large organization nameservers sending icmp packets to dns servers.

Chris L. Morrow christopher.morrow at
Sat Aug 11 01:32:48 UTC 2007

On Thu, 9 Aug 2007, Stephane Bortzmeyer wrote:

> On Wed, Aug 08, 2007 at 03:20:56PM -0700,
>  william(at) <william at> wrote
>  a message of 23 lines which said:
> > How is that an "anti DoS" technique when you actually need to return
> > an answer via UDP in order to force next request via TCP?
> Because there is no amplification: the UDP response packet can be very
> small.

actually because it forces authentication of the source (authentication
being that the source is a real-live host asking for dns services). Beyond
that trick, the deviecs I've seen/used also catalog the rates of queries
from individual hosts and force a cached answer to be generated locally if
the loads get too high (per source).. Sorry this is a bit late to the
punch :)

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