A method of enabling a Gateway User plane, GW-U, node in a core network of a mobile communication network to perform mobility operations based on a type of Radio Access Technology, RAT, used by a User equipment, UE, for conveying Internet Protocol, IP, user data over an IP Connectivity Access Network, IP CAN, bearer in an IP CAN session between said UE and an external IP network, wherein said method comprises the steps of: - receiving (23, 63), by a Gateway Control plane, GW-C, node, a Session Create message for creating said IP CAN session between said UE and said external IP network; - transmitting (24, 64), by said GW-C node, an Establishment Request message towards a Policy and Charging Rules Function, PCRF, node, for retrieving policies for said IP CAN session; characterized in that said method comprises the steps of: - receiving (28, 68), by said GW-C node, an Establishment Response message, wherein said Establishment Response message comprises an indication being one of: - an indication that an access node in a Radio Access Network, RAN, is to insert type of RAT in said IP user data packet; - an indication that a Gateway User plane node is to determine said RAT type by implementing a Reinforcement Learning Agent, RLA, operating with an observation space comprising possible RAT types, a reward space comprising a reward referring to said RAT type, and an action space comprising a set of user plane traffic enforcement actions; - selecting (29, 69), by said GW-C node, a Gateway User plane, GW-U, node, based on said indication; - transmitting (30, 70), by said GW-C node, a Session Establishment Request message to said selected GW-U node, wherein said Session Establishment Request message comprises said indication. - receiving (23, 63), by a Gateway Control plane, GW-C, node, a Session Create message for creating said IP CAN session between said UE and said external IP network; - transmitting (24, 64), by said GW-C node, an Establishment Request message towards a Policy and Charging Rules Function, PCRF, node, for retrieving policies for said IP CAN session; - receiving (28, 68), by said GW-C node, an Establishment Response message, wherein said Establishment Response message comprises an indication being one of: - an indication that an access node in a Radio Access Network, RAN, is to insert type of RAT in said IP user data packet; - an indication that a Gateway User plane node is to determine said RAT type by implementing a Reinforcement Learning Agent, RLA, operating with an observation space comprising possible RAT types, a reward space comprising a reward referring to said RAT type, and an action space comprising a set of user plane traffic enforcement actions; - an indication that an access node in a Radio Access Network, RAN, is to insert type of RAT in said IP user data packet; - an indication that a Gateway User plane node is to determine said RAT type by implementing a Reinforcement Learning Agent, RLA, operating with an observation space comprising possible RAT types, a reward space comprising a reward referring to said RAT type, and an action space comprising a set of user plane traffic enforcement actions; - selecting (29, 69), by said GW-C node, a Gateway User plane, GW-U, node, based on said indication; - transmitting (30, 70), by said GW-C node, a Session Establishment Request message to said selected GW-U node, wherein said Session Establishment Request message comprises said indication.