large organization nameservers sending icmp packets to dns servers.

Mon Aug 6 15:57:08 UTC 2007

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.
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