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BT Infinity to Plusnet Fibre - 12mb Speed Drop

N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

BT Infinity to Plusnet Fibre - 12mb Speed Drop

As the title really, I used to get around 72Mb down/ 18mb up with BT infinity and decided for a change as I heard things were better over here again, more for the user etc.
I was quoted as getting 66mbit minimum when signing up (same as when I first upgraded infinity to the 72mb band), unfortunately I can not perform this test again as I am already with your product now. But today I got this email:
Now that your service has now been active for 14 days, we thought we'd let you know the speed as it stands today, by way of comparison.
Estimated line speed: 8Mbps (this bit I find really cheeky).
Current line speed: 61.2Mbps
The only line stats I could find with BT:

Initial line stats with Plusnet:

Current line stats with Plusnet:

TBB speedtest:

BT wholesale checker:

Estimated line speed from my plusnet profile:
    60Mb (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 2014-11-16 13:31:42
Current line speed:
    61.2 Mb
BT speed checker:

I would have taken up to date speed tests and a BT line test before migrating, but I thought all that sly fox stuff of  pulling a fast one with speed estimations, line contention and all that from the ADSL/ADSLmax days were gone. I haven't even had to touch my ADSLGuide account in years, that was back when plusnet got bought over (by pipex IIRC) and I had to migrate because of the rediculous FUP introduced Wink
Unfortunately I took a phone line out with yourselves too, so there isn't much I can do about it until the contracts are up but hope that you actually try to rectify this Sad.
Is there any particular reason why you can not maintain the same level of service as BT? They had told me when I asked for my MAC key that they're the only ones that could service my line to the best possible speeds. But I just took it as retentions lying, trying to hold onto my custom.
16 REPLIES
Community Veteran
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Registered: 29-01-2009

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Quote from: N3ViT
Is there any particular reason why you can not maintain the same level of service as BT?

Even BT can't maintain the same level of service over time. It is impossible - and the reason is an effect known as crosstalk, which is interference from other FTTC subscribers. This becomes more of a problem as take-up increases, which is what is steadily happening. It is an unfortunate fact of physics for all of us.
For a fuller explanation, see my post over on this thread.
In your case, the underlying issue is the sync speed that your modem is achieving with the DSLAM in the green cabinet; this speed of 61.2Mbps is what limits the download speeds to around 59Mbps. Plusnet can't affect the modem's behaviour - so this is exactly what would be happening if your ISP were anyone else, including BT (though different makes of modem do show slightly different sensitivities, and the sync can vary a few Mbps).
As the estimate was for 60Mbps, and the line speed is actually 61Mbps, you are unlikely to get an engineer's visit unless there is some other indication of a fault on the line.
Edit: To make it clear, my comments apply to perfectly normal lines ... but there could be some kind of fault on there too. I'd expect a Plusnet CRT rep to add something here, after performing a test on your line, and possibly recommending that you proceed through their faults procedure.

Quote
but I thought all that sly fox stuff of  pulling a fast one with speed estimations, line contention and all that from the ADSL/ADSLmax days were gone.

It is, but the effects of crosstalk on VDSL2 are more significant than they were for ADSL. Much more significant.
BT Wholesale (as in the checker result you showed) provide a range of speeds for a reason, but the significance of that range is lost on most people. They think, sometimes quite obstinately, that once speed X is achieved, they have the right to keep it. Unfortunately, BTW provide (and interpret) the range to mean that they expect your speed to vary within that range quite legitimately.
(For info, the range is calculated from the speeds seen on "similar lines"; they initially decide on similar lines based on the properties of the line between the cabinet and the DP, and make a standard allowance for the drop wire. The top speed in the estimate comes from the 80th percentile of those similar line (ie the top 20%), while the bottom of the range comes from the 20th percentile (ie the bottom 20%) - so some similar lines go slower. And the estimate can change, if BT decide that they are comparing your line to the wrong batch of "similar lines" - for example if you have a length of drop wire that is much longer than standard.)
Quote
They had told me when I asked for my MAC key that they're the only ones that could service my line to the best possible speeds. But I just took it as retentions lying, trying to hold onto my custom.

