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Dialogic Corporation
An application has no ability to specify which H.225 message types it wishes to receive UU-IE in,
and should therefore be capable of handling UU-IE contained in any of the specified H.225
message types.
The maximum data length for the Global Call parameter used for the UU-IE content is configured
at system start-up. The maximum data length for this parameter is configured by setting the
max_parm_data_size field in the IPCCLIB_START_DATA structure. The default size is 255 bytes
(for backwards compatibility), but applications may configure it to be as large as 4096 bytes.
Applications must use the extended gc_util_..._ex( ) functions to extract any GC_PARM_BLK
parameter elements whose data length has been configured to be greater than 255 bytes.
4.19.1 Enabling Reception of User-to-User Information
The ability to retrieve UU-IE from inbound H.225 messages is an optional feature that is enabled or
disabled on a virtual board basis at the time the gc_Start( ) function is called.
The mandatory INIT_IP_VIRTBOARD( ) function populates the IP_VIRTBOARD structure
with default values. The default value of the h323_msginfo_mask field in the IP_VIRTBOARD
structure does not enable access to any of the supported additional information types (Q.931
message information elements, tunneled signaling messages, or User-to-User information
elements). To enable any of these features for an ipt device, the default value of the
h323_msginfo_mask field must be overridden with a value that represents the appropriate logical
combination of the defined mask values. To enable access to User-to-User IEs, the value
IP_H323_RETRIEVE_UUIE_ENABLE must be set in the mask. The following code snippet
enables Q.931 message IE access on two virtual boards and enables UU-IE access on the second
board only:
INIT_IPCCLIB_START_DATA(&ipcclibstart, 2, ip_virtboard);
INIT_IP_VIRTBOARD(&ip_virtboard[0]);
INIT_IP_VIRTBOARD(&ip_virtboard[1]);
ip_virtboard[0].h323_msginfo_mask = IP_H323_MSGINFO_ENABLE;
/* override Q.931 message default */
ip_virtboard[1].h323_msginfo_mask = IP_H323_MSGINFO_ENABLE |
IP_H323_RETRIEVE_UUIE_ENABLE;
/* override Q.931 message and UU-IE defaults */
Note: Features that are enabled or configured via the IP_VIRTBOARD structure cannot be disabled or
reconfigured once the library has been started. All items set in this data structure take effect when
the gc_Start( ) function is called and remain in effect until gc_Stop( ) is called when the
application exits.
Table 17 relates the supported H.225 messages that can contain UU-IE fields to the Global Call
event types that are used to notify the application of the message’s arrival.
Table 18. H.225 Messages and Global Call Events for Receiving UU-IE
H.225 message Global Call event used to notify application
Setup GCEV_OFFERED
Proceeding GCEV_PROCEEDING †
Alerting GCEV_ALERTING
† The GCEV_PROCEEDING event is maskable.