A method for performing a handover between core networks (208, 232) in a communication network, the method being performed by an interworking mobility management entity, eMME, within a first core network, comprising: receiving (2302, 2402), from a first control plane mobility management and/or session management entity (316, 218) within the first core network supporting a first radio access technology, RAT, a handover request for performing a handover of a user equipment, UE, from a first wireless access network utilizing the first RAT to a second wireless access network utilizing a second RAT, identifying data flows (610a-610e) within one or more active Data Network Session, DNS, connections of the UE to be handed over from the first wireless access network to the second wireless access network, wherein the one or more active DNS connections are connections (600a, 600b, 600c) between the UE and one or more user plane gateways (224a, 224b, 224c) in the first core network through the first wireless access network before the handover, wherein the active DNS connections are connections for communicating, before the handover, the data flows (610a-610e) between the UE and one or more external data networks (226a, 226b) connected to the user plane gateways (224a, 224b, 224c); for each of the identified data flows (610a-610e), determining a mapping between the data flow and a corresponding Packet Data Network, PDN, connection and a corresponding Generic Tunneling Protocol, GTP, tunnel within the corresponding PDN connection for communicating over the second wireless access network, wherein the interworking mobility management entity, eMME, supports multiple data flows on a single PDN connection; providing mapping information indicating the determined mapping between the data flows and the corresponding PDN connections and the corresponding GTP tunnels within the corresponding PDN connections to an interworking serving gateway, eSGW, within the first core network, wherein the PDN connections are connections (PDN1, PDN2) between the UE and the eSGW through the second wireless access network after the handover, the PDN connections (PDN1, PDN2) comprising one or more GTP tunnels between the eSGW and the second wireless access network and the PDN connections being further mapped onto one or more additional GTP tunnels (900a, 900b, 900c) between the eSGW and the one or more user plane gateways (224a, 224b, 224c). receiving (2302, 2402), from a first control plane mobility management and/or session management entity (316, 218) within the first core network supporting a first radio access technology, RAT, a handover request for performing a handover of a user equipment, UE, from a first wireless access network utilizing the first RAT to a second wireless access network utilizing a second RAT, identifying data flows (610a-610e) within one or more active Data Network Session, DNS, connections of the UE to be handed over from the first wireless access network to the second wireless access network, wherein the one or more active DNS connections are connections (600a, 600b, 600c) between the UE and one or more user plane gateways (224a, 224b, 224c) in the first core network through the first wireless access network before the handover, wherein the active DNS connections are connections for communicating, before the handover, the data flows (610a-610e) between the UE and one or more external data networks (226a, 226b) connected to the user plane gateways (224a, 224b, 224c); for each of the identified data flows (610a-610e), determining a mapping between the data flow and a corresponding Packet Data Network, PDN, connection and a corresponding Generic Tunneling Protocol, GTP, tunnel within the corresponding PDN connection for communicating over the second wireless access network, wherein the interworking mobility management entity, eMME, supports multiple data flows on a single PDN connection; providing mapping information indicating the determined mapping between the data flows and the corresponding PDN connections and the corresponding GTP tunnels within the corresponding PDN connections to an interworking serving gateway, eSGW, within the first core network, wherein the PDN connections are connections (PDN1, PDN2) between the UE and the eSGW through the second wireless access network after the handover, the PDN connections (PDN1, PDN2) comprising one or more GTP tunnels between the eSGW and the second wireless access network and the PDN connections being further mapped onto one or more additional GTP tunnels (900a, 900b, 900c) between the eSGW and the one or more user plane gateways (224a, 224b, 224c).