In the draft https://datatracker.ietf.org/doc/html/draft-li-apn-framework-04, we have listed the APN Attribute Conveying Requirements https://datatracker.ietf.org/doc/html/draft-li-apn-framework-04#section-5.1, the [REQ 1d] is that “APN ID MUST be acquired from the existing available information of the packet header without interference into the payload.” In the Section 6 of the same draft, the design of the APN ID is also described as https://datatracker.ietf.org/doc/html/draft-li-apn-framework-04#section-6.2 including user group id and application group id. The individual user will not be exposed.