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[sevenlayermuddle]

@Jeff,

I'm sceptical about that delay doubler.  According to the patent paper, it only ever gets incremented (up to a maximum of 5), it never ever gets decremented other than by manual intervention.  Whilst it would be possible to implement such a system, it would not be conducive to optimising the network.   It would mean that the first time your line suffers a high margin it might take 14 days to recover, then many years later the same thing happened, it could take 28 days, and so on.  Doesn't add up, to me.

The purpose of the delay doubler seems to be to prevent frequent oscillations between states, by adding an exponentially increased delay.  That's reasonable, if a line keeps yo-yo-ing between, say, 12 and 15dB then it's reasonable to slow down the transition.  But where a line is not oscillating, merely progressing through the states as a result of some line-fault being cleared, I find it hard to see that the doubler would serve any purpose.  For that reason, I'm inclined to think that the description in the patent paper may be incomplete.

Also, as I said when I posted the link to that patent, we don't know for sure whether it describes BT's currently deployed DLMs.

- 7LM

[Mick]

When errors decrease below a certain threshold your router will resync and you should get a better connection rate.  However, said threshold is not the same for all punters.  It depends on your stability setting (there's super stable, stable and standard).  If you ring your ISP and ask them to raise a ticket with BT so that they change your line stability setting from super stable to stable, you will discover that your snrm will drop (say from 12 to 9dB) and although the errors will increase your line will seem to not care about it.

If by reducing from super stable to stable you can hold a connection without continuous resync's then you're sorted.  No need to phaff with router settings to force it to work against the DLM.  The DLM will work for you as opposed to against you.  If you're brave and your connection can take it then wait for a month or so and ask them to drop it again, this time to standard setting.  However, if you're on a long/noisy line you will find that it will become very unstable.  So I suggest that only go one step at a time.

Good luck and let us know what happened with the lottery! 

[sevenlayermuddle]

@Mick,

All of that may be true, but my ISP is Demon.   Demon's call centre, since moving to India several years ago, have a vague idea how to talk you through the windows setup menus, or even configure individual routers, if you ask them nicely.  But when it comes to interpreting ADSL line stats, target margins and DLM queries, you may as well ask the cat.

But TBH, for me, this is largely just an exercise in working out how DLM operates, and maybe how to beat it.  

Stability options are described in that BT patent paper and scare me a little, as I really don't imagine many of the Indian call-centres (not just Demon) are going to have the slightest idea what to do with them.

- 7LM

[waltergmw]

@ 7LM,

We know of a much better cat here to consult !

I agree entirely re Asian call centres. I'm dealing with a disconnection for a monthwith 6 engineer site visits and 5 modems to fix an authentication problem which vanished by magic over the week end when the real people here were persuaded to pay attention. ( I did happen to say in high places "Crass stupidity" though !)

Kind regards,
Walter

[sevenlayermuddle]

Yes, I suspect it's a common problem with call foreign centres.  The worst I ever had was with a car insurance firm, but I'll resist telling you all about it.   Suffice it to say there could be a secure future for any polite and well-behaved cats, especially those with any knowledge at all of ADSL or car insurance.

Anyway, I've been running for a few days now with target increased from 12 to 18dB.  I'm not hugely optimistic as, even at 18dB, I'm getting typically 150 ES per day and twice that many CRCs.   That's only 6 ES an hour, which isn't much, but my hunch is that won't be good enough for another target reduction.  I'll let you know if it happens, but don't hold your breath.  

At least the Netgear seems to hang onto the connection.  It hasn't dropped once in the last 4 weeks, other than by my intervention or by DLM when the target dropped to 12.    In contrast the Thomson, which was in use when the target got raised, was crashing(i.e. rebooting) & reconnecting up to several times a day.  Admittedly, the Thomson didn't have my current massive SNR margin, so it would have been more vulnerable to noise storms that may have been making it crash, but I'm still working on the theory that the underlying problem, that caused DLM to raise my target, was probably a duff router more than anything else.

- 7LM

[Mick]

There is a solution to such problems:  move ISP!

There's no reason to hesitate for a minute voting with your feet, if the service you are getting is not to your satisfaction.  Businesses with call centres in India are targeting mass market customers who rarely if ever ring up support, only to be told to go away and reboot their MSWindows OS.

That said I managed to get very good level of support from a BT broadband support centre, but only after I insisted that they do not know how to resolve my problem and they should pass me over to the second line support.  I spoke to some guy in Ireland and got impeccable service and excellent technical knowledge out of him straight away!

These days switching over to an ISP with UK support, who do not throttle traffic, is quite easy.  If you continue paying money to companies who chose to outsource their relationship management with you to script reading Indians, then you will continue getting instructions to reboot your PC.  The worst thing is that such companies will continue doing just that!  Making money by reducing the value they offer to their customers.

