A method of transmitting broadcast signals, includes link processing input packets to generate link layer packets, wherein a link layer packet of the link layer packets includes a header and a payload, wherein the payload of the link layer packet includes a segment of an input packet or concatenated input packets, wherein the header of the link layer packet includes a first field for identifying whether the payload includes the segment or the concatenated input packets, and wherein the header further includes a second field for identifying a number of the concatenated input packets and third fields that are inserted to the header in the same order as the concatenated input packets present in the payload in response to the first field representing that the payload includes the concatenated input packets; physical processing the link layer packets into the broadcast signals; and transmitting the broadcast signals.