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Standard User aspiers
(newbie) Wed 09-Feb-11 13:05:21
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time between ADSL drops always a multiple of 60 seconds


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Hi all,

Here's a really odd problem...

First, I should provide a bit of background. In November I reluctantly switched from Zen ADSL to Orange LLU, because here on the infamous LNPOP (Poplar) exchange any non-LLU speeds seem pretty much guaranteed to be dismally slow. (Whether that changes when FTTC finally arrives here next month remains to be seen ...)

From November to mid-January, the line was pretty stable albeit operating around 2-3Mbps, far below the estimated speed of 9Mbps provided during the sales process. However a few weeks ago, the line started dropping extremely frequently: sometimes up to 50 times a day, other times not even once a day.

I have both my Draytek VG2820n and Netgear N150 routers configured to send syslog messages to my desktop machine, so I have a precise record of when the line drops occurred. When I started doing some analysis on the last few days of drops, I noticed that the duration between drops was virtually always an almost exact multiple of 60 seconds. For example, in the last 2 days alone, the duration between drops was 660 seconds (plus/minus one or two seconds at most) on 21 occasions, it was 600 seconds on 17 occasions, 240 seconds on 12 occasions, 360 seconds on 8 occasions and so on.

This seems very peculiar to me, and I am wondering if it could provide a clue as to the cause of the drops. Surely these almost exact multiples of 60 seconds indicate that each drop is somehow correlated to the next, which would be impossible if the drops were simply caused by a faulty connection somewhere? It's also interesting to note that prior to the last few days, this pattern doesn't seem to occur, so maybe it's a new type of fault.

I'd love to know if anyone has ever seen anything like this before.

Thanks,
Adam
Administrator MrSaffron
(staff) Wed 09-Feb-11 13:09:30
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Re: time between ADSL drops always a multiple of 60 seconds


[re: aspiers] [link to this post]
 
Or could simply be some code in the routers doing the following:

Start timer at 0 i.e. first time we resynced
8 seconds in oops some errors, correct them if we can (interleaving)
No errors for a few seconds
More errors
No errors
60 seconds have passed, how many errors in the last minute? Mmm a lot lets resync to try and resolve the issue

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User aspiers
(newbie) Wed 09-Feb-11 13:17:28
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Re: time between ADSL drops always a multiple of 60 seconds


[re: MrSaffron] [link to this post]
 
That had occurred to me, but how would it explain that for instance sometimes exactly 4 minutes pass between drops, and other times exactly 38 or even 55 minutes? If what you're proposing is the case, wouldn't it be more likely that there would be a fixed length between drops?


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Standard User BatBoy
(legend) Wed 09-Feb-11 13:20:20
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Re: time between ADSL drops always a multiple of 60 seconds


[re: aspiers] [link to this post]
 
Why is it dropping - noise?



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Administrator MrSaffron
(staff) Wed 09-Feb-11 13:23:29
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Re: time between ADSL drops always a multiple of 60 seconds


[re: aspiers] [link to this post]
 
Because it might repeat that cycle every minute, and that the noise itself may be down to some device on a timer, or as regular as a train passing near by

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User aspiers
(newbie) Wed 09-Feb-11 13:33:15
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Re: time between ADSL drops always a multiple of 60 seconds


[re: MrSaffron] [link to this post]
 
Sadly no trains in this country are that predictable! What kind of device did you have in mind? I do not have any other devices connected to the phone circuit in my flat.

I think your suggestion of a repeated cycle in the router (or the DSLAM at the other end?) makes the most sense - in which case, wouldn't that make noise the most likely cause? i.e. noise which only sometimes exceeds the threshold that the router is willing to tolerate? If the drop was being triggered from the exchange side, presumably I would have noticed the same pattern when using my Vigor router - but I haven't.
Standard User aspiers
(newbie) Wed 09-Feb-11 13:34:29
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Re: time between ADSL drops always a multiple of 60 seconds


[re: BatBoy] [link to this post]
 
That's what I'm trying to figure out! I have a fault raised with Orange but despite occasionally getting through to a good person on the fault management team, they've achieved zero progress in several weeks.
Administrator MrSaffron
(staff) Wed 09-Feb-11 13:39:47
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Re: time between ADSL drops always a multiple of 60 seconds


[re: aspiers] [link to this post]
 
Anything that creates noise that can be picked up by an AM radio can potentially cause problems with ADSL

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User aspiers
(newbie) Wed 09-Feb-11 13:45:35
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Re: time between ADSL drops always a multiple of 60 seconds


[re: MrSaffron] [link to this post]
 
So I heard, I also saw http://www.kitz.co.uk/adsl/rein.htm but I don't have a portable AM/MW radio. Any recommendations for a cheap one which would serve well for this purpose?
Standard User BatBoy
(legend) Wed 09-Feb-11 13:47:17
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Re: time between ADSL drops always a multiple of 60 seconds


[re: aspiers] [link to this post]
 
Monitor using Routerstats or DMT.



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