SIP REFER with Replaces

To support enterprise and call center applications, the Oracle® Enterprise Session Border Controller provides the ability for one party participating in a three-way call to request direct connectivity between the other two parties and to leave the call silently when that connectivity is established. SIP supports this function using the Replaces header in a REFER message, also known as REFER with Replaces.

The most common application of REFER with Replaces handling occurs in a high-level sequence like this:

1. The customer calls a customer service line and reaches—via the Oracle® Enterprise Session Border Controller—an IVR/ACD (Interactive Voice Response system/Automatic Call Distribution system). In some architectures, these are two separate elements.
2. Based on the customer’s selection from the menu of options, the IVR/ACD contacts an agent via the Oracle® Enterprise Session Border Controller.
3. Since the ultimate goal is for the IVR/ACD to drop out of the path, it sends a REFER with Replaces to the Oracle® Enterprise Session Border Controller. This message indicates the Oracle® Enterprise Session Border Controller should replace the IVR/ACD endpoint in the call leg with the agent’s endpoint.
4. The Oracle® Enterprise Session Border Controller processes the REFER with Replaces, issuing ReINVITEs to the customer with the agent’s parameters.
5. The IVR/ACD drops out of the media path once the bridged call between the customer and the agent is established.

   Note that direct media connectivity between endpoints must be possible in order for the REFER with Replaces to be carried out properly. For example, if both endpoints (such as the customer and agent from the example above) are behind the same firewall, direct media connectivity should be possible. However, if one endpoint is behind a firewall and the other is not, then direct media connectivity may not be possible.

   For licensing capacity purposes, note that a bridged session counts as a single call.