Doublt about DNS Client...
cbuxton at menandmice.com
Mon Mar 10 16:34:17 UTC 2008
The RFC's don't say, if I recall correctly.
Some stub resolvers (the most common DNS clients) try again for up to
75-81 seconds. Some retry only a few times, maybe as few as 2 queries
total. The only constant (or near constant) seems to be that the delay
between the first query and the second is 5 seconds.
Some versions of nslookup time out after 2 seconds.
Of course, the actual application that requests a name lookup from the
stub resolver often will only wait 5 seconds. Or it might wait until
the stub resolver gives up. It depends on the application.
However, there's a difference between not getting an answer and
getting a negative answer. In the case of a negative answer, the name
server responded with a final answer. Thus, the client (stub resolver,
nslookup, dig, whatever) stops right there - it does not try a
different name server to try to get a positive answer. A negative
answer is an answer.
Men & Mice
On Mar 10, 2008, at 2:13 AM, Raghavendra wrote:
> Hi All,
> Can anybody tell me what is the maximum polling time and polling
> retries restricted by DNS client RFC?
> I saw in some dns client codes they poll after every 5 seconds and
> for 4 times in worst case this will turn out to be 20 seconds
> waiting time and in best case 5 seconds.
> Where as in windows nslookup it takes less than a seconds to reply
> for dns queries..in both positive and negative response cases.
> Just want to know is these values left to coder's choice? or RFC has
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