Re: [BEHAVE] using IPv4-mapped DNS/DNS64 resolvers for dual-stack/IPv6-only hosts

["Dan Wing" <[e-mail]>]

> -----Original Message-----
> From: WashamFan [mailto:[e-mail]] 
> Sent: Monday, March 08, 2010 10:29 PM
> To: Dan Wing
> Cc: [e-mail]
> Subject: Re: [BEHAVE] using IPv4-mapped DNS/DNS64 resolvers 
> for dual-stack/IPv6-only hosts
> 
> Hi Dan,
> 
> IMO, whether normal DNS or DNS64 should be used depends
> on what applications residing in the host would be used.
> 
> Assume there are 2 applications installed on a DS host.
> one is DS suitable application (e.g., firefox browser),
> the other is IPv6-only application. When the DS suitable
> application is used, normal DNS is prefered. When the
> IPv6-only application is used, DNS64 is prefered.

I admit that I had not considered that.

Can you please name an IPv6-only application that runs on
a dual-stack host?

-d


> In that regard, detecting the type of the hosts
> make little sense to me. applications used rather than
> the host they reside in matters to this issue.
> 
> Thanks,
> washam
> 
> ----- Original Message -----
> From: Dan Wing <[e-mail]>
> Date: Tuesday, March 9, 2010 11:21 am
> Subject: Re: [BEHAVE] using IPv4-mapped DNS/DNS64 resolvers 
> for dual-stack/IPv6-only hosts
> To: 'Zhen Cao' <[e-mail]>
> Cc: [e-mail]
> 
> 
> >  
> >  
> >  > -----Original Message-----
> >  > From: Zhen Cao [mailto:[e-mail]] 
> >  > Sent: Monday, March 08, 2010 7:13 PM
> >  > To: Dan Wing
> >  > Cc: [e-mail]
> >  > Subject: Re: [BEHAVE] using IPv4-mapped DNS/DNS64 resolvers 
> >  > for dual-stack/IPv6-only hosts
> >  > 
> >  > Late catch-up with one comment on the approach:
> >  > 
> >  > if a dual stack host sends a query to first DNS 
> (::ffff:192.0.2.1) 
> > but
> >  > fails to get any resultsr, it will failover to the second DNS 
> >  
> >  Right.
> >  
> >  > and there will be the same problem that traffic will be 
> translated 
> > 
> >  > via NAT64?
> >  
> >  Yes.
> >  
> >  So that means the first DNS server better be working.  
> >  
> >  I expect the industry can accomplish that.  _One_ way to 
> accomplish 
> > that is to
> >  operate both servers on the same physical server, 
> listening on two different
> >  IP addresses, and responding differently based on the 
> incoming packet.
> >  
> >  
> >  So far, based on email discussion, this is the only viable 
> idea that 
> > does not
> >  require modifying the host.  (I consider the DHCPv6 
> manipulations in 
> > my draft
> >  to be non-viable, even though they do not require 
> modifying the host).
> >  
> >  -d
> >  
> >  
> >  > Thanks,
> >  > Zhen
> >  > 
> >  > On Sat, Feb 13, 2010 at 4:00 AM, Dan Wing 
> <[e-mail]> wrote:
> >  > > A few weeks ago there was an active thread on BEHAVE and 
> >  > [e-mail],
> >  > > worrying about how a network containing a mix of dual-stack 
> >  > hosts and
> >  > > IPv6-only hosts would work.  Ideally, to prevent 
> >  > unnecessary address family
> >  > > translation, the dual-stack hosts should use a 'normal' DNS 
> >  > resolver and the
> >  > > IPv6-only hosts should use a DNS64 resolver.  However, it 
> >  > is difficult to
> >  > > detect if a host is dual-stack or is IPv6-only.
> >  > >
> >  > > So, I wrote an Internet Draft describing details of several 
> >  > approaches that
> >  > > had been discussed on the mailing list, and attempted to 
> >  > provide a list of
> >  > > advantages/disadvantages to each.
> >  > >
> >  > >
> >  > > While writing them down, I came up with another approach 
> >  > which uses an
> >  > > IPv4-mapped address in the list of IPv6 DNS servers.  An 
> >  > IPv6-only host cannot
> >  > > use that address, so it would use the next DNS server on the 
> > list; a
> >  > > dual-stack host can use such a DNS server.  Details are in:
> >  > >
> >  > > 
> >  > http://tools.ietf.org/html/draft-wing-behave-dns64-config-02#s
> >  > ection-3.1
> >  > >
> >  > > Please comment on this approach.  For whatever it's worth, 
> >  > the idea seems to
> >  > > work.
> >  > >
> >  > > -d
> >  > >
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