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416 Dialogic
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Global Call IP Technology Guide — November 2007
Dialogic Corporation
gc_ReqModifyCall( ) — request modification of call attributes
To request a change in the attributes of a media session in 3PCC mode, a call control application
explicitly constructs an SDP offer containing the desired new attributes, and then inserts it into the
GC_PARM_BLK as a parameter element of the following type (see Section 5.2.2.2, “IPSET_SDP
Parameter Set Identifier”, on page 345 for more details):
IPSET_SDP
IPPARM_SDP_OFFER
• value = properly constructed SDP offer
To request a change in the DTMF mode, the application inserts into the GC_PARM_BLK a
parameter element of the following type:
IPSET_DTMF
IPPARM_SUPPORT_DTMF_BITMASK
• value = IP_DTMF_TYPE_INBAND_RTP or IP_DTMF_TYPE_RFC_2833
To cancel a pending re-INVITE request, the application inserts into the GC_PARM_BLK the
following parameter:
IPSET_MSG_SIP
IPPARM_SIP_METHOD
• value = IP_MSGTYPE_SIP_CANCEL, size = sizeof(int)
Note: When using this parameter value, this must be the only parameter element inserted
into the GC_PARM_BLK.
Termination Events
GCEV_ MODIFY_CALL_ACK
Successful termination event for call modification request. Indicates that the network or
remote party accepted and acknowledged the request with a 200OK, and that the library has
acknowledged the 200OK. In 1PCC mode, this event also indicates that any media changes
that were proposed and accepted have been completed.
GCEV_MODIFY_CALL_REJ
Unsuccessful termination event for call modification request, indicating that the request was
rejected. The network or remote party declined and rejected the request by sending a 3xx, 4xx,
5xx, or 6xx response code in reply to the re-INVITE, and the library automatically sent an
ACK. The specific response code can be retrieved from the Global Call METAEVENT by
calling gc_ResultInfo( ). If the response code from the remote party was a 408 Request
Timeout or 481 Dialog/Transaction Does Not Exist, the call that was being modified is
disconnected automatically, and a GCEV_DISCONNECTED event is generated to the
application. For all other response codes, no modifications to the existing dialog or media
session are performed and the current state remains as it was prior to the attempting the
modification request.
GCEV_MODIFY_CALL_FAIL
Unsuccessful termination event for call modification request, indicating that the signaling of
the request failed. Some possible reasons include a failure in the message transport, a timeout
awaiting the response from the network or remote party, attempting to modify a call which is
not currently connected, or attempting to initiate a request to modify a call while another
modify request transaction is still pending. More specific information can be retrieved from the
Global Call METAEVENT by calling gc_ResultInfo( ). On failure, no modifications to the