[dns-operations] On server selection algorithms in dns resolvers

David C Lawrence tale at akamai.com
Tue Nov 24 19:27:26 UTC 2015

Mark, please correct me if I am wrong (as I am sure you will!) but as
I recall BIND9's adb didn't make a distinction between the SRTTs of
different addresses on a name, but rather calculated an SRTT for the
name as a whole.

Thus this:

    ns1.example.com A   (1 ns typical RTT)
                    A      (100 ms typical RTT)

would behave differently from:

    ns1.example.com A   (1 ns typical RTT)

    ns2.example.com A      (100 ms typical RTT)

in that the former definition would see the address used much
more frequently than the latter, because both the 1 ns and 100 ms RTTs
would be plugged into the calculation of the SRTT of ns1.example.com

Still true?  (Ever true?)

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