Grant Parnell was once rumoured to have said:
> On Sat, 5 Jan 2002, James wrote:
> 
>> Is there any good beginners documentation on doing this? Can someone advise 
>> me on what is the best setup, coax them together, ethernet or what? A Hub? Do 
>> I need a static IP? Is it best to have a static IP? I will be using my ISDN 
>> as a dialup anyway to avoid $700/month charges for an always on permanent 
>> ISDN connection.
> 
> If your ISP is not Telstra, have a chat to them about doing Data Over
> Voice (DOV) with your ISDN. You need to connect the ISDN directly to an
> ISDN card to do this though++, which can also save you the cost of an NTU
> (Network Terminating Unit). Doing DOV means you can connect all day
> (possibly all week) for the cost of 2 local calls (1 for each of 64K).

You MUST have an NTU.  ISDN comes out of your phone socket at
line-voltage, not at logic level.  NTUs fix that.

OnRamp home highway will provide you with a "NT1-Plus" NTU, which is a
smart-NTU which features data capabilities as well as ISDN->PSTN
bridges internally so you can use ordinary phones with it.

You connect the RJ45 SBUS port off the back of the NT1-Plus to your
ISDN card or BRI interface on your router.

If you don't plan to use voice at all on the line, check to see if you
can get a standard NT1 at lesser cost against the NT1-Plus.

Furthermore, DoV is a pure hack.  It works by tweaking bits of the
packet headers.  If a place can receive a ISDN data call, and is
configured to accept voice calls, it almost certainly will work with
DoV.  YMMV.  Checking with your ISP isn't a bad idea as to wether
their hardware can recieve DoV calls.  Also note that, DoV is not
guaranteed to work at all - DoV calls get Voice prioritization over
the switches, which can result in routing over lower-quality lines.

You do NOT need an ISDN card in a PC to do DoV - you just need
hardware that can use the hack.  PCs typically can if their drivers
have the support, but Cisco Access Routers with the right IOS software
can also perform this trick.

Also, do NOT count on your calls being connected fulltime.  Telstra
dumps OnRamp HH calls after 24 hours connected.  I wrote a tiny little
daemon, ijolt, to keep a 64Kbps connection open at all times to work
around this problem.  If/When I get MPPP working with the access
server we dial into, I will add MPPP capibilities to ijolt.  At this
point, this is highly unlikely as I'm in the process of prepping a
FreeBSD box to take over (since our problems seem to exist in the
disgustingly hackish manner in which multilink ppp is implemented in
linux 2.2) [for the interested, and experienced, our problem is
between a Traverse NetJet-S on a linux 2.2.19 box connecting to a Bay
Networks RAC8000 - the RAC8000 rejects the additional sessions due to
a failure to negotiate MPPP correctly.]

<plug>
  ijolt can be downloaded from http://kitsumi.cowspiracy.org/ijolt.tgz
</plug>

Seriously, if you want a fulltime Multilink PPP connection, buy a
cheap Cisco, or don't use Linux until somebody finally fixes
isdn4linux properly.

C.
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