On Wed, 29 Oct 2003, Juan Rodriguez Hervella wrote:
> On the other hand, I think that applications which
> query the DNS shouldn't be real-time applications, so I see this
> feature is not very useful.
How do you see people browsing the web get to the websites then, if not
using DNS? That's enough realtime in my book -- the user waits while the
request(s) is being processed.
I really don't understand what you're trying to say..
> If I understood Stig well, he said that people was
> turning off IPv6 because of delaying issues. Doing that is not an option if
> you want to allow your app. to run over "IPv6 AND IPv4". If you can not cope
> with such delays, maybe you shouldn't be using the DNS at all.
Then what? Distributed hosts file? ;-) ?
> The problem here is that most of the times this feature will fail back
> to the worst case, which is the normal getaddrinfo behaviour, because
> it's not as easy as checking for global IPv6 configured address, as Itojun
> has already said. We might come up with a lot of scenarios where this
> option might fail to improve the response time (e.g: only link-local
> addresses, global addresses but no default route, proper link local IPv6
> configuration but some black-hole on outer routers.....).
I fail to see the point here:
- if only link local addresses: fixed AI_ADDRCONFIG would fix
- if global but no default route:
a) without the on-link assumption: automatic immediate no route
message and fallback to the next address
b) with (current) on-link assumption: problematic (which is why the
assumption must be killed :-)
- if global, default route, but blackhole somewhere:
silently discarding packets is evil practice anyway and nothing can
be done about that, whether in case of v4 or v6.
- if global, default route, everything works, but some DNS server munges
the AAAA queries: can't help with that, but because v6 would be
used, that has to be fixed by fixing the servers anyway.
.. so my perception is that this would fix all the problems related to
partial IPv6 deployment I could think of w/ the elimination of the on-link
assumption pretty well.
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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