Because the minimum length of an Ethernet frame is 64 bytes, the flag header has a 40-bit “padding” field. To meet this requirement, we purposely make the length of the flag header to be 6 bytes so that together with a 14-byte Ethernet header, a 20-byte IP header, an 8-byte UDP header, and a 16-byte msg, the total length of an IoT message is 64 bytes.