Aargh DLM

My UPS has just thrown a wobbler and caused multiple disconnects, which has caused DLM to intervene. It has lowered my previous 79999 with few errors down to 72040 again no errors. How long is it going to take to come back? I move to PlusNet tomorrow so getting them to do something is going to be easier than fighting BTs 'customer service'.

Has it turned on interleaving?

Yes at a depth of 1141 down, up is still fast path. Normally my connection is not interleaved up or down.

I believe a post on the Plusnet website about the DLM states that it takes around 8+1 days of no errors for the DLM to give you improvements. But can slow you down at any time it sees fit.

I had an idea it was going to be a long wait. This is the first time that DLM has taken an interest in my line, i've had Infinity 2 (80Mb) for just over two years now.

In the past when I had really bad issues with speed drops to 10Mbps (>2 years ago, star wiring ignored by installer) it took nearly three weeks for DLM to start significant improvements, and then another week to get to a full speed (around 70Mbps for my line). I think that the DLM may have been updated to respond a bit quicker now, and also that it responds quicker after relatively minor issues. Good luck

This is the first time that DLM has taken an interest in my line, i've had Infinity 2 (80Mb) for just over two years now.

And it was your equipment that caused its intervention, you shouldn't really be complaining.

True, however I think that DLM is too quick to respond to short outages, I think that the activation threshold should be a little longer.

I understand that BT is testing seamless rate adaption alongside vectoring, Hopefully that will ultimately replace DLM and benefit those of us who get errors rarely but enough for DLM to throttle our lines.

I haven't seen any reliable source say SRA is being tested by Openreach, but even if it is it will be as a part of the DLM, not a replacement.

TheHorseman's problem is that interleaving has been introduced. That will certainly not be ditched.

it might replace banding but SRA doesnt manage interleave levels.

I think that g.inp that has been mentioned is effectively a seamless variant of interleaving where it only applies delays for short periods when needed.

Edited by Chrysalis (Wed 16-Jul-14 08:42:04)

ISPReview reports:

In reference to www.ispreview.co.uk/index.php/2014/05/bt-prepare-phase-2-vectoring-...:

The new trial will also include both Physical Retransmission (G.INP) and Seamless-Rate-Adaptation (SRA) technologies, which Openreach said they�re �very interested in testing� and see as being useful to help augment the benefits provided by vectoring.

DLM is a somewhat generic term: no doubt that BT will continue to manage line characteristics to ensure they are reliable, but technologies like SRA and G.INP should offer an improvement to customers whose lines can have many days between the errors that trigger DLM.

g.inp I can see some nasty downsides tho, if its frequently going on and off, its going to be an artifical jitter. As sudden changes of latency for certian types of use will be noticeble by the end user. SRA isnt so nasty as its just a reduction of burst speed. The end user experience will be for the most part the same.

Really what BT need is a option on the line to have no management that changes latency. We know they wont turn off DLM, but an option where they only adjust sync speed but leave delay alone would be nice.

Edited by Chrysalis (Wed 16-Jul-14 10:55:46)

In reply to a post by Zarjaz:

This is the first time that DLM has taken an interest in my line, i've had Infinity 2 (80Mb) for just over two years now.

And it was your equipment that caused its intervention, you shouldn't really be complaining.

So next time you have an electrical device that goes a bit mad I should ask UK Power Networks to cut your mains voltage down to 110v (from 230) or maybe drop the frequency to 40 Hz from 50...

DLM should *not hinder* a connection, and should not take days to recover from an occurrence.

you are worried about dropping from 80 to 72............

I am lucky to get 4 on a very good day!

In reply to a post by TheHorseman:

I move to PlusNet tomorrow so getting them to do something is going to be easier than fighting BTs 'customer service'.

