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Global Call IP Technology Guide — November 2007 93
Dialogic Corporation
IP Call Scenarios
3.3.6.4 REFER Subscription Expires
Figure 36 illustrates a scenario in which the REFER subscription expires, causing both party A and
party B to time out. After the timeout, the Transferee application receives a GCEV_XFER_FAIL
termination event and the Transferor application receives a GCEV_INVOKE_XFER_FAIL
termination event. The original primary call is left connected and in the GCST_CONNECTED
state from the perspective of both party A and party B.
Figure 36. SIP Call Transfer Failure - REFER Subscription Expires
A
(Transferring,
Transferor)
App
A
(Transferring,
Transferor)
IP CCLib
B
(Transferred,
Transferee)
App
B
(Transferred,
Transferee)
IP CCLib
C
(Transferred To,
Transfer Target)
App
C
(Transferred To,
Transfer Target)
IP CCLib
GCEV_REQ_
XFER(CRNp)
Pre condition: Primary call between A and B is connected (not shown).
202 Accepted
GCEV_ACCEPT_
XFER(CRNp)
GCEV_
INVOKE_XFER_
ACCEPTED(CRNp)
NOTIFY(100 Trying)
Subscription-State=active; expires=300
200 OK
REFER
gc_InvokeXfer
(CRNp)
gc_AcceptXfer
(CRNp)
Parties A and B remain connected.
Post condition:
Cause = IPEC_SUBS_EXPIRED
GCEV_
INVOKE_XFER_
FAIL(CRNp)
Subscription
expires
Subscription
expires
Cause = IPEC_SUBS_EXPIRED
GCEV_XFER_
FAIL(CRNp)