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ISDN Call Processing Overview
November 2009 319
Notification of incoming calls comes via a SETUP_IND message
which contains the B-channel number the network would like to set
the call up on. By turning on negotiation, you can specify a different
(specific) B-channel on which to establish rather than the one
requested by the network. In this case, a CALL PROCEEDING
message will not get sent to the network and it is your responsibility
to notify the network of the desired B-channel via any one of the
following three messages: L4L3mCALL_PROCEEDING_REQUEST,
L4L3mALERTING_REQUEST, and L4L3mCONNECT_REQUEST.
Note: If using more than one of these messages, you should be
consistent on the B-channel value.
You might want to do B-channel negotiation in situations where
each of the channels is hard-code mapped to different locations
depending on the type of call (data, voice, fax) received. If an
incoming call to a channel is not the type of call that is handled by
that (network-assigned) channel, then it must be (re)established on a
channel that can handle the type of that call, or else the call won’t be
handled properly.
This feature is turned on by setting:
l43.data.enable_protocol.level3.cnfg.q931.b_chan_negot=1
in the ENABLE_PROTOCOL message. In the case where the
network indicates that the B-channel it is offering is non-negotiable,
and the l43.data.enable_
protocol.level3.cnfg.q931.proc_on_exclusv field was set
when the protocol was enabled, the calling process will proceed with
a CALL PROCEEDING message being sent to the network without
requiring you to indicate one. The network indicates that the
B-channel it is offering is non-negotiable. The user had agreed to
proceed by having set the proc_on_exlusv field.
Connect Acknowledge is reported to the module but is not
automatically reported to the host via the Bfv API. In order to
retrieve L3L4mCONN_ACK_IND, set the field below to 1 in your
ENABLE_PROTOCOL message:
l43.data.enable_protocol.level3.cnfg.q931.subscribe_connack=1
The stack can consider the call connected after sending the
L4L3mCONNECT_REQUEST message or wait until it receives the
CONNECT ACKNOWLEDGE from the network. If you do not want
to wait for the network response, set the field below to 1 in your
ENABLE_PROTOCOL message:
l43.data.enable_protocol.level3.cnfg.q931.no_rx_conn_ack=1