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Fibre capped at 20Mb

kankali
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Registered: ‎31-10-2011

Fibre capped at 20Mb

Hi,
I have had fibre for just under a year an normally syncs at 23Mb.
For some reason it has now been capped at 20Mb. This despite the fact that the line is very stable with a normal uptime of 10 days.
I phoned the helpdesk but they say that the BT database says the line should only achieve 14Mb so there is nothing they can do.
Any chance I can have a DLM Reset, or turn the interleaving off to get this uncapped?
Many thanks, David
jim:green Title amended at request of poster mod:end
17 REPLIES
Community Gaffer
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Re: Fibre capped at 20Mb - one for the PN Team please

Unfortunately not, we have no tools to perform a remote reset on a fibre line. In order to get a line reset we need to raise a fault, get this accepted (which would be the sticking point as you're above the estimate for your line) and then an engineer would need to visit, fix something and then reset the line. Sorry to be the bearer of bad news.
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 Chris Parr
 Plusnet Staff
kankali
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Re: Fibre capped at 20Mb - one for the PN Team please

Chris,
Thanks for the quick response. I am not sure how BT get away with these speed estimates when a line has been running way above that since it was activated.
Any chance we can turn the interleaving off - I seem to remember seeing in another post that this was possible.
Regards, David
Community Gaffer
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Re: Fibre capped at 20Mb - one for the PN Team please

Again that's not something we can do remotely unfortunately, the tools we have for fibre are limited to orders or fault testing. There's very little else we can do I'm afraid.
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 Chris Parr
 Plusnet Staff
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Re: Fibre capped at 20Mb - one for the PN Team please

Quote from: David
I am not sure how BT get away with these speed estimates when a line has been running way above that since it was activated.

There's a technical issue known as crosstalk, which affects VDSL2 much more noticeably than with ADSL. This crosstalk is interference from other subscribers, whose lines share some part of the cable bundle back to the cabinet. As take-up increases, so does crosstalk - and take-up is indeed increasing.
Over time, speeds drop a little, and errors increase ... and perhaps DLM gets involved too. It is well understood (by BT, at least) that the speeds attained at initial activation are not necessarily kept forever - which is why the estimated range remains valid - even if you once got a higher speed.
I gave a more detailed description a while back, but its tough to make it easily understandable.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
kankali
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Re: Fibre capped at 20Mb - one for the PN Team please

WWWombat
Many thanks for replying. My line started at 27Mb so when it gradually dropped to 23Mb I hoped we had got the crosstalk out of the way.
I still don't understand why it has suddenly dropped to 19Mb as the line has been very stable with a 15 day uptime normally. Would this happen if the cross talk increased or would I see more line drops?
I can't see the error counts - I was kind of hoping the PN staff would have more insight - but all I seem to get is "your lines overachieving blah blah blah"
Thanks, David
kankali
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Re: Fibre capped at 20Mb - one for the PN Team please

And this is what I currently see on the Modem/Router if that is of any help

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Re: Fibre capped at 20Mb - one for the PN Team please

Quote from: David
My line started at 27Mb so when it gradually dropped to 23Mb I hoped we had got the crosstalk out of the way.

Hard to tell. It really depends on those lines whose copper pair runs close to yours in the different cables deployed between you and the FTTC cab (including the tie cables between PCP and FTTC cab). For the worst case, the impact can be truly horrible.
Quote
I still don't understand why it has suddenly dropped to 19Mb as the line has been very stable with a 15 day uptime normally. Would this happen if the cross talk increased or would I see more line drops?

