[dns-operations] Too Open (Was: OpenDNS makes your Internet work better
paul at vix.com
Wed Jul 19 16:13:04 UTC 2006
> >> Not true. By having a mix of anycast and unicast service addresses,
> >> at least those unicast service sites don't have the problem of being
> >> dependant on the routing advertisement needing to be withdrawn if
> >> the pod should go down.
> > What happens to the packets for the down unicast server?
> They cease to be sent. 8-) AFAIK, most DNS resolvers keep track which
> servers are down (or are lame) and query them only occasionally, to
> see if the problem still persists. Some of them even store the RTT.
> You can't do such optimizations at the application level if all name
> servers are hidden behind very few anycast addresses.
this is an argument for multiple NS RRs and/or multiple A RRs per NS,
with each A RR being a distinct anycast cloud (or a distinct stripe of
a non-fate-sharing anycast cloud, as in UltraDNS's case). it is not,
in and of itself, an argument for mixed anycast/unicast nameservers.
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