What "all the ethernet control frame juju" might you be referring to? I don't recall Ethernet, in and of itself, just sending stuff back and forth.
I did not read the 100G Ethernet specs, but as far as I remember FastEthernet (e.g. 100BASE-FX) uses 4B/5B coding on the line, borrowed from FDDI. Octets of Ethernet frames are encoded to these 5-bit codewords, and there are valid codewords for other stuff, like idle symbols transmitted continuously between frames. Gigabit Ethernet (1000BASE-X) uses 8B/10B code on the line (from Fibre Channel). In GE there are also special (not frame octet) PCS codewords used for auto-negotiation, frame bursting, etc. So I guess these are not frames that you see, but codewords representing other data, outside Ethernet frames. András