TTLs and Timeout Question

listmail listmail at entertech.com
Tue Mar 29 19:07:28 UTC 2011


On Tue, 29 Mar 2011 10:52:49 -0700, Kevin Oberman wrote
> > From: "listmail" <listmail at entertech.com>
> > 
> > I'm investigating the failure of a slave server during a network outage at a
> > primary server.
> > 
> > The SOA TTL was 1 week on most zones, but the individual records had short
> > TTLs, on the order of an hour. The outage lasted long enough for these shorter
> > TTLs to expire.
> > 
> > My question is: Will a BIND slave server stop serving RRs when their
> > individual TTLs have expired, or only when the SOA TTL has expired?
> 
> Bill,
> 
> You are getting issues confused. TTL is the time for a server to 
> cache data for which it is not authoritative. For an authoritative 
> server TTL is irrelevant. Also, the TTL in the SOA is the TTL for 
> negative cache entries, not cached data. (And, if the server is 
> authoritative, it is NOT cached data.)
> 
I guess I didn't state my question very well. When I referred to the SOA TTL,
I was referring to the "expire" field, not the negative cache timeout field.

> The relevant field in the SOA is the "expire' field. If the server 
> has either transferred the zone from the master server or confirmed (via
> serial #) that the current data is still current. If the data is
> expired, the slave will stop serving it. Until then, it will serve it
> and TTL has absolutely nothing to do with this.
> 

So is this correct: A slave will continue serving RRs regardless of their TTL,
as long as the "expire" value in the SOA has not expired?

If true, I need another theory as to why the slave stopped serving records.

Thanks,
--Bill



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