SIP response codes in Voice Platform

When you perform a transfer, SIP generates a response code to indicate the outcome of the transfer. Upon receiving this code, Voice Platform assigns a value to the transfer variable based on the response. In some cases, Voice Platform also throws an event based on this response.

The table below summarizes the different SIP response codes that Voice Platform may receive, the value that is then assigned to the transfer variable, and the event that is thrown (if any):

SIP response	Value assigned to <transfer> variable	Event thrown (if any)
BYE from A before REFER	undefined	connection.disconnect.hangup
cancelled before REFER	near_end_disconnect
NOTIFY 200 OK (VBS sends BYE)	undefined	connection.disconnect.transfer
404 Not Found	undefined	error.connection.baddestination
408 Request Timeout	noanswer
486 Busy Here	busy
503 Service Unavailable	undefined	error.connection.noresource
504 Server Time-out	network_busy
200 OK (VBS sends BYE)	undefined	connection.disconnect.transfer
BYE from C	far_end_disconnect
BYE from A (after call to C)	undefined	connection.disconnect.transfer
(No response)	noanswer
(Other 3xx/4xx/5xx/6xx)	unknown
BYE from C with Reason header set to “network_disconnect”	network_disconnect

For more description of these outcomes, see the discussion of the <transfer> element.

For more information about these SIP response codes, see SIP RFC 3261, Section 21, Response Codes.