A method of transmitting a broadcast signal is discussed. The method includes generating, by a broadcast transmitter, a plurality of input packets comprising broadcast data, generating, by the broadcast transmitter, link layer packets carrying the input packets, wherein a link layer packet among the link layer packets includes a header and a payload, wherein the header includes information about whether an additional header following the header exists or not, wherein the header includes information indicating least significant bits (LSBs) of a length of the payload, and when the additional header exists, the additional header includes information indicating most significant bits (MSBs) of the length of the payload, and wherein the link layer packets include signaling information for header compression of the input packets when the input packets are compressed internet protocol (IP) packets, and transmitting, by the broadcast transmitter, the generated link layer packets through a physical layer pipe (PLP).