The prevent invention relates to a software defined network (SDN), providing a switch migration method for a SDN which is capable of recognizing that the switch migration mode has been changed from the openflow switch migration in which one of multiple slave controllers connected to a network switch enters the master mode towards another openflow switch migration in which the master mode controller to which packets are inputted by the switch enters the slave mode as well as providing the switch migration process with no packet being lost.
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