[na85]

>although it's sometimes implemented via software means such as cryptographic tunneling rather than a physical gap.

I've never heard the term "air gap" refer to something that is actually only segmented in software, crypto or no.

[KMag]

Department of Defense requires air gaps between red and black[1] networks, but blackers[2] exist that can tunnel red traffic over block networks.

[1]https://en.wikipedia.org/wiki/Red/black_concept

[2]https://en.wikipedia.org/wiki/Blacker_(security)