An operation method of a server in a communication network includes receiving a connection request message from each of a plurality of gateways connected to the server; identifying a service level of a terminal that has transmitted the connection request message based on information included in the connection request message; selecting a first gateway corresponding to the service level among the plurality of gateways as a gateway to which the terminal is to be connected; and transmitting a connection approval message, which is a response to the connection request message, to the terminal through the first gateway.