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[gt94sss2]

My FTTC line - which had been quite stable - resynced last night at around 2am due to DLM following some very odd behaviour on my line.

Just before the resync by SNRM shot up a lot (i.e. from 12/13 to over 21!) and my attainable sync speeds jumped from around 65MB DS/ 20MB UP to 90/30 - and its almost as if this dramatic change triggered the resync...

Things I have noticed following the DLM change:

- G.INP increased for the first time since it was enabled last year from 47 to 48;
- the attainable sync speeds are now lower than before  ;
- the downstream now sync rate now appears as 39999 rather than 40,000.

I know others have previously said my line has a lot of crosstalk and note that from 8/9 April my QLN stopped reporting anything for tones between 2270 -2790 (approx)

Does anyone have any ideas what may have happened? AFAIK while it rained last night here in London, there were no power cuts or storms

Obviously it would be nice to have that attainable sync that high (never seen those speeds before) - perhaps its a sign of what vectoring could bring?

My full stats are on MDWS but I attach some graphs as well. Its a Huawei cab and I'm around 500m away from the cab..

[kitz]

Are you sure it was a DLM initiated resync.   I cant see any DLM parameters have changed.

- G.INP increased for the first time since it was enabled last year from 47 to 48;
- the attainable sync speeds are now lower than before  ;
- the downstream now sync rate now appears as 39999 rather than 40,000.

I wouldn't worry about the 39999/40,000 this frequently happens and is something to do with framing size.   
Next time you sync it could change back again, or it may stay at 39,999.   Mine can vary between 79987 - 80000.

Same with B0 INP, these too tend to vary depending on framing parameters and sync speed, rather than a fixed figure.   Wombat and I are interested in finding out how such things as the R & N values relate to each other.  We know that they do, but just havent gotten to the bottom of it yet to be able to find the formula to work out the relationship. 

To me it looks like some geographic outage rather than DLM.    One of your cross-talkers got knocked off line the same time as you..  however you came back up first which is why you momentarily saw the increase in SNRm and attainable.   As soon as your crosstalker sync'd it knocked your SNRm back down again from 23dB.

You have however lost 0.7 dB of SNR that I cant account for (12.6 -> 11.9 SNRm).
However the 3 upstream bands have split and your upstream is now higher.   
Sometimes odd things do happen after resyncs due to outages and SNR can go a bit skewy for a while.   There's quite a lot of us who experience this. iirc Eric's line does it after outages.   It also usually corrects at next sync.

[gt94sss2]

Are you sure it was a DLM initiated resync.   I cant see any DLM parameters have changed.

I assume its as a DLM change since the modem shows a Last Retrain Reason: 1 and as the level of B0 INP changed (which I have always assumed is set by DLM)

Following the resync, I also note that the number of ES on my line has fallen sharply - it was never that high at between 100-150 ES a day, though enough to show as one 'amber' light on the UP on MDWS but is now much lower.

Same with B0 INP, these too tend to vary depending on framing parameters and sync speed, rather than a fixed figure.   Wombat and I are interested in finding out how such things as the R & N values relate to each other.  We know that they do, but just havent gotten to the bottom of it yet to be able to find the formula to work out the relationship.

If it helps, I changed back to DSLStats 5.7.3 before the resync instead of running 5.6.1 so the software should have captured the additional values at the time of the resync

To me it looks like some geographic outage rather than DLM.    One of your cross-talkers got knocked off line the same time as you..  however you came back up first which is why you momentarily saw the increase in SNRm and attainable.   As soon as your crosstalker sync'd it knocked your SNRm back down again from 23dB.

I can understand why you might think it might be a geographic outage given that SNRM shot up to 23 but I was awake at this time and there was no power cut here.

I have had SNRM figures in the 13-14 range before (but never higher) and seen the impact of crosstalk on my line - but the changes never been as dramatic as this. Usually I might see 0.5-0.6dB as the largest impact of this. Am not sure a single instance of crosstalk would cause a 9-10dB fall in SNRM?

[S.Stephenson]

A Lot of modems can sync up in one minute, so it might not necessarily be one crosstalker.

See below what effect a power cut can have (my modem is on a UPS)