The Inter Operator Identifier (IOI) is shared between sending and receiving networks, service providers, or content providers. The orig-IOI parameter is used by the originating network in the requests whereas the term-IOI parameter is used by the terminating network in the responses. 

As a P-CSCF, the SBC has the following abilities:

  • Use the orig-IOI in the REGISTER requests only. 
  • Include the orig-IOI in all the SIP requests and responses. While generating responses for any UE terminated requests, the SBC as a P-CSCF copies the orig-IOI parameter received in the P-Charging-Vector header of the request to the P-Charging-Vector header of the response, and also includes a term-IOI parameter. Both the orig-IOI and term-IOI parameters contain configured "Inter Operator ID" for the network.

 

The "Inter Operator ID" value associated with the Trunk Group towards the IMS core is used for the configuration.

Call Flow Depicting Insertion of Orig-IOI and Term-IOI at P-CSCF

 

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