I have read the SuperUser blog post here about how Windows checks if there is an internet connection using NCSI. Is there an equivalent in the Mac world?
EDIT: I just found the post below at gossamer threads Posted by lorenzo at google Nov 15, 2012, 4:08 AM
"The Apple algorithm has drawbacks too. To wit: 1. It biases in favour of IPv4 by trying the A record first. 2. By always preferring the fastest protocol, even on a perfect dual-stack network it will use IPv6 only ~50% of the time (unless IPv4 is degraded). 3. It imposes twice the connection load on server operators. 4. It's non-deterministic, which some websites don't like as they tie your cookies to your IP address."
I just haven't found any more details of the algorithm, eg what url / dns they use. My Google searches produce a lot of irrelevant information - can anyone point me in the right direction?