job screening question

Thu Jul 5 17:45:54 UTC 2012

This is exactly the issue comcast6.net is currently experiencing :). They seem to be blocking ICMP completely and that is causing my HE IPv6 tunnel to be unable to access their site from a browser. 

On Jul 5, 2012, at 1:41 PM, William Herrin wrote:

> On Thu, Jul 5, 2012 at 1:20 PM, Darius Jahandarie <djahandarie at gmail.com> wrote:
>> On Thu, Jul 5, 2012 at 1:11 PM, Oliver Garraux <oliver at g.garraux.net> 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.
> 
> Regards,
> Bill Herrin
> 
> 
> -- 
> William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
> 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
> Falls Church, VA 22042-3004
> 