A network node having ATCF for use in eSRVCC includes an SDP analyzing unit that acquires information regarding a codec contained in a SDP offer/SDP answer, a data storage unit that holds at least one of information regarding a codec supported by ATGW or a neighboring MGW, information regarding transcoding supported by the ATGW or the neighboring MGW, and information regarding a codec supported by a neighboring CS network, and a determination unit that determines whether transmission of the SDP offer for codec re-negotiation from the ATCF to a communication terminal is allowed using the information regarding a codec acquired in the SDP analyzing unit and information retrieved from the data storage unit.