PDU layer: This layer corresponds to the PDU carried between the UE and the DN over the PDU Session.
When the PDU Session Type is IPv4 or IPv6 or IPv4v6, it corresponds to IPv4 packets or IPv6 packets or
both of them; When the PDU Session Type is Ethernet, it corresponds to Ethernet frames; etc.
GPRS Tunnelling Protocol for the user plane (GTP-U): This protocol supports tunnelling user data over
N3 (i.e. between the 5G-AN node and the UPF) and N9 (i.e. between different UPFs of the 5GC) in the
backbone network, details see TS 29.281
. GTP shall encapsulate all end user PDUs. It provides
encapsulation on a per PDU Session level. This layer carries also the marking associated with a QoS Flow
defined in clause 5.7. This protocol is also used on N4 interface as defined in TS 29.244
The user plane for W-5GAN is defined in Clause 6 of TS 23.316