DSL modem recommendation

Ted Mittelstaedt tedm at toybox.placo.com
Wed Feb 23 11:23:33 GMT 2005

Hi Mark,

  Well, looks like I was able to bypass that login thingie, here's
the info:





>From the looks of it, they are using standard DMT issue, not G.Lite,
with the Alcatel chipset, VPI/VCI 0/38

This is a really good universal combination.  Many DSL modems will
work fine.  But there's 1 modem that I would strongly recommend
in this instance over any other modem:

Westell C90-36R516-01

Why?  Here's why:

1) These are dumb bridged modems so they aren't interfereing with
your BSD box.

2) Westell has updated firmware and a diagnostic utility that
talks to the modem, and has a secret command key sequence that
will tell all of the good line stats (signal to noise ratio,
received and transmitted power, etc.) which are vital to

3) Since these modems were obsoleted and were used by Bell Atlantic,
there are tons of them on the used market for very cheap.

4) Other ISP's I've talked to have said these things are rock
solid reliable.  I have never had one of them fail in service
for any of our customers either.

5) It has an honest-to-god Alcatel DSL chipset in it, not the
globespan which is becoming more popular (primariarly because
it's cheaper)

Now, note the following: if you have a very spotty DSL line, then
get the following:

Westell B90-36R515

NOT the B90-36R515-01!!!

Why?  Because the 36R515 has a design flaw in it- it massively
overexceeds the transmitted power allowable for DSL - this is
why Bell Atlantic quickly switched over to the -01 model - that
will sometimes allow you to punch though a crummy line and
get a stable connection.  But the downside is it's DSP microcode
is non-upgradable.  You don't want to use it unless you have to.

Now because this is NOT a PPPoA modem, you must run PPP on your
FreeBSD box.  The big advantage is that since your FreeBSD box
is the PPP terminator - not the DSL modem/router - you get a
legal public number on the ppp interface in the BSD box, which
means if you want to set it up as a server your in business.

The only possible problem is that these Westells were sold
only in the US, they take 24 volt AC (NOT DC!) and come with a 24 volt
AC adapter.  But, you can just go to any junk store and buy
a 24 volt UK style AC adapter and cut off the useless US-style
adapter from it's cord and solder the cord onto your adapter.
(or use a voltage converter from 220-to-110)  The adapter is
NOT AUTOSENSING so don't attempt to just plug into UK power
or you will blow the modem up.

The modem isn't particular about 50-60 hertz so no worries
there.  I also don't think you would have a problem with 
the UK/US phone line voltage difference either.

You also will need to change the VPI/VCI setting to 0/38 it
is normally 0/35, westell has a utility for that.

If you are a bit sqeamish about this, then looking at the PIPEX
recommendation page, go for a ZyXEL Prestige 630

STAY AWAY from ANY dsl modem that does NOT have an ethernet
jack on it!!!  Such as the USB speedtouches that Pipex
was handing out for free!!  There's a reason they are free!!
You can't pay people (who know anything) to take them!!!


> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org
> [mailto:owner-freebsd-questions at freebsd.org]On Behalf Of markzero
> Sent: Wednesday, February 23, 2005 1:56 AM
> To: Ted Mittelstaedt
> Cc: freebsd-questions at freebsd.org
> Subject: Re: DSL modem recommendation
> > What is your DSL provider, what telephone company are they using?
> > Are you running bridged or ppp mode DSL?
> > 
> > DSL modems all use proprietary implementations of the DMT protocol,
> > while many will interoperate with different DSL providers and
> > DSLAMS, not all will.
> > 
> > Ted
> Hi Ted, the relevant info:
> ISP: Pipex UK - www.pipex.net
> TelCo: British Telecom
> I am currently connecting to them via PPPoA (I assume this is what
> you're referring to, I'm not as knowledgeable as I'd like to be about
> DSL).
> Cheers,
> Mark
> -- 
> PGP: http://www.darklogik.org/pub/pgp/pgp.txt
> B776 43DC 8A5D EAF9 2126 9A67 A7DA 390F DEFF 9DD1

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