3GPP 23.501 v20.2.0 — the document's own text
5.8.2.22 Handling of Payload Headers
Taught in 13. Where the packets actually go (The 5G system architecture, in depth), 5. The connection, and what is promised on it (The 5G system architecture, overview).
Support of Handling of Payload Headers is an optional UPF feature as defined in clause 5.6.17.
The SMF receives Header Handling Control information in a PCC rule (as described in clause 6.3.1 of TS 23.503 [45]), it forwards the Header Handling Control information to the UPF via N4 interactions. The SMF adds the Header Handling Control information relevant for the UL direction, if any, into the FAR that corresponds to the UL PDR of that PCC rule and the Header Handling Control information relevant for the DL direction, if any, into the FAR that corresponds to the DL PDR of that PCC rule.
If the Header Value parameter contains a reference to information to be added by SMF, the SMF shall overwrite the Header Value parameter with the indicated information of the corresponding PDU Session.
If SMF determines based on local configuration that it shall receive notifications related to the Handling of Payload Headers, it can modify the Header Handling Reporting of the header handling actions of interest by setting it to "yes" and by adding itself as an endpoint. In addition, the SMF shall add its Notification Target Address and a Notification Correlation ID to the Header Handling Reporting Endpoints sent to UPF.
When UPF receives a Header Handling Control Rule from SMF over N4 (see clause 5.8.5.6), it contains a Header Detection Reference (see clause 5.6.17.2) which points to a predefined configuration in UPF which includes the details of the protocol and possibly the message for which a header handling action shall be performed (e.g. HTTP, HTTP message). The interpretation of the Header Detection Reference is part of the SLA and thus, implementation specific.
The Header Handling Control Rule contains other explicit Header Handling Control information to be used for handling the traffic that matches the Header Detection Reference, see clause 5.6.17.2.
When the Header Handling Control Rule includes Header Handling Reporting information, UPF may send notifications related to the Handling of Payload Headers to SMF and/or NEF/AF. The enforcement of a requested action is a Header Handling event. If reporting has been requested, UPF reports the events of the actions executed. If Reporting suggestion information is received, the UPF performs as defined in clause 5.8.2.17. When One-time-report has been indicated for an action, the first occurrence of the action per packet flow is reported.