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Standard User ajdroberts
(newbie) Mon 05-Oct-15 16:06:20
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SNR Resets and really slow speeds (1.9mbps!)


[link to this post]
 
If this post is not in the best place could a mod. please move it or tell me how to?

I've had all sorts of disconnection problems recently and, over the years, various 'supply' issues (usually my line being damaged by tree branches rubbing). I'm on an all-copper, 20th Century ADSL exchange (Swaby, 01507 48*****)

2 weeks ago my original problem that Plusnet was dealing with was persistent disconnections that made the line unusable. I changed modems (from a good Netgear to a 'cooking' Plusnet-supplied Thomson), ADSL filters and performed no end of resets. Nothing worked and though the Thomson seemed to be less susceptible to the problem it somehow all sorted itself out after a week or so. Plusnet and I don't know how or why,

Perhaps it was the week's dry weather as the phone line noise which I often get in wet conditions was clear, though as soon as any noise did appear the BB disconnections returned. Having said that, the BB has usually been ok in the past, even when the phone goes down completely.

Anyway, now that I have a "good" line, I complained about the fact that a friend gets 2x my speed. He gets 3.5mbps - which is good around here in rural Linc's - and a couple of miles away from the exchange - as am I, though in a different village. I have a direct line to the exchange (and not on a cabinet as he is) and get an average of 1.9mbps.

BUT, after discussion, Plusnet did an SNR reset a few days ago (from 15db to 6 and immediately I got nearly twice my best speed over the years - 3.6mbps. This has gradually dropped back, over a couple of days, to 1.9 - apparently as a result of an automatic de-rating process. Annoying as when I had the higher speed all was well at my end. Plusnet has just done another reset with the same boost in speed but they expect the speed to drop back to 1.9 again.

Assuming that the line is capable, as it seems to be, can anything be done to prevent this aggressive speed de-rating to an apparently excessively conservative figure? Presumably it'll have to be done by BT at the exchange but obviously I have no contract with them and so no line of enquiry. Plusnet say they have no control over it either.

Thanks for any advice

Edited by ajdroberts (Mon 05-Oct-15 18:02:13)

Standard User RobertoS
(elder) Mon 05-Oct-15 16:21:17
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
In reply to a post by ajdroberts:
Assuming that the line is capable, as it seems to be, can anything be done to prevent this aggressive speed de-rating to an apparently excessively conservative figure? Presumably it'll have to be done by BT at the exchange but obviously I have no contract with them and so no line of enquiry. Plusnet say they have no control over it either.
It will be because the BT Wholesale DLM, which monitors the line 24/7, is detecting high error rates, which would after a while cause you to lose connection and connect possibly at a very low speed. You are unlikely to notice the errors as they happen, but they will gradually knock out the relevant frequencies the noise occurs on, using spare capacity on other frequencies. (Bit-swapping).

To prevent this it sets a higher Noise Margin, which causes a controlled reduction is speed. Lowering the speed reduces the error rates. After a few stabs it arrives at a balance between speed and stability.

Plusnet need to be getting your intermittent (weather-related?) fault sorted out. Not just resetting the DLM. That's like pumping up a flat tyre without mending the puncture.

The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site - www.robertos.me.uk. Domains, site and mail hosting - Tsohost.
Connection - AAISP Home::1 80/20. Sync 59999/14372kbps @ 600m. - BQM
Standard User gt94sss2
(experienced) Mon 05-Oct-15 16:59:16
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
Next time you get a noisy line, report it as a voice/line fault to whoever you pay your line rental too - don't mention adsl or broadband speeds at all.

If they are able to fix your voice line, your broadband speeds/SNR will improve in due course


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Standard User 961a
(member) Mon 05-Oct-15 17:21:04
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
Download and install RouterStats or RouterStats Lite (depending on the router you are using)

http://www.vwlowen.co.uk/internet/files.htm

Leave router & computer on 24/7 for a couple of days

Record and report no of disconnections

How far are you from the exchange (line length, not as the crow flies)?

Your symptoms are indicative of line fault damage. Wind, rain, trees. As you say, dry calm weather, problem disappears

Assemble diary to present to ISP/Openreach using routerstats

Some routers will hold connection much better than others
Standard User ajdroberts
(newbie) Mon 05-Oct-15 20:09:42
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: 961a] [link to this post]
 
Thanks each of you for all the very quick advice.

I have installed RouterStats ok and will be passing on the numbers to PlusNet

The 2.6 miles I mentioned is the line length, not as the crow flies. Plusnet, to their credit, are keeping a good log of all my disconnections which at the moment are as normal (ie nearly none except when the phone line is noisy).

Edited by ajdroberts (Tue 06-Oct-15 02:10:27)

Standard User RobertoS
(elder) Mon 05-Oct-15 23:28:00
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
It's your login to the router GUI.

The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site - www.robertos.me.uk. Domains, site and mail hosting - Tsohost.
Connection - AAISP Home::1 80/20. Sync 59999/14372kbps @ 600m. - BQM
Standard User ajdroberts
(newbie) Tue 06-Oct-15 02:09:52
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
It's your login to the router GUI.

Thanks - got that and edited my earlier post to say I was now using the full, not Lite, version as unexpectedly there was a Setup for my router there.

What figures might I best give to my ISP to indicate that my line can stand a lower than 15db SNR. I seem to get on fine with 6db which gives me 3.5mbps when the SNR has just been reset by PlusNet.
Standard User BatBoy
(sensei) Tue 06-Oct-15 02:20:42
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
The reset indicates you line can support a lower SNRM, but the reason it keeps on rising is because of a line fault.

You need to get the line fault fixed so your line is stable with a 6dB SNRM.
Standard User 961a
(member) Tue 06-Oct-15 09:22:40
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Re: SNR Resets and really slow speeds (1.9mbps!)


[re: ajdroberts] [link to this post]
 
In reply to a post by ajdroberts:
..... all my disconnections which at the moment are as normal (ie nearly none except when the phone line is noisy).


Indicative of line fault caused by cable rubbing against trees damaging/removing insulation also allowing damp in cables when it rains. Or faulty/damp junction box

An experienced broadband engineer should be able to identify how far along the line from your master socket the fault is and if there are further faults back towards the exchange

Plusnet should be able to arrange this for you. Press them for this to happen

Correction of the fault(s) should enable an SNR of 6 with a stable line which should enable a significant improvement in speed
Standard User ajdroberts
(newbie) Fri 09-Oct-15 13:05:29
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Re: SNR Resets and really slow speeds (1.9mbps!) SOLVED


[re: 961a] [link to this post]
 
Thanks everyone for your advice.

Despite repeated assurances from PlusNet that the line was testing ok, they conceded after 14 days of testing that an engineer visit was the last thing they could try - I was resisting until all other tests had been exhausted as I faced a charge of £50 if it were a problem at my end.

Anyway, the BTO chap found a fault in an underground stretch of cable about a mile away, changed to a new pair, and all is now fine.

Apparently the standard ISP line test isn't sensitive enough to detect many problems and it is the BTO engineers equipment that can find the less intrusive faults that I had.
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