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[Chrysalis]

I am leaving it alone now as its still stable and I am enjoying the extra speed, DLM seems happy as well as I am still on fast path.

[NewtronStar]

I am leaving it alone now as its still stable and I am enjoying the extra speed, DLM seems happy as well as I am still on fast path.

So lets see your happy with your SNRM as it is, we just thought you may need some advise, have a happy ISP connection 

[Chrysalis]

The original post was about the graphs not working, but yeah I was obviously curious why my modem was syncing at 4db after a what looks like a DLM change, one manual reset and it stayed at 4db, so I decided to leave it alone now.

[Bald_Eagle1]

To remain at 4dB is most unusual following a resync (unless perhaps you have been swicthed to a super fast profile rather than standard profile or BTOR are 'experimenting' with Target SNRM at less than the usual 6dB).

Although, as mentioned previously, I would have expected adjustments in 3 dB steps.

As crosstalk appears to have increased in visible steps on my connection over the last 12 months, I did see reductions in SNRM in smallish, but sudden steps, followed a few days later with a resync at lower speed & SNRM back to around 6dB again.

[Chrysalis]

The only logical explanation is I am on a target snrm lower than 6db.  It did not drop to 4db 'during' a sync prior to the resync, during dlm hours it changed right at the resync event.

It does seem a few of you guys are getting confused by comparing whats happened to me to varying snrm on a live connection, thats not what happened here.

Either that or there is some kind of fault with my modem/cabinet causing this.

[NewtronStar]

Either that or there is some kind of fault with my modem/cabinet causing this.

I don't know its like the FTTC physics has gone out the window for your line, I would have thought by now to may have had a Retrain and the SNRM being set back to 6dB and I would just as you said leave it alone and see how this goes.

Do you have any current stats (folder) showing the pbParams during this event from 6dB to 4dB.

[kitz]

iirc Chrys has said a couple of times now (or at least mentioned it in another thread) that hes come straight up from sync with what looks like a target SNRm of 4dB.   

I find it rather an odd figure for BT to be using though..   if it was 3dB then I could perhaps understand it.   
But 4dB is rather strange.  Purely because it takes 3dB to load 1 bit,  thats why target SNRs are always incremented in steps of 3dB and why we see 3,6,9,12 etc.  Even 3.5 I may go hmmmm perhaps as it may be something to do with rounding..  but 4? 

[Chrysalis]

kitz the 3 snr per one bit remember is on the actual snr, not the snr margin.

so eg. if a tone has 38snr with a 6db margin it will utilise 32snr, of course it cant use all 32 as only 30 is a multiple of 3, so 2 db is spare.  drop the snr margin by 2 db and it has 34db meaning it can use 33 instead of 30, so extra bandwidth.

not all isps even use a 6db margin, I have seen isps often use 7db instead of 6db (which to me is a more logical choice), some use 10db, I have seen some use 8db as well.

[kitz]

kitz the 3 snr per one bit remember is on the actual snr, not the snr margin.

so eg. if a tone has 38snr with a 6db margin it will utilise 32snr, of course it cant use all 32 as only 30 is a multiple of 3, so 2 db is spare.  drop the snr margin by 2 db and it has 34db meaning it can use 33 instead of 30, so extra bandwidth.

not all isps even use a 6db margin, I have seen isps often use 7db instead of 6db (which to me is a more logical choice), some use 10db, I have seen some use 8db as well.

mhmmm yes re SNR.  I was thinking more of what BT 'usually' do with the target SNR and seem to follow the guideline of min 6 dB for adsl (which needs a min of 2 bits per bin..  and min 3dB for adsl2+ which only needs a min of 3dB to load a bin.
Im also surprised that no-one else seems to have reported seeing it either if it was a new feature.


re other isps... Sky use 7dB, but their system is backwards and afaik its just 7dB + interleaving depths.  It even starts off low and IMHO is designed to save the network with as much bandwidth as possible.  Right down to not allowing full upstream speeds, instead you will only get a portion of your downstream, regardless or not if the line could cope.  I dont like Sky's DLM, can you tell?   

A classic example would be my parents line, which because of skys DLM crippled them at 1600 kbps and massive interleaving and iirc around 450 kbps up.   The couldnt seem to get to the next step up and the help desk wasnt much use so dad gave up.   Theyve now been on Plusnet for 2 months syncing at around 7.5Mbps and 800kbps up...  and no interleaving, although tbh I wouldnt be surprised if it did get interleaved at some point.   

[Chrysalis]

I agree on both accounts, sky's DLM been stupid, and me been the only one to report this, so its unlikely its a new profile.

The reason I say 7 db makes more sense is this.

With a 7db target snrm, bitswapping can load 2 extra bits on the tone and there is still a 1db margin, although its tiny its still a positive number, whilst with 6db it would be 0db left.

[Chrysalis]

seems since 30 july or so I been getting standout crc errors from around 3pm to around 9pm , the worst occured on 2 august and has been a daily occurance.

I only noticed as I was looking at my data for another reason, it starts off as a gradually increasing crc error rate then suddenly stops, a pattern I had numerous times before that has dissapeared following reporting to openreach and they come back stating no fault found (but issue dissapears). So sort of like a triangle shaped error graph.

Funny enough tho I am still on this 4db fast path, no DLM action and I have been using my connection during those hours with no noticeble issues.

[NewtronStar]

Funny enough tho I am still on this 4db fast path, no DLM action and I have been using my connection during those hours with no noticeble issues.

Hi Chry the more i think about this 4dB profile your on my mind go's to the VDSL modem hardware which the stats are extracted by telnet, I am just wondering if the Hardware (HG612 or ECI modem) is telling the telnet fibs.

The only way I know to dismiss the hardware as the cause is to acquire the same hardware (HG612 or ECI modem) and test.