Re: [dhcwg] DDNS-DHCP [6]: Relationship between DNS TTL and DHCP lease length

Bruce Campbell writes:
> So... if a record is due to expire in 1500 seconds, and you know that the
> slave 'should' transfer the zone again via axfr in 1300 seconds (via SOA
> values), you will merrily supply a 2 second TTL on said records

Correct. Yes, short TTLs cause minor increases in the frequency of DNS
lookups, but long TTLs cause administrative headaches. If the next AXFR
is delayed, the old data will stick around longer than it should. 

> Still, when new records are created, you have to propagate the information
> outwards.  Rsync, AXFR and IXFR are all unsuitable for this in a
> frequently changing environment due to their associated overhead.

Actually, rsync and tinydns-data can make any number of updates to a
multiple-megabyte database in well under a second on a typical computer.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago

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