DirectAccess multisite selection algorithm

I'm curious how a DirectAccess multisite deployment determines what the "closest" entry point is.

Microsofts documentation indicates it uses an "algorithm" but doesnt detail what or how that algorithm works.  Does it use ping or a hop count to the entry point to determine which entry point is closer?

Could I get an answer on how a non-GSLB DirectAccess multisite deployment detects its "closest" entry point?

Thanks in advance,

Jonathon