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

"D. J. Bernstein" <djb@cr.yp.to> Fri, 20 June 2003 20:09 UTC

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From: "D. J. Bernstein" <djb@cr.yp.to>
To: dhcwg@ietf.org, namedroppers@ops.ietf.org
Subject: Re: [dhcwg] DDNS-DHCP [6]: Relationship between DNS TTL and DHCP lease length
References: <200306200103.h5K13rWl030720@sandelman.ottawa.on.ca> <15427.1056102254@munnari.OZ.AU>
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tinydns has supported time-to-die since version 0.85 in February 2000.
It automatically reduces the TTL as the time-to-die approaches, and then
eliminates the record. See http://cr.yp.to/djbdns/tinydns-data.html.

The obsolete AXFR replication protocol is unable to copy time-to-die
information. This is one of the many reasons that I recommend rsync for
replication. See http://cr.yp.to/djbdns/tcp.html#intro-axfr.

Client systems running the clueless ``nscd'' program will keep data for
an hour no matter what the TTL says, but at least there's some limit.
Perhaps nscd will be fixed someday.

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

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