Server behavior - recursive - port unreachable

Kevin Darcy kcd at chrysler.com
Mon Jun 21 19:37:41 UTC 2010


No, there is no "fast fail" mechanism as you suggest. In a 
properly-architected DNS-resolution infrastructure, there are multiple 
upstreams configured at every link of the resolution chain. By the time 
one link in that chain (e.g. server1) has exhausted all of its upstreams 
(server2a, server2b, server2c), if it sends back a "fast fail" to the 
downstream (client), the downstream will most likely have moved to _its_ 
next upstream (server1b, server1c, etc.), so it ignores the "fast fail" 
response, and what value did it add, really? It's just a waste of 
bandwidth/resources.

                                                                         
                                                 - Kevin

On 6/18/2010 5:31 AM, Christophe Lermytte wrote:
>
> Hello,
>
> I'm trying to find out what the server behavior should be in the 
> following situation:
>
> client -> server1 -> server2
>
> client asks server1 to recursively resolve a name
> server1 does not know and asks server2
> server2 sends an ICMP Port Unreachable to server1
>
> Is there something server1 can send to client, instead of making 
> client wait until it gives up?
>
> Thanks,
> CL
>
>
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