The ways in which secure SIP affects Blueworx Voice Response call transfer operations are described.
The following two types of call transfer are possible when secure SIP is used:
Blueworx Voice Response initiates a transfer by sending a REFER message to the calling device, including the contact details for the party to be transferred to. It is then up to the calling device to establish the connection by using UDP, TCP, or TLS.
A Blueworx Voice Response application can specify a sip: or sips: address and this will be passed to the calling device. However, Blueworx Voice Response has no control over the transport protocol that the calling device uses to establish a connection to the party that the call is being transferred to. Also, Blueworx Voice Response has no information on the ability of the calling device to support secure SIP.
In this case Blueworx Voice Response establishes a new call to the party to be transferred to. This call is set up as a standard outbound call with the same secure SIP considerations as any other outbound call. When this second call is established, Blueworx Voice Response passes details of it to the calling party by using a REFER Replaces mechanism. The calling party then takes this call from Blueworx Voice Response and drops the original call to Blueworx Voice Response.