VDSL Performance & Tuning

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3712 posts

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#693573 30-Sep-2012 11:45

@stevehodge, that's pretty much what I've observed too. A bit non-intuitive and I have little idea how DSL actually works, but maybe there's a constant low level of communication between modem and DSLAM and the error rate is only measured against that so it will be consistent regardless of usage?

On another note, my error rate has settled back down nicely after switching the target SNRM (Intended signal-to-noise ratio on Line settings page) back to what should be 14. Oddly it's actually stayed at 13db though - it's not unusual for it to drop to 13 during periods of the day in the past but it's now been sitting at 13 constantly since rebooting. Still, nice low error rates I'm just gonna leave it alone now!

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SamF

1578 posts

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#693619 30-Sep-2012 14:21

Looking good sidefx!!

stevehodge

393 posts

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#693650 30-Sep-2012 16:53

sidefx:
On another note, my error rate has settled back down nicely after switching the target SNRM (Intended signal-to-noise ratio on Line settings page) back to what should be 14. Oddly it's actually stayed at 13db though - it's not unusual for it to drop to 13 during periods of the day in the past but it's now been sitting at 13 constantly since rebooting. Still, nice low error rates I'm just gonna leave it alone now!

I wouldn't worry about the SNRM with the errors being so low. I notice you've set the RFI slider down a notch - did you see any difference when you did that?

sidefx

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#693715 30-Sep-2012 19:04

stevehodge:
I notice you've set the RFI slider down a notch - did you see any difference when you did that?

When I initially started tweaking things, I first dropped SNRM down one notch - that changed CRCPM from around 0.15 to 0.1 then I dropped both SNRM and RFI down another notch and that dropped CRCPM to 0.02 which finally seemed to get things moving with DLM changes (may have been coincidence I suppose). But since I changed SNRM and RFI at the same time I'm not sure how much affect SNRM had vs RFI. I sorta suspect it was mostly SNRM but don't want to fiddle too much right now ;-) Maybe in a couple of weeks I'll bump it back up to see.

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

helis

96 posts

Master Geek

#694132 1-Oct-2012 13:05

So figured I'd try a small change

Increased the SNR by 2 instead of 1. Router re synced this morning. No DLM change though. Errors are very low though. I'm technically out of my 10 day phase so will be interesting to see if when it drops to DLM1 if the errors stay in check compared to last time where they were over 1CRCPM.

The FEC errors are also the lowest I have ever seen on my connection.

SamF

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#694500 1-Oct-2012 20:59

Errors are looking good now. The only way to tell what your errors are like on DLM-1 is to actually be on DLM-1 :) You can adjust from there, but I'd say you'd be looking pretty good. My errors jumped from 0.2 to 3 going from DLM-2 to DLM-1, so based on that (possibly approaching worst case as my line has issues I believe) you'd be looking at maybe 0.15, which would be fine on DLM-1 from what I've seen of other's connections.

helis

96 posts

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#694929 2-Oct-2012 16:06

SamF: Errors are looking good now. The only way to tell what your errors are like on DLM-1 is to actually be on DLM-1 :) You can adjust from there, but I'd say you'd be looking pretty good. My errors jumped from 0.2 to 3 going from DLM-2 to DLM-1, so based on that (possibly approaching worst case as my line has issues I believe) you'd be looking at maybe 0.15, which would be fine on DLM-1 from what I've seen of other's connections.

Well on Saturday when I went from DLM-2 to DLM-1 My CRCPM went from 0.08 to 0.95. So Even though I am sitting on 0.02 CRCPM I fear as soon as it moves to DLM-1 in a week or months time that my errors will skyrocket up again. if it happens like that again I will be dropping my SNR back down and just settling for speed over latency until I can get my new cat6 cable in.

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SamF

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#695234 2-Oct-2012 23:22

Hmm, yeah, you'll need to get those errors down if you want to stay on DLM-1.

varix

111 posts

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#695948 4-Oct-2012 09:15

Hi everyone, first post here in a while.
Last night I was connected to Snap VDSL. Was pretty excited about it all as I can see the cabinet out my kitchen window and was hoping for some real awesome speeds.
After reading through here I have learned alot about DLM etc and had no idea of this prior.

