At 22:01 28/02/2001 +1300, Daniel Omundsen wrote:

Thanks for responding :)

>>From what we can figure out so far, in many cases the problem is modems
>losing synchronisation with the network and having to retrain. The theory is
>that this is most likely caused by line noise.
>
>When your neighbor kindly fires up his electric arc welder and puts a
>sustained burst of noise on your line, the ADSL signal is disrupted. In some
>cases this causes the modem to renegotiate the entire connection which takes
>about 30 seconds or so. You can see this happen if you unplug and then
>reconnect your modem.

This is exactly the sort of thing (environmental interference) that I
suggested earlier in the thread could be *one* possible cause of
micro-outages, but I was soundly laughed out of town at the suggestion. I'm
glad to see some validation here, even if its only a theory at this stage.

Given the data rates involved, the nature of telephone lines and the
environment they're in one would have to be crazy not to at least consider
it. I don't know the exact figures but I'd guess there must be frequency
components up to the 10Mhz range or more, and given how long phone lines
are, they'd make rather nice antennas at those frequencies, twisted pair
notwithstanding :) I sometimes wonder about the amount of crosstalk between
close pairs that all have ADSL active - not so much a problem now that it
is still few and far between, but perhaps a problem in the future as it
becomes more common.

>(There is no point debating the rights or wrongs of this implementation by
>the way, it just happens like that. The gear we use in NZ is standard
>off-the-shelf stuff used extensively overseas as well as here. I'd be
>interested in any feedback as to whether users of devices other than Nokia
>see the same thing - Asus, D-Link, Zyxel, Alcatel, Cisco, etc. Do Lucent
>have an ADSL router, Josh? What does it do?)

Perhaps one way to improve the feedback about the problem would be to
describe WHAT information from the modem you're looking for in particular,
and how to get it from the various commonly used ADSL routers.
(Undocumented commands that provide more detailed information, for
instance?) I'm sure that most people on this list would be more than happy
to provide log snippets from their routers if it would help get the
problem(s) solved.

>It doesn't happen to everyone by the way, it is entirely dependant on the
>quality of the line and what noise is present in the neighborhood. For the
>majority of users that are affected it is not a big deal, browsing is
>interrupted for a few seconds and that is all. The only problem is if it
>happens in the middle of a big download and you have to restart. That seems
>rare though - it has only happened three times in the last month at my place
>according to the modem logs, and I have never noticed it while actually
>surfing.

I would respectfully suggest that claiming the majority of users use
jetstream just to web browse, and therefore its not much of an issue to
them is flat wrong. At the moment Jetstream is expensive, and the type of
people that are forking out for it are typically either businesses or
"power users" who are likely to be using it for VPN, ssh, and other
long-life connections just as much or more than web browsing.

I myself use ssh to remotely admin servers a lot and it can be *extremely*
annoying losing connections unexpectedly, I'm forced to either use
something like screen so I can log back in again without what I'm doing
getting killed, or a dialup connection, which I never have any problems
with. This is rediculous. I'm sure theres plenty of other people on this
list in the same boat, and to us, micro-outages might as well be
MAJOR-outages.

It doesn't happen to me too often compared to some of the people on this
list by the sounds of it, but it catches me out often enough to be annoying.

Regards,
Simon

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Received on Thu Mar 1 10:09:27 2001