Abstract: In one aspect, a control plane Interworking Function (IWF-C) is used to establish a Packet Data Unit (PDU) session in a data communications network. A create session request is received, for example from a Mobile Management Entity (MME). A create session management context request is generated by the IWF-C and transmitted to a Session Management Function (SMF). A create session management context request response is received from the SMF. A create session request response is generated by the IWF-C and sent, for example to the MME. In other aspects, control plane policy interworking and user plane interworking is provided between components of 4G and 5G networks.