Overlay as a link

Hi, When youre doing overlay networking, i.e., you have tunnels from one virtual machine in a DC to another in another DC, then can i consider a tunnel between the two virtual machines as a "physical link" that exists in a regular network? I am wondering on what possibly can be the difference between a tunnel being considered as a link and a true physical link. I could run routing algorithms on both. The tunnel would only be considered as an interface. Or i could run BFD on both. Once difference that i can think of is that while you can send multiple frames together on a tunnel (for example if there are ECMP paths within the tunnel), you may not be able to send multiple frames at the same time on a physical link. Anything else? Glen