VDSL Performance & Tuning

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41 posts

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#675476 22-Aug-2012 13:43

SamF: Speedtest is still the best for general throughput. But the main thing is to watch for disconnections or high CRC error rates.

Speedtest was 28.8 last night was 23.8 ish before making the change. CRC errors are not as high as those in an earlier post. I'll keep an eye on it.

I'm guessing though, that there are not too many services capable of sending out data at the high rates we are testing. I'm not aware of any HD TV streaming services, etc in NZ.

sidefx

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#675484 22-Aug-2012 14:11

If you want to get near that max that speedtest is showing with a "real" application, try a recent ubuntu torrent.

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SamF

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#675543 22-Aug-2012 17:00

WOW!! Got a resync yesterday morning and things are a bit different!

Still on DLM-2, my sync is up by 0.5mbit, receive bitswap is on - none of this is unusual - I've seen this combination before, HOWEVER, my CRC errors are through the ROOF!! 8 / min or around 500 per hour!!

I have NO idea why there has been such a radical change all of a sudden! Good news of course is that DLM is actually working. Maybe I'll leave it and see what happens after a week...

sidefx

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#675628 22-Aug-2012 20:22

@SamF: Good to know, though sounds like a bit of a double edged sword if the only thing that's changed is CRC errors are way up :P

Fingers crossed I see some sort of change in the next couple of days. My CRCs have dropped further and now hovering at 0.13 per minute. If no change soon I'm gonna start playing with SNR tweaking! Been dying to but haven't wanted to mess up potential DLM changes lol.

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jjnz1

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#675636 22-Aug-2012 20:34

Since changing my SNR to 6, my fritz box has done something very weird... take a look...
My SNR has automatically dropped to 2, and my unrecoverable errors have gone from 5050 per hour to 160.

Speeds still the same. Latency now 8ms which suits me fine.

SamF

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#675637 22-Aug-2012 20:37

Hah! Who'da thunk it!? Which DLM Profile were you on before?

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#675640 22-Aug-2012 20:44

SamF: Hah! Who'da thunk it!?? Which DLM Profile were you on before?

1ms, so DLM-1 I guess.

SamF

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#675643 22-Aug-2012 20:52

Geez, with 5000+ errors per hour!!??

sidefx

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#675645 22-Aug-2012 20:58

I'm guessing he didn't have 5000 per hour before SNR tweaking :P

(EDIT: And his previous screenshot confirms that... a whole bunch of zeros on the Unrecoverable Errors graph... hmmm now I'm just tempted to put the SNRM up to see if I can get errors low enough that DLM will drop back down to DLM2. Still not clear if it's just a function of errors or what else affects it though?)

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sidefx

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#675686 22-Aug-2012 21:57

A bit of reading on DLM documentation, mainly from ISPs in other countries, seems to indicate that DLM is purely a function of MTBE and MTBR... Still not sure what acceptable values for either would be though or how they're weighted. Anybody have any ideas??

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SamF

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#675695 22-Aug-2012 22:04

Yeah, that's what I've read as well. No ideas how they're weighted, but I've seen examples of perfectly stable lines on DLM-1 with up to 3 CRC errors per minute (or 180/hr).

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#675773 23-Aug-2012 08:12

Instinct:
SamF: Speedtest is still the best for general throughput. But the main thing is to watch for disconnections or high CRC error rates.

Speedtest was 28.8 last night was 23.8 ish before making the change. CRC errors are not as high as those in an earlier post. I'll keep an eye on it.

I'm guessing though, that there are not too many services capable of sending out data at the high rates we are testing. I'm not aware of any HD TV streaming services, etc in NZ.

Quickflix streams 720p, but only with a Sony Blu-ray player. Otherwise only SD.

David.

sidefx

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#675809 23-Aug-2012 09:23

I think I read somewhere that 1080p on youtube only needs somethign like 4mbps. And depending on what they mean mean by "1080p\HD" most streaming services still only need up to around 8 mbit (so they recommend 10mbit) So if you mainly want to watch streaming content and only have one client (or maybe even 2) then a decent ADSL2+ is probably fine.

The advantage as I see it of VDSL is that huge increase in upload and it shines when downloading large files (steam, ftp, torrents, etc) from a decent source.

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Instinct

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Geek
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#676061 23-Aug-2012 17:35

Just checked and I'm sure the CRC errors are down. I'm now set at -40 with a SNR displaying at 8.

I'm wondering if the Fritz is doing other things inside to 'tune' the connection as last night there were several hundred CRC errors in a hour an dnow I'm down to around 8 in 15 minutes..

stevehodge

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#676070 23-Aug-2012 18:00

Instinct: Just checked and I'm sure the CRC errors are down. I'm now set at -40 with a SNR displaying at 8.

I'm wondering if the Fritz is doing other things inside to 'tune' the connection as last night there were several hundred CRC errors in a hour an dnow I'm down to around 8 in 15 minutes..

I think it's more likely to be other traffic on adjacent lines that causes bursts of errors. So long as your connection is stable I wouldn't worry too much. My connection has been rock solid with as many as 100 CRC errors per 15 minutes and DLM has not downgraded my configuration (it's still DLM-1).

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