🚀 go-pugleaf

Greg Jarman (amigo@Deakin.Edu.Au) wrote:
: Which ISDN cards does linux support, if any?
: Can I simply run PPP via isdn?

Here's my experience..

I get asked two or three times a week about using my experience using Linux 
with ISDN internet connectivity, so here's a standard answer that I hope 
answers your questions..

There are two different basic types of boxes that you could use for 
making a network connection over ISDN.  These boxes can be used to 
connect just about anything so this information isn't particularly Linux 
specific.  There are some PC ISDN cards (the DataFire, ISDN-Tek, 
WaveRunner) geared toward DOS/Windows/Novell environments, but I don't 
know of any Linux support for them although I wouldn't put it past 
somebody to be working on it right now.

There are several different external ISDN adaptors (Adtran ISU128, Quick
Access Remote, Motorola's new series) which are all basically similar in
that they function very similarly to a modem.. they connect to the BRI at
the wall and then offer RS232/RS530 or V.35 connections to your machine. 
PC V.35 cards are available (though several hundred dollars) but I don't
know of any V.35 support under Linux.  V.35 would allow fast synchronous
transfer between the PC and the adaptor.. instead you'll have to use a
serial port.. a 16550A can run at 115kbps for an ISDN link that has been
made at 64K (if the adaptor supports translating the sync 64K on the ISDN
to the async 115K DTE) or an async 115kbps ISDN link.  Just run pppd or
dip on top of that.. just like a modem (they even use the AT command set). 
This isn't an optimal solution but these boxes are pretty affordable (the
Adtran ISU128 does dual channel bonding and offers RS232/530/V.35 for
around $700 or so). 

The best solution (if you can afford it) would be an ISDN router.. the
cheapest entries in this area are along the lines of the Ascend Pipeline
50 (talk to ascend.com) which routes or bridges between an ethernet
segment and the ISDN.  The p50 can make two separate connections (64K
each) or one combined connection (128K), has profiles and routing for a
few different possible remote connections, Stac data stream compression,
and some packet filtering.  It sells for around $1300.. Ascend has other
routers with more complex abilities at correspondingly higher prices. 
I've heard about a box made by Gandalf (no contact information) which does
about the same things for $800-$1000 but couldn't recommend it.  While 
the router solution is easy and flexible, there's no real clear standards 
and there's no guarantee of compatibility except within a single product 
line.  Check into it before you buy.

I use Southwestern Bell's National ISDN-1 service (available in Austin 
since June 1994, now available in Dallas, Houston, and supposively most 
of the rest of the state in 1996) which provides two usable 64K channels 
in a single "BRI".  Calls within your local area (the same ones used here 
for voice calls) are completely unmetered and available at a flat cost of 
$70 per month ($15 of which is taxes).  Internet connectivity over ISDN 
has become common in Austin for approximately $250/month for a dedicated 
128kbps connection and cheaper ISDN-on-demand services (only put up the 
link when packets actually need to be transmitted since channels can be 
opened and closed very quickly).

Except for the first few shaky months of ISDN while Southwestern Bell 
worked out the bugs, I've had a very good experience with it.. it's 
very reliable and (at least with flat rate pricing here) affordable 
connectivity for those who need more than a modem but don't want to pay 
leased line or T1 costs. Your mileage may very.  Totally my opinions.

kevin
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