name: IMPI
full_form: IP Multimedia Private Identity
context: If the UE has an already active TLS session, then it shall use this to protect the REGISTER message for re-registration. When the P-CSCF receives a REGISTER message protected by a TLS session whose TLS Session ID is associated with an IMPI from a previously successful registration (cf. O.2.2), then the P-CSCF shall proceed as follows: - If the IMPI is present in the REGISTER message the P-CSCF shall verify that the IMPI in the REGISTER matches the IMPI associated with the TLS Session ID. If the IMPIs match, then the P-CSCF shall forward this REGISTER message together with a TLS integrity protection indicator indicating the logical value "authentication complete". - If the IMPI is not present in the REGISTER message the P-CSCF shall not include any TLS integrity protection indicator. When the S-CSCF receives a REGISTER message with a TLS integrity protection indicator indicating the logical value "authentication complete" it may authenticate the user by means of SIP Digest, according to
description: The IP Multimedia Private Identity (IMPI) is a critical network attribute used for authentication and identification purposes within the IMS network. It is associated with a TLS session ID and plays a key role in securing REGISTER messages during re-registration processes.
explanation: IMPI is classified as a Parameter because it serves as an identifier for authentication and is utilized in conjunction with other network attributes, such as TLS Session IDs, to ensure secure communication within the IMS network. The context highlights its importance in verifying the authenticity of REGISTER messages.
section_title: O.4.3	Authenticated re-registration
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biotag_Description: O,B-Parameter,I-Parameter,I-Parameter,I-Parameter,O,O,O,O,O,O,O,O,O,O,O,O,O,O,B-Network,O,O,O,O,O,O,B-Protocol,O,B-Parameter,O,O,O,O,O,O,O,O,O,O,O,O