I stumbled across this:
http://www.nanog.org/mtg-0310/pdf/wessels.pdf
Look for the (unnumbered) slide "Distribution of Queries to
Nameservers" and the ones following it.
At 14:47 -0800 12/4/07, Edward Lewis wrote:
I knew this came up before:
http://lists.oarci.net/pipermail/dns-operations/2007-September/002021.html
Note that the RFC's text says "implementation" and not "application"
or "protocol." There isn't a standard DNS algorithm for choosing
the server to be queried, the algorithms are up to the implementers
(as the algorithm isn't an inter-operability issue) of DNS instances.
I looked for a bit but can't find an excellent paper in which a
research stood up different name servers with no connectivity to
others and then measured the number of (unanswered) queries sent to
each of the root servers. One server implementation sent them all
to A, one sent 1/13th to each of the 13 servers, others did other
distributions. This mostly demonstrated the spectrum of strategies.
Note that DNS has reasons not to follow what's in 3484 - namely that
DNS servers are supposed to be far flung, finding a local one is not
going to be advantageous (as opposed to other application data
sources).
At 21:44 +0000 12/4/07, Tony Finch wrote:
Rule 9 of RFC 3484 specifies that the IP addresses (v4 and v6) returned by
getaddrinfo() should be sorted according to the size of their common
prefix with the local host's chosen source IP address. This defeats DNS
round robin load balancing which has led to some severe operational
problems. DNS round robin needs to be documented in an RFC, and RFC 3484
should be updated with rule 9 deleted or substantially modified for
compatibility with DNS round robin.
Ian Jackson has written a thorough description of the problem from the
perspective of a proposal that Debian's version of glibc should have the
troublesome sorting behaviour removed:
http://lists.debian.org/debian-ctte/2007/11/msg00029.html
FreeBSD's getaddrinfo() only implements Rule 9 if the kernel's address
selection policy is configured, which is not done by default so DNS round
robin is passed through.
Tony.
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Edward Lewis +1-571-434-5468
NeuStar
Think glocally. Act confused.
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