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[jeffbb]

Hi

quote :Whilst asking - is noise margin better to be higher or lower?

as SLM says Noise margin is trade off with connection speed . The default aimed at is 6db when you connect .see link for a fuller explanation regarding  SNR,SNR margin, target SNR .
http://www.kitz.co.uk/adsl/linestats.htm

Regards Jeff

[jeffbb]

Hi
a bit more On SNR Margin on routerstats graph.

Its Good if Margin goes up with No loss of synch speed (no disconnection) ,this indicates that there is less noise is on the line .

Its Normal to have gradual decrease in SNR margin during evening and busy periods . As long as its not so low as to cause serious errors or disconnections

Its good if It goes down after a reconnection at a higher connection speed . That can happen when the target SNRM has been reduced by the DSLAM after a long period of good line stability.

The important thing is  to look at both The SNR margin and Synch speed together .
Regards Jeff

[kapt69]

Jeff
Thanks
Have re-read the link - seems like I need a higher margin because of my long line.
Also shows (I think) why SNR margin is higher now speed has reduced a little.
I just hope this speed stays though because looking at the table for BT's Fixed Rate limitations it says attn needs to be 43 - 60db to attain speed of 1Mbps and mine is 63db. (speed 1216kbs)
Also SLM: thank you for the explanation & your insight as to what goes on at the exchange. I don't believe for a minute that you were joking. You obviously have inside knowledge! What you failed to address was why they always use my connection for the vacuums - not that I'm paranoid of course. - Q does anyone know if BT has 'privatised' its cleaning & if it happens in the evening? (I know - should be posted in another forum -sorry)
Regards
K

[kitz]

>> BT's Fixed Rate limitations it says attn needs to be 43 - 60db to attain speed of 1Mbps and mine is 63db.

Yes... and if your router is showing 63dB, then theres a possibility that it could actually be more than that as most routers will only record up to 63db.
There is a strong possibility that your line would not be able to sustain 1Mb fixed rate services.  It may sync at 1Mb during the day, but it would likely have problems in the evening when its normal for SNR to dive.  With fixed rate theres no messing with target SNR and adapting speeds, so you then get into the situation where the line just wont sync at all in the evenings, hence why BT would only put lines like yours on 512kb. - Thats what the 500 limit showing on your line is all about and why it will stay marked as 500.

Rate Adaptive dsl (max dsl) -  which is the product that youre on -   works slightly differently and your line will always sync at the highest rate it can whilst still giving you a slight margin for error (thats what the target SNRM is all about).   Maxdsl works worse on some long lines which fluctuate a lot, but yours is one of those that it appears to work so much better on, as its giving you the higher speeds that you just wouldnt get on fixed rate.

>> seems like I need a higher margin because of my long line.

If the DLM thinks you need it then it should automatically adjust.. this will cost you some decrease in speed.
If you sync at less than 1152 kbps at any time then it will take your IP profile down with it. 

You have a decent router that should hang on at the lower SNRMs, but unfortunately no router can do anything about if the SRNM gets too low that you start racking up errors (retransmits)...  which will appear as slow speeds. 

Each line is different but you should be okish down to about 3dB, as hopefully bit swapping will be able to cope down to that level. 
I cant recall if routerstats lite version lets you record CRCs on your router? - If so it may be an idea to log those.
Its when you see lots of CRCs racking up that your connection will 'feel slow'.

[kitz]

>> What you failed to address was why they always use my connection for the vacuums.

   
I know what you mean..   but seriously its normal for all lines to see drops in SNR(M) in the evenings.
More people are at home, and its dark, therefore a much higher chance that people are going to be switching on electrical items which will cause EMI  or REIN

More people tend to use broadband in the evenings, which in itself causes something called crosstalk.  The more lines that are carrying data to and from the DSLAM then the more chance of your own line picking up some of this crosstalk.  All lines will pick up a certain amount of crosstalk..  I live very near the exchange but I too suffer from its effects and unfortunately theres not much that can be done about it :/

EMI and crosstalk is a major bane to adsl and it comes from everywhere. 
Christmas is normally one of the worst periods when everyone starts putting up their xmas tree lights.

Unfortunately due to the law of physics, its going to be those lines that are more attenuated, to suffer and see the effects the most.
Your signal strength isnt as strong, therefore any noise is going to have more of an impact.

[kapt69]

Thanks again Kitz.
Just as an aside - I had my PC back from 'the shop' yesterday. started it this morning and whilst looking at routerstats on the laptop I've been 'borrowing' saw that the SNR margin was fluctuating much more than I have become used to since being introduced to the software.
Having now taken the PC back to a (different) shop - please don't ask! - the graph seems much more stable. Can a wired PC have a (possibly detrimental) effect on the line? It might just be a coincidence of course.
By the way IP profile still 1000 - BUT conn. speed down to 1152 and saw comment :

If you sync at less than 1152 kbps at any time then it will take your IP profile down with it. 

