[dns-operations] TTL=0

Greg Choules gregchoules at googlemail.com
Sat Jan 19 00:05:34 UTC 2019


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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