What you see as a stable line isn't necessarily what the modem sees, or what DLM as a consequence acts upon. Again, it is hard to describe what would be visible to you. Certainly things can be going "wrong" in a way that you wouldn't really see anything, even line drops, unless you had access to good statistical monitoring.
I tried to describe this in a different post for someone who was having a similar hard time in understanding the impact (look in the middle, for a list of 10 items).
In your case (from limited evidence, mind), it looks like DLM has intervened. Your speed is 19,999 - which suggests you have been banded/capped at 20Mbps by DLM. This would come about because it has found it tricky to manage the number of errors on your line, and that various settings for FEC and interleaving hadn't been successful enough - ie errors kept happening.
Quote
I can't see the error counts - I was kind of hoping the PN staff would have more insight - but all I seem to get is "your lines overachieving blah blah blah"

The most useful thing they can add is a line profile, that would confirm what DLM settings are in place. You'd at least know what had happened, even if you still end up incapable of doing anything about it.
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Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
kankali
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Re: Fibre capped at 20Mb

WWWombat
Thanks again for the thorough answer.
Yes when I started to resync at 19,999 every time that's when I thought something was up
I really need some input from the PN team to tell me what the profile etc is. I've phoned twice with no success so lets see if they reply on the forum.
One final thought - we're heavy users - 300GB per month - I suppose that will lead to more errors over a 24 hour period than the average user. Does the DLM take this into account - or could this be the cause of the issue.
Regards, David
Terranova667
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Re: Fibre capped at 20Mb

the amount you download / upload has no baring on anything DLM couldn't care less it looks at errors and the amount your getting in a given time and makes it's decision what to do about them at times to harshly imo.
errors don't come from downloading / uploading so no it wouldn't be the cause, as stated already if the line is deemed fine then cross talk is the only other cause i have gone from 65Mb down to 51Mb which is deemed to be due to cross talk sadly nothing can be done at present, we just have to wait and hope BTO gets their butts in gear and gets vectoring out ASAP.     
Community Gaffer
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Re: Fibre capped at 20Mb

The profile is now banded, meaning until the banding is removed you won't be able to connect higher than 20Mb.
Profile Name 0.128M-20M Downstream, Interleaving High - 0.128M-3.7M Upstream, Error Protection Off
Fortunately the line is appearing very stable at the moment, so the band should increase as long as it remains so. There's a good article on FTTC DLM here: http://community.plus.net/library/browsing/fttc-dlm-what-it-is-how-it-works/
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 Chris Parr
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kankali
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Registered: ‎31-10-2011

Re: Fibre capped at 20Mb

Terranova,
Thanks for clarifying.
Chris,
Finally. Confirmation that the line is banded. I specifically asked if this was the case when I called the PN team, but I was told the line wasn't banded.
So how long is this piece of string. i.e. how long does the line need to be stable before the banding comes off.
As far as I am aware the line has always been stable since it settled at 23Mb, 9 months ago.
Thanks, David
kankali
Grafter
Posts: 92
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Registered: ‎31-10-2011

Re: Fibre capped at 20Mb

Chris @ PN,
Do you have an estimate of how long the line has to be stable? From what I can see it has been stable for 13 days, 4 days and 13 days in the last month but the line is still banded.
Regards, David
Terranova667
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Re: Fibre capped at 20Mb

sadly that is DLM's call and there isn't anything that can be done about it, I have had interleaving put on my line by DLM even though i had engineers deem the line to be perfect, as i said previously it acts way to harshly imo
it's not really the stability that matters the most although i wish it was as i said previously it looks for the amount of errors it sees in a given time period and makes a choice what to do either add or remove certain things like interleaving or banding, Imo DLM  should act if your line can't remain stable not do something just because it sees some errors and thinks the line might become unstable it's like the minority report in that regard some may think it's over the top preventiveness is a great thing i don't it's extremely quick to add things to the line but Very Very slow to remove them if it wants to do that.
As for the time frame you might as well ask how long is a piece of string it could be days, weeks, its not unheard of to go months before it chooses if at all to do anything.
kankali
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Registered: ‎31-10-2011

Re: Fibre capped at 20Mb

Terranova,
I did mention the "piece of string" in my other post - BT seems to have the longest piece in the world  Smiley
Chris refered to line stability in his post - hence my question.
Its seems like we are in the bad old days of ADSL1 and BT's profiles which reduced in 2 hours then took days and days to go up again.
Regards, David