[asterisk-users] p2p or p2mp for BRI

[Philipp von Klitzing]

Hi!

> The 'M' in PtMP stands for 'Multi'. Basically PTP is the standard ISDN
> protocol, and PtMP is an extension of its logic to make ISDN (BRI) phones
> behave somewhat like analog phones: allow you to connect several of them
> on the same line.

In other words:

While you *must* have exactly one central PBX with PTP, you *can* have a 
central PBX or you can use BRI decentrally because PtMP is organized as a 
bus system. In the case of HylaFax, for example, this means that with 
PtMP you can run chan_capi (Asterisk) and capi4hylafax in parallel on the 
line so that they do not depend on each other at all (no need for 
IAXmodem, no fax timing issues).

Numbering: With PTP you can usually obtain a number block of 2-10 
consecutive numbers, while with PtMP you will probably get 2 or 3 (up to 
10) individual numbers that do not have to be consecutive. At least 
that's the way it works in Germany and Belgium.

PTP can be easily enlarged with more BRI lines, whereas with PtMP this is 
more difficult (due to line hunting from Telco to you, choosing an 
outgoing DID/MSN etc).

Finally: Make sure that ISDN equipment (card, gateway) and driver 
supports the mode that you decide for. In the case of Asterisk chan_capi 
is a good choice, mISDN is not - but if you are in the US then I am have 
no cluee how good "National ISDN" support is with chan_capi.

Philipp