Line Errors

[tomharrison]

Evening all you lovely people

I posted a couple of weeks ago about poor speeds during peak time which initially looked like contention. Since then I've been on the phone and emailing IDNet pretty much every other day with problems with my connection. I was (and am now - will explain later in this post) on a 15dB downstream SNR after a thunderstorm many months ago knocked out the router and caused lots of resyncs in not much time at all. Since then the line appeared to have been stable but my target SNR was refusing to lower to anything other than 15dB. IDNet got BT to reset the target SNR to the default 6dB (very quickly I must add) and my downstream sync shot up from 4400kbps to 6880kbps - pretty damn good considering a 47dB attenuation!

This was done on Monday. Since then I had a loss of sync Monday night but resynced at around 6600kbps downstream without any real issues, however I lost sync again yesterday evening and I've now been put back on the 15dB target SNR with a sync back down around 4.5 meg.

Been on the phone to IDNet tonight and they noticed a large number of errors on the upstream side of the ADSL connection. This struck me as odd since my router (Netgear DG834G v4) is connected through a filtered faceplate at the master socket - therefore eliminating any external noise from my extension wiring. If anything I'd expect there to be more errors on the downstream side .

What was even more odd was that IDNet were seeing a downstream SNR of 15dB, but upstream was only 11dB, yet my router is reporting an upstream SNR of 23dB. This figure has also been reported by two other routers (DG834G v2 and a Belkin), so I'm pretty confident that it's not the router. Either the DSLAM is giving erroneous readings or something sinister is going on somewhere  !

Both IDNet and myself are completely confused as to what's causing these errors, so I've got the router plugged into the test socket now with a microfilter. I'm getting the same sync and line stats as before, so I'm pretty confident that the upstream errors are going to remain. IDNet said they would get BT to look into it next week for me if it persists .

Anybody got any ideas as to what is causing large errors on the upstream side only, aside from extension wiring which I think has been ruled out?

Sorry for the long post BTW !

[Rik]

Don't worry about the length, Tom, it saves us firing a ream of questions at you. Can you post your router's stats please? (OK, I had to ask one ).

Errors on the u/s side are almost always caused by local noise. If they persist when you're using the test socket, that would suggest your line is picking up noise, possibly as simple as cross-talk in the cable, possibly something more heavyweight, such as industrial plant or even a rogue Sky box in the vicinity. The resetting of your target NM to 15db is probably bad news as BT tend not to be willing to try a manual re-targeting a second time, arguing that the line clearly cannot sustain a 6db target.

All you can do is work with support and get BT involved to look at the line once you've established, by using the test socket, that it's not your internal wiring.

[tomharrison]

Thanks for the swift reply, Rik .

Can you post your router's stats please?

Of course

ADSL Link     Downstream     Upstream
Connection Speed    4480 kbps    448 kbps
Line Attenuation    47.0 db    29.5 db
Noise Margin    15.1 db    23.0 db

As you can see, all looking pretty stable right now, except for that 15dB margin!

Errors on the u/s side are almost always caused by local noise. If they persist when you're using the test socket, that would suggest your line is picking up noise, possibly as simple as cross-talk in the cable, possibly something more heavyweight, such as industrial plant or even a rogue Sky box in the vicinity. The resetting of your target NM to 15db is probably bad news as BT tend not to be willing to try a manual re-targeting a second time, arguing that the line clearly cannot sustain a 6db target.

I had a funny feeling BT would be reluctant to try another manual re-target .  The only local source of interference I could think of immediately is we have two DECT phones in the house, however we've had these for years and they've never caused any issues before. (I also believe that DECT operates in the higher frequency bands anyway - somewhere around 1800-1900MHz if I remember correctly).

[Rik]

You're right, Tom, aside from the NM, the figures look OK. Obviously, the NM is hitting the sync speed, but that's the only obvious issue there. I half wonder whether a 2700 router might help your line (go on, tell me that's what you're using ).

DECT phones should be clear of the ADSL range but they can put out harmonics. My instinct, though, is that this is external noise. It might just be worth re-booting the router with the DECTs powered down and unplugged, though, to see if it has an effect (look for an increased sync speed - I'd try that in the morning rather than now, though).

[tomharrison]

I half wonder whether a 2700 router might help your line (go on, tell me that's what you're using ).

Haha, not quite... I'm on a Netgear DG834G v4. Upgraded from a v2 last month as I'm sure it was just a matter of time before it gave up !

DECT phones should be clear of the ADSL range but they can put out harmonics. My instinct, though, is that this is external noise. It might just be worth re-booting the router with the DECTs powered down and unplugged, though, to see if it has an effect (look for an increased sync speed - I'd try that in the morning rather than now, though).

Yeah, it's worth giving it a go I guess. Like you say though, I'd be very surprised if it is the DECTs causing the problem.

For what it's worth, I've seen a couple of BT vans lurking around my area this week - one made a vist to somebody just down the road to me too. Makes me wonder if there have been a few problems locally?

[Rik]

It's entirely possible, Tom. We had some Openreach vans working up the road a few months ago, following which I gained 500k of sync speed, so sometimes they do some good.

Whereabouts are you, geographically? I have a spare 2700 you could borrow to see if it helps.

[tomharrison]

Whereabouts are you, geographically? I have a spare 2700 you could borrow to see if it helps.

Thanks for the offer, Rik - very kind . I'm in Derbyshire, just north of Derby. Don't know if that's anywhere near you at all?

[Rik]

I'm in Milton Keynes. I can post it to you, so you'd have it Tuesday or Wednesday, hopefully. No rush to return it as I'm away from next Friday until July 6. If you're interested, PM me your address and I'll do the rest. It will be set up for IDNet, all you'll need to do is put your username and password in. Make sure you remove these before returning it.

[tomharrison]

Thanks for that, Rik . I need to leave the Netgear connected and untouched this weekend for IDNet to be able to satisfy BT that the issues aren't with my wiring, so I wouldn't want you to go to the trouble of sending it if it turns out it's completely unnecessary!

I'll let you know how things go over this weekend and into early next week anyhow and go from there.

Thanks again

[Sebby]

Unfortunately, the DSLAM is often very sensitive to errors - I also had problems in the past where I was on a 6dB target margin for a few years, and then all of a sudden, the exchange wouldn't allow it. IDNet got it reset, but it kept increasing on its own, despite no loss of sync. Eventually I managed to get a manual 9dB margin set.

It would be nice to find the cause, but I have to be honest, it's probably happening somewhere outside of your property from what you've said, and BT are not always overly interested. Still, hopefully IDNet will be able to work their magic.

[Simon]

Just to chip in with something probably completely worthless, I wonder if some external damage was done by the thunderstorm, as you seem to have had these problems since then?

[Rik]

Entirely possible, Simon, a storm can generate an electric chair effect for electronics attached to a phone line.

[tomharrison]

Yeah, I guess there is a good chance that the storm may have caused some damage Simon . We'll see what BT can say about it!

Been connected to the test socket now for 21 hours and I'm seeing just under 2000 CRC errors - not sure if this is downstream or upstream though. Anybody know if these errors are a normal amount for this length of time?

Line stats remain virtually the same, but downstream SNR slightly lower than usual for this time of day:

ADSL Link     Downstream     Upstream
Connection Speed    4448 kbps    448 kbps
Line Attenuation    47.0 db    29.5 db
Noise Margin    13.9 db    23.0 db

[Rik]

I see about 15000 errors a day on my interleaved line. Before BT (a) turned interleaving on and (b) raised the target margin to 9db, the figure was 1000000. I'd say you have a significant amount of noise triggering the errors given your target margin, but it could probably be reduced to 9db.

[tomharrison]

Thanks, Rick

[tomharrison]

Bit of an update for anybody who's interested..

IDNet re-tested my line and still see the errors on there when connected via the test socket. This is what I expected since the router is connected via a filtered faceplate normally. In fact, my SNR was more unstable through the test socket than the faceplate - must have been the filter!

Basically, it looks like it's probably just a line quality issue. They did suggest going around the house with a MW radio de-tuned and receiving static only to locate any interference. Going to try outside later where the line enters the property. You may have been onto something with the DECTs, Rik - the base unit was generating some slight interference so it's since been moved away from the router.

One thing I forgot to mention is my router (and one of two wireless repeaters) are connected through a UPS. I've disconnected that for the time being, to see if that improves matters:). I could well have picked the wrong day to rely on main electricity though as my local forecast is a moderate chance of heavy rain, hail and thunderstorms from 11am onwards !

I'll report back once I've done my detective work 8).

Thanks for all your input, folks

[Rik]

Good hunting, Tom.

[tomharrison]

Well I've been round with the radio - only interference I could find was the DECT phones. Followed all the extension wiring outside and the area from the NTE5 to the underground junction box with no luck . SNR is holding very well at the moment though - routerstats is showing an almost linear graph for the downstream SNR . We'll see how many errors are produced throughout the day...

[Rik]

  Tom. Moving the DECT unit may be enough.

[Sebby]

[tomharrison]

Another update for you (hopefully the last one)!

I disconnected the UPS attached to the router and repeater and moved the DECT base unit and handset away from the router and left the connection overnight. Despite a loss of sync during the thunderstorm things have been more stable. IDNet did another line test and reported that the line errors were now in the 10s and not the 100s . Also more comforting was that the Upstream SNR was 22-23dB, as opposed to 10dB (consider the upstream sync is only 448kbps too) .

Brian got back onto BT for me and they have very kindly reset my target SNR to 6dB again, and I've just resynced at 7136kbps, up from ~4500kbps. I hope this time that with the interference removed, the target SNR will stay put, or at least only increase to 9 or 12dB if needs be .

It's a shame I had to disconnect the UPS from the router, but it does look like the culprit unfortunately. At least my systems are still protected by a separate UPS upstairs!

Once again, thanks to all for your help and advice, and kudos to IDNet for being so helpful . Phone answered after 2 rings every time, always called me back promptly and they always went out their way for me, considering the fault was nothing to do with them.

This is why I insist on paying the premium for such a quality service .

[Rik]

Thanks for the update, Tom. Some routers don't seem to get on well with UPS, I can only think that the waveform doesn't suit the power supply. I do get away with using an APC UPS, but it's about 1.5m away from the router on the far side from the phone connection.

[tomharrison]

I think you're probably right, Rik. In hindsight it was probably a bad idea to place the UPS next to the master socket and have the router sitting on top of it .

I've got a feeling that the UPS didn't have AVR on it either, so the output voltage wouldn't have been smoothed out in any way (it was only a budget one from Maplins). My Belkin 1200VA upstairs has the full works though - even has a woman in a soothing voice telling me the power's failed and shutdown begins in 5 minutes

[Rik]

Mine is a power conditioning model, Tom, I feel they are worth the bit extra for the degree of protection they give. Given the circuity inside them, though, it's as well to keep them clear of the router and phone line.

[tomharrison]

Given the circuity inside them, though, it's as well to keep them clear of the router and phone line.

Quite agree, speaking from experience