large organization nameservers sending icmp packets to dns servers.

Leigh Porter leigh.porter at
Mon Aug 6 16:13:51 UTC 2007

But why would they care where the nameserver is? Point 2 would seem to
be a little stupid a thing to assume. Also, what happens if, at that
moment, the ICMP packet is stuck in a queue for a few ms making the
shortest route longer.


Valdis.Kletnieks at wrote:
> On Mon, 06 Aug 2007 11:53:15 EDT, Drew Weaver said:
>> Is it a fairly normal practice for large companies such as Yahoo! And
>> Mozilla to send icmp/ping packets to DNS servers? If so, why?
> Sounds like one of the global-scale load balancers - when you do a (presumably)
> recursive DNS lookup of one of their hosts, they'll ping the nameserver from
> several locations and see which one gets an answer the fastest.
> Yes, it's a semi-borkken strategy, because it assumes that:
> 1) ICMP is handled at the same rate as TCP/UDP packets in all the routers
> involved (so there's no danger of declaring a path "slow" when it really isn't,
> just becase a router slow-pathed ICMP).
> 2) That the actual requester of service is reasonably near net-wise to the
> server handling the end-user's recursive DNS lookup.

More information about the NANOG mailing list