From what I gathered, CSMA detects that a medium is idle by checking for the occurence of the interpacket gap (IFS, 96 bits of 0s).
I'm wondering however what happens when you send an Ethernet frame which includes an IFS as its payload over the wire. Intuitively, it should cause another sender listening on the wire to immediately start its transmission, thus causing a collision. Is that expected or am I missing something?