1. A method for transmitting data by a transmitting User Equipment (UE) in a Device to Device (D2D) communication network, the method comprising:receiving a packet data convergence protocol (PDCP) service data unit (SDU) from a higher layer;
identifying a type of data included in the PDCP SDU;
generating a PDCP protocol data unit (PDU) comprising the PDCP SDU and a header; and
transmitting the generated PDCP PDU to a receiving UE,
wherein the header comprises information indicating the type of the data included in the PDCP SDU, and
wherein in case that the type of the data included in the PDCP SDU is an Internet Protocol (IP) packet type, the generating of the PDCP PDU comprises setting the information to a predefined value indicating that the type of the data included in the PDCP SDU is the IP packet type and performing a header compression of the PDCP SDU.