Effects of Very Short TTLs

[Barry Margolin]

In article <806v2l$a26$1 at nntp.msstate.edu>,
Boyd Nation <boyd at Ra.MsState.Edu> wrote:
>We have a small DNS setup that requires the ability to make dynamic changes
>that propagate fairly quickly.  I know, or at least I think I know, that
>setting very short TTLs, on the lines of five minutes, will cause an
>increase in network traffic, but that's negligible in this case.  Are there
>any other effects that I should be aware of?

Be aware that BIND on the slave servers will not ordinarily check for zones
whose Refresh times have run out more often than every 15 minutes, so a
change on the master server could take 15 minutes to propagate to the slave
servers.  Thus, it could take up to 20 minutes for a change to propagate
(and even longer if the slaves are very busy, since they might not get a
chance to refresh the zone immediately when the 15 minutes is up).

If you use BIND 8 it will make use of the NOTIFY protocol, so the change
should propagate to slave servers almost immediately.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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