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Date:      Tue, 19 Mar 96 16:22:14 MET
From:      Greg Lehey <lehey.pad@sni.de>
To:        jkh@time.cdrom.com (Jordan K. Hubbard)
Cc:        hackers@freebsd.org (FreeBSD hackers), isdn@muc.ditec.de (Distribution List; FreeBSD ISDN)
Subject:   Re: ISDN: "modem" or board? (Was: Microsoft "Get ISDN"?)
Message-ID:  <199603191524.QAA18365@nixpbe.pdb.sni.de>
In-Reply-To: <1645.827248160@time.cdrom.com>; from "Jordan K. Hubbard" at Mar 19, 96 7:09 am

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>> > You, uh, would?  64+64 = 128Kb/s using my own calculator! :-)
>>
>> No, that's abusing your calculator.  Async bytes are 10 bits (8 bits,
>> start and stop), whereas sync bytes are 8 bits.  So you'd need at
>
> I know, and with async I get 115.2Kbps not 128K.  I believe that that
> B channels do 64Kbps assuming 8 bits per byte, not 10, so my
> calculator remains unabused.

Watch my lips. A B channel gives you 64,000 bits per second.  When you
add one start bit and one stop bit for every 8 bits, you end up with
80,000 bits.  Bind two such channels together and you have 160,000
bits every second.  Stuff them down a hose which can only take
115,200, and you have 44,800 bits that get lost.  Of course, if you
have a 115,200 connection at the other end, too, you can run it, but
you lose 28% of the bandwidth.

>> Aha.  Yes, you can.  With a card, there is no chat script or login, no
>> more than there is if you connect to a different system via Ethernet.
>
> Well, I still need to dial but I guess I can see where I would not have
> to stick a getty on the board.

Sure.  All you need is the correct entries in inetd.conf.

>> If it does it automatically, you end up paying twice as much for your
>> connection, even if you don't need the bandwidth.  You need some form
>
> Not at all.  Centrex ISDN is what folks like Amancio and I use.

Then it's a question of tarifs.  You mean that you can call from
Milpitas or wherever you are to Concord, and you don't pay any more
for two B channels than for one?

>> You want me to order a couple for you?
>
> I'm not sure it would work here - that's what Teles in the US told
> me when I suggested buying a couple of the German ones, anyway.

They could well be right.  That's one of the reasons why we're waiting
for you to install the stuff :-)  I don't think it would be the
boards, though: they're so primitive that I don't think there would be
anything to change.  My bet is that the CAPI would be different.  That
could pose severe problems for the FreeBSD implementation, at least
until we find out what the differences are.

OBTW, the Teles CAPI is user-friendly: it installs under Windoze,
whatever that might be.  It doesn't use Windoze, it just needs it to
install.  When I told the support line that I thought it an imposition
to have to buy Windoze to install the CAPI, they didn't understand my
problem.

Greg



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