Anyway, have you tried to elevate the request to an "engineer" and see if you can get any joy out of that?  Really, all you're asking is for demon to raise a call with BT on your line, to change your stability setting from super stable to stable.  You will still get resync's after the change, but it would take 2 to 3 times higher FECs to trigger a resync.  Meanwhile, your snrm will reduce and stay there without you needing to fight against the DLM logic.

[HPsauce]

That said I managed to get very good level of support from a BT broadband support centre, but only after I insisted that they do not know how to resolve my problem and they should pass me over to the second line support.  I spoke to some guy in Ireland and got impeccable service and excellent technical knowledge out of him straight away!

This is how my friend (whose travails I asked about here recently in another thread) finally got BT moving. Multiple complaints and eventually escalating to someone sensible, who also sounded Irish. Took him nearly a month though....

[sevenlayermuddle]

@Mick,

Thanks for the advice, but as I tried to say, this is really just an experiment.  I have no great need for a lower margin, or for a higher speed, I'm just trying to get some satisfaction from tricking DLM into doing so.  I wouldn't get the same satisfaction from asking an ISP to press a button.   

For the record, moving ISP is not always an easy option.   We run a very popular website which in its infancy had a ......demon.co.uk domain name.  Since about 2002 it's had a .com domain, but the old demon web page still exists and just redirects to the .com.  Last time I looked, there were still hundreds if not thousands of links to the old demon address, and if it were taken off the air (by closing my demon account) these links would break.

The same applies to email addresses.  Despite setting up mail redirects using the .com addresses, and notifying everybody years ago and repeatedly, we still get a surprising amount of mail addressed to .demon.co.uk.  Some of it is mail that I'd not want to lose, even though it may be people I've not heard from in years.
 
One final point..., the only way to get a query escalated to a knowledgeable engineer at demon seems to be to submit a formal complaint, in writing, to the parent company.  That did the trick last time around, when they were owned by 'Thus', but the whole process took about three weeks from initial email to satisfactory outcome, and life's just too short to face up to that hassle every time you need something done. 

Thanks anyway for the advice.   

- 7LM

[jeffbb]

Hi
@7lm
quote Also, as I said when I posted the link to that patent, we don't know for sure whether it describes BT's currently deployed DLMs.

quote [0071] In the present embodiment, each line is categorised by the first sub-
function of the DLM function

0075] In the present embodiment, each line is processed once every 24 hours to determine how the line should be
categorised,

Throughout  the document the above phrase is used !.

From what I understand the pattern is actually to include the  ability to disregard Wide area events from being included . Much of the document refers to present embodiment.
There are a few other changes ,but the Delay counters etc seem to be as is now .

Regards Jeff

[sevenlayermuddle]

Much of the document refers to present embodiment.

The word 'embodiment' is just a legal term commonly used in the legal jargon of patent claims.   I'm no lawyer, but as fas as I know 'embodiment' just translates to a particular detail that is an exemple/subset of the invention, it needn't mean it's actually been physically deployed on a large scale, or even on a small, scale.   See http://en.wikipedia.org/wiki/Claim_(patent)

Also, FYI, see also another DLM patent from BT, that mentions nothing about delay Doublers... http://www.freepatentsonline.com/EP1953959.html

but the Delay counters etc seem to be as is now .

My own experience directly contradicts the doublers.  My target went all the way up to 15dB last year, then eventually I got it back down, 3dB at a time, to 6dB again.  Then recently it crept up again through 9, 12 and 15dB.   If the doubler were implemented, that would have left me with a doubler value of at least 3 (depending how you interpret it), so it would take at 16 weeks to for my target to reduce again from its recent hike.  In fact, it reduced from 15 to 12 in just over 3 weeks.

I'd dearly like to say 'There, I told you so' next week, when my target gets reduced again to 9dB.  Sadly I don't think that'll happen as, even with a hugely generous SNR margin, I'm just not sure my error rates are  good enough at the moment.     

- 7LM

[sevenlayermuddle]

I'd dearly like to say 'There, I told you so' next week

Well, guess what, 9dB (reduced from 12) target now, exactly 14 days after cranking up my target margin once again.  Unfortunately,  I can't actually say ' I told you so', as I qualified the above with excuses lest it didn't happen, but all the same -  I'm feeling enthused.



Error rates this past few days have been about 25 ES, 40 CRC per day, which is pretty good.  Over the past two weeks however, since I cranked up my margin again, it's been 1935 ES in total, so an overall average about 140 per day or 6 per hour.  So the signs are that miniscule error counts are not necessarily a prerequisite, whilst there's still more evidence to the theory that masses of spare margin does seem to help.





 

[DrTeeth]

This just illustrates why LLU is so great.

DrT