Many companies use a point-to-point ISDN connection instead of the more common point-to-multipoint connection. Point-to-point connections offer two significant advantages:
- Because extension numbers can be used (DDI – Direct Dialing In), all terminal devices can be directly reached via a common external switchboard number plus an extension number as a suffix.
- A larger number of B channels can be used with the same range of telephone numbers, whereas with a point-to-multipoint connection there are only two B channels, typically supporting up to 10 telephone numbers.
ISDN P2P connections are available either as a basic rate interface (BRI) with two B channels or as a primary rate interface (PRI) typically with 30 B channels. LANCOM VoIP Routers support the ISDN basic rate interface only. To be able to use more than four B channels, a P2P connection can be switched to multiple basic rate interfaces with the same range of telephone numbers.