A device for an Application Function, AF, node, the device comprising: at least one processor; and at least one memory for storing instructions and operably electrically connectable to the at least one processor, wherein the instructions, based on being executed by the at least one processor, perform operations comprising: transmitting, to a Session Management Function, SMF, node, a request message for requesting subscription to an AF notification for a User Plane, UP, related event; based on i) a condition for the AF notification having been met and ii) an early direct notification is requested by the AF node, receiving, from the SMF node, a notification message for the UP related event, wherein the notification message includes a target Data Network Access Identifier, DNAI, of a Protocol Data Unit, PDU, session; and based on inability to immediately process a subsequent operation according to the notification message, wherein the subsequent operation includes an operation of a relocation of an application server, transmitting, to the SMF node, a response message in response to the notification message, wherein the response message includes a temporary negative response, wherein, based on transmission of the response message including the temporary negative response, a negative response is not transmitted, and wherein the notification message includes information informing a change of a UP path, and wherein the request message includes information informing that the SMF node should wait for reception of the response message after transmitting the notification message. at least one processor; and at least one memory for storing instructions and operably electrically connectable to the at least one processor, wherein the instructions, based on being executed by the at least one processor, perform operations comprising: transmitting, to a Session Management Function, SMF, node, a request message for requesting subscription to an AF notification for a User Plane, UP, related event; based on i) a condition for the AF notification having been met and ii) an early direct notification is requested by the AF node, receiving, from the SMF node, a notification message for the UP related event, wherein the notification message includes a target Data Network Access Identifier, DNAI, of a Protocol Data Unit, PDU, session; and based on inability to immediately process a subsequent operation according to the notification message, wherein the subsequent operation includes an operation of a relocation of an application server, transmitting, to the SMF node, a response message in response to the notification message, wherein the response message includes a temporary negative response, wherein, based on transmission of the response message including the temporary negative response, a negative response is not transmitted, and wherein the notification message includes information informing a change of a UP path, and wherein the request message includes information informing that the SMF node should wait for reception of the response message after transmitting the notification message. transmitting, to a Session Management Function, SMF, node, a request message for requesting subscription to an AF notification for a User Plane, UP, related event; based on i) a condition for the AF notification having been met and ii) an early direct notification is requested by the AF node, receiving, from the SMF node, a notification message for the UP related event, wherein the notification message includes a target Data Network Access Identifier, DNAI, of a Protocol Data Unit, PDU, session; and based on inability to immediately process a subsequent operation according to the notification message, wherein the subsequent operation includes an operation of a relocation of an application server, transmitting, to the SMF node, a response message in response to the notification message, wherein the response message includes a temporary negative response, wherein, based on transmission of the response message including the temporary negative response, a negative response is not transmitted, and wherein the notification message includes information informing a change of a UP path, and wherein the request message includes information informing that the SMF node should wait for reception of the response message after transmitting the notification message.