1. Configuration Guide
  2. SIP Signaling Services
  3. SIP SIP-I Interworking
  4. Interworking Call Flows with Diversion Information

Interworking Call Flows with Diversion Information

For networks in which there are devices that do not support SIP-T or SIP-I (and support native SIP alone), the (SBC) supports SIP Diversion interworking. This feature enables such devices to function properly in instances that require SIP-T/SIP-I style ISUP message encapsulation in ISUP requests, and to receive any call forwarding information in the message according to ISUP standards.

The SBC interworks a SIP INVITE request to SIP-T one by inserting an ISUP IAM body based on the INVITE; this includes redirection information based on the Diversion header. This feature can also perform the reverse translation. That is, it can interwork a SIP INVITE that does have the ISUP IAM body to a non-ISUP INVITE. In this case, the SBC generates the necessary Diversion headers based on the IAM’s Redirection information.

Criteria that generates this interworking includes:

  • You have set the sipi-behavior option to iam-anm (Native interworking).
  • There is a sip-profile applied to the call that has the redirection parameter set to isup.
  • There is an accompanying sip-isup-profile applied to the call that specifies an ISUP version.
  • SIP or ISUP signaling includes call forwarding information.

The SBC also performs additional processing for IAM, ACM, CPG, ANM and CON ISUP messages, interworking important information from SIP messages to ISUP. The SBC does not perform this interworking in the reverse direction, from SIP-I to SIP.