question on DSL signal

Tim Daneliuk tundra at
Mon Feb 4 21:49:17 UTC 2008

David Banning wrote:

e drop-in drop-out problem.
> To any average computer user, these lines might appear normal -
> when a page stops loading for a minute they just live with it, and
> forget about it.
> So here's my question:
> 1. is there anyone who has a lot of experience monitoring DSL lines
>    that can tell me how common this is?

I cannot speak to the frequency of connection loss, but I have seen
huge variability (over months) in *speed* if the premise is
far away/at the limit of the DSL connection distance.  DSL
is quite fussy about the distance between the CPE and the
phone company CO locations.  But "distance" here is logical
or electrical distance - almost always greater than straightline
between the CO and the premsise.  Why?  Because phone company lines
run in raceways (usually underground) that do not take the
shortest path.  Moreover, as construction and other changes
in the neighborhood mandate, trunks are changed, lines spliced,
pairs moved and so on.  So... the "electrical" distance from
CO to premise is typically further than the straight distance.

This constant fiddling with the phone company infrastructure causes
all manner of sins including intermittent electrical noise, disconnection,
modem retraining, and just plain poor signal-to-noise ratio.  And -
in my experience - it can vary all over the place, from as low as 30% to 100%
of claimed channel capacity.

Welcome to DSL - where you are once again at the mercy of the phone company.

> 2. Is there any way to avoid it?

Yes - switch to different fabric.  I live near a large metro area,
and the local cable company finally figured out that there was
money to be made offering their very fast/reliable cable service
to businesses.  For $10/mo *less* than I was paying for
1.5/384 DSL with 8 static IPs, I now get 6.0/1.5 w/5 static IPs
from Comcast.  My only regret is that I could not continue to
do business with Speakeasy, which is hands down the best ISP
I've ever seen.  The Comcast package has thus far (about 4 months)
been flawless.  They have a separate support group for business
customers, they handled my reverse DNS perfectly and promptly,
and - if I remain on the local backbone for testing - the system
actually peaks to over 20Mb/sec.

If you're not too far away from the CO you can try adsl2,
but if your copper is lousy for dsl, it will be lousy for
that as well.

The real answer is to get your ISP to light the fires under
their phone company provider and make them fix their copper
properly.  Good luck with that.  The phone company - at least
in the US - isn't particularly obligated to make DSL work.
They only have to hit some signal-to-noise standard.  After
that, it's up to your DSL provider to make it happen.

> 3. I have used three different DSL modems, but the are all home
>    quality: an Alcatel Speed Touch, a Speedstream 5260,
>    and a Westell Wirespeed. Would spending more money on
>    another type of modem help? If so, what is recommended?

Maybe not more money, but trying different devices can help.
The Broadext modems I used were twice the speed of the old
Speedstreams on the same circuit.  Newer chipsets should be
more noise immune, but they cannot fix lousy copper in
the phone system.

> Any comments would be helpful.

One other thing to check.  There should be a grounding wire
coming off the NID (the box on the side of the building
where the phone co terminates their copper).  The wire is
typically clamped to a stake in the ground.  Make sure that
the wire/stake surfaces are clean, and the clamp is tight
to ensure the best possible earth ground connection.  Once
you cleaned/tightened this, it's not a bad idea to cover it
with grease to keep moisture out.  A small bit of electrical
resistance on an earth ground can translate into very nasty
noise spikes when there is an inductive noise source (like
an electrical motor starting) somewhere near you.

Good luck.  The phone company was built around a voice
model with a 300-3000 Hz bandwidth design criteria.  That's
been vastly improved as the phone backbones went all digital
in the past 40 years, BUT, the "last mile" copper is/was
the last thing to change.  Oddly, even when they build new
buildings (as was the case in my premise), they often don't
do a great job with the copper.

P.S. If all else fails, there's satellite and/or cellular internet.
      However, these are both rather expensive, not that fast,
      and have significant latency problems.  Latency isn't that
      big a deal for data downloads, but it rears its ugly head
      when you want to stream audio/video or any other kind of
      quasi "real time" data.

I feel your pain ;)

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