DNN — Data Network Name — which network you are asking to reach
Sessions, flows and slices
Where it sits
What it is
What it is. The Data Network Name — the name of the network you are asking to reach. TS 23.501 §5.9.6, used at PDU session establishment per §5.6.1. It is the 5G spelling of what LTE called the APN, and it does far more than label a destination.
What the DNN actually selects. The device offers a DNN; the network resolves it into a whole chain:
which SMF will own the session · which UPF will anchor it · therefore where the packets exit onto a real network (the N6 interface) · and which policy applies to it.
So internet, ims and enterprise-vpn are not three labels on one pipe — they are three
different anchors, three exit points, and three sets of rules.
The default, and what happens when the name is wrong. TS 23.501 §5.6.1: subscription information per S-NSSAI may carry a Subscribed DNN list and one default DNN. If the device names no DNN, the AMF uses the default for that S-NSSAI; if none is configured, a locally configured one.
If the DNN the device asked for is not supported and the AMF cannot select an SMF by querying the NRF, the specification is blunt: the AMF "shall reject the NAS Message containing PDU Session Establishment Request... with a cause indicating that the DNN is not supported" — unless the PCF supplied a policy to perform DNN replacement.
DNN replacement is the interesting escape hatch. The operator can configure the network to quietly substitute a different DNN for the one the device asked for, per S-NSSAI. So the name the device sends is a request, and the name the network uses may not be it — which is why the SMF is given both the requested and the selected DNN.
It is paired with the slice, never alone. Discovery, subscription and policy are all keyed on (S-NSSAI, DNN) together: the slice says what kind of network, the DNN says which one.
Read on
This concept is read as part of one argument in ref-session, alongside the rest of its group.
Before this concept, the hierarchy says to learn the following — the full chain, in order: