No IPv6 by design to increase reliability...

Thu Jan 17 19:45:00 UTC 2019

I was having a debate with someone on this. Take a critical web site, 
say one where you want 100% global uptime, no potential issues with end 
users having connectivity or routing issues getting to your IP. Would it 
be advantageous to purposely not support a AAAA record in DNS and 
disable IPv6, only exist on IPv4?

My argument against this was "Broken IPv6 Connectivity" doesn't really 
occur anymore, also, almost all browsers and OS IP stacks implement 
Happy Eyeballs algorithm where both v4 and v6 are attempted, so if v6 
dies it will try v4. I would also argue that lack of IPv6 technically 
makes the site unreachable from native IPv6 clients, and in the event of 
an IPv4 outage, connectivity might still remain on IPv6 if the site had 
an IPv6 address (I've experienced scenarios with a bad IPv4 BGP session, 
but the IPv6 session remained up and transiting traffic...)

Thoughts?

-John