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[aesmith]

ADSL only retrains to set the speed between modem and DSLAM when it first connects, or after a disconnection.  So on ADSL if you connected at a slow rate, say because there was noise on the line, then conditions improve, your modem won't automatically speed up.  In those circumstances a controlled disconnect and reconnect will let the modem synch at a new higher speed in line with the improved conditions.

Did I read that FTTC changes synch rate on the fly?   If so then the above comments won't apply to FTTC.

[burakkucat]

Did I read that FTTC changes synch rate on the fly?

That would be SRA (seamless rate adaption) but, as far as I am aware, no xDSL service makes use of SRA in the UK. (I know that certain modems/routers will show in its configuration that SRA is turned on and I will always turn it on, as a matter of routine.)

If so then the above comments won't apply to FTTC.

In this case, your comments are true for G.Dmt, ADSL2, ADSL2+ and VDSL2.

[gt94sss2]

That would be SRA (seamless rate adaption) but, as far as I am aware, no xDSL service makes use of SRA in the UK. (I know that certain modems/routers will show in its configuration that SRA is turned on and I will always turn it on, as a matter of routine.)

SRA used to work on ADSL UKonline/Easynet LLU. I'm not sure if it currently works on Sky.

BT decided not to roll it out for ADSL - they were supposed to be trialling it for FTTC along with Vectoring and G.INP but I haven't heard anything about it since.

[Moderator edited to remove some trailing lines that appeared to have been overlooked when this post was created.]

[WWWombat]

I don't think there's a way to interfere positively with DLM

Oh, I see. I just remember turning off the router for more than 15 minutes and then turning it back on can help. But, thanks for letting me know. I'll know now for future.

The 30 minute thing is a way to make sure that your negative impact (turning off the modem) isn't interpreted too negatively by DLM.

There is NO way to positively affect DLM.

All you can do is leave it alone, and wait patiently. And even then, you don't know that negative things aren't happening anyway.

Note that DLM really determines your line to be in one of 3 states each day: bad enough that intervention should scale up; good enough that intervention can be scaled back; in between, where the level gets neither better nor worse.

Real deintervention requires a number of consecutive "good" days. However, multiple interventions within a few days are likely to increase the number of consecutive days needed to clear again. And the odd duff day in between might be enough to start the counter again.

Plusnet have a page. I don't know that it will help.
https://community.plus.net/library/browsing/fttc-dlm-what-it-is-how-it-works/

You might have started to figure why no one fancies playing with DLM much.

[kitz]

If you turned it off it sent a dying gasp to the DSLAM so DLM knows it's not a fault and does nothing.

Although the MSANs/DSLAMs are capable of detecting the dying gasp it doesnt take any note of it when it comes to the DLM.   Dying gasp may be useful in the event of a 'Wide Area Event', but when it comes to individual lines then the BT DLM uses its own method of detecting unforced retrains.  It is definite that BT use the 15min bin period to check for unforced retrains.

What we dont know is the start time of those 15 min bins.   I tend to believe they run in time with the clock.   Therefore if you powered down at 26 mins past the hour, the new bin will start at 30 mins past.   You need to have no activity in the 30-45 mins past the hour for DLM to record an unforced retrain, so you could safely resync at 45.01 mins past.   The 30 min suggestion by some was just to ensure that there was a whole 15min bin with no recorded activity just in case it didnt start in line with the clock.     
The actual algorithm is shown on the DLM page.

TBH if Im just doing one or two resyncs I never bother waiting, because you are allowed 'x' certain number per day ('x' depending on the profile selected by your ISP).

[kitz]

The 30 minute thing is a way to make sure that your negative impact (turning off the modem) isn't interpreted too negatively by DLM.

Oops sorry wombat I may have duplicated some of your post which I hadnt seen when I'd started mine about the 30mins

You might have started to figure why no one fancies playing with DLM much.

I did wonder the other day, why on earth anyone would want to play with it, due to the length of time it may take to recover.

William if this is the first time the DLM has intervened then it may be more forgiving.    My line is usually very stable but during a line fault I got hammered with several dlm interventions.    Once the fault was fixed it righted itself in about 4 days.    ie day1 reduced the speed cap one step, day 2 decreased the amount of interleave, day3 totally removed speed cap, day 4 totally removed interleaving.   

