I suspect they changed the algorithm, in light of recent research findings
about attackability. See
http://www.cs.technion.ac.il/~gnakibly/papers/WOOT13.pdf
- Kevin
From: bind-users-boun...@lists.isc.org
[mailto:bind-users-boun...@lists.isc.org] On Behalf Of MURTARI, JOHN
Sent: Monday, February 08, 2016 1:36 PM
To: bind-users@lists.isc.org
Subject: Resolver optimization of auth selection - Truth or Myth?
Folks,
Just trying to settle a question on BIND based resolver
operation. When given multiple authoritative servers for a zone, does it
optimize selection based on auth server response times? For example:
-------
I'm located in Sydney, Australia and my ISP has a couple of
BIND based resolvers also located there. I'm trying to get to
www.example.com<http://www.example.com> and it happens to have three
authoritative servers, ns{1,2,3}.example.com with a single unicast IP and
located as follows:
ns1.example.com - Signapore, ns2.example.com - Los Angeles,
ns3.example.com - New York
We'll assume DNS round trip time (RTT) are proportional to
distance from Sydney; also, the fine folks at example.com have set a 10 minute
TTL on all their resource records and have never heard of anycast IPs. They
are also very reliable, so we're not considering the effects of a
non-responsive server.
So.....do the BIND resolvers in Sydney begin to notice their
quickest source of responses is ns1 and when cache data expires, do they go
there first? Or, are did the people at example.com waste money trying to
locate one of their authoritative servers in Singapore to better serve their
Australian visitors?
-----
I did do a little searching on this and found what seemed to be
a decent paper, no date, but covered up to BIND 9.8:
http://irl.cs.ucla.edu/data/files/papers/res_ns_selection.pdf
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?
Any clarification on this is welcome.
Thanks!
John
----------------
John Murtari - jm5...@att.com<mailto:jm5...@att.com>
Ciberspring
office: 315-944-0998
cell: 315-430-2702
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