ttl delegations question

[phn at icke-reklam.ipsec.nu]

Matus UHLAR - fantomas <uhlar at fantomas.sk> wrote:
> Hello,

> there are some domains that have TTL for their own records lower than TTL
> for glue records in their superior domains. e.g.:

> uhlar at fantomas% dig ns documentum.com. @a.gtld-servers.net
> [...]
> documentum.com.         172800  IN      NS      ns10.documentum.com.
> documentum.com.         172800  IN      NS      ns11.documentum.com.
> [...]
> ns10.documentum.com.    172800  IN      A       198.182.5.170
> ns11.documentum.com.    172800  IN      A       198.182.5.174

> uhlar at fantomas% dig ns documentum.com. @198.182.5.170
> [...]
> documentum.com.         3600    IN      NS      ns10.documentum.com.
> documentum.com.         3600    IN      NS      ns11.documentum.com.
> [...]
> ns10.documentum.com.    3600    IN      A       198.182.5.170
> ns11.documentum.com.    3600    IN      A       198.182.5.174

> I'd like to ask, if BIND searches for e.g. MX record of documentum.com.
> domain, which TTL does it use? 

The TTL of the MX record :
;; ANSWER SECTION:
documentum.com.         1H IN MX        10 leopard.documentum.com.
documentum.com.         1H IN MX        10 cheetah.documentum.com.

plus the additional :
;; ADDITIONAL SECTION:
leopard.documentum.com.  1H IN A  198.182.5.226
cheetah.documentum.com.  1H IN A  198.182.5.225


> in first lookup, bind receives NS and A records with TTL 172800,
> in second lookup it receives the same NS and A records with TTL 3600.

> I'd like to know, which ttl is used in both cases? is it always the
> longer/shorter? Does TTL from zone override the glue TTL? 

The RR that should be used is the one from the zone. Delegation
and glue-records is used to "prime" the process.

> Does this behaviour differ between different BIND versions?

I think bind-8 will be "poisined" by the delegation records while
bind-9 does "The Right Thing".

> -- 
> Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
> Warning: I wish NOT to receive e-mail advertising to this address.
> Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
> I drive way too fast to worry about cholesterol. 


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        IPSec  Sverige      ( At Gothenburg Riverside )
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