Re: [DNSOP] Should be signed

"George Barwood" <> Fri, 19 March 2010 15:32 UTC

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From: George Barwood <>
To: Nicholas Weaver <nweaver@ICSI.Berkeley.EDU>
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Date: Fri, 19 Mar 2010 15:32:57 -0000
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Cc:, Nicholas Weaver <nweaver@ICSI.Berkeley.EDU>
Subject: Re: [DNSOP] Should be signed
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>> There are advantages besides messages being lost.
>> It also prevents spoofing of fragments, and limits amplification attacks.

>It doesn't limit amplification attacks by much if at all

It cuts the response from 4K to 1.5K, and I think fragmentation that contributes
to these attacks being damaging.

>  and spoofing of fragments is not likely to be happening in large responses, because large .responses will almost invariably be due to DNSSEC.

Resolvers may set DO=1 but not validate everything ( or even anything ).

Taking .SE as an example, by sending an open resolver that doesn't/cannot randomize ports the query [ NS SE ] ,
if the .SE servers don't conceal the IP ID, only 1 spoof packet is needed, and poisoning is easy and certain, is it not?

Note: the .SE example does not truncate, it's very unusual for a response to be truncated with a EDNS @ 1450.

I think it's best to have a conservative value as the default setting, and that is 1450 bytes.