Anyways, here are my stats:

I am a little concerned with how slow my upload is. I was hoping for max upload as this was the main reason I moved to VDSL. I am sure you will all tell me that DLM should improve this, thats what I am hoping for anyway.
Also a little strange that Attainable throughput is set to 0 on Send, is this normal?

sidefx

3712 posts

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#695953 4-Oct-2012 09:27

@varix: Welcome! :) Nice Line attenuation there... but yeah that Send current throughput doesn't look good.

Is that about what you're seeing on speedtests?

What does your spectrum graph look like?

Do you have a master splitter installed?

Are you on Naked VDSL or with phone line?

I assume you haven't tweaked the Target SNRM at all? Interesting that it's put you on 9db...

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

varix

111 posts

Master Geek

#695956 4-Oct-2012 09:34

:(

Speedtests are matching my line speeds.

Here is spectrum graph:

I have been told there is a splitter because there is an alarm in the house (we have just moved in and I have had a quick look for it, not 100% sure what I am looking for).

Naked VDSL, no phones plugged in to any jackpoints, have the modem plugged directly into a jackpoint with no filters, and as far as I can tell its in a jackpoint that is closest to the Demarc on the side of the house. Perhaps I should try changing around different jackpoints in the house? If the house has a splitter does it mean DSL is only available on a single jack or can it be multiple, could it result in one jackpoint getting a crappy DSL single and another getting a good signal?

I havent touched any of the tweaks, they are all sitting on the far right.

sidefx

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#695961 4-Oct-2012 10:21

Yes if you have a splitter there will most likely be a specific jackpiont you need to plug the modem into. The master splitter (probably) just looks like a small black box around the size of a cigarette box with 2 wires connected to it from the line coming from the road, then one pair that goes to the modem and the other to the rest of the phone jackpoints in the house (and alarm) - you don't want to plug the modem into any of these.

If you have an ETP somewhere on the outside of your house the splitter might be in there, but the DSL output from it will go to a specific jackpoint

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

varix

111 posts

Master Geek

#695973 4-Oct-2012 10:49

Ok so is it still possible to pick up DSL on a jackpoint that isn't designed to be used for a modem if there is a splitter installed?
There is a jackpoint that looks suspicious as it doesnt match the rest in the house I have just moved the modem to it and it have me an attainable throughput figure of about 3500. But did not increase the performance at all. My attenuation went from 6-7.
I have since moved the modem back to where it was and attenuation went down to 6 but attainable throughput went down to 0 again, very strange.

sidefx

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#695977 4-Oct-2012 11:00

varix: Ok so is it still possible to pick up DSL on a jackpoint that isn't designed to be used for a modem if there is a splitter installed?

Yes certainly, but you then have the modem plugged in with all POTS devices (including alarm) and as I understand it these can (and almost certainly will, especially the alarm) interfere with the DSL signal. Also even having empty jackpoints can cause reflections(? I think this is the term?) which cause issues for DSL. VDSL is very sensitive to this sort of thing (more so than ADSL) so it's very important that you have a master filter and the modem connected to the right "side" of the master filter.

Either that or find the master jackpoint, disconnect all other jackpoints (including alarm) and then have the modem plugged directly into that one single jackpoint which should be connected to nothing other than the line in from the road... this is the route I took and it's seems to have worked out well in the end ;-)

PS: I am essentially just a hobbiest in this area; everything I've learnt in this area is from these forums and DIYing so some of my terminology might be a little off ;-) HTHs though

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

varix

111 posts

Master Geek

#695986 4-Oct-2012 11:08

Man I owe you a lot of beers! It looks like we are making progress potentially.
I cracked open the jackpoint that is closest to the demarc and look what I found:

Im not sure what a splitter looks like but I am guessing this is one, does this mean that if my modem is plugged into this jackpoint then it could be causing issues? Or is this jackpoint the one that the modem should be plugged into because it is on the correct "side"?

You can see there are two cables going back into the wall, my guess is that one of these is from the demarc, and the other is going into the house? In which case, all of the jackpoints, including this one are being filtered?

Easiest fix would be to replace this panel/splitter with a normal BT jack, and only terminate the demarc side cable to the jackpoint? (We dont need any other jackpoints live)

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