Configuring different TTLs in multiple RRs for the same domain name, TYPE, and CLASS

Dave Warren davew at
Thu Mar 24 22:11:27 UTC 2016

On 2016-03-24 09:50, Barry Margolin wrote:
> The problem with this is that when the Office 365 records expire and are
> removed from the cache, but the other records have not, the server will
> not know that it should re-query for the O365 records. It still has TXT
> records in its cache, and it will return them in response to a query.
> It won't go back to the authoritative server until ALL the TXT records
> expire. During the period between the short TTL and the longest TTL, it
> will be as if the short-TTL records don't exist at all.

Or if a caching resolver did make a "note to self" that there are 
missing records that need to be replaced, what would be the point of 
keeping any records with a longer TTL? A resolver would still be sending 
the same queries to refresh the entry with the shortest TTL anyway, so 
it wouldn't reduce the query volume.

Dave Warren

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