3.1.1.6.5 Structure of Source Packets used for FEC Encoding
Only for the FEC Encoding operations, Source Packets are prepended with a 2 byte RDPUDP_PAYLOAD_PREFIX (section 2.2.2.3) header. This header is used only for the FEC encoding and decoding operations, and is not transmitted to the terminal client. This field contains the size of each Source Packet, specified in the network byte order. When a datagram is recovered using FEC, the first 2 bytes constitute of this header, and specify the size of the recovered datagram to the decoder.