Why is $TTL required for the root hints?

Kevin Darcy kcd at daimlerchrysler.com
Mon Sep 24 15:24:46 UTC 2001


Roy Arends wrote:

> On Sun, 23 Sep 2001, Jesper Dybdal wrote:
>
> > I have just upgraded from BIND 8.2.3 to 9.2.0rc3.
> >
> > I was surprised to see that BIND 9 insists on my having a $TTL in the root
> > hints file.
> >
> > What is the meaning - if any - of the TTL value for the root hints?
>
> Every record BIND caches will need to have a TTL value as is required by
> rfc1035.

Well, that's true, but irrelevant. The root hints -- "SBELT" in RFC parlance --
are a separate resource from the CACHE (see RFC 1034, Section 5.3.2 --
"Resources"). The fact that master-file format is used for both sets of data,
is a BINDism. TTLs are meaningless to SBELT/hints. I vote for the hints file to
have no TTL requirements. If it's true, as Barry suggests, that
BIND *converts* the hints into cache entries when the root servers are
unavailable, then it should make up a reasonable TTL value for those entries if
and when it does that conversion.


- Kevin




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