A packet transmission method comprising: generating an information block including information payloads, the information payloads including source payloads having a variable length and each of the information payloads having a same information payload length; generating, based on the information block, a forward error correction, FEC, source packet block that includes a plurality of source packets, each of the plurality of source packets including a source payload identifier, ID, of the source payload, wherein the source payload ID includes a sequence number (ESI_SN) of an information payload included in the source packet; generating an FEC repair packet block that includes at least one repair packet based on the information block and FEC coding, each of the at least one repair packet including a repair payload corresponding to the source payloads and a repair payload ID of the repair payload; transmitting FEC configuration information including the information payload length and an identifier of a scheme for generating the information block; and transmitting the FEC source packet block and the FEC repair packet block, characterized in that the sequence number (ESI_SN) of the j-th source payload is obtained by incrementing the sequence number of the (j-1)-th source payload by A(j-1), wherein A(j-1) = ceil (S(j-1)/T), where T is the information payload length and S(j-1) is the size of the (j-1)-th source payload within a source flow starting with j=0, wherein said sequence number (ESI SN) starts from a random value for j=0 and is initialized to 0 after reaching a maximum integer value determined based on a predetermined number of bytes, and wherein the T is smaller than the maximum length of the source payloads in the source flow. generating an information block including information payloads, the information payloads including source payloads having a variable length and each of the information payloads having a same information payload length; generating, based on the information block, a forward error correction, FEC, source packet block that includes a plurality of source packets, each of the plurality of source packets including a source payload identifier, ID, of the source payload, wherein the source payload ID includes a sequence number (ESI_SN) of an information payload included in the source packet; generating an FEC repair packet block that includes at least one repair packet based on the information block and FEC coding, each of the at least one repair packet including a repair payload corresponding to the source payloads and a repair payload ID of the repair payload; transmitting FEC configuration information including the information payload length and an identifier of a scheme for generating the information block; and transmitting the FEC source packet block and the FEC repair packet block, characterized in that the sequence number (ESI_SN) of the j-th source payload is obtained by incrementing the sequence number of the (j-1)-th source payload by A(j-1), wherein A(j-1) = ceil (S(j-1)/T), where T is the information payload length and S(j-1) is the size of the (j-1)-th source payload within a source flow starting with j=0, wherein said sequence number (ESI SN) starts from a random value for j=0 and is initialized to 0 after reaching a maximum integer value determined based on a predetermined number of bytes, and wherein the T is smaller than the maximum length of the source payloads in the source flow.