Yup. If they did that, BT would be acting entirely illegally. BTO and BTW have to offer the underlying service in a way that is entirely equivalent to every other ISP.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Deleted unintended extra post.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

I can appreciate that speeds/sync will fluxuate, but that is completely separate to why I am trying to figure out how around 12mb got dropped while my line settled with Plusnet. I understood there was a risk that I'd lose a few meg while migrating, but it makes no sense at all that I've had a maintained speed avg of 70mb (say 68-72mb given good and bad days) for over 18 months with BT for it to just drop after a migration.
I can't see that a couple of my neighbours have suddenly started taking an interest in HAM radios or anything like that, the only variable is the migration so surely you can see why I am raising a question.
To top it off, my ping has increased in games by about 10-15ms too.
Community Veteran
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

1 - speedtests are not a accurate way to determine sync speed, however we can determine from your BT wholesale test which reports the profile, wwwombat correctly calculated the sync speed for you.
2 - with that said tho the speedtest from infinity indicates a sync speed in my opinion of at least 74mbit.  But these speedtests can give false results with certian a/v software.
Moving from infinity to plusnet even if was different DLM paramaters would not make a day 1 sync change.  So I dont know what answer to give here, it all seems a bit odd.
Ultimately tho in regards to trying to get a fix, your problem is the estimate is 60meg, and you are above that.
I got no idea how plusnet came to a 66meg estimate a sI would expect them to use the low range of the clean estimate which for your line is 60mbit.  It is possible since ordering BT wholesale lowered that estimate, I hope you kept a copy of the point of sale estimate.  But even if you did support staff and openreach seem to only honour the 'current' estimate.
Ask for plusnet to do a line test, that will determine if you are interleaved.
N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Yea, Kaspersky used to interfere with the speedtests on me, but I now use a Malwarebytes/bitdefender combo that has been playing nice with speedtest and others.
Yea I don't have high hopes of anyone doing anything to resolve it for me as to me it looks like my profile was buggered over the migration and well... I've still got 60mb. I don't want BT out at all, that isn't what I am after as they'll do nothing and try to charge me for the pleasure.
Just searched through my old emails, and it does indeed look like I was quoted a different estimate from the speedchecker when I was signing up. Mores the fool for me for not reading the email and getting in contact sooner. Should have not bothered playing about with the provider at all to be honest, never had any issues with it at all during my contract. Was just a bit miffed at BT offering new customers £20pm and trying to lock me into another 18mth contract to lower the price of mine...
In what way do I raise this request so that it doesn't get escalated to a BT visit, just a support ticket?
Community Veteran
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Registered: 11-12-2013

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

you can ask on this forum or in a ticket, they probably will not book a visit without finding a problem anyway, this is a remote test that is carried out online.
Community Gaffer
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Hi there,
Your fault ticket hasn't dropped out for us yet anyway, it looks like it hasn't been fully submitted. If you did want us to look into any faults, just go back over the faults checker ensuring you answer all the questions at the end and we'll take a look.
If this post resolved your issue please click the 'This fixed my problem' button
 Chris Parr
 Plusnet Staff
N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Apologies, I hadn't realised that was opening a ticket. I'll go back and complete that.
e: completed. Also found the user panel. I'll need to take a proper look about my account when I get time.
awahwah
Grafter
Posts: 31
Registered: 16-11-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

You are not alone with speed drops when moving from BT to PN. i currently have a fault ticket open with Support too for the very same thing. also, watch out for any congestion, there seems to be a bit more with PN then experienced with BT, which is odd as they use BTO network.
Still, I have to try to remember, this is costing £5 a month less. May be there is a reason for PN service being cheaper.
N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Cheers for the input awahwah, unfortunately BT were doing price matching when I migrated so there was no proper reason other than a change Sad
Community Veteran
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Are you using the same modem (and/or router) as you used with Infinity?
The change to Plusnet (or any other FTTC ISP) should not change your sync with the cabinet unless you have changed from , say, HH5 using the internal modem to a (faulty?) BTOR modem (or maybe a faulty PSU on a new router causing interference?)
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.
Community Veteran
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

Quote from: N3ViT
I can appreciate that speeds/sync will fluxuate, but that is completely separate to why I am trying to figure out how around 12mb got dropped while my line settled with Plusnet

