[dns-operations] TTL=0

Andrew Sullivan ajs at anvilwalrusden.com
Sat Jan 19 00:36:08 UTC 2019


Section 8?
-- 
Andrew Sullivan
Please excuse my clumbsy thums.

On January 18, 2019 19:05:56 Greg Choules <gregchoules at googlemail.com> wrote:
> Hi Andrew.
> Which bit of 2181?
>
> On Fri, 18 Jan 2019 at 23:55, Andrew Sullivan <ajs at anvilwalrusden.com> wrote:
> Seems to me RFC2181 already answered this years ago.
> --
> Andrew Sullivan
> Please excuse my clumbsy thums.
>
> On January 18, 2019 17:21:40 Greg Choules <gregchoules at googlemail.com> wrote:
>> Hi Fred.
>> No, I am not talking about dscacheutil or any particular client software. I 
>> just want to know whether, in the opinion of the world's DNS professionals, 
>> recursive servers should or shouldn't ever send answers from cache with TTL=0.
>>
>> cheers, Greg
>>
>> On Thu, 17 Jan 2019 at 23:15, m3047 <m3047 at m3047.net> wrote:
>> Who cares about the RFC? In practice, SOME caching resolvers (and that's
>> being charitable) WILL answer with TTL=0. I've had to live with PFSense
>> deployments which did this.
>>
>> Which in turn leads to things like (for Mac users):
>>
>> dscacheutil -flushcache
>>
>> Is that what you're talking about?
>>
>> On Thu, 17 Jan 2019, Greg Choules wrote:
>>> [...]
>>>
>>> Is there ever a case, for cached answers, that the recursive server would
>>> answer the client with TTL=0? Or would that be illegal? RFC1034 states that
>>> records with TTL=0 "should not be cached". Note "should" and not "must".
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