VDSL Performance & Tuning

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#975341 27-Jan-2014 20:10

SamF: So what did your line do after that?

at that point, was the DLM change, and then it went back to normal (noise wise) although synced a hell of alot slower - and i have been stuck with slower than should be expected speeds from that point..

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SamF

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#975343 27-Jan-2014 20:11

Well, congrats everyone, we're now at 200 pages!!

To celebrate, I have some interesting information from a very well informed source inside Chorus! I'll post it very soon!

SamF

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#975344 27-Jan-2014 20:12

hio77:
SamF: So what did your line do after that?

at that point, was the DLM change, and then it went back to normal (noise wise) although synced a hell of alot slower - and i have been stuck with slower than should be expected speeds from that point..

Hmm, so it dropped you from DLM-1? Might have to do a manual reset!!

hio77

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#975345 27-Jan-2014 20:14

SamF:
hio77:
SamF: So what did your line do after that?

at that point, was the DLM change, and then it went back to normal (noise wise) although synced a hell of alot slower - and i have been stuck with slower than should be expected speeds from that point..

Hmm, so it dropped you from DLM-1? Might have to do a manual reset!!

i dont recall if it dropped me or not, ill go back and find out in a bit..

tinkering with vps dedi currently, so console windows EVERYWHERE..

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#975346 27-Jan-2014 20:15

SamF: Well, congrats everyone, we're now at 200 pages!!

To celebrate, I have some interesting information from a very well informed source inside Chorus! I'll post it very soon!

oooo Exciting!

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SamF

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#975357 27-Jan-2014 20:23

So, as mentioned, I have some information from a source at Chorus who describes himself as: "the Layer 2 Access Solution Designer, responsible for access equipment for UFB, DSL, voice, etc. (and the management systems, including the 5530 Network Analyser and DLM)". Based on this, I think we can assume that he knows what he's talking about LOL :D I'm not sure if he wants to be specifically identified so that's all I'll tell you about him for now.

In any case, I asked him to take a look at the main thread post and he generously agreed to do so. After looking at the information, this was his response:

Hey Sam,

I dont have and haven't used a fritzbox, so I've ignore the FB specific stuff.

All in all it's great, nice and detailed! I can see a few minor tweaks around the explanation of items, etc as below.
Feel free to include or not as you feel necessary :)

Let me know if there is anything else you need or any other questions you have!

-------------------------------

Impulse Noise Protection (INP):
Impulse Noise Protection is the number of INP symbols used for the interleaving algorithm.

Signal-to-Noise Ratio Margin (SNRM):
I'm trying to think of another way to explain this, as your explanation seemed slightly confusing.
Perhaps along the lines of - SNR is the difference between what is considered as the 'noise floor' and the signal strength. the closer your signal is to the noise floor, the more likely you are to have errors on your line and therefore, resynchronization to a lower bitrate to maintain the SNR.
This could then be considered and unstable line, resulting in a DLM profile switch.

Carrier Record:
Not sure what this is either. its not a term I've seen used on anything but a Frtizbox...

Line distance to Cabinet
As you know, can be quite inaccurate especially where there are multiples/bridge taps on the line as this affects attenuation, but not the physical line distance between the cabinet/exchange and the house.

Internal Wiring
1)
Not anymore we aren't. for VDSL a centralised splitter install should be considered mandatory. it is now the same price as a standard install ($100 if I remember correctly)
It will also help future proof if other technologies are introduced (i.e VDSL bonding/vectoring, etc) - note this is a personal opinion, don't read into this as Chorus will introduce these things!
Vectoring is, essentially, impossible in an unbundled network :)

2)
I Would still recommend a centralised splitter. it filters out any other noise which could cause issues.

Nice comparison pre and post splitter install! :)

DLM:
"Lines are considered stable if there are no spontaneous resyncs for 48hrs"
It is not only basd on spontaneous resyncs. the 5530 Network Analyser and DLM moitor noise, attenuation, bitswaps, errored seconds, SES, etc, etc to determin line stability.

Increasing Sync Speeds
Might be worth noting that increased errors can result in increased frame loss which can impact TCP performace causing a drop in actual throughput despite an apparent increase in sync rate.
i.e driving the syncrate up with SNR margin tweaks when on DLM-1 (no interleaving) causing errors on the line could impact TCP.
Eventually, DLM will switch you to another profile increasing latency by introducing interleaving.
interleaving also has an associated sync speed drop removing most of the sync speed you tried to obtain by messing wiht the SNR.

Cheers,
x

I also asked him for some more specific information about DLM and how it works, but as I suspected this is commercially sensitive unfortunately, so we're stuck with what we already know on that front!

I also asked him whether he'd be willing to field some questions from people on this thread, and he's going to check with various parties as to whether this would be ok for him to do. In any case, post your questions and I'll start making a list in preparation.

I'll be amending the main post with this new information soon.

