named tcp dos?

Randy Bush randy at
Thu Aug 2 20:47:21 UTC 2018

>>>>> ... are there that many folk doing tcp out there?
>>>> All name servers fall back to TCP when they receive truncated
>>>> replies.
>>> we know the protocol.  [ and we know folk have idiot middleboxen ]
>>> what i was asking was the distribution of this in the wild
>> one word: DNSSEC

> Indeed, DNSSEC is a prime example. My point was that TCP queries to
> your servers are determined largely by the size of the RRSETs you
> serve. If your answers don't fit in 512 bytes (without EDNS) or ~4096
> bytes (with EDNS), you're going to be serving over TCP.

as i said, let's assume we know the protocol.

> Obviously you're way more likely to see TCP queries from systems that
> don't support EDNS. Perhaps you have many such systems (and or idiot
> middleboxen) querying you?

two $dayjobs are interfering with my trying to schedule the time to
actually measure what i am seeing on my servers. :)  there are a fair
number of zones here, including a large cctld with a lot of signage.
so my guess (i.e. no real measurements [0]) is that at least that server
sees a higher tcp ratio than the average bear.,

but if i get those data, are they 'normal?'  are they similar to what
others see?


[0] - i confess to being a measurement researcher in one of my real
      lives.  so i take measurement a bit seriously.  but i have not
      been measuring dns for a couple of decades.

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