Methods and apparatuses for alternative data over non-access stratum, donas, data delivery in a roaming scenario

1. A method performed by a Visited Session Management Function, V-SMF, in a core network of a cellular communications system to enable Data over Non-Access Stratum, DoNAS, data delivery in a roaming scenario, the method comprising:

sending from the V-SMF to a Home Session Management Function, H-SMF, a Packet Data Unit, PDU, session create request during PDU session establishment for DoNAS data delivery for a User Equipment, UE, wherein the PDU session create request comprises an indication that a control plane interface between the V-SMF and the H-SMF can be used for DoNAS data delivery, in a roaming scenario; and

receiving a response from the H-SMF, wherein the response from the H-SMF

provides an indication that the control plane interface between the V-SMF and the H-SMF is to be used for a data path for the DoNAS data delivery for the UE, and

wherein tunnel information for uplink traffic towards a Home User Plane Function, H-UPF, is not provided in the response.

2. The method of claim 1 further comprising:

prior to sending the PDU session create request to the H-SMF, receiving a create SM context request from an Access and Mobility Management Function, AMF; and

after receiving the response from the H-SMF, sending a create SM context accept message to the AMF.

3. The method of claim 1 , further comprising:

receiving a message from the UE comprising a data container comprising user data for the DoNAS data delivery between a Network Exposure Function, NEF, and the UE; and

sending a message to the H-SMF that comprises a data container comprising the user data.

4. The method of claim 1 , further comprising:

receiving a message from the H-SMF comprising a data container comprising user data for the DoNAS data delivery; and

sending a message from the V-SMF to the UE comprising a data container comprising the user data.

5. The method of claim 1 , wherein the DoNAS data delivery is via an extension to an existing Session Management Function, SMF, service operation.

6. The method of claim 1 , wherein the DoNAS data delivery is via the following data path:

UE↔V-SMF↔H-SMF↔NEF↔Application Function (AF)/Service Capability Server (SCS)/Access Stratum (AS).

7. A core network entity adapted to perform the method of claim 1 .

8. A method performed by a Home Session Management Function, H-SMF, in a core network of a cellular communications system to enable Data over Non-Access Stratum, DoNAS, data delivery in a roaming scenario, the method comprising:

receiving from a Visited Session Management Function, V-SMF, a Packet Data Unit, PDU, session create request during PDU session establishment for DoNAS data delivery for a User Equipment, UE, wherein the PDU session create request comprises an indication that a control plane interface between the V-SMF and the H-SMF can be used for DoNAS data delivery;

deciding whether to use the control plane interface between the V-SMF and the H-SMF for the DoNAS data delivery, or to use a user plane interface between a Visited User Plane Function, V-UPF, and a Home User Plane Function, H-UPF, for the DoNAS data delivery for the UE;

wherein if it is decided that the control plane interface is to be used for DoNAS data delivery;

sending a response to the V-SMF, wherein the response provides an indication that the control plane interface between the V-SMF and the H-SMF is to be used for a data path for the DoNAS data delivery for the UE, and

wherein tunnel information for uplink traffic towards a Home User Plane Function, H-UPF, is not provided in the response.

9. The method of claim 8 , further comprising:

receiving a message from a Network Exposure Function, NEF, comprising a data container comprising user data for the DoNAS data delivery between the NEF and the UE; and

sending a message to the V-SMF that comprises a data container comprising the user data.

10. The method of claim 8 , further comprising:

receiving a message from the V-SMF comprising a data container comprising user data for the DoNAS data delivery; and

sending a message from the H-SMF to a Network Exposure Function, NEF, comprising a data container comprising the user data.