Out of ideas....

[Rik]

I'll join you, Jimbo. 

[Jimbo]

I'll join you, Jimbo. 

Haha cheers!  I'm not letting them go tomorrow until something is done.    I'm going to explain everything to them.  I just pray the person that comes is understanding... 

[Rik]

In my experience, if you're friendly towards BT engineers, they're helpful people.

[Glenn]

1st thing I do is to ask if they want a drink, then tell them the symptoms I get on the line.

[Jimbo]

Thanks guys.  Yeah definately.  Cups of tea and coffee all round. 

I'll post back tomorrow with what they say.

[Rik]

 

I do just the same as Glenn - it makes a world of difference I find.

[Sebby]

Best of luck.

[Jimbo]

Sigh!

Bloke came out first thing this morning.... but was only here to inspect the pole.  I said, look, it's the cable with the issue.  When I told the lady on the phone I said the pole was back in the ground and had been for a good few months.

So this chap couldn't do anything to help and said I had to re-raise the call with BT. 

BUT.  IDNet have promptly replied to my email (thanks!) and said that they will re-raise a query to bt for intermittent sync.  And will update me when I hear back.

So should I wait... or go ahead and log the fault with BT again???

[Rik]

See what IDNet can do first, Jimbo.

[Jimbo]

See what IDNet can do first, Jimbo.

Roger that.  I replied to the email from IDNet saying hopefully they'll have more joy with BT than me.  Just seem to be going in circles at the moment. 

[Rik]

It's always a problem when dealing with BT, as the separation of the business has made it less easy for the customer to get anything done.

[Jimbo]

Yeah it's just frustrating though mate.  Hey ho!  I won't give in. haha. Oh and router information for today incase anyone gives a damn. lol

Internet has dropped 4 times today.

Currently @1760kbps (that's better! but won't last I know...)

Current Noise Margin:   15.0 dB (Downstream) 19.0 dB (Upstream)
Current Attenuation:   60.6 dB (Downstream) 31.5 dB (Upstream)

So, if I understand correctly as I'm trying to get my head around this lingo. But as the speed increases your noise margin decreases.  Is that correct?  If some kind fellow could explain in lamens terms (SNR, SNR Margin, Attenuation.... and what values are good, that would be ideal!)

Thanks.

[Rik]

Signal to noise ratio defines how 'loud' the signal is against the background noise on the line. It's expressed in db, like most values.

In practice, though, we have no idea what the SNR is, instead we use noise margin, however that may be labelled. The margin is the degree of headroom the signal has over the noise, it's a quantity rather than a ratio. Think of it as filling a vessel three-quarters full. The liquid to space ratio would be 3:1, but the space would be 25% (unfortunate that I use an analogy with two different units, but you get my drift. )

That headroom is the absolute minimum amount of signal that the router needs to work. In practice, it's a bit more flexible, and most routers will work if the noise margin creeps down. There comes a point, however, at which it can't tell signal from noise and so resets the connection.

In general terms, the lower the attenuation, the faster the speed your line is capable of. Initially, a new Max connection will be given a target NM of 6db, and the DSLAM will sync with the router as fast as it can for that noise margin. As a line trains and in general use, the DSLAM may adjust the target noise margin if it detects instability in the connection, and that's what's happened to you - it's been raised to the maximum value of 15db (it goes in 3db steps). Each 3db costs you 5-700k of connection speed.

In an ideal world, you'd want attenuation as low as possible, practically that means in the teens, with a full speed (8128) sync, and a noise margin as high as possible. If you had a sync of 8128 with a NM of 15db, it would mean your line was working with extra headroom and could easily run flat out.

Just to complicate the issue, BT also uses interleaving and error correction on poor lines, and this will improve stability, but it increases your ping times, or latency.

[Jimbo]

Awesome Rik.  That's much clearer.  8)

Just to say, I totally don't have any issue or blame IDNet for any of this poor speed.  IDNet are great, and offer great service and support!!   

[Rik]

The vast majority of problems we see are purely down to the creaking BT infrastructure. When IDNet do get it wrong, they'll hold their hands up and say so. It's why we like them so much.

[drummer]

Thanks for that SNR description Rik as I've now finally got it, despite you trying to educate me on this in the past.

*Sound of penny dropping*

Mucho Karmico.

[Sebby]

SNRM and all that surrounds it is a weird concept, and certain one that I found difficult to grasp, but it makes sense in the end.

It's things like target SNRM that make matters confusing; one person is telling you that a high SNRM is good, and then the next says that the target is 6dB. Both are true, but there's more to take into consideration.

(That's just an example, by the way!)

[Rik]

Thanks for that SNR description Rik as I've now finally got it, despite you trying to educate me on this in the past.

*Sound of penny dropping*

Mucho Karmico.

Thanks, Drummer. 

[Jimbo]

Just to update.  IDNet, fantastic as always are getting an Engineer out.   I may, or, may not be charged but they think it could be an old overhead line with alumnium in it.  So just waiting on a time and day now.

Woo hoo!

[Rik]

Overhead and aluminium. Not a nice combination, Jimbo. ;(

[Jimbo]

Overhead and aluminium. Not a nice combination, Jimbo. ;(

Do you know much about why alumnium does not work?  I just know that most cables are copper... guess it's all do to with conductivity and stff.

[Sebby]

Overhead and aluminium. Not a nice combination, Jimbo. ;(

Unless it's a plane.

[Rik]

 

[Sebby]

[Simon_idnet]

I've got another analogy to illustrate noise margin for you:

Suppose we are having a conversation in a field and you're standing 40 yards
away. I'm shouting so you can hear me. But because you're so far away I'm
shouting quite slowly so you can pick-up my words. Now, suppose there's a
main road next to the field. When traffic comes by I might have to slow down
even more and maybe repeat some words that got lost. Then a convoy of
lorries goes by. I have to give up for a bit and then start the last
sentence again from the beginning.

The noise margin works like this:

The Exchange transmits at a certain volume (I've yet to be able to find out
exactly what the level of the signal strength is that the Exchange actually
does transmit at, but that's academic), let's call it 100dB. Some of the
signal is lost in the telephone wire - the longer the wire, the greater the
loss, known as attenuation, measured in dB. Suppose you're on a line that
has a signal loss of 40dB. That leaves you with 60dB of signal strength to
use for data which therefore dictates the speed (bandwidth) that your line
can operate at.

However, all phone lines act as aerials and pick-up electrical
interference - noise. So, some of that bandwidth is reserved as a buffer to
soak up the background noise. This is because a slower, stable connection is
preferable to a fast, flaky connection. The starting point for the size of
the buffer is 6dB (this is the Target Noise Margin). We're now left with
54dB to use for data traffic, thus your speed is slightly lower than a
perfect, crystal-clear phone line could achieve.

As long as the background noise doesn't exceed 6dB you've got a perfectly
stable connection. But if there is a burst of noise that is greater than 6dB
then your router will be unable to maintain its lock on the signal from the
Exchange and it will lose its synchronisation - it will have to reconnect.
If the reconnect takes place while the high noise is still present then your
router will have to negotiate a slower speed (i.e. higher noise margin) with
the Exchange.

If the Exchange detects that your line is susceptible to these high noise
events and thus frequent reconnects then it will reset the target noise
margin for your line to be higher than 6dB. If it is set at, say, 15dB then
you're now down to 45dB of signal from Exchange that is reaching you and
therefore your speed is slightly slower again.

So, to be stable a noisy line needs a higher noise margin and will therefore
run slower.

Regards
Simon