Inbound HMR Challenge

Since inbound manipulations take place before the message reaches the core of Oracle® Enterprise Session Border Controller SIP processing, the SIP proxy takes the manipulated header as what was directly received from the client. This can cause problems for requests leaving the Oracle® Enterprise Session Border Controller for the UAC because the dialog will not match the initial request sent.

So the unmodified header must be cached because for any subsequent request (as in the case of a BYE originating from the terminator; see the diagram below) the Oracle® Enterprise Session Border Controller might need to restore the original value—enabling the UAC to identify the message correctly as being part of the same dialog. For out-of-dialog requests (when the To, From, or Call-ID headers are modified) the original header will be stored in the dialog when the msg-type out-of-dialog is used.

The Oracle® Enterprise Session Border Controller performs the restoration of original headers outside of SIP manipulations. That is, there are no manipulation rules to configure for restore the header to their original context. The Oracle® Enterprise Session Border Controller will recognize the headers have been modified, and restore them to their original state prior to sending the message out on the wire. Restoration takes place prior to outbound manipulations so that any outbound manipulation can those headers once they have been restored.