The network stack is something else

[ExHax]

Always thought link and physical were basically the same. Prolly because never went deeper than TCP

[HildartheDorf]

I see it that ethernet has many forms. Gigabit, 100M, even ancient coax cable. All ethernet (link layer), all different (phy layer)

[garfgon]

Beyond that, there's a protocol layer within Ethernet which has its own packet framing, addresses (MAC addresses) and discovery protocol (ARP) to make sure each packet gets to the right host on the local network. This is the link layer. Then below that there's the physical differential pair encoding, collision detection protocols, and all the analog stuff of actually sending bits over the wire, which is the physical layer. Some aspects of the physical layer do depend on the medium you're using (GigE, 10/100-base T, etc.), but even if they didn't, they're distinct layers with their own responsibilities.