TD 92326GB
2009-03-10 / Ver. E
Installation and Operation Manual
VoIP Gateway
156
Differences between the QSIG variants:.
22.5 The Assignment of B Channel Numbers for PRI Connections
Sometimes collisions occur on PRI connections, even if a mechanism is defined in ISDN to
determine how incoming and outgoing calls are to be assigned to different B channels.
By default the VoIP Gateway assigns the B channels for outgoing calls starting at the
bottom (i.e. 1, 2, ...). If this results in any collisions, the assignment must be changed in
such a way that the B channels are assigned starting at the top (i.e. 30, 29, ...). This is
done using the “Assign Channels from Top” setting. If you are uncertain which
assignment mechanism is the right one, select “from top” for PRI1 and “from bottom” for
PRI3.
The recommendation is that the channel assignment should be opposite of the attached
PBX setting.
22.6 Single Digit Dialling on Terminals on Point-to-Multipoint Connections
Normally, single digit dialling (overlapped sending) is not used to call terminals (i.e. devices
in TE mode) on point-to-multipoint connections. Under certain circumstances however, it
is possible for gateways to be connected to a PBX system in “point-to-multipoint” mode
and then also support incoming single digit dialling (overlapped receive). In this case, an
incoming SETUP message is answered as required in the standard, with a SETUP_ACK
message. Some PBXs however do not expect this sort of message from terminal
equipment and terminate the call at this point. In such a case, the “No overlap receive”
setting prevents the VoIP Gateway from answer the incoming SETUP message with
SETUP_ACK.
22.7 Suppression of specific Protocol Elements
Not all ISDN implementations are prepared to receive certain information elements (so
called IEs) which conform to the standards. Such IEs can be created, for example when
linking up different PBXs or transmitting H.323 calls to an ISDN interface and vice-versa.
If malfunctions are caused by the transmission of certain IEs, the VoIP Gateway can
remove them from the transmitted messages by suppression of the transmission of IEs:
Variant CR
Length
(Call reference
length)
CHI Type
(Channel ID coding)
Numbering of
the B channels
Use
QSIG-PRI-
ECMA1
2 bytes
As for primary rate 1 to 15, 17 to 31 S0, PRI
QSIG-PRI-
ECMA2
2 bytes
As for primary rate 1 to 30
PRI
a
a.If the setting QSIG-PRI-ECMA2 is used for TEL it behaves as if the setting were QSIG-
ECMA1.
Setting Effect
Suppress sending of HLC
No high layer compatibility information elements are
transmitted.
Suppress sending of FTY
No facility information elements are transmitted.
