My ITSP published a very technical specification that states:
The UE shall not add the IMPU in the user part of the SIP URI that is used as the Contact
Address. This would reveal the IMPU to the called party even in case OIR is applied.
The full specification is available here: https://www.telefonica.de/file/public/1158/SIP-Interfaces.pdf?attachment=1
Could someone with a deeper understanding please explain in a less technical fashion, what exactly this means for correctly setting up my outbout registrations in pjsip.conf, especially in regard to the configured ‘Contact’ header field? From my (limited) understanding, I am NOT supposed to put my DID number in the user portion of the ‘Contact’ header?