Hi Pardeep,

 

This may help (Ref: http://www.unix.org.ua/orelly/networking_2ndEd/dns/ch02_06.htm):

Queries come in two flavors, recursive and iterative (or nonrecursive). Recursive queries place most of the burden of resolution on a single name server. Recursion, or recursive resolution, is just a name for the resolution process used by a name server when it receives recursive queries. As with recursive algorithms in programming, the name server repeats the same basic process (querying a remote name server and following any referrals) until it receives an answer.

Iteration, or iterative resolution, refers to the resolution process used by a name server when it receives iterative queries. Iterative resolution, on the other hand, doesn't require nearly as much work on the part of the queried name server. In iterative resolution, a name server simply gives the best answer it already knows back to the querier. No additional querying is required. The queried name server consults its local data (including its cache), looking for the data requested. If it doesn't find the answer there, it finds the names and addresses of the name servers closest to the domain name in the query in its local data, and returns that as a referral to help the querier continue the resolution process. Note that the referral includes all of the name servers listed in the local data; it's up to the querier to choose which one to query next.

Simply speaking, the recursive query asks the DNS server to fetch the exact answer. So it answers even for non-authoritative records. Whereas in Iterative, the server gives the best answer from its cache. It may be referall to an uathoritative DNS server for that domain and stops there. DOesn't really go and fetch answer from those.

Best Regards

 

Arminder S Girgla

Moderator

----- Original Message -----

From: Pardeep Sharma

To: itspardeep.sharma@...

Sent: Sunday, September 10, 2006 6:02 PM

Subject: [linux_chandigarh] about DNS Query(read it must)

Hi Dear my all Linux Friends

How r u

Friends I know well about DNS and also its resolution from client to server.

 

Actually i m confusing about thoerotically to find difference between Iteration query and Recursive Query to DNS by client.Plese anyone can describe me in simple way.

 

I m waiting for reply from my linux borthers

Regards:

Pardeep Sharma

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