User`s guide

Dialogic
®
System Release 6.0 PCI for Windows
®
Release Update, Rev 62 — January 30, 2008 194
Dialogic Corporation
an unattended transfer. In this case, the gc_InvokeXfer( ) call only includes the CRN of
the primary call.
Transferee or Transferred Endpoint (Party B)
This endpoint behaves in the same manner as in unattended transfer with one exception:
the INVITE that is sent from Party B to Party C for the transferred call contains a Replaces
header that is obtained from the replace parameter in the Refer-To header of the REFER
from Party A.
Note that the primary call cannot be disconnected prior to making the transferred call
during an attended transfer because the primary call database contains the Replaces
information that is required to establish the transferred call.
Transfer Target or Transferred-To Endpoint (Party C)
This endpoint behaves in much the same manner as in an unattended transfer with one
additional feature and one additional responsibility.
If the Replaces header exists in the incoming INVITE, Global Call automatically matches
the Replaces value with any existing connected call on Party C. If a matching call (the
secondary or consultation call) is found, that call’s CRNs is passed to the application as a
GCPARM_SECONDARYCALL_CRN parameter in the GC_PARM_BLK that is attached to
the GCEV_OFFERED event.
The party C application must also drop the secondary/consultation call when the transfer
completes. Unlike H.450.2 call transfer, Global Call does not automatically disconnect the
secondary call once the transferred call answered at the party C.
1.51.1.5 Successful SIP Attended Call Transfer Scenarios
This section describes the basic scenario for successful SIP call transfer and the
scenarios for recovery from two conditions that can block transfer completion. The
scenarios include:
• Successful SIP Attended Call Transfer
• Attended Transfer When REFER Is Not Globally Supported
• Attended Transfer When Contact URI Is Not Globally Routable
The scenarios all illustrate the optional GCEV_INVOKE_XFER_ACCEPTED event, which
is disabled by default. The Transferor application can enable and disable this event at any
time after the line device is opened using the gc_SetConfigData( ) function.
For simplification purposes, none of the figures indicate the opening and closing of logical
channels (and the associated media sessions) because the control procedures are
consistent with typical non-transfer related SIP calls.