FTTC speeds varying again

[#1]

Since getting my new fibre connection the speed has been stable at around 73 Mbps for several weeks at a time (at least when I test it) and then starts flapping around until PN 'fix-it' following me raising a ticket, then repeat.
So after a few months since the last episode of stable test speeds, it has started to flap around again between 30 and 73 Mbps – see attachments.
All tests are wired – the wireless is actually turned off.  BT modem never switched off.  Router on for over 15 days.  My current line speed is 77.4 Mbps and has been since I was connected.
Usual questions: a) should the speed vary? b) why is it stable for many weeks and then starts to vary?

[#2]

Hi fp,
Speeds can vary to be honest, however I'd say it would still be worth going through our faults process to see what we can find out and if anything can be done.
I have made some checks on your account and can't see any potential or obvious causes for what you've mentioned.
If you decide to press on with this just raise a fault at http://faults.plus.net and feel free to drop a reply here after you've done so.

[#3]

Thanks.
It seems to be constant at 73Mbps this morning.  But that was the case previously, with the speed varying usually at peak times.  This may have been coincidence e.g. when I measure it most, rather than when other people are also most likely to be using the internet.
Would you explain why the speed varies – by a factor of two or more at times, sometimes within the space of minutes.  Am I sharing my 73 Mbps bandwidth with other users, for example?

[#4]

Can you try this speed test http://www.thinkbroadband.com/speedtest.html this evening and post the results? It will give a better idea if there's congestion.

[#5]

Stable at 73 Mbps during the morning and early afternoon.  Just logged on and now down to 50Mbps at peak time.  See attachments.
Same pattern as previous episodes of this issue.
Wired test.  Wireless off.  BT modem never switched off.  Router on for more than 16 days.

[#6]

How long has it been doing this?
My speeds are also a bit all over the place tonight.

[#7]

First noticed it yesterday, after a few months of apparent stability following the last similar episode - when I raised a ticket and PN 'solved' the problem.
This has haunted me since I got fibre earlier this year .... stable speed test of 73Mbps for weeks, then flapping around at peak times, then PN take action and back to stable speed, repeat.

[#8]

Hi
Having a few FTTC installs now, I have learnt few things, first you need your router as close to the NTP (network termination point) as you can, one install ran 20Mb/3Mb until I ripped about 40m of random cabling and junction boxes out the office and then had a pretty good 55/12Mb after that, if you use the BT supplied modem to convert to a PPPOe connection it is better to extend on the Ethernet side than the Modem line.
Whilst the supplied modem/router solution is pretty cluttered the modem doesn't seem bad, I have moved to Drayteks or Cisco unit on most sites but I haven't seen an advantage by loosing the modem, the PlusNet router is not bad either, I ended up dumping the config, editing it and reloaded it as I lost eh will to live on the web interface, but that aside it is pretty good (for free!) don't forget FTTC is still a contended service, the DSLAM is in the green box down the road and if half the neighbourhood have signed up and are watching Netflix on 4K tvs you are gonna see a drop in line speed, if you want mad speed it will cost, and cost a lot, make sure you kit is as well setup up as it can be, router near as poss to the intake point, if you need to get internet elsewhere look at Ethernet-over mains solutions, I use a lot of the TP-link ones as they have a 2 port switch and wirless on the nodes, they are as cheap as chips and work well.
For a few quid a month anything over 50Mb is great, make sure you use what you get!!

[#9]

Thanks for the explanation.  I had not realised I was effectively sharing bandwidth with the neighbours.  My recollection (perhaps incorrect) is that I had been told I was not sharing and should get the same speed all the time, even at peak hours.  Would a PN moderator clarify this point, please.
The BT modem is very near the house 'telephone point'; and I am close to the street green box.  I agree that the PN supplied router is fine using ethernet cable.  There should however be a warning sticker that the continual frustration caused by trying to connect via the rubbish wireless may lead to bad language and even brain haemorrhage.

[#10]

your recollection is almost certainly wrong.
FTTC is still an "up to" product and has always been marketed as such.

[#11]

My confusion is whether the 'up to' refers to the speed your specific connection may achieve (due to proximity to the green street box, electrical connection between the box and your house etc) or bandwidth sharing - or both.  So having established you can get X Mbps is that what you get all the time or only when no one else is using the internet, which has been the case for me recently - at least when tested.
I have been down to 11 on a connection that clearly supports 70.  My main aim has been to understand why.  If it is simply because I am sharing my 70 Mbps bandwidth with others at peak times because there is not enough to go round (for whatever technical or economic reasons) then as far as I recall this has not been said. 
BTW for avoidance of doubt, I am happy with PN.

[#12]

the figure you are given at the point of sign up is the theoretical maximum the line is capable of.
actual speeds may vary due to many reasons, however as more people use the FTTC cabinet, the higher the risk of speed drop.
you then also have the possibility of congestion as the cabinet or exchange due to over subscription.
then to add on top, you have certain times of the day where traffic will be higher than other times, and as such that also has an effect on speeds.
your speed range should always be around the bt wholesale speedtest ranges though.
anything below that and you may have a line or equipment fault somewhere.
at no point will any ISP say that we guarantee ANY speed at any point of the day.

[#13]

The first thing to do in all cases where speed seems to drop is to run the BTw Performance test (don't go rebooting modems - ignore the red preamble - except make sure no other programs are using the Internet and wireless is off, use a wired ethernet connection) and at the end of the first run, click the Further Diagnostics button, enter just your Phone number and Run the Further Diagnostics Test. The BT IP profile (downstream) is the thing you need to check first as this will tell you if your sync speed with the Cab has changed. That sounds unlikely in this particular instance, it seems like a typical case of congestion.
As far as congestion is concerned, if it is only momentary, then there's not really anything to worry about, this has been the case for years with ADSL as well. If you get a slow speedtest, run another, also use different testers - TBB, speedtest.net etc. It's worth remembering that testers can get congested as well.
Where you start to get low speeds for extended periods, then this sounds like more serious congestion, most times it won't be your local Cab, it will be further upstream at the exchange or a main node ie.somewhere on BT's back-haul network.
This is where running a TBB BQM can also come in useful BUT remember if you are not on a fixed IP address and it changes, you MUST cancel your monitor set up and create a new one. I don't have the time to get involved in another thread atm, but AndyH is a bit of an expert in this area and will hopefully post back with more info & advice.