[dns-operations] Questions on DNS Flag day 2020 proposal

Jerry Lundström jerry at dns-oarc.net
Mon Jun 17 08:46:10 UTC 2019

Hi Davey,

On 6/17/19 10:23 AM, Davey Song wrote:
> The fear of penalty exists from the saying : "According to this group,
> starting with February 1, 2020, DNS servers that can't handle DNS queries
> over both UDP and TCP may be pushed out of the DNS ecosystem and stop
> working."

"We" never said that about 2020, there is a lot of misunderstanding and

What is your source?

>>From the perspective of resolver, I can guess the UDP-only resolvers are
> penalized without the ability of TCP fallback, because they will get more
> Truncated response after the flag day. Because before the flag day, there
> are large chance for them to survive by receiving a large response (> 1220
> octets).

DNS is not UDP-only, it's been in the RFC from the start, read Ondrej's

> But for authoritative server, if there is no penalty for them as you said,
> how do DNS-flag-day people enhance this plan on authoritative server ? I'm
> curious about the technical detailed because I have been often asked on
> this.

The so-far technical details for authoritative are on:


If you let us know what is unclear with this then maybe Ondrej or Petr
can extend the technical details.

I also recommend watching the video from RIPE78 and/or reading the slide:



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