PDU session
Updated
A PDU session is a data session of a device on a 5G standalone network, connecting it to a data network identified by a DNN, the 5G name of the APN. It is set up by the SMF and carried by one or more UPFs, as specified in 3GPP TS 23.501 and TS 23.502.
In practice
A private APN keeps its role in 5G under the name DNN: devices still choose the network they want to reach by name, and that name still decides where their traffic goes.