does bind depends on system DNS settings for lookup?
clists at buxtonfamily.us
Thu Nov 19 16:33:12 UTC 2015
On Nov 18, 2015, at 3:50 PM, Darcy Kevin (FCA) <kevin.darcy at fcagroup.com> wrote:
> "Iterative" resolution means following the delegation hierarchy (by sending queries with the RD flag set to 0) to get an answer; "recursive" resolution means sending a query off (with the RD flag set to 1) and relying on the other party to get a complete answer back to you.
> The confusion comes in when it is stated that a DNS node provides "recursive service". What that means, is that, *as*a*provider*, the node receives and honors recursive queries from its clients, but *as*a*consumer*, it typically uses iterative resolution to get the answers. So it's essentially "recursive" on one side (queries come in with RD=1), "iterative" on the other (queries go out with RD=0). Once one understands the provider/consumer distinction, things become a lot clearer.
Where do these definitions come from? I don’t use those words in quite those ways. I’ve thus far been unable to locate a definition of “recursive resolution” or “iterative resolution” in the RFCs.
In the usage I’m used to, “iterative resolution” isn’t a thing; this phrase has no defined meaning to me. What you’re describing here is what I’ve been calling “recursive resolution”, or “recursion”.
What you’re describing as “recursive resolution” is actually just a “recursive query” to my mind, a query asking for the server to perform the recursive algorithm (“RD” = “recursion desired”). Recursion, or recursive resolution, is the recursive algorithm that queries authoritative servers; each iteration of this algorithm involves sending an iterative query.
I can find references in RFC 1034 to “recursive service”, which matches up with my usage of the phrase “recursive resolution". I can also find “recursion”, again matching my usage. The phrase “iterative service” in the RFC describes the way a server handles a query if recursion is either not available or not desired.
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