5G P-Access-Network-Info format of SIP messages

For 4G, the PANI (P-Access-Network-Info) header, contains the TAC and ECGI in the following format: MCC + MNC + TAC_in_hex + ECI_in_hex, and, correct me if I am wrong, TAC_in_hex is padded with zeros to the left to 4 hexadecimal digits, and ECI_in_hex to 7 digits.

What is the format for 5G PANI? Will the TAC be included?

Given that gNodeb is variable in length, is there a way to split the NCI in gNodeb and Ci from the PANI header?

Finally, how is it possible to distinguish between a 5G and 4G PANI header? For example, 4G includes “utran-cell-id-3gpp” as access network info in PANI. Does 5G include recognizable strings like this?

The P-Access-Network-Info header is used in Session Initiation Protocol (SIP) messages to provide information about the access network used by the User Equipment (UE) for the session.

With the introduction of 5G, the P-Access-Network-Info header has been updated to support the new 5G access networks.

The format of the P-Access-Network-Info header for 5G is as follows:

P-Access-Network-Info: 5G-GUTI=IMSI-552820000000001;5G-TMSI=12345678;5G-TA=0;

This header includes the following information:

5G-GUTI (5G Global Unique Temporary Identifier): This is a temporary identifier assigned to the UE by the network.
5G-TMSI (5G Temporary Mobile Subscriber Identity): This is a temporary identifier assigned to the UE by the 5G core network
5G-TA (5G Timing Advance): This is the timing advance value used by the UE for the session.

By including this information in the P-Access-Network-Info header, the network and other entities in the session can make better decisions about how to handle the session and optimize the user experience.

Could you provide references such as RFC or 3gpp TS ? Thank you.