Power Off & DLM

[#1]

Quote from: alext05

We would care about the advice OR has given if we knew what it is. I am, for one, interested, but you seem to be unable to bring yourself to quote OR or to link to the original source (or your previous quote).

Openreach hold regular briefings on differing aspects of NGA. They have covered DLM in substantial depth as it's important that their customers, ISPs, are able to understand how and why it works. Chris Pettitt previously covered this for Plusnet and wrote an explanation as to how DLM works.
I cannot publish the documents and presentations for obvious reasons. I have written on another thread about the recent MTBR changes and how it impacts the 3 DLM profiles. Everything I wrote comes from how Openreach information is briefed to ISPs. There is another DLM workshop this month I believe and this will hopefully cover the 14 profiles in each speed band.

[#2]

All this info about briefings that OR holds is, of course, interesting but we are here in a public forum where folks are trying to help OP (and others that might find it useful) with a very specific issue and you have contradicted a fellow forum user without giving any explanation as to what exactly that was suggested is different to OR advice and why. That is trolling, but I am sure you didn't mean it.
A member of Plusnet staff has provided an advice in good faith too and it sounds sensible and simple, but obviously we don't know whether the advice is Openreach approved.
And since you are not willing to provide a better informed version of the advice, then we would be following the advice of the more helpful members of this community. At our own risk of course.

[#3]

The  DLM guide that Chris did doesn't help here because all it tells you is what DLM does and why nothing on how to prevent anything such as in regards to the question asked "how long should the modem be powered off for before powering back up". 
I have in the past powered off and powered up the modem both quickly and as Anotherone suggested both times i lost Sync speed that never recovered the latest of which cut my up Sync in half, As i have a OR ECI modem I had no means of knowing what was going on, whether it was DLM related or something else, so I'm unsure what is the best way to do it as it effected me either way.
 

[#4]

It's not trolling at all.
Perhaps it would be easier if that other user explained his advice, what it is based on and link the empirical evidence?
As I said on this thread http://community.plus.net/forum/index.php/topic,139060.0.html the guidance is 30 secs.
@ Terranova667 - DLM reacts the day after, so if you lost sync speed the same day as a result of a reconnect it will DLM (equally unless a banded profile is applied, DLM will not be at play)

[#5]

Quote from: AndyH

As I said on this thread http://community.plus.net/forum/index.php/topic,139060.0.html the guidance is 30 secs.

and as kitz told you on that thread the 30secs. is a red herring.
The absolute minimum should be 30 minutes, and the precautionary advice is 1 hour!!
I'll address some of your other remarks later.
I'll also pickup on some of the other useful comments

[#6]

This is fine - if you could show where 30 minutes comes from and why you think it is correct.
It conflicts with Openreach information. I will see if I can post something else.

[#7]

Try reading the link that Andrue posted
I will take asbokid's & kitz advice and information way and above anything you have to say unless you can explain it and back it up without posting in such an abrupt "dictatorial" style.

[#8]

I'm not sure why you're making personal comments on here? Just because I disagree with something you've said, does not mean I am dictatorial or talking rubbish. You come across as very insecure.
Back to the issue in hand - I cannot post the internal Openeach documents. If people don't believe me, then it's up to them but I am not going to bother helping people out if I am discredited without fair reason.

[#9]

Hi All,
On the link AndyH gave, Kitz stated.
"As far as the DLM is concerned then a resync in the same 15min period counts as a retrain and strike one for the forced event counter.
30 mins ensures at least one complete 15 min period and the sync to be classed as an unforced event so discounted by the DLM"
I'll be waiting 30 MINUTES + if I ever need to power cycle the modem.
ATB
SN

[#10]

Quote from: AndyH

As I said on this thread http://community.plus.net/forum/index.php/topic,139060.0.html the guidance is 30 secs.

Thanks a lot for providing a link to the original discussion. It has some interesting info.

[#11]

I would have hoped that with the dying gasp being sent and the DSLAM recognising it for what it was you could power cycle the modem as often as you want without any problems. I 'installed' a UPS two weeks ago and during that I must've power cycled the modem twice in the space of five minutes (I got confused by the tangle of cables   ) and DLM didn't react.
As a computer programmer with over three decades of experience I've seen (and written ) some stupid code but I'd like to think that whoever writes the DLM software would have the sense to ignore power cuts. After all there's nothing DLM can do to fix a dodgy power supply.

[#12]

It seems that relying on the dying gasp is a forlorn hope. I'd long hoped it was true, but anecdotal evidence suggests it isn't used. Now I know from experience...
Meanwhile, DLM does seem to pay attention to district-wide power cuts. If a large proportion of modems are affected around the same time, the problem gets classified in a way that is not detrimental to the individual line.
But for individual lines, no such thing happens.
I've recently been suffering from problems where the house RCCB has been tripping out, taking out everything in its path. When this first happened, with a few power failures over the course of a couple of days, DLM gradually fiddled with my line profile more and more - giving me altered G.INP settings (increasing the INP setting that was used for retransmission, and altering the FEC/interleaving settings used for non-retransmitted protection), then later the same weekend, it banded speeds down from 80/20 to 74/19. Things recovered reasonably quickly - over the course of a few days, rather than months - when the trips stopped. I normally have the modem stats being logged - and it would have been good to see the changes made. Unfortunately, all those power cuts made me reticent to leave the computer on logging all of the changes!
What I *can* say, from semi-vague recollection, is that it took quite a few power failures before DLM made any changes at all. But once it did, then each new failure caused a slight change to the profile.
We're still having periodic problems with the RCCB (it seems to happen with seriously rainy weather, so the previous batch was just after the election, with a new batch last night), but UPS's have fixed the impact to broadband and the computer.

[#13]

@ WWWombat - In the OR FTTC manual, it does state "dying gasp functionality is included on the Openreach modem, but is an optional requirement for CPs to implement on their devices." It is something OR push for on CP tested devices though because it will reduce unnecessary (chargeable) engineer visits.
Part of the daily reported Openreach line data includes:
- Total 24hr Unforced Retrain Count
- Total 24hr Full Initialisations
- Total 24hr Failed Initialisations

[#14]

Interesting stuff. I was going to query a proper power cut but that has just been answered.
I reckon I was off for about an hour and I seem to have retained my normal ally restricted speed. I know I should have powered down the router first in the controlled manner described but with decorating on the go the big switch was easier and quicker.

[#15]

Quote from: Kremmen

Next week I'm wallpapering and I'm going to have to turn the lecky off for a short period to get behind the wall socket that the modem is powered by. Does the leaving it off for half hour minimum still apply to avoiding DLM issues?

You don't need to switch the electricity off, just to push a bit of wet paper behind the faceplate, provided you are a bit careful.