In the optional implementation solution provided by the fourth aspect of the disclosure, the fifth message may include configuration information used by the user terminal to receive the data packet (that is, the function of the information is to inform the user how to receive data), or it may include the configuration information for the user to process the data packet after receiving the data packet (the function of the information is to inform the user how to process the data. For example, the configuration information may be the new security key information used by the user terminal after the node migrates in the network. Then the user may use the security key to process the received data packet).
Taking the user terminal as the execution subject, the above optional embodiment may further include step 4-1-2 as shown in 
In addition, in order to configure the user, the above implementation solution 1 may also include an interaction process between the target donor node/source donor node and the first node. Alternatively, the interaction process may include: