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

Ted Lemon writes:
> What's your experience with this - do you have any measurements about what 
> happens in practice as the time to die approaches?

Clients throw the record away shortly after the time-to-die, and ask for
new data when they need it, exactly as desired. Exception: some broken
programs like nscd keep the record for a while.

The overall effect is similar to what happens when you manually set a
low TTL. The advantage is that setting a time-to-die allows extra
caching before the time-to-die; a low TTL doesn't. (There's also a
user-interface advantage of scheduling the change in advance, but this
isn't a protocol issue.)

> we were concerned that if you do something like this, the effect is
> going to be a refresh storm as the time to die gets closer

Please define ``refresh storm.'' Do you describe TTL-0 records as
causing ``refresh storms''?

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

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