DNS forwarders

[JINMEI Tatuya / 神明達哉]

At Thu, 15 Jan 2009 11:52:37 -0600,
"Thilanka Samarasekera" <tsamarasekera at gmail.com> wrote:

> Can someone tell me how a BIND 9 server selects what forwarder its going to
> use? I read that BIND 8 used roundtrip time through a ping but I cannot find
> how BIND 9 does that. Does it round-robin between the forwarders that are
> set? Thanks in advance.

BIND9 servers generally sort forwarders by smoothed average response
time (srtt) and tries the servers in the sorted order (preferring the
"faster" ones, of course).  Roughly speaking, it uses the same
algorithm as BIND8 (though they don't "ping" the forwarders).

If you need further details about how the SRTTs are calculated you may
want to refer to the following paper:
http://www.sonycsl.co.jp/~kjc/papers/placement.ps

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.