[dns-operations] To A or to AAAA - was Re: Signaling client

Doug Barton dougb at dougbarton.us
Mon Jan 17 21:40:30 UTC 2011

On 01/17/2011 13:28, Edward Lewis wrote:
> The reason for this rambling tirade is that Doug's part right but falls
> short when it gets to determining "address records they cannot use."
> That's impossible to "compute".  I might have a v6 set up in my house
> but be on a ISP that can route me to f.root-server.net/AAAA but not
> m.root-servers.net/AAAA (I've seen this).  An application can't possibly
> know a priori to ask for f's AAAA and not m's AAAA. Trying both will
> tell me, but not until I try.
> Applications need to be more aggressive and rugged in trying to reach
> whatever they want off the 'net.

I agree with your thorough response, mine was designed more to indicate 
that the right layer for the solution is _not_ the DNS.

That said, while I do agree in general that applications/OS' should have 
better heuristics in regard to connectivity I think that it should at 
least be possible for them to be smart enough to know what transports 
they definitely cannot use, and avoid breaking themselves by asking for 
them.  :)



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