That's a good start. Understanding that other subscribers can affect your line is important here... because it truly isn't "completely separate."
I'm not talking about the likelihood for speeds to fluctuate - that doesn't tend to happen. I am talking about speed drops, and particularly ones that comes in both small amounts and in a subsequent larger drop. Your line has shown symptoms of both ... in a way that is typical of all fibre lines, on all providers. The important point, though, was that this can happen anytime, on any day, migration or not. It is random, because it depends on the actions of other people.
NB: There is no "settling in" with Plusnet that takes 10 or 14 days for fibre. A new or regraded line resets DLM, which will start to monitor within 24 hours and intervene, if necessary, from 48 hours onwards. However if your line didn't regrade with the shift to Plusnet (which is the likely case here, given the 80/20 package both before and after) then it is very likely there was *no* inherent reset of DLM at all. If that is the case, there was no settling-in period either.
That means you should indeed be thinking of this as a problem that happened to your line, and not particularly something caused by the switch to Plusnet.
Quote
so surely you can see why I am raising a question.

Sure. I understand how suspicious it looks. I also understand how annoying it is to see precisely these drops - it is frustrating to see speed drops here & there, knowing what your line used to be capable of.
But I choose to spend my time answering posts like these because I know what the ISPs (and BT especially) don't tell you about the deep down working of FTTC. I do this to try to remove the frustration. I don't do this because of blind devotion to Plusnet.
When I look at the details you have provided, I see all the evidence of crosstalk impact that you would have had if you stayed with BT (**) - perfectly standard; annoying, but standard. I don't see any evidence of Plusnet's internal network affecting you (and I would say, if I did see that); there is plenty that Plusnet could improve (like my house move!). I don't see any evidence of congestion either.
Quote
I understood there was a risk that I'd lose a few meg while migrating, but it makes no sense at all that I've had a maintained speed avg of 70mb (say 68-72mb given good and bad days) for over 18 months with BT for it to just drop after a migration.

There is indeed some amount of risk from the things that Plusnet do internal to their network, which are different to the things that BT Retail do internal to their network. However, there is almost (*) nothing that Plusnet does to your phone line that causes the sync speed differences. And that appears to be where you are seeing the differences. Your modem, though, could be making a difference (**), if you changed that in the process.
Let's look at those sync speed differences...
It looks like, from the speedtests given, that you had a sync speed of perhaps 74Mbps with BT around 30 months ago. Your initial download speed from Plusnet suggests your sync speed was around 71-72Mbps. A small drop of 2-3Mbps is well within the amounts I'd expect to gradually accumulate due to crosstalk; in fact, it is quite small.
This at least shows that your time with Plusnet likely started out just fine.
The final speed test from Plusnet matches up with the BTW test, which itself shows an IP profile of 61.4Mbps; that maps to a sync speed of perhaps 63.4Mbps. That would make for a 8-9Mbps drop; that is well within the kind of drop that is seen when DLM intervention occurs. Again, it can happen at any time, randomly.
It currently looks like you've experienced a gradual increase in noise - which is visible in reduced speeds when a new sync occurs - ending, finally, with a sudden intervention of DLM.
Keeping speeds for 2 years, then seeing a few small drops, then seeing a big drop as DLM intervenes is not an unexpected effect. I saw precisely the same thing in the second house that I had FTTC in. I watched the noise gradually increase over that time, watched the attainable speed drop from 90 through the 80's then down to 78 (when the actual speed dropped too), and watched the error rate increase over that time too - until eventually, an extra burst of noise added to the regular errors was enough to trigger DLM intervention - which dropped the speed by a further 7Mbps. Within the two years though, I got one large drop early on, one medium drop late on, but the attainable stayed between 81 and 83 for the best part of a year inbetween.
The first house we had FTTC in was rather different - because DLM had to intervene from day 3 (after watching 4% packet loss for the first 2 days).
Quote
To top it off, my ping has increased in games by about 10-15ms too.

Then it sounds definite that DLM has intervened: the first, low, level of intervention adds 8ms to the downstream transmission at the DSLAM, and this usually translates to around 10ms extra on round-trip latency.
I don't set much stock by the Ookla ping times, but  this also shows between the first & last speedtest. The TBB ping graphs monitor this better, if you have a static IP and you can set your router to respond to WAN pings (lots of graphs visible here); IMHO this is by far the best tool for monitoring your line for long periods, even if it doesn't include a speed test.
Quote
I can't see that a couple of my neighbours have suddenly started taking an interest in HAM radios or anything like that, the only variable is the migration

