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<div>Hi Paul,</div>
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<div><span>i think you mean TC=1.</span><br>
<span></span><br>
<span>this supposed anti-ddos behaviour is, i heard from somewhere, patented. at </span>
<br>
<span>least, there's a variant where the first UDP query get TC=1 and only after the
</span><br>
<span>client demonstrates that they heard your TC=1 and properly followed up with a
</span><br>
<span>TCP transaction, is UDP answered normally. that variant is, i think, patented.</span><br>
<span></span><br>
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This Riverhead patent, maybe?
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<div><a href="https://patentimages.storage.googleapis.com/pdfs/US6907525.pdf">https://patentimages.storage.googleapis.com/pdfs/US6907525.pdf</a></div>
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<blockquote type="cite">
<div><span>Paul</span></div>
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