

[#8]

Reply #1 from x47c will probably be most of the explanation, but no line is totally immune from noise/interference and you may have had some that has contributed to this. If this was only a passing momentary thing, such as can be caused by a thunder and lightning storm for example, then the DLM may recover some of that speed in due course. Just keep an eye on it periodically and as long as it isn't up and down like a jojo or on a continual downward trend, things should be OK. HTH.
PS. you can ignore the Upstream profile, it always says 20 on FTTC whatever the real profile is!

[#9]

OK Thanks Anotherone

[#10]

One other thing to keep an ear open for is any crackling or other noises on the line when using the phone. Also watch if you have any problems with incoming or outgoing calls.