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. -- f.a.n.finch <[EMAIL PROTECTED]> http://dotat.at/ FISHER GERMAN BIGHT HUMBER THAMES DOVER WIGHT PORTLAND SOUTHWEST 5 TO 7, INCREASING GALE 8 AT TIMES. MAINLY ROUGH. RAIN THEN SHOWERS. MODERATE OR POOR BECOMING GOOD. _______________________________________________ DNSOP mailing list [email protected] https://www1.ietf.org/mailman/listinfo/dnsop
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