DSL Speed reduction :(

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17 Oct 2002
Posts
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Hi guys,

Oh the trials an tribulations of my broadband connection :D

This evening my internet began playing up and wouldnt sync for more than 30-40 seconds. This carried on for about 5-10 minutes before it eventually synced and was happy and has been for a few hours now.

However where I used to sync and be quite stable at 2000kbit its now... 1100kbit.

Whats happened all of a sudden? :(
 
WRT actually what has caused the line instability, it could be any manner of things - work on the lines, damage somewhere, etc etc

Bit of background though as to why the sync level has fallen (apologies if you already are fully aware of how variable DSL syncs work);

The line trains using a variable SNR margin (signal to noise ratio), so if there is a problem with sync, the target SNR (tolerance between signal and the ambient noise level) for the line will raise at the exchange, step by step, thereby causing the sync to lower each time until it is stable.

Unfortunately this then sticks to its higher SNR target resulting in a permanent lower sync even after any issues on the line have passed. With my very squiffy line at Hill Green i had to get my SNR target reset by my ISP on more than one occasion due to problems such as this.

A quick bit of info you could grab is the SNR (downstream) stat off your router...if that is very high then the above has happened. You could try a reset with the ISP and see where it ends up training to.
 
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Sounds like a line issue, possibly crosstalk, or perhaps even something connected to one of your sockets causing signalling problems.

This will most likely cause your ISP to lower your line profile until it syncs, meaning that when it eventually does re-sync, it will be at a lower "stable" speed.

You can get your ISP to reset your profile, but if it's dropping sync regularly I'd want that sorted before having it reset, otherwise you'll be going round in circles.
 
I had an issue yesterday where my line wouldnt hold any kind of sync, turned out to be the power supply on my daughters pc.
 
I had an issue yesterday where my line wouldnt hold any kind of sync, turned out to be the power supply on my daughters pc.

Funny you should say that... we used to get fairly frequent drops when my brother had his PC the otherside of the wall from the router/main socket - I hadn't correlated it but its been a lot more stable since he moved out.
 
Well, its all stable again now and works fine.

Only at half the speed I was synced at before :confused:

I've changed no settings, connected nothing extra to the phone line, infact the router is plugged directly into the master socket and all extension wiring is disconnected anyway as it has been for ages.
 
As we are saying mate, the DSLAM has probably adjusted your SNR. What is it showing? (downstream).
 
It is showing:

Connection Speed 1376 kbps 448 kbps
Line Attenuation 63.5 db 31.5 db
Noise Margin 15.6 db 9.0 db

This is what I used to have:

ADSL Link Downstream Upstream
Connection Speed 2016 kbps 448 kbps
Line Attenuation 63.5 db 31.5 db
Noise Margin 8.3 db 9.0 db

The noise margin appears to have doubled.

It was perfectly stable at 2mbit before?
 
There we go, it has raised automatically to the DSLAM maximum target of 15db. The line would likely be stable at half that which would typically result in a sync of around 2200k IME. It needs to be reset :)
 
Get the line reset to 6dB target, then if you notice an instability just turn the router off for a bit so the DLM does not start "tweaking"
 
Well nothing has changed so far but today the ridiculous stability is back. Literally it is taking me ages to post this as the connection wont stay up more than 15 seconds.

Line stats at present:

ADSL Link Downstream Upstream
Connection Speed 1312 kbps 448 kbps
Line Attenuation 63.5 db 31.5 db
Noise Margin 16.6 db 7.0 db

:(
 
Getting the SNR target reduced won't help if hes getting instability with a much higher margin.

Unfortunatly trying to track down whats causing the instability can be a nightmare - it could be someone using shortwave radio in the area, a light switching, faulty transformer somewhere along the line, etc. etc.

If you have any long extensions try fitting a microfilter to the end of them before the phone - even if they are filtered at the faceplate/main socket end - I know it shouldn't make any difference but for me it (reproducibly) stopped my line picking up interference from my neighbours CB radio.
 
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[TW]Fox;15901484 said:
Well nothing has changed so far but today the ridiculous stability is back. Literally it is taking me ages to post this as the connection wont stay up more than 15 seconds.

Line stats at present:



:(

TBH mate after what we discussed if it is still training to that ridiculous SNR, and you are finding it really unstable at lower SNR's than that (by forcing them using your router to experiment) then it sounds as if there is an actual fault somewhere. I thought it would pass, but it doesnt look like it is. As Rroff says, it can be anything causing this instability on the line, so it really does need investigating if it carries on.

If/when you report the fault do not say that it works, but is slower, as they only have obligation to provide a connection, with no speed guarantee. Say that it isnt stable under any circumstances :)
 
spoken to your ISP yet? they can run a line test to check for faults.

have you tried another filter? cable to the router? eliminated any electrical noise from nearby appliances?
 
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