[nsd-users] Featurerequest for nsd4

John Peacock jpeacock at messagesystems.com
Tue Jan 29 16:34:27 CET 2013


On 01/29/2013 08:13 AM, W.C.A. Wijngaards wrote:
> TTL=10 seconds instead of this feature, would that not have almost the
> same semantics, except for higher server load before the timestamp is
> reached?  Is it about server load, and I think not, because the
> timestamp creates a high server load peak, where a normal changeover
> with a fixed TTL spreads out the query volume.

With a short TTL, you are guaranteed a high load for an extended time 
(basically as long as it takes to expire the previous longer TTL).  The 
whole point of this feature is to decrement the TTL gradually up until 
the old record expires, then immediately switch over to the new record 
(with a more reasonable TTL).  In practice, this means you only have a 
higher load for a relatively brief interval.  Essentially, the server 
always serves up the appropriate TTL so that this records information 
will expire at the same time, no matter when the client requested the 
records.

I have to say I loved this feature when I used tinydns (years ago) 
because it meant I could switch over DNS records at night (when load was 
low) without interruption and without having to be awake... ;-)

John


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