Application notes for the P-called-party-id header field

P-called-party-id scenario for the head field

P-called-party-id applies to the case where UAS need to know the purpose of Request-uri in the request before the agent overwrites the target to the contact address: AOR. UAS follow a set of different scenarios or use their filtering services for the request target. When UAS registers a few AOR, and unless this extension is used, UAS is not aware of his proxy registration server, Registrar gives the AOR of INVITE requests. At this point, the extension will appear more valuable.

Usage of the P-called-party-id header field

The P-called-party-id header field redirects the proxy target to the Request-uri in the request before the AOR is provided to the broker server and UAS. This information can be used by subsequent proxy servers on the path of the UAS.

Typically, a SIP proxy inserts a P-called-party-id header before the target relocation Request-uri. Fill in the field with Request-uri before Request-uri is rewritten as the contact address.

The UA process

UAC cannot insert the P-called-party-id header field in any SIP request or response message. UAS may receive SIP requests that contain P-called-party-id header fields. The header fills in the Request-uri that the proxy server received the request message before being transferred to UAS. UAS can use P-called-party-id to provide services based on the called party URI. For example, filter calls by date and time, customize presentation services, customize tones, and more.

Processing flow of Proxy server

A proxy server that requires access to the user's contact information can insert a P-called-party-id header field into the list of requests. The proxy server must fill in the field with the Request-uri in the SIP request message it received. To prevent the called party ID from being sent incorrectly, it is important that the proxy server that is plugged into the P-called-party-id have user information. For example, this information can be obtained through the registration process.

A proxy server or application server can use and provide services based on its content when it receives a request that contains a P-called-party-id header. SIP Proxy cannot insert the P-called-party-id header in the registration request.

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Application notes for the P-called-party-id header field