While searching how the PHY LINK status is determined, I stumbled across this answer :
In 100BaseTX Ethernet, link pulses aren't used, but instead, link status is detected and maintained via the continuous reception of Idle ("/I/") 4B/5B codewords (Figure 13 in AN1120).
Where the idle code message is coming from? is it sent directly by the PHY (layer one protocol) or it's coming from the MAC (layer 2) or even above?
Should both parties continuously send the Idle code ?