[nsd-users] reloading NSD zone configuration
Greg A. Woods
woods at planix.ca
Sun Apr 26 03:06:17 UTC 2009
At Wed, 22 Apr 2009 19:31:23 +0200, Erik Romijn <erik at erik.io> wrote:
Subject: Re: [nsd-users] reloading NSD zone configuration
> Hosting zones for users, and promising them very quick set-up and master
> change times because they are very impatient :)
> But, if what I want can't realistically be done, 5 minutes would
> probably be acceptable.
Apparently your users think the DNS is more dynamic than it really is!
(and indeed more than it is meant to be!)
5 minute updates are more than adequate given the realistic minimum TTL
for any record is 5m anyway -- i.e. use that as your justification if
Realistically users shouldn't expect DNS updates even that often -- I'd
suggest advertizing a 30 minute minimum setup time cycle just for your
own sanity, never mind that of the software and protocols.
Indeed there are lots of instances of application-level caching which
can last as long as 30 minutes irrespective of the TTL in the RR
delivered to the application (eg. M$-IE).
Assuming you have truly geographically diverse authoritative nameservers
for all these hosted zones (as you should), then you're also going to
have to moderate your SLA for your DNS hosting based on whatever you can
expect for reach-ability of those remote nameservers too.
Manage your user expectations up front and they hopefully won't blow up
at you when things don't go exactly as planned.
Greg A. Woods
+1 416 218-0098 VE3TCP RoboHack <woods at robohack.ca>
Planix, Inc. <woods at planix.com> Secrets of the Weird <woods at weird.com>
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