The neighbours don't have to take up HAM radio; they just need to subscribe to FTTC. And it isn't necessarily the neighbouring houses that matter - it is the twisted pairs in the cable bundle that neighbour your pair for the longest distance that matter most; these could be neighbouring houses too, but they could be a fair way off.
Other people taking up FTTC is actually the biggest variable. Take-up is increasing around 1% each month - so that's likely an extra 3 lines in the cabinet each month, each adding some amount of crosstalk to your line. Every line in the cabinet shares at least some portion of common cabling.
Obvious questions:
How many days (from the first day that Plusnet had your line) did you keep the 68Mbps speedtests for?
On which day (from the first day that Plusnet had your line) did you get the 59Mbps speedtests?
Have you changed modem?
(*) - The "almost" there is because BTW allow 3 settings for fibre lines, that affect how DLM interprets the error counts while deciding whether to intervene; the settings are "standard", "stable" and "super stable". Swapping between ISPs could cause a change to that setting, and could cause a line that was "OK" with the old ISP to suddenly requiring  DLM intervention with the new ISP. That, of course, only happens if the new ISP has tighter, more stable, settings.
Plusnet chooses the loosest "Standard" setting that has the highest error thresholds for DLM; therefore a switch to Plusnet shouldn't ever make DLM treat the line as requiring higher stability. I don't know what setting BT-Retail uses.
(**) - As I mentioned before, a different modem could show less sensitivity to noise on the line, and therefore get a slightly higher error count from the same external situation ... leading to a higher likelihood of DLM intervention. Did you change modem, or did you carry on using the BT hub?
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
N3ViT
Newbie
Posts: 7
Registered: 11-12-2014

Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

I am trying to get the jist of your post. Is it what, that DLM has kicked in because of migration and thus slapped my speed down or that this would have happened anyway? I can believe the former but I can't believe the latter that it was just ultimately bad timing after consistently good speeds/pings before hand. It's just too coincidental. Its like claiming a sore head would have happened anyway, regardless of me banging my head. I can appreciate it if the migration has triggered DLM by default and that has seen some unneeded reason to rectify my line.
Quote from: WWWombat

NB: There is no "settling in" with Plusnet that takes 10 or 14 days for fibre. A new or regraded line resets DLM, which will start to monitor within 24 hours and intervene, if necessary, from 48 hours onwards. However if your line didn't regrade with the shift to Plusnet (which is the likely case here, given the 80/20 package both before and after) then it is very likely there was *no* inherent reset of DLM at all. If that is the case, there was no settling-in period either.

Just regurgitating what I received on text/e-mail, it's been a while since I was last with a LLU provider and I don't know what shenannigans goes on with non-BT ISPs these days so I took them at their word.
Quote from: WWWombat
That means you should indeed be thinking of this as a problem that happened to your line, and not particularly something caused by the switch to Plusnet.

Unfortuantely I just got round to checking the ticket and got line stats back and confirmation that no action would be taken.
Quote from: WWWombat
It looks like, from the speedtests given, that you had a sync speed of perhaps 74Mbps with BT around 30 months ago. Your initial download speed from Plusnet suggests your sync speed was around 71-72Mbps. A small drop of 2-3Mbps is well within the amounts I'd expect to gradually accumulate due to crosstalk; in fact, it is quite small.
This at least shows that your time with Plusnet likely started out just fine.

And this I was fine with, somewhat expected.
Quote from: WWWombat
The final speed test from Plusnet matches up with the BTW test, which itself shows an IP profile of 61.4Mbps; that maps to a sync speed of perhaps 63.4Mbps. That would make for a 8-9Mbps drop; that is well within the kind of drop that is seen when DLM intervention occurs. Again, it can happen at any time, randomly.

And this again feels like someone telling me I would have had a sore head regardless of banging my head.
Quote from: WWWombat
It currently looks like you've experienced a gradual increase in noise - which is visible in reduced speeds when a new sync occurs - ending, finally, with a sudden intervention of DLM.

And these syncs happen randomly? So why did this one happen to be the catalyst?

Yes, from the info they gave me back, it does look like DLM has now taken affect:
Quote
0.128M-67M Downstream, Interleaving High - 0.128M-20M Upstream, Error Protection Off

Quote
Take-up is increasing around 1% each month - so that's likely an extra 3 lines in the cabinet each month, each adding some amount of crosstalk to your line. Every line in the cabinet shares at least some portion of common cabling.

