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Author Topic: Bitswapping  (Read 36335 times)

kitz

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Re: Bitswapping
« Reply #30 on: June 02, 2012, 10:39:45 AM »

But Kitz how many bitswaps to u get in a day or an hour or minute?

A fair few....  I dont have any way of measuring, other than monitoring via DMT tool and the bit swap notification that flashes up.
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kezzaman

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Re: Bitswapping
« Reply #31 on: June 02, 2012, 11:33:04 AM »

The other day i had 720 downstream and..... (drum roll).... 2880 upstream bitswaps in 1 hour...

Thats seems like a ridiculous amount to me.

Other days about 500 downstream per hour and 0 upstream.

and on occassions with bitswap disabled im still getting upstream bitswaps, at a similar rate of 2880 per hour. Its usually either that or zero.

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snadge

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Re: Bitswapping
« Reply #32 on: June 02, 2012, 12:25:52 PM »

upstream is on lower frequencies which attenuate less, they are strognger and less susceptible to noise unlike the higher frequencies - so it would seem odd that your having so many bit-swaps in upstream... infact (i may be wrong) but as upstream is such a small amoutn of total bandwidth sitting on the strong part of the spectrum there should ZERO (or very little bit swapping) - this to me would indicate a problem you have on your line thats causing massive amounts of noise on the low end... the upstream doesnt carry many bits too start with and your having almost 3000 swaps per hour??? sounds like a fault/problem to me

can you post up you connection stats and SNR/BitSwap/QLN/Hlog graphs using our graphing scripts (assuming you have a compatible netgear) - if not, but you can use DMT Tool, I could graph them out for you if you hand me the logs.. let me know if you can run DMT Tool and will send you the destructions on what to do... you could also post up a screenshot of DMT in the meantime

...just too add, if your getting bit-swaps with it turned off...then it aint really turned off , also, if it were turned off then its likely your connection would just degrade and keep doing so until its unable to sync - bits/tones will become un-usable and will not be recovered because BS is turned off - i think anyway
« Last Edit: June 02, 2012, 12:29:59 PM by snadge »
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kitz

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Re: Bitswapping
« Reply #33 on: June 02, 2012, 01:16:39 PM »

>> he other day i had 720 downstream and..... (drum roll).... 2880 upstream bitswaps in 1 hour...

TBH I really dont know for sure..  but Im unsure if it is excessive. Bitswapping happens so very fast.   Bit swap is one of the first lines of defence in keeping a line stable and therefore I wouldnt be too surprised if a bitswap count far exceeds any error count on some lines on some occasions... I guess it depends on the individual line and the type of noise fluctuation?


Added:-  just found this

Quote

Eventually, depending on the speed of swapping (usually 20-100 swaps per second is a good number), the optimum 19.3 dB will be restored, although standards only mandate an ability to implement 1.25 swaps/second.

However, a vendor's modem can request swaps more frequently and if they are implemented by the other modem, profit from the increased speed of swapping. For 20 - 100 swaps/second, the new bit distribution in our example would be implemented in a couple of seconds without any bit errors or loss of service or additional errors (beyond those that occur for other reasons). This bit swapping process is seamless without errors, and without service interruption or need for retraining.

Even your highest figure is within the 1.25 swaps per second. 


>> infact (i may be wrong) but as upstream is such a small amoutn of total bandwidth sitting on the strong part of the spectrum there should ZERO (or very little bit swapping)

Funny enough I suspect (but cant prove) that most of my bitswap occurs on my upstream - as my upstream SNRM is more variable than my down.
 
It would only take tiny fluctuations of SNR for bitswap to kick in, and if you have a few subchannels that constantly fluctuate (rather than a specific noise burst) it could materialise as lots of bitswaps but show no CRC or more serious type errors.

>> if your getting bit-swaps with it turned off...then it aint really turned off , also, if it were turned off then its likely your connection would just degrade and keep doing so until its unable to sync - bits/tones will become un-usable and will not be recovered because BS is turned off - i think anyway

Totally agree.


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

Edited to add.

Dont know enough about this..  and Im out of time now and have to go out.
but a thought just occurred..  no doubt someone will correct me if Im wrong, but from scanning the link, its possible that low level cross talk could be causing the bitswapping?

This all be moot anyhow.

« Last Edit: June 02, 2012, 01:31:07 PM by kitz »
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kezzaman

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Re: Bitswapping
« Reply #34 on: June 02, 2012, 04:53:34 PM »

This is my SNRM with the bitswapping stoppping at 05:44 after i disable it with command - adsl configure --bitswap off



When i disable bitswapping it will only sometimes stop bitswapping on the upstream like i said before, but it always stops on the downstream.

Snadge i struggled to get those graphing scripts to work, the reason why i got them was to record a bitswap graph but i worked it out manually, i get approx 48 bitswaps per minute or none at all on upstream.

Heres my stats, 1st image is 2 mins after a reboot the 2nd is 4 hours (bitswap disabled):



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burakkucat

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Re: Bitswapping
« Reply #35 on: June 02, 2012, 06:50:23 PM »

Just a sudden thought.