Enjoy, and happy 200th page day everyone! :D

hio77

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#975363 27-Jan-2014 20:34

great to hear a chorus guy is interested in giving input here!

iknow this thread seems to be regarded as "too long to bother with" persay.. seems to scare a few off, nothing we can do about that though, its a great thread of history :)

wouldnt be surprised if things are a little sensitive.. but then, ild expect that to be more of the gritty stuff that wouldnt concern us.

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sidefx

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#975387 27-Jan-2014 21:22

Yup, nice one! Good info there. The SNR tweaking warning is interesting and fair enough I guess, but in my experience it's genuinely increased my real throughput without any adverse affects (well other than when I've pushed it too far in the past, of course! :P And I guess that's sort of what he's saying - i.e. push it too far and things *might* go pear shaped)

Hmm now, after a long period of keen interest in VDSL and tweaking my connection I haven't really touched it lately, so while I seem to remember having many questions originally I'm struggling to remember them now, lol.

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SamF

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#975410 27-Jan-2014 21:45

sidefx: Yup, nice one! Good info there. The SNR tweaking warning is interesting and fair enough I guess, but in my experience it's genuinely increased my real throughput without any adverse affects (well other than when I've pushed it too far in the past, of course! :P And I guess that's sort of what he's saying - i.e. push it too far and things *might* go pear shaped)

Yeah, that's how I read it, which is definitely fair warning. I think there are a number of lines out there (mine included) which are not quite good enough for 17a, but still have some decent headroom.

I found his comment on the splitter to be the most interesting; I wasn't aware that the splitter actually filtered on the Internet side!

hio77

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#975411 27-Jan-2014 21:49

SamF:
sidefx: Yup, nice one! Good info there. The SNR tweaking warning is interesting and fair enough I guess, but in my experience it's genuinely increased my real throughput without any adverse affects (well other than when I've pushed it too far in the past, of course! :P And I guess that's sort of what he's saying - i.e. push it too far and things *might* go pear shaped)

Yeah, that's how I read it, which is definitely fair warning. I think there are a number of lines out there (mine included) which are not quite good enough for 17a, but still have some decent headroom.

I found his comment on the splitter to be the most interesting; I wasn't aware that the splitter actually filtered on the Internet side!

i always understood it to be a simple pass-through on the internet side...

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SamF

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#975425 27-Jan-2014 22:34

Apparently not, according to our expert!

BMarquis

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#975565 28-Jan-2014 09:11

SamF: Apparently not, according to our expert!

I have no problem with being identified, I just couldn't commit to a Q&A session (yet) :)

For the splitter install, in the original post I missed this statement:
"and disconnect all other phone jacks"

So if you disconnect everything else, there is no real need for a splitter.

In saying that - if you are going to be running a new cable, why not put a splitter in - it's about future proofing, in case you go back to a phone service provided from the exchange... think PSTN, a Baseband IP service or some kind of emergency disaster recovery situation (although in an emergency you might be less concerned about xDSL stability)

Personally, I'd put one in, because it doesn't cost much and could alleviate ALOT of future pain (for you or the next owners/tenants)

Cheers,
Brent

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#975908 28-Jan-2014 14:22

BMarquis:
SamF: Apparently not, according to our expert!

I have no problem with being identified, I just couldn't commit to a Q&A session (yet) :)

For the splitter install, in the original post I missed this statement:
"and disconnect all other phone jacks"

So if you disconnect everything else, there is no real need for a splitter. In saying that - if you are going to be running a new cable, why not put a splitter in - it's about future proofing, in case you go back to a phone service provided from the exchange... think PSTN, a Baseband IP service or some kind of emergency disaster recovery situation (although in an emergency you might be less concerned about xDSL stability)

Personally, I'd put one in, because it doesn't cost much and could alleviate ALOT of future pain (for you or the next owners/tenants)

Cheers,
Brent

ah! i had my suspicions! welcome to the thread :)

Q&A sounds interesting, i just hope the "make me internet faster", "why did i loose X profile" etc questions dont crop up much for ya. as with anything your always welcome to simply not be able to give an answer, nobody's gonna shoot you down for it! we all know there are probably some things that you just cant say or do.

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SamF

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#975966 28-Jan-2014 15:06

hio77:
Q&A sounds interesting, i just hope the "make me internet faster", "why did i loose X profile" etc questions dont crop up much for ya. as with anything your always welcome to simply not be able to give an answer, nobody's gonna shoot you down for it! we all know there are probably some things that you just cant say or do.

This is why I was thinking I would collate some questions and present something coherent for answers, but now Brent has jumped in, coat and all, well, I can no longer protect him LOL :D

hio77

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#975971 28-Jan-2014 15:07

SamF:
hio77:
Q&A sounds interesting, i just hope the "make me internet faster", "why did i loose X profile" etc questions dont crop up much for ya. as with anything your always welcome to simply not be able to give an answer, nobody's gonna shoot you down for it! we all know there are probably some things that you just cant say or do.

This is why I was thinking I would collate some questions and present something coherent for answers, but now Brent has jumped in, coat and all, well, I can no longer protect him LOL :D

to be fair, most of questions like that simply dont exist in here.. think the thread scares them off ;)

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