The present disclosure provides a data transmission method of a system in an IP based broadcasting network, the data transmission method comprising the steps of: generating an MPEG media transport protocol (MMTP) packet using a media processing unit (MPU) for a service; generating an IP packet using the MMTP packet; generating a layer 2 (L2) packet using the IP packet and generating a layer 1 (L1) packet stream using the L2 packet; and transmitting the L1 packet stream, wherein absolute time information of the system is included in one of a transmission frame of the L1 packet stream and the L2 packet.