North American Network Operators Group
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Re: large organization nameservers sending icmp packets to dns servers.

  • From: John L
  • Date: Mon Aug 06 14:10:13 2007
  • Cleverness: None detected

Why would they ping rather than just sending the query to all of the
NS and see which one answers first?  It's an IP round trip either way.


If you have sites in San Fran, London, and Tokyo, and you launch a ping from
all 3 and see which one gets there first, you'll *know* the RTT from each site.

If you just send DNS replies from all 3, you don't have a good way of telling
which one got to the destination first.

Um, unless I seriously misunderstand the client DNS cache wants to know which server is closest. So it sends DNS queries to all three NS at the same time. Then it waits for the answers. Whichever one answers first is the closest. What am I missing?

Regards,
John Levine, [email protected], Primary Perpetrator of "The Internet for Dummies",
Information Superhighwayman wanna-be, http://www.johnlevine.com, ex-Mayor
"More Wiener schnitzel, please", said Tom, revealingly.