Refer-To Header Processing

When a Refer-To header is present in a REFER request that arrives at the SIP B2BUA after the incoming request is properly translated according to its SIP-NAT, the SIP B2BUA follows these steps:

1. The SIP B2BUA parses the Refer-To URI.
2. If the user part of the Refer-To URI contains the refer to URI prefix, the SIP B2BUA searches the Contact header mapping for a match of the user part of the URI.

   If the user part of the Refer-To URI does not contain the refer to URI prefix, the SIP B2BUA leaves the existing Refer-To URI unchanged.

3. If the user part of the Refer-To URI contains the refer to URI prefix and a match of the Refer-To URI is found, the SIP B2BUA replaces the existing Refer-To URI with the URI of the corresponding Contact URI stored in the matched record. This replacement enables the NAT function to properly decode the replacement URI and change it back to the form originally received by the Oracle® Enterprise Session Border Controller. As a result, the correct conference ID is restored in the Refer-To header prior to the request being sent to its next hop.

   If the user part of the Refer-To URI contains the refer to URI prefix but a matched URI cannot be found, the SIP B2BUA will leave the existing Refer-To URI unchanged and will write a WARNING level log message to record the failure.