LANCOM 1722 VoIP – LANCOM 1724 VoIP
Chapter 1: Introduction
26
EN
To answer these questions, we differentiate between the following constella-
tions:
If ISDN terminal equipment can be reached over an ISDN TE interface on
the LANCOM, it is described as "upstream". From the perspective of the
LANCOM, the ISDN terminal devices are on an external line. This ISDN ter-
minal equipment is normally not classified as being for local users, and so
no entries for ISDN users are necessary.
ISDN terminal equipment at an upstream ISDN PBX...
can make internal calls to SIP users if the corresponding telephone
numbers are configured as internal MSNs in the ISDN PBX.
can receive internal calls from SIP users if the internal MSNs of the
ISDN equipment are output to the ISDN line by the call-routing table,
for example over a standard route.
can only make calls over SIP lines if the PBX is able to output certain
call numbers over its internal ISDN bus. Otherwise, all calls not
matching with its internal MSNs would be forwarded by the ISDN PBX
to the public telephone network.
can only receive calls from an upstream SIP PBX if entered into the
LANCOM as an ISDN user and registered as such with the SIP PBX.
If ISDN terminal equipment can be reached over an ISDN NT interface on
the LANCOM, it is described as "downstream". For the LANCOM, this is
then a local subscriber that can be reached via the list of registered users.
As ISDN terminal equipment cannot send domain information to register
at the LANCOM, it must be entered as an ISDN user so that it can be rec-
ognized by the VoIP system.
ISDN terminal equipment at a downstream ISDN PBX...
can make internal calls to SIP users by entering the character for an
outside line as required by the PBX and then dialing the SIP user's
internal number. The PBX then forwards the call to the SIP user's
internal number—without the outside-line access code—over its
external ISDN bus to the LANCOM.
can receive internal calls from SIP users as long as the entry for the
ISDN user contains the correct allocation of the internal number to the
appropriate MSN. The LANCOM takes a call to the ISDN user's inter-
nal number, translates it to the MSN, and outputs it to the allocated
ISDN bus. The PBX receives the MSN as if it were an external call and
forwards it to the corresponding ISDN terminal equipment.