Does that mean the sword of Damocles is about to drop???!!!

[orainsear]

It is possible that the PSU was sending noise back into the mains wiring, or it could have been emitting electromagnetic radiation, which was interfering with your router.

With a relatively long line it may also be worthwhile having a look at the BT Business Hub (2Wire HGV2700), which can be obtained from well known auction sites.

[kapt69]

Here we go again.
IP profile now 750
Download speed 698kbs.
After 8 lovely days of around 980kbs 
I have both routerstats and the lite version running - have tried to keep laptop on most of day to keep tabs on what is happening.
Think Lite version takes snapshots every hour in Corel Photo Album 6  format() - hope this may help. I did notice yesterday downward 'spikes' to zero 4 or 5 times in SNR margin graph.
May rectify itself - but just in case thought I'd post the situation before it heads further down.
Any ideas?

[sevenlayermuddle]

We can tell from the reported attenuation (63dB) that you are on a very long line.  As Kitz has already mentioned,  lot of routers stop counting at 63 so things may be even worse than they appear.  So it's safe to assume you have a very weak signal, which will struggle to provide you with any decent speed.

All you can do is try to make the most of things.  You could try a different router, as suggested by Orainsear, but your existing Netgear DG834GT has a fairly good reputation for long lines.  I wouldn't rule out a different router as the one that's best for your line may not be the same as is best for another line, though I think I'd be inclined to look for other ways to improve things first.

Check out Kitz's guidelines at:
 http://www.kitz.co.uk/adsl/socket.htm . 
In particular, if you have any extension wiring in your house, then you could see a huge improvement just by disconnecting the ring wire as described in above link.

One caution... if you start experimenting with wiring changes, then make sure you power off your router off before disconnecting any cables.  And don't power it off/on more than two or three times in an hour.  Failure to observe these cautions could cause the BT equipment to think your line is 'unstable, whereupon it will reduce your speed even further (by raising that target SNR margin).  You really do not want that to happen as it can be a devil of a job to get it put right.

[orainsear]

>> And don't power it off/on more than two or three times in an hour.  Failure to observe these cautions could cause the BT equipment to think your line is 'unstable

Without wishing to derail this thread, surely some control logic can be added to get around this power off situation and how it can upset the profile.

Perhaps an end user controlled PPP disconnect could alert the DSLAM into a state whereby if the modem is powered down within say 30 seconds then the profile is untouched.

[sevenlayermuddle]

Perhaps an end user controlled PPP disconnect could alert the DSLAM into a state whereby if the modem is powered down within say 30 seconds then the profile is untouched.

In theory, the router is meant to send a 'dying gasp' message upon power-off, I believe the theory is that the PSU electronics will have enough residual energy to keep the line active for the extra few milliseconds it takes.  Again, in theory, that could tell the DSLAM that it's just a power-off, not instability,  and nothing to worry about.   

In practice there is some scepticism about whether domestic routers actually send dying gasps, perhaps even more scepticism about whether the DSLAM and DLM take any notice. 

I'd seriously be interested in contributing to a thread about suggested 'improvements' to DLM, just on the off-chance any good ideas got back to the design team.   It's a fair bet that the designers are actually interested in DSL, and so there's a good chance they might  read these forums, even if they never dare identify themselves. 

[kitz]

AFAIK  all routers are supposed to send the dying gasp message.  Its how the DSLAM interprets this.  There is supposed to be an actual recorded error message state specifically for this situation (Loss of Power).
I suppose the problem occurs as to which situations an LoP gets recorded.   
Even that isnt going to over-ride any IPprofile changes though, and I wonder if that count has anything to do with upsetting things too. 

I know on my own line that IPprofile problems that Ive had in the past have mostly all been related after powercut type events. Once when a visiting electrician simply just turned off power before working on my lighting by simply switching off everything at the fuse box rather than just pulling the circuits needed had an effect on me for some weird reason.  But then again Im on the type of line that had more than its fair share of problems with stuck profiles.:/

[sevenlayermuddle]

My comments & cautions to Kapt69 were really more about DLM and it's pesky target margin, rather than the IP profile.

I can't resist mentioning, however, my IP profile does suffer whenever I have a power cut, simply because the router always gets a lousy sync speed if it powers itself up at the same time as everything else when the power comes back on.   If I'm at home during a power cut, then I switch the router off at it's mains socket, which allows me to power it up manually some time later after everything else has settled down.  That way it connects at it's usual speed and avoids the profile drop.

[kitz]

>> My comments & cautions to Kapt69 were really more about DLM and it's pesky target margin, rather than the IP profile.

Sorry if I didnt make myself too clear..  I think I was just musing and wondering if BTs DLM takes into account any IPprofile changes when deciding how stable a line was.

[kapt69]

Just to clarify : these 'breaks/downward spikes' - whatever they are called in the Noise graph - are these a breakdown in the telephone line connection? They seem to happen without any noticeable effect whilst I am on-line. (or at least I don't notice anything until I check the graph).