[Weaver]

I don't think there's a way to interfere positively with DLM

Agreed. However, sometimes I have wanted to interfere negatively with DLM (slightly). In the past there have been occasions when a modem or a line has started to misbehave, with high rates of packet loss (PPP LCP packets that is, I'm not talking about TCP). On such occasions I have found it very valuable to turn the modem off, then wait thirty seconds, then straight back on. This reduces the downstream sync rate very slightly, and seems to have a huge beneficial effect, restoring stability completely.

[ejs]

I don't think there's a way to interfere positively with DLM

Agreed. However, sometimes I have wanted to interfere negatively with DLM (slightly). In the past there have been occasions when a modem or a line has started to misbehave, with high rates of packet loss (PPP LCP packets that is, I'm not talking about TCP). On such occasions I have found it very valuable to turn the modem off, then wait thirty seconds, then straight back on. This reduces the downstream sync rate very slightly, and seems to have a huge beneficial effect, restoring stability completely.

This is probably not really anything to do with the DLM, it's just the modem attaining a slightly lower speed based on the conditions at the time (which must have deteriorated since the connection was established). The retrain would be counted by the DLM, but if it was just the one in the day, it won't make any difference.

[William Grimsley]

I've had 1 OH Frame Error on Downstream and 15 OH Frame Error's on Upstream as well as 1 ES on Downstream and Upstream. I am presuming this is down to the strong winds today? Is this a sign that a fault may be starting to occur as G.INP is on?

[kitz]

1 Err Sec is nothing.    It happens to most lines - in fact most lines get far more than 1 E/Sec per day.
It most definitely is not the sign of a fault.    Anything can cause it down to the flick of a light switch.    If theres a thunderstorm its easy to rack up lots. 

According to MDWS I got 196 yesterday, and I think its around that most days.   DLM doesnt care.

[William Grimsley]

Yes, we have a (suprisingly) stable line now after Openreach replaced the line on our lane after many years of frequent line faults! However, having said that I have got a higher than normal Downstream SNR Margin (dB) of 9.2 due to DLM intervening because of all the disconnects and reconnects of the DSL cable I did about a week ago. So, we shall have to see how many ES I get when DLM increases the Rate and decreases my interleaver depth.

[Chrysalis]

I fear you may have read my post a few days ago where I stated I turned my modem off for 30+ mins to recover my sync speed?

That wasnt to do with recovering DLM but the fact I had synced at 69mbit with spare snrm indicating a 75mbit attainable speed so I knew I would recover my sync speed, I delayed it 30 mins to not upset DLM, but it wouldnt have made DLM up the profile if I was on a stability profile.

If you are trying to get DLM to improve your profile, the best thing to do is leave the line alone so no disconnections, assuming the rate of ES is within the DLM green stability threshold.

[William Grimsley]

I fear you may have read my post a few days ago where I stated I turned my modem off for 30+ mins to recover my sync speed?

That wasnt to do with recovering DLM but the fact I had synced at 69mbit with spare snrm indicating a 75mbit attainable speed so I knew I would recover my sync speed, I delayed it 30 mins to not upset DLM, but it wouldnt have made DLM up the profile if I was on a stability profile.

If you are trying to get DLM to improve your profile, the best thing to do is leave the line alone so no disconnections, assuming the rate of ES is within the DLM green stability threshold.

Yes, I did your post and that's why I thought it would improve my speed but obviously it wouldn't work because of my high Downstream Noise Margin (dB) figure.

I've left the Billion BiPAC 8800NL router alone for over 3 days now so hopefully my line rate will increase soon.

[NewtronStar]

I've left the Billion 8800NL router alone for over 3 days now so hopefully my line rate will increase soon.

It is going to take time and I always say 14 days without any manual disconnects this time frame seems to work well with lines that have been hit hard by the DLM, we must also remember the DLM also has an insight into our history.

The best way for a quick DLM recovery is to have as little history as you can IE: no disconnects no high DS/US errored seconds no SNRm swings below 3.0dB

[Weaver]

Newtronstar is exactly right.

There's no way to actively 'mend' sulky DLM, apart from uneventful good behaviour. If my understanding is correct (from Kitz), the switch off 30+ mins thing won't fix anything. It's just a way of keeping you out of trouble if you have to do a lot of switching on/off or disconnecting in one day.