[asterisk-users] OT - Avantages of ISDN PtP and PtmP

[Steve Davies]

2008/9/29 Olivier <oza-4h07 at myamail.com>:
> Hi,
>
> Reading  http://www.asteriskguru.com/tutorials/bri.html , it seems PtP is
> the way to connect businesses but if you read
> http://public.swbell.net/ISDN/connect.html you would think the opposite.
>
> Can anyone elaborate a bit PtP or PtmP respective advantages ?
>

IMHO:

PtMP should only be used if you have Multiple devices connected to
your ISDN (Hence the Multiple part in its name) - This setup means
that for each outgoing call, the calling device has to negotiate
almost from scratch, access to a B-channel, and every inbound call is
sent (broadcast) to every connected device to give it the chance to
grab it. This is an almost compeletly chaotic and stateless
environment (I know, of course there IS state, just a lot less of it).

PtP on the other hand is stateful - The one device negotiates a
connection when it comes up, and monitors the line constantly, so it
knows if (for example) the line goes down. Calls in both directions
are sent to the one known endpoint, directly addressed to a B-channel
that it already knows should be available.

Also, if a call comes in to an unrecognised DDI/address, PtMP can only
time-out (no-one grabs the call) where PtP can dynamically know that
the call is rejected and handle it "properly"

For 99% of Asterisk installs, where Asterisk is managing/routing all
calls on a line, PtP is going to be the right choice.

Cheers,
Steve