Call routing procedure on outgoing calls
|
User
|
dials
|
correct call route
|
correct user
|
mapping, number in use
|
Destination line
|
|
VoIP telephone
|
14
|
None
|
VoIP softphone
|
14
|
Internal
|
|
VoIP telephone
|
11
|
# (Standard)
|
|
#: 11
|
ISDN
|
|
ISDN telephone
|
14
|
- PBX
|
VoIP softphone
|
14
|
Internal
|
|
VoIP telephone
|
0 555 555
|
0#
|
|
00241#: 0 555 555
|
ISDN
|
|
ISDN telephone
|
0 555 555
|
- PBX
|
|
555 555
|
ISDN outside line
|
|
VoIP telephone
|
0 0123 666 666
|
00#
|
|
0#: 0123 666 666
|
SIP provider
|
- Internal call between two VoIP terminal devices.
- Internal call from VoIP to ISDN. In the first pass (without the standard
routes), the number '11' does not match any of the routes. Similarly,
no matching entry can be found in the list of registered users. In the
second pass, the standard route meets '#' (entry in the call
routing table depicted above) and directs the call to the ISDN line unchanged.
The PBX receives the call on its internal ISDN bus, recognizes the called
number as an internal MSN and again forwards the call to the internal
ISDN bus to which the respective ISDN terminal device is connected.
- Internal call from ISDN to VoIP. The ISDN PBX recognizes the destination
number '14' as an internal MSN and directs the call to the corresponding
internal ISDN bus. The Call Router receives the call to '14', does not
find a matching entry in the call routing table but does find an entry
in the list of registered users.
- External call from the VoIP into the local telephone network. The
entry in the call routing table depicted above matches the
number dialed. The Call Router completes the area code for the local
telephone network and sends the call out to the ISDN line. Only now does
the SIP PBX removes the '0' outside-line access prefix and completes
the call to '0241 555 555' via the ISDN outside line.
- External call from ISDN into the local telephone network. The ISDN
PBX recognizes the destination number as an external destination, removes
the '0' outside-line access prefix and completes the call to '555 555'
via the ISDN outside line.
- External call from VoIP into the national telephone network. The
entry fits in the call routing table here. The call router
removes the '0' prefix for access to the outside line and completes the
call to '0123 555 555' via the SIP line. If the SIP line is not available,
then the call is made over the ISDN line. In this case, the '0' is not
removed from the destination number in order to gain access to an outside
line through the PBX.