But my download nor ping diminished before, so what happens? Does it built up over time and just let a massive burst out? Or is it a case that a lot of other people in our town joined up FTTC at the time I migrated?
Obvious questions:
How many days (from the first day that Plusnet had your line) did you keep the 68Mbps speedtests for?
I only tracked it for a couple of days, and once I thought it wasn't going anywhere I didn't track it much more.
On which day (from the first day that Plusnet had your line) did you get the 59Mbps speedtests?
from speedtests, "12/7/2014". But I hadn't hadn't been looking into it much at the time as I have been really ill recently. The main reason why I haven't seen much action of this or chased it up recently.
Have you changed modem?
No, same old white Hauwei that BT supplied me with (not unlocked either). The internet went down on the prev night of when it was meant to go live, and I couldn't get access until I contacted Plusnet that day. They checked it and said it should be enabled, then my username/pass worked with my router. Got an email saying the eng visit would happen that day after that contact, but I just assumed that it didn't happen because my current modem was fine.
Quote from: WWWombat
(*) - The "almost" there is because BTW allow 3 settings for fibre lines, that affect how DLM interprets the error counts while deciding whether to intervene; the settings are "standard", "stable" and "super stable". Swapping between ISPs could cause a change to that setting, and could cause a line that was "OK" with the old ISP to suddenly requiring  DLM intervention with the new ISP. That, of course, only happens if the new ISP has tighter, more stable, settings.
Plusnet chooses the loosest "Standard" setting that has the highest error thresholds for DLM; therefore a switch to Plusnet shouldn't ever make DLM treat the line as requiring higher stability. I don't know what setting BT-Retail uses.

As above, it appears DLM is acting strong on my line: 0.128M-67M Downstream, Interleaving High - 0.128M-20M Upstream, Error Protection Off
Quote from: WWWombat
(**) - As I mentioned before, a different modem could show less sensitivity to noise on the line, and therefore get a slightly higher error count from the same external situation ... leading to a higher likelihood of DLM intervention. Did you change modem, or did you carry on using the BT hub?

There's been no modem change, I didn't take their router either. I've had an ASUS RT-n66u for the past 16 months too. As I said, all has been dandy on the line up until migration.
I did setup a ping graph around the time I opened the support ticket (it has calmed down now, but there was a lot of spiking max ping beforehand):
http://www.thinkbroadband.com/ping/share/ec1aee0cb831806d71a892fa9340c0c1.html
Some of the internal stats, let me know if others are more useful:
Type Date                         Direction         Profile Speed
TAP-1 11-12-2014 (12:47) DownStream 61371 58400
TAP-1 11-12-2014 (12:47) UpStream         20000 11160
SVLAN - Total of 30 VPs. This circuit is currently on SFBB00000125 which is showing BLUE.
VP Data - Blue - 22 , Green - 7 , Amber - 1 , Red - 0
TAGs (Clean): Download: 60 Mbps - 79.3 Mbps / Upload: 19.5 Mbps - 20 Mbps
WLR - PASS
My main question is, will DLM tone itself down over a reasonable time? Or is it set once its went Rambo on my line? I think I can make do with the speed decrease until my contract is up if nothing can be done to fix it.
Plusnet Help Team
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Re: BT Infinity to Plusnet Fibre - 12mb Speed Drop

As far as I'm aware and don't quote me on this just yet but a fibre migration from another provider will cause your DLM to be reset.
With DLM on fibre the effects can kick in without you losing your connection. You'll briefly lose sync however you reconnect straight after so the session with us is kept alive.
It looks at some point that your line had a high burst of errors that forced DLM to intervene. Unfortunately we can't see that data however this will most likely be the case.
As long as your connection stays stable and there are no further errors in time DLM will tone down the interleaving on your line. We have no way of resetting it remotely and the only people who can are Openreach engineers. They'll only do this after fixing a issue with the line so we can't just send them out to do a reset.
The DLM isn't actually causing your poor speed issues. The DLM dats states that the band applied to your download connection is 0.128M-67M which means your modem can sync anywhere between those speeds. Your modems currently syncing at 63.4 so it isn't even at the top of the band.
There probably won't be much that we can do about the speeds I'm afraid. WWWombat has covered all the reasons why this could happen but our suppliers will only investigate speed issue if they drop below 25% of the original estimate and if we were to send out a engineer there would be relatively little he or she could do.
If this post resolved your issue please click the 'This fixed my problem' button
 Matthew Wheeler
 Plusnet Help Team