job screening question

William Herrin bill at
Thu Jul 5 17:41:42 UTC 2012

On Thu, Jul 5, 2012 at 1:20 PM, Darius Jahandarie <djahandarie at> wrote:
> On Thu, Jul 5, 2012 at 1:11 PM, Oliver Garraux <oliver at> wrote:
>> Seems fairly straightforward to me.  It'll break path MTU discovery.
> Since Bill said "(not IP in general, TCP specifically)", I don't think
> PMTUD breaking is what he's looking for.

No, path MTU discovery is the answer I'm fishing for. The stack
notifies TCP of the fragmentation needed message and TCP handles it
within the TCP stack. Managing path MTU discovery is specific to each
layer-4 protocol even if the trigger message (destination unreachable,
fragmentation needed but DF set) is the same.

If a candidate gives me a more clever answer, I'd take that too. :-)

"This would block all IP traffic." is not a correct answer. It's not
even a naively incorrect answer.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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