SIP-SIPI Interworking Call Flows

When configured for SIP-SIP-I interworking, the OCSBC inserts and removes ISUP signaling information into SIP signaling messages as MIME bodies. You can also configure manipulation and/or translation rules to refine your interworking. The diagrams below present the order in which the OCSBC processes the relevant configuration objects, resulting in incremental changes. You must configure interworking manipulation ensuring that the changes caused by the latter processing are based on the results of preceding processing.

The diagram below shows a call initiated by a SIP endstation. The OCSBC interworks the call to SIP-I using your configuration and passes the call to the media gateway for SIPI to ISUP interworking. The OCSBC inserts the IAM as an ISUP MIME body part in the INVITE. The OCSBC also removes ACM presented by the SIP-I network from the 180 Ringing message.

Similarly, the diagram below presents the opposite IWF behavior wherein the OCSBC detects an INVITE coming from SIP-I, removing the IAM and inserting the ACM, as appropriate.

Similarly, the diagram below presents the ISUP version (format) behavior wherein the OCSBC detects an INVITE coming from SIP-I, interworking the ITU-IAM to SPIROU-ACM, as appropriate.

To complete the picture, note the OCSBC providing SIP-I output to the media gateway, which interworks between SIP-I and the PSTN.

Refer to ITU-T Recommendation Q.1912.5 for SIP to ISUP message mapping tables to verify expected responses and their interworking.