[dns-operations] Signaling client protocol to authority

[Mark Andrews]

In message <AANLkTinXJwnmm7yqAZzxtMXYkXjViQY_A6og+zmFrnL7 at mail.gmail.com>, Dan Col
lins writes:
> On Sun, Jan 16, 2011 at 1:46 PM, Patrick W. Gilmore <patrick at ianai.net> wrote:
> > The problem is end users who have no v6 connectivity ask for quad-A, and they 
> do it over v4.
> 
> Forgive me, but...exactly. Isn't that the problem? Not that a DNS
> server sends them an AAAA record that they can't use, but that they
> asked for an AAAA record that they can't use. The problem lies in the
> client that's making requests for an address using a protocol that it
> ought to know it can't use, and the problem is absolutely not that the
> server is doing exactly what the client asked it to do.

The problem is that client application developers have naive recovery
strategies for multi-homed servers.  The problem is applicable to
any unreachable address (IPv4 or IPv6) which is not being reported
to the application and you have a multi-homed server.

> It isn't the job of a DNS server to decide what the DNS client actually wants.

+1000

> --Dan
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org