Re: [dhcwg] DDNS-DHCP [6]: Relationship between DNS TTL and DHCP lease length
Bruce Campbell <bc-namedroppers@vicious.dropbear.id.au> Tue, 24 June 2003 17:11 UTC
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Date: Tue, 24 Jun 2003 13:29:20 +0200
From: Bruce Campbell <bc-namedroppers@vicious.dropbear.id.au>
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Subject: Re: [dhcwg] DDNS-DHCP [6]: Relationship between DNS TTL and DHCP lease length
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[ TTD for clients ] On Mon, 23 Jun 2003, David Vixie wrote: > [robert campbell] > > What do clients see from tinydns? Eg, for a record of 'dying.example.com' > > which should expire at T+1500, would it be: > > > > So, Client A and Client B have _nearly_ the same RR set, just with > > different TTLs. > > no. ttl does not affect rrset identity. per [rfc2136 1.1.1] et al. Right. So it would be easy to implement TTD inside a nameserver (ref tinnydns), and provide records to clients with appropriate TTLs without fear of increasing traffic abnormally (the clients won't come back until the record expires), and, theres no protocol change involved. End of argument as far as DNSEXT is concerned. [ propagating TTD information to slaves ] Paul Bernstein wrote: > If you insist on corrupting the zone by retrieving it through AXFR, > you'll get 2-second TTLs from my AXFR server. Of course, the record also > won't disappear until the next AXFR. The effects on the secondary, and > on clients talking to the secondary, are the same as if you had manually > set a 2-second TTL in the first place. 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, thus causing the slave to incur unneeded traffic from clients who effectively cannot cache the record at all and must requery for the record each time they want it. ( For instance, someone taking 3 seconds to reach a web page and clicking on the 'Next' link, resulting in the record being looked up again ) Of course, you'd argue that its because the slaves are using an outdated protocol, but it strikes me that you've coded your nameserver to be intentionally irritating. 'Wow'. Supplying TTLs for expiring records based on the SOA TTL/etc values (with dropping back to 2 second TTLs for those records which should be expired before the slaves next refresh themselves) would be more sensible. 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. Dynamic updates sent from the master to each slave are more prompt, although you still have the housekeeping of removing the records once they should have expired (in the absence of remove-after values being able to be sent), and liable to be lost (but will get picked up on the next zone transfer). Wait, aren't we back at the start again? --==-- Bruce. _______________________________________________ dhcwg mailing list dhcwg@ietf.org https://www1.ietf.org/mailman/listinfo/dhcwg
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Ralph Droms
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Robert Elz
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Ted Lemon
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Ralph Droms
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Robert Elz
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Mark Stapp
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Ted Lemon
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Edward Lewis
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… D. J. Bernstein
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Michael Richardson
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Robert Elz
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… D. J. Bernstein
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Ted Lemon
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Bruce Campbell
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… D. J. Bernstein
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Paul Vixie
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Paul Vixie
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… Bruce Campbell
- Re: [dhcwg] DDNS-DHCP [6]: Relationship between D… D. J. Bernstein