In article
<2d106eb50710150849q350af366i21209801084f90a mail.gmail.com> you write:
>
>On 10/15/07, Mark Andrews <Mark_Andrewsisc.org> wrote:
>>
>> In article
<ECD70626-8EB0-4651-8A3E-51D783571389daork.net> you write:
>> >
>> >
>> >On 15/10/2007, at 8:24 PM, Martin Hannigan
wrote:
>> >
>> >> [moresnip]
>> >>
>> >> The way I read the portion of the thread
related to resolver behavoir
>> >> was that the resolver behavior was being
discussed. Not the client.
>> >> The resolver should have an attribute to
select the preference between
>> >> A vs. AAAA. Otherwise, it's setting
network policy through code.
>> >>
>> >> My question was if there is an option to
adjust this, where is it? I
>> >> don't see it. I'm not a BIND uber-expert.
If there is no option, there
>> >> quite possibly ought to be one.
>> >
>> >I guess the question could also be asked as to
whether BIND honours
>> >the host's configuration of the address
selection policy - which
>> >seems more likely than implementing it itself.
>> >
>> >For those who missed it - OS level address
selection policy won't
>> >apply to BIND without specific code, as BIND is
a recursive resolver
>> >so won't be calling getaddrinfo(3).
>> >
>> >--
>> >Nathan Ward
>>
>> named actually measures the response times to
individual addresses
>> and uses those to determine which servers to query.
Named also
>> uses what addresses it has before attempting to
determine if there
>> are alternate addresses.
>>
>> Address selection policies are kind of meaningless
in this environment.
>
>How so? I think it's valuable to be able to decide for
myself if I
>want preference for AAAA or A. If I understand what I am
reading, and
>am properly recalling past threads here, this would seem
important
>since it affects the user experience.
>
>As far as how it sets network policy goes, any time
something sets a
>preferred mode over other options and is not modifiable,
it's akin to
>setting policy. History has shown that most of us agree
with this.
>
>If I'm not interpreting this correctly, I'm all ears
(eyes).
>
>[ Note, I'm not making any assumption that anyone has
set out to set
>internet policy through software. ]
>
>-M<
getaddrinfo() is based on the assumption that there is
*not*
a cache response times etc. named builds such a cache.
To
do that however it needs to actually query the addresses.
It also has to have all the addresses to make that
determination.
Named works with partial information rather than going out
and fetching complete information then making the query.
Doing that would slow down the resolution process.
Most applictions also make exactly one connection and
making
sure that is optimal is useful. Named makes millions of
connections. It's a completely different class of
application.
Named is also pretty much agnostic about whether IPv4 or
IPv6 transport is used. At the moment it still tends to
be IPv4 as there is very little AAAA glue even when there
are AAAA records for the nameserver.
Mark
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