The US frequencies are lower than those of DS. In other words, they are somewhat "closer" to the very low frequencies used by the human voice. Could a substandard (or failing) micro-filter / centralised filter / SSFP be responsible? Would a "swap-out" prove to be a useful experiment?  :-\
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Blackeagle

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Re: Bitswapping
« Reply #36 on: June 02, 2012, 09:15:29 PM »

Just a sudden thought.

The US frequencies are lower than those of DS. In other words, they are somewhat "closer" to the very low frequencies used by the human voice. Could a substandard (or failing) micro-filter / centralised filter / SSFP be responsible? Would a "swap-out" prove to be a useful experiment?  :-\

Wouldn't that only apply though if the bitswapping was occuring when the 'phone was in use ? You can use an ADSL(2/+) modem/router on a line without a filter as long as you don't want to use a phone on it too.
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burakkucat

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Re: Bitswapping
« Reply #37 on: June 03, 2012, 12:42:15 AM »

Wouldn't that only apply though if the bitswapping was occuring when the 'phone was in use ? You can use an ADSL(2/+) modem/router on a line without a filter as long as you don't want to use a phone on it too.

Well, yes, that is utterly true. Including VDSL2. After all, the "filter" (whatever sort it may be) is only in series with the telephony connection.

Hmm . . . But what if the passive components of the filter are "breaking down"?  ???
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kezzaman

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Re: Bitswapping
« Reply #38 on: June 03, 2012, 06:46:56 AM »




Added:-  just found this

Quote

Eventually, depending on the speed of swapping (usually 20-100 swaps per second is a good number), the optimum 19.3 dB will be restored, although standards only mandate an ability to implement 1.25 swaps/second.

However, a vendor's modem can request swaps more frequently and if they are implemented by the other modem, profit from the increased speed of swapping. For 20 - 100 swaps/second, the new bit distribution in our example would be implemented in a couple of seconds without any bit errors or loss of service or additional errors (beyond those that occur for other reasons). This bit swapping process is seamless without errors, and without service interruption or need for retraining.

Even your highest figure is within the 1.25 swaps per second. 


I was thinking about this 1.25 per second figure, do you think they might have just been talking about Downstream with its 478 Bins because it did mention 19.3dB which im guessing is output power?

So what if it depends how many bins are in use for calculating whats a reasonable amount of bitswaps per second...
I am just guessing but if what im thinking is true, then by dividing 1.25 by 478 we can work ot how many bitswaps per second per bin is acceptable and then multiply that by the number of bins in the upstream (25) we can compare it to my bitswap per second.

1.25 / 478 x 25 = 0.065 Bitswaps per second

and im getting approximately 0.8 bitswaps per second

Obviously all this could be irrelevant if my theory about number of bins mattering, but its just something i thought about.
« Last Edit: June 03, 2012, 11:13:18 AM by kezzaman »
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kezzaman

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Re: Bitswapping
« Reply #39 on: June 06, 2012, 04:02:14 PM »

its possible that low level cross talk could be causing the bitswapping?

Say if it is crosstalk what show i do next?
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GigabitEthernet

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Re: Bitswapping
« Reply #40 on: June 06, 2012, 04:26:30 PM »

Did you get disconnected as the DS connection rate (19695 Kbps) is higher in the first picture than the second (19563 Kbps).
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snadge

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Re: Bitswapping
« Reply #41 on: June 06, 2012, 04:42:30 PM »

Did you get disconnected as the DS connection rate (19695 Kbps) is higher in the first picture than the second (19563 Kbps).

those differences dont mean anything really...its never exactly the same each re-sync, had it been several hundred KB's or MB's then there may be cause for concern,

does the bit-swapping affect the actual upload throughput? have you tried upload testing? you should get about 0.8Mbps with a 1050k sync (I get 0.9Mbps with 1170k sync)

I dunno what problems you have with the graphs.. if you followed the instructions and installed the folder too the root of the C: Drive (not D or any other letter) then the scripts should work , well, if your using a netgear and login is admin/password
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kezzaman

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Re: Bitswapping
« Reply #42 on: June 06, 2012, 04:54:02 PM »

>>> Did you get disconnected as the DS connection rate (19695 Kbps) is higher in the first picture than the second (19563 Kbps).

No.

>>> does the bit-swapping affect the actual upload throughput? have you tried upload testing? you should get about 0.8Mbps with a 1050k sync (I get 0.9Mbps with 1170k sync)

No i get about 0.84 which is about right.


I could proberly get ur graphs to work if i went back and followed the instructions properly, but what information are you hoping to get from it?
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snadge

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Re: Bitswapping
« Reply #43 on: June 06, 2012, 04:59:28 PM »

the QLN graph may show something (Quiet Line Noise - Router Stats and DMT dont graph these important stats)

it may show something happening on low end which may tie in with the over actiove bitswapping on your low end
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kezzaman

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Re: Bitswapping
« Reply #44 on: June 07, 2012, 10:30:07 AM »

I followed the instructions for using those graphs.

The graphs appeared in the current stats folder but they dont seem to be plotting anything, i ran the start log the cmd script ran but after that the graphs stayed blank. I dont know what im doing wrong...

My router is netgear dg834gt.

(the folder is in my C: drive folder.
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