An SDN network system, comprising at least one N th level controller comprising a first N th level controller and at least two (N+1) th level controllers (121, 122) comprising a first (N+1) th level controller and a second (N+1) th level controller, wherein the first (N+1) th level controller and the second (N+1) th level controller belong to the first N th level controller, wherein N is an integer greater than or equal to 1, wherein the SDN network system further comprises a first node (141, 142) belonging to the first (N+1) th level controller (121, 122), a second node belonging to the second (N+1) th level controller and boundary nodes (131, 132) belonging to the first (N+1) th level controller (121, 122), wherein one of the boundary nodes (131, 132) is configured to connect to a node belonging to a different (N+1) th level controller, wherein the first (N+1) th level controller (121, 122) is configured to: receive a first message sent by the first node (141, 142) belonging to the first (N+1) th level controller (121, 122), wherein the first message comprises an identifier of the first node sending the first message; send a second message to the first N th level controller to which the first (N+1) th level controller (121, 122) belongs in response to determining that the first message is a cross-domain message comprising an identifier of the second node belonging to the second (N+1) th level controller, wherein the second message comprises an identifier of the first (N+1) th level controller (121, 122); characterized in that the first N th level controller is configured to receive the second message sent by the first (N+1) th level controller (121, 122) and perform decision processing according to status information of the first (N+1) th level controller (121, 122) and status information of the boundary nodes (131, 132) of the first (N+1) th level controller (121, 122), wherein the status information of one node indicates a usage state of the node, and the first N th level controller is further configured to receive a plurality of second messages sent by other (N+1) th level controllers (121, 122) belonging to the first N th level controller, and wherein the performing decision processing comprises performing decision processing according to the second message, and wherein the decision processing comprises: making a decision on a data route, or making a decision on a network topology, or updating status information of the first (N+1) th level controller managed by the first N th level controller, or updating status information of the boundary nodes of the first (N+1) th level controller. receive a first message sent by the first node (141, 142) belonging to the first (N+1) th level controller (121, 122), wherein the first message comprises an identifier of the first node sending the first message; send a second message to the first N th level controller to which the first (N+1) th level controller (121, 122) belongs in response to determining that the first message is a cross-domain message comprising an identifier of the second node belonging to the second (N+1) th level controller, wherein the second message comprises an identifier of the first (N+1) th level controller (121, 122); characterized in that the first N th level controller is configured to receive the second message sent by the first (N+1) th level controller (121, 122) and perform decision processing according to status information of the first (N+1) th level controller (121, 122) and status information of the boundary nodes (131, 132) of the first (N+1) th level controller (121, 122), wherein the status information of one node indicates a usage state of the node, and the first N th level controller is further configured to receive a plurality of second messages sent by other (N+1) th level controllers (121, 122) belonging to the first N th level controller, and wherein the performing decision processing comprises performing decision processing according to the second message, and wherein the decision processing comprises: making a decision on a data route, or making a decision on a network topology, or updating status information of the first (N+1) th level controller managed by the first N th level controller, or updating status information of the boundary nodes of the first (N+1) th level controller.