Dynamic discovery of network functions in mobility interworking across radio access technologies

1. A device, comprising:

a processing system including a processor; and

a memory that stores executable instructions that, when executed by the processing system, facilitate performance of operations, the operations comprising:

detecting user equipment (UE) in a fifth generation (5G) network;

determining, by the processing system, that the UE has crossed a threshold and is leaving a coverage area of the 5G network;

discovering, by the processing system, a mobile management entity (MME) in a Long-Term Evolution (LTE) network covering an area that the UE is within, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) in the LTE network provides access to a packet data network (PDN) through a user data plane function (UPF);

transferring, by the processing system, metadata associated with the UE to the MME;

handing over, by the processing system, cellular services to the LTE network; and

providing access, by the processing system, to the PDN through the PGW-C/SMF and through a Serving Gateway (SGW), after the handing over.

2. The device of claim 1 , wherein the MME provides services to the coverage area of the LTE network.

3. The device of claim 1 , wherein a network repository function (NRF) discovers the MME responsive to a message received from an access mobility management function (AMF) in the 5G network.

4. The device of claim 3 , wherein the message is passed over a first Representational State Transfer (REST) Application Programming Interface (API).

5. The device of claim 3 , wherein the transferring is performed by the AMF passing messages over an enhanced N26 interface to the MME using a second REST API.

6. The device of claim 3 , wherein the NRF discovers the MME without using a domain name service (DNS) protocol.

7. The device of claim 3 , wherein the NRF and the AMF are virtual network elements.

8. The device of claim 1 , wherein the processing system comprises a plurality of processors operating in a distributed computing environment.

9. A non-transitory, machine-readable medium, comprising executable instructions that, when executed by a processing system including a processor, facilitate performance of operations, the operations comprising:

detecting user equipment (UE) in a fifth generation (5G) network;

determining that the UE has crossed a threshold and is leaving a coverage area of the 5G network;

discovering a mobile management entity (MME) in a Long-Term Evolution (LTE) network covering an area that the UE is within, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) in the LTE network provides access to a packet data network (PDN) through a user data plane function (UPF);

transferring metadata associated with the UE to the MME;

handing over cellular services to the LTE network; and

providing access to the PDN through the PGW-C/SMF and through a Serving Gateway (SGW) after the handing over.

10. The non-transitory, machine-readable medium of claim 9 , wherein the MME provides services to the coverage area of the LTE network.

11. The non-transitory, machine-readable medium of claim 9 , wherein the processing system comprises a plurality of processors operating in a distributed computing environment.

12. The non-transitory, machine-readable medium of claim 9 , wherein a network repository function (NRF) discovers the MME responsive to a message received from an access mobility management function (AMF) in the 5G network.

13. The non-transitory, machine-readable medium of claim 12 , wherein the NRF discovers the MME without using a domain name service (DNS) protocol.

14. The non-transitory, machine-readable medium of claim 12 , wherein the NRF and the AMF are virtual network elements.

15. The non-transitory, machine-readable medium of claim 12 , wherein the message is passed over a first Representational State Transfer (REST) Application Programming Interface (API).

16. The non-transitory, machine-readable medium of claim 15 , wherein the transferring is performed by the AMF passing messages over an enhanced N26 interface to the MME using a second REST API.

17. A method, comprising:

detecting, by a processing system including a processor, user equipment (UE) in a fifth generation (5G) network;

determining, by the processing system, that the UE has crossed a threshold and is leaving a coverage area of the 5G network;

discovering, by the processing system, a mobile management entity (MME) in a Long-Term Evolution (LTE) network covering an area that the UE is within, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) in the LTE network provides access to a Packet Data Network (PDN) through a user data plane function (UPF);

transferring, by the processing system, metadata associated with the UE to the MME;

handing over, by the processing system, cellular services to the LTE network; and

providing access, by the processing system, to the PDN through the PGW-C/SMF and through a Serving Gateway (SGW), after the handing over.

18. The method of claim 17 , wherein a network repository function (NRF) discovers the MME responsive to a message received from an access mobility management function (AMF) in the 5G network.

19. The method of claim 18 , wherein the NRF and the AMF are virtual network elements and wherein the metadata comprises status, heartbeat timer, Internet Protocol address, capacity, priority, load, locality, services supported, or a combination thereof.

20. The method of claim 18 , wherein the NRF discovers the MME without using a domain name service (DNS) protocol.