Re: [BEHAVE] Happy Eyeballs and DNS64 not sending synthetic AAAA RRs

["Stephan Lagerholm" <[e-mail]>]

Thu 8/4/2011 3:25 PM, Dan Wing:
> A nuance to this problem is that some networks will have a mix
> of hosts:
> 
>   (a) IPv4-only, which use a 'normal' DNS server
>   (b) dual stack hosts, which use a 'normal' DNS server
>   (c) IPv6-only hosts, which use a DNS64 server so they
>       can use a NAT64 to visit IPv4-only servers.
> 
> http://tools.ietf.org/html/draft-wing-behave-dns64-config-03 discusses
> the pros/cons of a bunch of mechanisms to provide the correct DNS
> server to all three of those host types.

The technique outlined in the draft doesn't work. Clients will not strictly
stick to the "ordered" list:
		::ffff:192.0.2.1       # 'normal' DNS server
		2001:db8:dddd::1234    # DNS64 server

If for example a client is trying to resolve
www.dns-will-timeout-for-this-domain.com then the client will switch to the
second DNS server in the list. In practice you will have about 50% traffic
to each server after a day or so. 

There are plenty of examples of domains that bind and other nameservers
never return an answer for. 

The right thing to do is to have different policies for the different
networks, potentially using views or other similar DNS mechanism.

/Stephan Lagerholm