The migration will reset DLM - mine did. Get that UPS fixed

In reply to a post by jchamier:

The migration will reset DLM - mine did. Get that UPS fixed

It doesn't seem to have done, I'm still on an interleave depth of 1141 when it is normally fastpath. The UPS is currently sitting in the spare bedroom awaiting a new battery. I may try a single power cycle of the modem and see if that makes any difference. If not then a call to PlusNet is in order.

In reply to a post by IamQ:

DLM should *not hinder* a connection, and should not take days to recover from an occurrence.

I agree, it really should take into account the previous behaviour of the line and only take action if the problem shows up again.

In reply to a post by TheHorseman:

In reply to a post by jchamier:

The migration will reset DLM - mine did. Get that UPS fixed

It doesn't seem to have done, I'm still on an interleave depth of 1141 when it is normally fastpath. The UPS is currently sitting in the spare bedroom awaiting a new battery. I may try a single power cycle of the modem and see if that makes any difference. If not then a call to PlusNet is in order.

My modem used to periodically get put on interleaving. Each time it stayed for 14 days before removed at 6am. I'm pretty sure that there's nothing PlusNet can do about it.

Edited by Andrue (Tue 22-Jul-14 18:45:55)

Well, a power cycle of the modem resulted in a drop to 71556 and interleave dropping a bit to 1133. Will have to see if PlusNet can get DLM reset for my line. I have never synced at less than 79999 in all the time I have had Infinity ( just over two years). So it's particularly annoying to have this happen now.

It's only had eight days so far though.

It doesn't remove interleaving that quickly, and without a lot of shenanigans I don't think an ISP can request it. ISP-triggered DLM resets are normally only when an engineer should have requested one after clearing a fault, and didn't.

In reply to a post by RobertoS:

It doesn't remove interleaving that quickly,

I think its down to error counts.

In the summer season my line generally runs without interleaving, and in the wet winter, interleaving is added and stays until the summer. It took about 2 weeks last year to remove the interleave.

This year I migrated to plusnet (2nd June) about the time it would have started to get reduced error counts, and the move reset the line (probably because I went from 80/20 to 40/10 and had to be kicked back to 80/20). Since then my connection sync speed has been 55790 down and 9183 up with no interleave. I've previously seen lower down and higher up - but with interleave enabled.

DSLstats tells me my ES/hour are 52.2 on download and 1.07 on upload. On the 40/10 profile I was 0 on both.

I am still thinking that a DLM profile change initiates a reset.

But no isp's seem to try it (maybe there is a deterrent in place?).

Also there is the option of changing the openreach product e.g. down to 40/10 then back up to 80/20. Plusnet probably don't do this due to it also initiating a new contract and possible setup fee's.

I seem to have a vauge recollection there's a charge of £10 for a profile/product change.

In reply to a post by R0NSKI:

I seem to have a vauge recollection there's a charge of £10 for a profile/product change.

It's would cost more than £10. Because they have to change product order via BT twices from downgrade to 40/10 then upgrade to 80/20. So, it probably cost £20. But, changing product is pointless because I don't think openreach willing to reset DLM at the cabinet.

Edited by adslmax (Wed 23-Jul-14 10:10:44)

I have raised a Question with PlusNet so will wait and see what they say. I will leave the connection alone and see what happens, I'll see if there is any change in the next 2-3 weeks.

It's annoying because for just over 2 years prior to the UPS fault the line has been perfect. 79999 sync and fastpath. I have also swapped modems in the past ( testing a spare I got from eBay) and DLM did not notice.

Not to hijack this thread, but in a similar situation. Went on holiday so left router powered off for a week. Came back, and noticed it sync'd at a slower speed. Reset a few times, but no joy.

Am now gonna leave it the 10 days.

But what I've also noticed is that the BT Adsl Checker has actually dropped my estimated download from 15.5 to 11

This all seems to have also occured now the infinity cabinet is live (And have it being installed 29/7).

Has anyone else ever seen the BT Adsl Check website reduce their estimated download speed?

