LinuxSA Mailing list archives

  From: Leigh Hart <hart@dotat.com>
  To  : <linuxsa@linuxsa.org.au>
  Date: Sun, 26 Nov 2000 16:41:39 +1030

Re: ADSL Enabled Exchange Areas: Updated 20/11/2000

G'day Daryl,

Daryl Tester <dt@picknowl.com.au> wrote:
> Mark Newton wrote:
> >
> > If you buy an ISDN card for your Linux box, you can place 64k
> > calls through the NT1 interface which are tagged as "voice"
> > calls (i.e.: 18c).  This effectively gives you a flat rate
> > 36c 128kbps call to ISPs which support it.
> 
> I'm curious about this.  I was under the impression that the way
> access servers differentiate between "data" and "voice" calls over
> ISDN (and hence the decision to route to a modem or bypass the modem
> straight to the PPP controller) was on the basis of that flag (bearer
> capability?  Been a while since I mucked with ISDN too).  How does
> this work then?  <Daryl prepares for his reality to be skewed yet
> again>

Yes, an ISP's access server usually uses the bearercap to determine
whether or not to send the incoming call to a modem DSP or to an HDLC
controller.

This is why most ISPs don't support DoV right now - there are two
ways for their access server equipment to understand the difference
between a DoV call vs a modem call (both turn up with a voice bearercap).

Some equipment tries to automagically sense if it is a modem or
a DoV call, other smarter gear uses a different incoming phone
number to signify that the incoming call is a DoV call.

The latter is a smarter way to go, obviously ;]

Cheers

Leigh
-- 
| "By the time they had diminished | Leigh Hart, hart@dotat.com |
|  from 50 to 8, the other dwarves | CCNA: http://www.cisco.com |
|  began to suspect 'Hungry' ..."  | PO Box 3057 Newton SA 5074 |
|   -- Gary Larson, "The Far Side" | http://www.dotat.com/hart/ |

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