The Ribbon SBC supports the X3 interface to intercept call content towards the mediation servers over TCP/IPsec.

The PCSI intercept call flow is listed below:

  1. The IMS network sends a SIP INVITE/18x/200 OK or re-INVITE/200 OK that contains a P-Com-Session-Info header. This header contains a correlation ID and one or more prospective target URI, which is looked into the target table maintained in the PSX Slave.

  2. When the S-SBC receives a P-Com-Session-Info header in any of the previously listed SIP messages, the S-SBC sends a policy request with the list. The PSX Slave uses this policy request to perform a lookup in the target table that the X1 provisioning interface created. Assuming that a target URI matches, the PSX provides the X3 transport address that is stored along with the target URI. This information is received by the S-SBC in the policy response. This interface uses Diameter+ over UDP.

  3. The S-SBC finds the LI information in the policy response and understands that the call must be intercepted. The S-SBC uses the correlation ID received in the SIP messages and the X3 transport address received from the PSX Slave to pass this information over the SBC Media control API over TCP to the M-SBC.

  4. The M-SBC validates the X3 transport address against the mediation servers configured under the CDC and intercepts the call content to the corresponding mediation server using the X3 interface.