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Author Topic: Bit Swapping ?!?!?!?!?!?!?  (Read 7454 times)

GunJack

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Bit Swapping ?!?!?!?!?!?!?
« on: December 23, 2010, 03:00:33 PM »

Guys,

am I being thick here, or is bit swapping only supposed to happen if & when it's required ??

The history of this:-

was on tiscali LLU (i know, I know, but they weren't too bad for me) on ADSL Max, and never had bitswapping ever - don't think it was enabled on their DSLAM. Have since been migrated over to the TT MSAN and ADSL2+, and ever since then my connection's been nice and fast and stable, with bit swapping pretty much constantly......

...until around 21:00 hrs last night, when not a single bit swap has happened right through to now (and still going without). No issues with the connection, snrm still nice and low (5dB :) ).

Now, my understanding was that bit swapping only happened if the noise conditions affected some tones, and then the bitswap compensated for that. If that's the case, does this mean that my line is stable enough not to need to swap, and will remain like this until the need arises??  Does that mean I can try tweaking my snrm down a touch more (greedy, I know ;) ) and the line should hold?

any thoughts anyone ???
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roseway

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #1 on: December 23, 2010, 04:01:24 PM »

All I know about bit swapping is here.
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  Eric

GunJack

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #2 on: December 23, 2010, 05:22:05 PM »

yeah, thanx eric, I had read that on several occasions, but it implies that any noise burst would be enough to resync the line if the bit swapping didn't happen, hence my reasoning that my line just hasn't needed it since 9pm last night or it would have resynced......confused? I am......
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GunJack

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #3 on: December 30, 2010, 09:11:14 AM »

After re-syncing and connecting to a different backhaul point, I get swapping again. Looks like it was just the node that I was connected to having a hissy-fit...oh well, the vagarities of ADSL2+....
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roseway

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #4 on: December 30, 2010, 09:54:34 AM »

Sorry that we weren't able to make any better suggestions, but it looks as though your conclusion is probably right.
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  Eric

geep

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #5 on: December 30, 2010, 12:19:14 PM »

I've been monitoring my line for almost 2 years now. I've noticed periods of several days when there is a lot of bit swapping, and other periods when there is almost none. I monitor the bit loading every 10 minutes.

It would be (slightly) interesting to know if there's any correlation with events like weather, sunspots, pressure, FTSE,
exchange rate, phase of moon etc., but life's just too short.

Cheers,
Peter
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kitz

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #6 on: December 30, 2010, 08:48:30 PM »

The bit swapping process only happens when needed.. ... when the SNR in a certain tone(s) falls too low.

Yes it can be turned off at the MSAN (or some routers), but not recommended as it will affect your stability and sync speed.
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GunJack

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #7 on: December 30, 2010, 09:17:34 PM »

Must admit I'm not complaining - on my best ever sync/snrm and it's very stable. High of 5.3dB daytime, low of 2.7dB nighttime :)  Current performance is....

[attachment deleted by admin]
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renluop

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #8 on: December 31, 2010, 05:24:58 PM »

Quote
backhaul point

Senior ignorance evident again: I'm ignorant of what backhaul is :o
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waltergmw

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #9 on: December 31, 2010, 06:34:59 PM »

Backhaul usually refers to the link from the exchange MSAN or DSLAM back to a Point of Presence,
or possibly where a Communications Provider connects to the Internet, but see here:-

http://www.kitz.co.uk/adsl/telephone_exchange.htm

http://www.kitz.co.uk/adsl/equip2.htm

http://www.kitz.co.uk/adsl/21cn_network.htm

Kind regards,
Walter
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renluop

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #10 on: January 02, 2011, 12:46:06 PM »

Thanks for the links. I think the old mind has taken in some of it (at my level :))

While I'm here



to all
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jeffbb

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Re: Bit Swapping ?!?!?!?!?!?!?
« Reply #11 on: January 08, 2011, 04:12:42 PM »

Hi

I had some bit swapping problems . I was using a netgear dg834gt . On reboot it would carry out bit swapping as normal but after some time it would not show any bit swaps , it is quite normal on quiet lines to have periods of very low rate of bit swapping . In this case however if it stopped It would not restart . The only way was to telnet and switch it back on. It would then run for some time then again would stop . Funnily it did not seem to make any difference to the performance . I took several prints of the bits / tone graphs and confirmed there was no difference between them. . I swapped to my Netgear dg834G v4 and have had no repeat of the problem ,just the normal fluctuations in the rate of bit swapping sometimes none for minutes at a time ,normally when its quiet (snr margin at its best). As I understand it the modem initiates the request for bitswapping (??) . If that is the case then it seems that my netgear 834  GT had some problem , not initiating the request.
Have you swapped routers ?
Regards Jeff

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