It has been nearly 19 hours since I power cycled the modem and in that time I have a downstream ES:2 and 5 for upstream other errors are not particularly high either.

It is also important to not that lots of people keep resetting their modems to try and get better results... The problem with that is the DLM will see it is further issues. The DLM doesn't know you are trying to get it back to a faster state. The disconnection counts are adding up. For anyone who was on Fast Path and it 'was' stable before, just leave it connected and stable. The connection in 99% of cases will go back to Fast Path after around 9 days.

Yes, that's why I left it 8 days before power cycling it (and only once). Unfortunately FTTC DLM is controlled by OpenReach who seem to be a law unto themselves.

I had an issue 5 weeks ago with a loose connection at the cabinet, it caused my line to go down when the phone was picked up, this meant a lot of loss of connections during the week.

DLM ended up putting Interleave on my line (high at 1215 with an INP of 8), it also banded my upstream speed to 6, after 2 weeks it moved the upsteam banding up to 7.2 and then a week later up to 8.5 (I only get around 8 anyway). During that time it did nothing to the downstream interleaving, 9 days after the upstream banding was sorted it finally lowered the downstream interleaving to 593 with INP of 3 (even though the errors I had were higher than the previous weeks due to the lightning storms).
I'm hoping it will remove the interleaving eventually as apart from a couple of weeks 6months or so ago my line hasn't had interleaving applied.
IMO it's a little quick in dropping speed but takes it's sweet a$$ time to put it back up/remove interleaving etc.

In reply to a post by IranianGiraffe:

IMO it's a little quick in dropping speed but takes it's sweet a$$ time to put it back up/remove interleaving etc.

I agree, I think that it should be slower to take action and be faster to remove interleave and up the speed. It could usefully take account of the lines previous behaviour too.

In reply to a post by jchamier:

I think its down to error counts.

In the summer season my line generally runs without interleaving, and in the wet winter, interleaving is added and stays until the summer. It took about 2 weeks last year to remove the interleave.

It's more the noise floor is higher in the winter months - heating systems, lighting etc.

If you look on a proper spectrum analyser you can see this very clearly - especially in a city area.

In reply to a post by IamQ:

It's more the noise floor is higher in the winter months - heating systems, lighting etc.

If you look on a proper spectrum analyser you can see this very clearly - especially in a city area.

That makes sense - people in the past who've looked at my stats and graphs have concluded my line probably runs through an industrial park. Sadly not, it only runs past a school on a main road. (I know my line route, as I had a BT SFI visit in 2010 who fixed a big fault and showed me the route of the line on his laptop).

In reply to a post by jroadley:

Has anyone else ever seen the BT Adsl Check website reduce their estimated download speed?

Yes, I've seen my estimate alter a couple of times, many others have also reported this.

It obviously uses live connections to update the estimates, this gives more accurate estimates, but also lower estimates if your line is having problems.

In reply to a post by RobertoS:

It's only had eight days so far though.

It doesn't remove interleaving that quickly, and without a lot of shenanigans I don't think an ISP can request it. ISP-triggered DLM resets are normally only when an engineer should have requested one after clearing a fault, and didn't.

DLM removed the interleaving from my line in the early hours of this morning. I am now back on fastpath, my sync speed is now back to 79999/19999. Just need to check my PlusNet profile now.
So it looks like business as usual

There you go !

How long was that then?

It was just over 15days from the initial UPS problem. It re-synced around 03:30 this morning. I still think that DLM it a bit too twitchy though.

At least it does revert if appropriate. The BT Wholesale ADSLx one doesn't, unless that's changed in its latest versions. Once interleaved, always interleaved, until a DLM reset.

In reply to a post by TheHorseman:

It was just over 15days from the initial UPS problem. It re-synced around 03:30 this morning. I still think that DLM it a bit too twitchy though.

I was almost right then. Are you sure you didn't disconnect or anything similar the day after, making it 14 days?

I did a power cycle of the modem 8 days after the initial problem but other than that no.