Minimum TTL?

Reindl Harald h.reindl at
Thu Feb 8 15:42:13 UTC 2018

Am 08.02.2018 um 16:39 schrieb Reindl Harald:
> Am 08.02.2018 um 16:34 schrieb Mukund Sivaraman:
>> On Thu, Feb 08, 2018 at 01:30:04PM +0200, Michelle Konzack wrote:
>>> Hello Harald,
>>> Am 2018-02-08 hackte Reindl Harald in die Tasten:
>>>> you miss the topic
>>>> many DNSBL's have a very short TTL and at the same time a limit of
>>>> queries froma single IP until you need to pay for the service
>>>> so if you have a inbound MX and the RBL has 2 seconds TTL and a botnet
>>>> is trying to deliver spam to you override the 2 scodn TTL with 90
>>>> seconds or whatever makes sense reduces the total amount of DNS 
>>>> requests
>>>> dramatically
>>> Sounds logic.
>>> And this feature was rejected by the Bind Developers?
>> If the RRset wants a TTL of N seconds, then that is the authoritative
>> instruction from the owner of the zone about how the data should be
>> used. We have to follow that. The RFCs so far do not allow increasing
>> TTL, though they allow decreasing it.
>> If a DNSBL zone has a TTL of 2 seconds, then talk to the zone owner
>> about why it is so. There ought to be a reason from their perspective
>> why it is set to 2s
> so what - nobody can force me to ask him the same question every 2 
> seconds and as long it's a local resolver for my own services the one i 
> have to ask about any why in doubt is the person i face in the mirror 
> every morning
> yes, you are free to decide that named don't need to support the users 
> wish of such a feature. but the result is that the user stops to use 
> named at all on a inbound-mailserver and is done

and BTW - i don't need to ask the zone owner because common sense has 
the answer already: to have answers as real-time as possible nad let as 
less as possible new listings slip through

it's still my decision as mailadmin if i need that accuracy

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