VDSL Performance & Tuning

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#677250 26-Aug-2012 19:56

Hmm... guess what time I mowed the lawn today:

I also noticed that the phone cable from the road pops up out of the ground about 15cm next to the main power cable running up the meter box; is that likely to increase errors on VDSL? Anybody have any idea how easy would it be (and is it legal??) to open the "mushroom" try an STP cable (or even just a proper UTP cable) to see what sort of difference it might make?

"I was born not knowing and have had only a little time to change that here and there." | Octopus Energy | Sharesies
- Richard Feynman

stevehodge

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#677266 26-Aug-2012 20:25

I also noticed that the phone cable from the road pops up out of the ground about 15cm next to the main power cable running up the meter box; is that likely to increase errors on VDSL? Anybody have any idea how easy would it be (and is it legal??) to open the "mushroom" try an STP cable (or even just a proper UTP cable) to see what sort of difference it might make?

Is there any point? Your error rate is already very low. I'm getting as many as 680 unrecoverable errors per hour and it's not keeping me off DLM-1 or causing dropouts.

sidefx

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#677267 26-Aug-2012 20:28

stevehodge: Is there any point? Your error rate is already very low. I'm getting as many as 680 unrecoverable errors per hour and it's not keeping me off DLM-1 or causing dropouts.

I'm trying to figure that out; My connection seems rock solid (no resyncs) and yeah my error rate looks fairly low, but it's still just leaving me on DLM3.

"I was born not knowing and have had only a little time to change that here and there." | Octopus Energy | Sharesies
- Richard Feynman

stevehodge

393 posts

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#677268 26-Aug-2012 20:30

sidefx:
stevehodge: Is there any point? Your error rate is already very low. I'm getting as many as 680 unrecoverable errors per hour and it's not keeping me off DLM-1 or causing dropouts.

I'm trying to figure that out; My connection seems rock solid (no resyncs) and yeah my error rate looks fairly low, but it's still just leaving me on DLM3.

Tried talking to Snap? See if they can get DLM reset on your line or something?

stevehodge

393 posts

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#677284 26-Aug-2012 21:08

sidefx:
I'm trying to figure that out; My connection seems rock solid (no resyncs) and yeah my error rate looks fairly low, but it's still just leaving me on DLM3.

Looking at the stats you posted earlier (36160 kbps sync down, 13 db attenuation), I'm not sure you can do much better in terms of throughput. The calculator at speedguide.net indicates 40000kbps for 13db attenuation and 37000 for 14. You're pretty close to that already. Obviously if latency is a big concern then one of the lower latency DLM levels would be better, but if throughput is your main aim then you might be better experimenting with the SNR margin target than worrying about error rates.

sidefx

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#677293 26-Aug-2012 21:17

yeah I'm completely happy with throughput, was just hoping I might get onto a lower latency profile.

"I was born not knowing and have had only a little time to change that here and there." | Octopus Energy | Sharesies
- Richard Feynman

SamF

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#677295 26-Aug-2012 21:22

I think the key is to simply wait for DLM to put you on DLM-1. There have been some people with pretty horrific lines on DLM-1 so I think most of us will get there eventually. I reckon DLM wasn't working correctly for the last few weeks and has only just started functioning properly again last week.

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Instinct

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#677819 27-Aug-2012 21:03

SamF: I think the key is to simply wait for DLM to put you on DLM-1. There have been some people with pretty horrific lines on DLM-1 so I think most of us will get there eventually. I reckon DLM wasn't working correctly for the last few weeks and has only just started functioning properly again last week.

I had DLM-1 for about 4 days. Now I'm back at 8ms :-(

Anyway, I've been playing around with the SNR and after having a stable a connection for a while after takin the SNR down to 8. I decided to take it down to 6 today... within a few hours the Fritzbox took it down to 5! It will be interesting to see what happens after a few days...

stevehodge

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#677849 27-Aug-2012 21:54

Instinct: I had DLM-1 for about 4 days. Now I'm back at 8ms :-(

Mine's dropped back to DLM-2 this morning. Seems odd given that it has been rock solid for well over a month on DLM-1. Now that I'm on DLM-2 I am seeing almost no CRC errors (down from as many as 700 per hour on DLM-1).

Anyway, I've been playing around with the SNR and after having a stable a connection for a while after takin the SNR down to 8. I decided to take it down to 6 today... within a few hours the Fritzbox took it down to 5!

You mean you set the SNR margin target to 6db and after a few hours the Fritz!box reported a SNR margin of 5db. Perhaps there was some noise on the line.

It'd be good to try to be precise about the terms to minimize confusion, especially since the Fritz!box interface isn't clear. The number reported on the DSL tab and in the graph on the statistics tab is measured SNR margin. The graph on the spectrum tab shows the measured SNR. The value you set is the SNR margin target.

SamF

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#677899 27-Aug-2012 23:50

stevehodge: Mine's dropped back to DLM-2 this morning. Seems odd given that it has been rock solid for well over a month on DLM-1. Now that I'm on DLM-2 I am seeing almost no CRC errors (down from as many as 700 per hour on DLM-1).

Interesting! This supports my theory that DLM hasn't been functioning for a lot of people recently. Either that or there has been some changes in the DLM thresholds.

SamF

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#679561 31-Aug-2012 07:59

I'm getting some weird / inconsistent error spikes at the moment:

Not quite sure what's going on there!! Also, considering I was away yesterday and therefore there was little to no traffic until 5pm, there were quite a few errors before that for the amount of traffic throughput!

If I don't get a favorable DLM profile change tomorrow morning (it'll be 7 days since my last sync), I'm going to try some SNR tweaks to decrease my sync rate slightly as there seems to be a narrow threshold that if I go over I get a heap of errors.

_Allan

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#679569 31-Aug-2012 08:32

Sam,
184 errors in one hour are certainly more than what you appear to experience during other parts of the day?
As for the timing, I can confirm that most of my unrecoverable errors occur when I am not using the system. I have the impression these errors occur from forces outside the home environment.

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sidefx

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#679580 31-Aug-2012 09:05

I would still be very interested to know what is considered an "acceptable" error rate for DLM to *upgrade* the profile. We've seen people with very high error rates on DLM 1 but all that means is that DLM requires very high error rates before *downgrading* the profile. Also interested to know if it's only CRC errors or also FEC errors that make a difference.

It seems it requires a very low error rate before it will *upgrade* the DLM profile. I've had a very consistent CRC error rate of 0.14 per minute and yesterday was 12 days without a single resync and still on DLM3. So I decided to put SNRM down a bit (Just using the stability settings in the fritzbox - I haven't touched SNRM before now) and that has now dropped the CRC error rate to ~0.1 so will leave it on that for a few days and see...

"I was born not knowing and have had only a little time to change that here and there." | Octopus Energy | Sharesies
- Richard Feynman