During a recursive query how does BIND decide which of the authoritative servers to query next?

During a recursive query how does BIND decide which of the authoritative servers to query next?

Post by Brandor » Sun, 21 Oct 2007 06:08:28


Example:

If name server NS1 is authoritative for FOO.COM, then my local name
server will resolve WWW.FOO.COM for me by asking the root name
servers. The root name servers will send the delegation information
(FOO.COM) with NS records to the authoritative name servers for
FOO.COM back to my local name server.

What does my local name server do next? I thought it sent a UDP query
to all of the authoritative name servers for FOO.COM, and then honored
the reply that came back first.

I however can not find any written corroboration that this is the way
it does or doesn't work, and I don't want to dig through the source
code.

Thanks,
Brian

--
- Brian Gupta

http://www.yqcomputer.com/
 
 
 

During a recursive query how does BIND decide which of the authoritative servers to query next?

Post by Kevin Darc » Sun, 21 Oct 2007 06:17:35


No, the NS records are tried one at a time until a valid, usable answer
is received. If there is historical information available about which
NS'es respond faster and/or more correctly than others, then this can be
used to establish a sequence in which they will be tried, otherwise it's
typically random. For more details see Section 7.2 of RFC 1035.


- Kevin