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[roseway]

I suspect that the current design of DLM is at least in part a consequence of the Assia case which was settled almost exactly a year ago.

http://www.ispreview.co.uk/index.php/2015/07/bt-and-assia-settle-dispute-over-fttc-broadband-linked-patents.html

[WWWombat]

The procedure goes from no error correction to interleaved and finally to G.INP.

Arguably, this could be the one permutation I don't think I've seen. Most lines have entered G.INP retransmission mode from fastpath (INP=0) mode - which is how my line entered on the first rollout 15 months ago.

When a line is more problematic, it still seems that, when it starts in interleaved mode (INP=3 or 4) it needs to be finessed into fastpath mode before DLM will consider shifting it into G.INP retransmission mode.

The best analogy I can think of is the gears of a car, where fastpath is neutral. Going from a forward gear to a reverse one always goes via neutral.

Having said that, I will stress that these seem to be the sane rules that used to apply before this year's ECI rollout/rollback. Now, all bets seem to be off... and I agree with roseway that the Asia settlement could have been a root cause in the change of behaviour.

[Interceptor121]

I think my connection was a bit unlucky due to severe weather and it is possible that things deteriorated quickly out of normality. In the first dlm reset when i moved to Bt from plusnet speed dropped as well thats why i got rid of the eci modem. I have had two DLM resets recently and none has moved from fastpath to GINP

[kitz]

I suspect that the current design of DLM is at least in part a consequence of the Assia case which was settled almost exactly a year ago.

http://www.ispreview.co.uk/index.php/2015/07/bt-and-assia-settle-dispute-over-fttc-broadband-linked-patents.html

that resulted in BT tweaking its NGA Dynamic Line Management (DLM) system, which left ASSIA to proceed with a claim for damages

I agree with roseway that the Asia settlement could have been a root cause in the change of behaviour.

Indeed.   There was a discussion on here about 18months ago during the court case proceedings when it became apparent that BT were tweaking the NGA DLM.  Its about 20 months ago that they locked down all the DLM info and it became hard to find out any new info.  From memory the court case was ~ Oct 2014 because it was 2014 when I was writing the DLM pages.   Again from memory but it was ~Oct/Nov 2014 when they removed the NGA DLM for about a week, then put in place the new one - discussion will still be in a thread somewhere on here.   
TBH all it looks like they may have done was tweak something that was logical[ish] into something less logical

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ETA

I even wrote a disclaimer on the DLM page in 2014  "Things ground to a halt just prior to the ASSIA court case and since then it has been nigh on impossible to get any new information about the BT DLM or changes made since that date.  The ASSIA court case appears to center around BT's ILQ system and the process steps and decisions undertaken to change and reverse DLM steps, which is why there is little information about this stage."   

[kitz]

Arguably, this could be the one permutation I don't think I've seen. Most lines have entered G.INP retransmission mode from fastpath (INP=0) mode - which is how my line entered on the first rollout 15 months ago.

The default after a [DLM] reset is "Error Correction Low" ie Interleave and INP 3.   
This is a situation we have seen many times and its also what Ian Lawrence said should happen.
After g.inp was removed on ECI cabs they immediately fell back to Error Correction Low until they were deemed stable enough for DLM to remove interleaving. You can see this happen on my line in April despite the fact there was no need for it.

Automated G.INP rollouts will go straight to G.INP then Interleave/Error correction only if necessary.   

As weve both discussed and observed in the past there does however appear to be 2 types of reset.
1) Complete reset which can only be performed by Openreach Engineer which puts the line on Open Profile
2) The automated DLM reset caused by a change of product or speed profile.  This one is strange as it usually resets to Error Correction Low and doesnt appear to remove any banding.

In theory it is possible for that permutation to occur if a line has been reset to open profile.


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ETA
In fact didnt Williams go from open -> Interleave -> G.INP

[licquorice]

Mine seem to go to Interleaving for a couple of days to open for a month to G.Inp after the change of Infinity1 cap reset (if I'm reading the graph right). Banding still applied.

[William Grimsley]

In fact didnt Williams go from open -> Interleave -> G.INP

Correct!

[Interceptor121]

Same here but I blame the ECI modem vintage 2013

[WWWombat]

In theory it is possible for that permutation to occur if a line has been reset to open profile.

I'm still not utterly convinced, but I agree that steps going via a DLM reset add a different dimension; I was really only referring to automatic behaviour.

Thinking further, it ought to be obvious that DLM should be able to step from G.INP retransmission to interleaving when it needs to intervene on an erroring line, and vice-versa to de-intervene.

Obvious, that is, before DLM went haywire on us.

In fact didnt Williams go from open -> Interleave -> G.INP

I must have missed it, but the threads were getting long back then, IIRC.