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**Klunk** · #25 July 4th 08, 08:52 PM posted to uk.telecom.broadband

On Fri, 04 Jul 2008 17:46:07 +0100, Alec passed an empty day by writing:

If your noise level changes at about sunset or sunrise this could be
related to radio interference and may be worst in the evening. Remember
adsl works on similar frequencies.

Remember the medium wave radio stations which were great in the evening,
well these are just the ones you do not want on your broadband line.
Would be worst on an overhead line.

Alec

"Invalid" wrote in message
...
In message ,
writes

On 3-Jul-2008, "Mortimer" wrote:

It can take up to 5 days to recover.

Which is precisely the point that the OP was making: it takes a long
time
to
recover from a brief period of noise.

Exactly, I'm the original poster, and find it takes a few days to
recover from a short burst of noise, even though my router log shows a
consistent 15.5db SNR.
I'm with Zen, and although well regarded, they cannot fully fill the
pipe, but that is the "up to" fact of life that we
all suffer from.
What tee's me off is how long it takes to recover.
Only solution I've found, which helps a little is to swap Draytek and
BT modems. This seems to force two retrains, the second when I put the
original one back again.
After a few hours, to several days later sync rate drops again.
I suspect that BT is deliberately using conservative settings so that
connections are slower and disadvantaged against their own product.
My modem is next to the BT NTE5, no
extension phones or wiring, in an
electrically quiet area, quality filter, and no SNR change when I
unplug the
phone. From the router it's CAT5.
This thread seems to be confusing at least three issues.

1)The speed at which the OP's router is currently connected.

2)The speed at which it would reconnect if rebooted

3)The BRAS profile speed.

As I understand it

1) Once the router has connected at a particular speed it will not
change unless it looses sync or is forced to do so by one end or the
other. In that sense ADSL is not dynamically rate adaptive, but does
so in steps. Once the router has lost sync due to a noise burst and
renegotiated a lower speed at reconnection (because the line is still
noisy) its speed will not recover again until another disconnection
occurs. A reboot when the line noise improves should get the speed back
immediately (subject to 2 below). Under these circumstances the router
will resync at 6dB or thereabouts

2) On a resync ADSLMax attempts to connect the line at a target noise
level (SNR) usually 6 dB.That establishes the speed at which it
resync's. If the line has a history of frequent disconnects (more than
10 in a 1 hour period?) the BT kit will increase the target SNR in
steps to improve the lines stability. Once the SNR has been increased
in this way it apparently takes several days or weeks of stable
running before the target SNR is reduced again. (An ISP can get BT to
change it manually). Under these circumstances the OP's router would
resync at 9, 12 or 15 dB each time it was rebooted.

3) BT set a BRAS speed, the maximum rate at which the ISP sends data.
This is (at least 500k?) lower than the stable rate for the link to
avoid buffering & retransmission in the BT network. This appears to
change every few hours. (daily?) depending on the stable speed of the
line.

I monitor my router using Routerstats (freeware). I am 4 km from the
exchange, all overhead wiring. During the day the SNR sits at 6 plus
or minus and the speed at 6250ish. Just before sunset it rises by 1 or
2dB for a couple of hours. At sunset it drops down to only 1 or 2 dB
and goes back up to 6 or 7dB at sunrise. My router often looses sync
at 11-12 pm when the noise level gets bad, and resyncs at 5800ish. If
it does drop out overnight, I reboot in the morning and it all goes
back to 6250/6dB. A couple of days with no dropout at night and I get a
5500 BRAS. After a couple of noisy nights it drops to 5000.

As I read this post, the OP has something very like my line. Occasional
drops due to noise bursts, but is waiting for another random event or
swapping routers to trigger a resync. The question is what happens if
the OP just reboots after the noise clears. I would expect the speed to
recover.

--
Invalid

Does radio Luxembourg still broadcast on MW? Man, that used to swamp
everything out in the evening!

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