Configure SIP Lines to Support Release Link Transfer

Director transfers calls using Release Link Transfer (RLT) whenever possible. RLT is sometimes called Release-link trunking. RLT is a form of traditional PSTN signaling that starts call transfer over a trunk.  In CIC 2.3.1 and later releases, the Telephony Services subsystem can perform RLT on SIP calls. When using SIP to call between CIC servers, Director tells Telephony Services to perform a Release Link Transfer. If RLT is possible and it succeeds, the caller and the agent connect while dropping the resources that the audio path required on the CIC server where the call enqueued originally.

To allow RLT (also called Putback Transfer), enable "Putback Transfer" on the SIP line in Interaction Administrator (using the Monitored Server, Lines container). This action allows removal of the transferred call from the system, forcing both the SIP call control and the RTP out of the CIC server. With Putback Transfer activated, a REFER message sends to the gateway and an INVITE message sends to the SIP-enabled destination. If the gateway doesn't support REFER messages, the call passes through the original CIC server and consumes its IP resources.