forwarding algorithm and timeouts

Bob Vance bobvance at
Mon Mar 26 18:04:04 UTC 2001

What exactly is the forwarding algorithm, assuming that "forward only"
is set.
Or where can I read about it (besides the source code :) ?

I checked the ARM, but only found this brief statement:

   "they are queried in turn until the list is exhausted or an answer
    is found.

Hmmm. I just looked in 'DNS and BIND, 2nd' and it says:

   "each forwarder is contacted only once, and it waits a short time
    for the forwarder to respond.
OK.  What is the timeout used before going to the next one in the list?
I would assume that it would have to be ~5 since we know that the stub
resolvers wait this long on their initial try.  Otherwise, we could get
several outstanding request from resolvers before the first forwarder
try times out.

Do all resolvers follow the algorithm described in 'DNS and BIND' ?
I.e., do WinX or MAC clients also try their list initially with 5
seconds, then re-do the list with 10 seconds, etc.?
Is this algorithm a requirement described in an RFC?


Tks        | <mailto:BVance at>
BV         | <mailto:BobVance at>
Sr. Technical Consultant,  SBM, A Gates/Arrow Co.
Vox 770-623-3430           11455 Lakefield Dr.
Fax 770-623-3429           Duluth, GA 30097-1511

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