[dns-operations] caches only resetting TTL? was Re: Where to find "DNS resolution path corruption"?

[Roy Arends]

On Feb 20, 2008, at 10:01 AM, Antoin Verschuren wrote:
> I'm usualy having a hard time explaining ISP's they should delete  
> their authoritative zone when authority is transfered away from  
> them. Most ISP's seem to think that a record allways expires in a  
> cache, and it then allways queries the root path for a new entry,  
> instead of only updating the TTL from the authoritative source they  
> allready have in their cache. They mistakenly think they are no  
> longer queried after their former parrent changed the delegation.
>
If a cached TTL for an NS record set decreases to zero, I assume it is  
not used (and deleted). In absence of this NS record set, the resolver  
has to query the authoritative server for the closest name (some  
ancestor) in its cache, and if all else fails, the root. A fresh NS  
record set, possibly with new information is then cached, not simply  
resetting the TTL of cached and possibly wrong information.

In short, you suggest that historic paths might still be used. IIMHO  
that is a software bug, as it seems to violate protocol.

Or did I miss something?

Roy

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