Re: large organization nameservers sending icmp packets to dns servers.

[Chris L. Morrow]

On Thu, 9 Aug 2007, Stephane Bortzmeyer wrote:

>
> On Wed, Aug 08, 2007 at 03:20:56PM -0700,
>  william(at)elan.net <[EMAIL PROTECTED]> 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 :)