Resolver optimization of auth selection - Truth or Myth?
barmar at alum.mit.edu
Mon Feb 8 19:26:29 UTC 2016
In article <mailman.189.1454958428.73610.bind-users at lists.isc.org>,
"Darcy Kevin (FCA)" <kevin.darcy at fcagroup.com> wrote:
> If you take a look at sections 4.1 & 4.2 - they seem to say
> BIND 9.8 gets it a little backwards and starts to prefer
> higher latency servers?
It doesn't say it prefers high-latency servers. It occasionally tries
the high-latency servers, because it decays the low-latency SRTT.
The purpose of this is to prevent permanently blackholing a server when
it's temporarily slow. So every now and then it will switch to the
high-latency server. If it's still high latency, it will lose preference
again, and it will go back to the low-latency servers. But if it has
gotten better, it will continue to be used.
Network distance is not the only reason for high latency, sometimes it
can be because of heavy load on the server, or a congested network link,
or other temporary conditions.
More information about the bind-users