[dns-operations] Name server turning off RD bit in response - just curious

Anand Buddhdev anandb at ripe.net
Tue Aug 7 12:16:40 UTC 2012

On 07/08/2012 13:40, Faasen, Craig wrote:

> RD is set to 1 in the query, but is 0 in the response.
> Which is not compliant with RFC 1035: "RD Recursion Desired - this
> bit may be set in a query and is copied into the response."
> Out of curiosity, any idea why a name server would want to change
> the RD bit ? (except to break an unsuspecting script ;)

Hi Craig,

In my opinion, the RD flag has no value in a response really. It's just
a way for a client to signal to a server that it wants the server to
perform recursive queries. While RFC 1035 requires the server to copy
the value of RD from the query into the response, a client shouldn't
even be bothering to look at RD in a response, and certainly should not
break if its value in the response doesn't match the query.



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