Re: [BEHAVE] I-D Action: draft-wing-behave-dhcpv6-reconfigure-00.txt

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

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On
> Behalf Of Brian E Carpenter
> Sent: Monday, October 31, 2011 1:22 PM
> To: Prashanth Patil
> Cc: [e-mail]
> Subject: Re: [BEHAVE] I-D Action: draft-wing-behave-dhcpv6-reconfigure-
> 00.txt
> 
> I don't get it. If a host is dual stacked it can be configured with
> any DNS server, as long as it is not a DNS64. If you can have a
> DNS64 directly visible, and a v4-only DNS server directly visible,
> you are on a dual stack network, so you can also have a dual stack
> DNS server directly visible.

It is anticipated that a network will have a mix of IPv4-only,
IPv6-only, and dual-stack hosts.  The hosts don't know if they
need a 'normal' DNS server or a DNS64, nor do we have a way
to tell them the difference.

This I-D attempts to provide a solution to that problem of a 
network with a mix of hosts that need to be configured with a 
'normal' DNS server and DNS64 server.  We believe the underlying 
idea (to "poke" a host to tell it something changed on the 
network) appears to have other applicability beyond the DNS/DNS64
use-case, as well.

-d


> Regards
>    Brian Carpenter
> 
> On 2011-11-01 05:05, Prashanth Patil wrote:
> > Hi Brian,
> > The idea behind the proposal is to provision a means by which traffic
> is
> > sent using IPv4 and not through the IPv6/IPv4 translator. The
> advantage
> > being that if NAT44 and NAT64 are deployed on the same network, it is
> > preferable to use NAT44 over NAT64 because of scale, performance and
> > application incompatibility issues (e.g., FTP) [RFC6384].
> > A "normal" DNS server does not have DNS64 capability. The IPv4-mapped
> > address for this "normal" server ensures that it can be reached only
> by
> > IPv4š. So if a host is IPv4-only, it will send a DNS query to the
> "normal"
> > server just to get the A records. If the host is dual-stack it will
> also
> > send a DNS query to the "normal" server to get both A and AAAA
> records. If
> > the destination address is an IPv4 address,  dual-stack host just
> gets A
> > records but not synthesized AAAA records. So this technique will
> ensure that
> > IPv4 is preferred over the IPv6/IPv4 translator prefix and also gives
> native
> > IPv6 higher precedence than IPv4.
> > If the host happens to be IPv6 only, then it cannot reach the
> "normal"
> > server because it has IPv4-mapped prefix as explained previously. So
> IPv6
> > only host can only reach DNS64 server. So this host will send the DNS
> query
> > to DNS64 to get AAAA records. Based on the destination address the
> host will
> > get IPv4-embedded IPv6 address or just the global IPv6 address.
> >
> > šNote: From RFC 6052
> > ³When presented with the IPv4-mapped prefix, current versions of
> Windows and
> > Mac OS generate IPv4 packets, but will not send IPv6 packets.²
> >
> > -Prashanth
> >
> > On 22/10/11 6:20 AM, Brian E Carpenter wrote:
> >> I have a basic question. Why does this draft define a 'normal'
> >> DNS server as one having an IPv4-mapped IPv6 address?
> >>
> >> That seems like a completely *abnormal* DNS server for a dual
> >> stack host. A dual stack host should normally have a DNS server
> >> with a regular IPv6 address that will return both A and AAAA
> >> records if they exist. Normally the server will be dual stacked
> >> anyway, and will return exactly the same response whether the
> >> query arrives via v4 or v6.
> >>
> >> A DNS server which only has an IPv4 address will also return
> >> A and AAAA records if they exist, so there is absolutely no
> >> difference as far as the dual stack host is concerned anyway.
> >> So what is the point in using the IPv4-mapped address?
> >>
> >> Regards
> >>     Brian
> >>
> >> On 2011-10-18 11:17, [e-mail] wrote:
> >>> A New Internet-Draft is available from the on-line Internet-Drafts
> >>> directories.
> >>>
> >>>     Title           : DHCPv6 Dynamic Re-Configuration
> >>>     Author(s)       : Dan Wing
> >>>                            Tirumaleswar Reddy
> >>>                            Prashanth Patil
> >>>     Filename        : draft-wing-behave-dhcpv6-reconfigure-00.txt
> >>>     Pages           : 10
> >>>     Date            : 2011-10-17
> >>>
> >>>     Some networks are expected to support IPv4-only, dual-stack,
> and
> >>>     IPV6-only hosts at the same time.  This makes prioritizing the
> DNS
> >>>     servers for hosts tricky due to a heterogeneous mix of protocol
> >>>     stacks causing optimal behavior to occur only when the host
> stack re-
> >>>     initializes.  The networks infrastructure is usually well
> equipped to
> >>>     be aware of single/dual-stack nature of hosts.  This
> specification
> >>>     extends DHCPv6 so that the DHCPv6 Relay Agent can dynamically
> >>>     influence the priority of DNS servers provided to the host, so
> that
> >>>     the host can use the optimal DNS server for resolution.
> >>>
> >>>
> >>> A URL for this Internet-Draft is:
> >>> http://www.ietf.org/internet-drafts/draft-wing-behave-dhcpv6-
> reconfigure-00.t
> >>> xt
> >>>
> >>> Internet-Drafts are also available by anonymous FTP at:
> >>> ftp://ftp.ietf.org/internet-drafts/
> >>>
> >>> This Internet-Draft can be retrieved at:
> >>> ftp://ftp.ietf.org/internet-drafts/draft-wing-behave-dhcpv6-
> reconfigure-00.tx
> >>> t
> >>> _______________________________________________
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> >>> or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
> >>>
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