Tech report on FlagDay2020, fragmentation, EDNS, Truncation, TCP...

Giovane C. M. Moura giovane.moura at
Mon Nov 23 08:16:53 UTC 2020


A couple of months ago there was a lot of discussion about the Flag
Day2020 on this list.

Inspired on that, we wrote a technical report that we now release [0]
and that covers the authoritative server side of the story on
truncation, fragmentation, large messages, TCP fallback, and the Flag
Day uptake.

>From the abstract:

``[...] We analyze 114 billion queries/response pairs from more than 43k
autonomous systems, covering two months and a week period (2019 and
2020), collected at the authoritative servers of the .nl, the
country-code top-level domain of the Netherlands. We show that
fragmentation, and the problems that can follow fragmentation, rarely
occur at such authoritative servers. Further, we demonstrate that DNS
built-in defenses – use of truncation, EDNS0 buffer sizes, reduced
responses and TCP fall back – are effective to reduce fragmentation.
Last, we measure the uptake of the DNS flag day in 2020.``

Feedback is always welcome, as usual.


Givoane C. M. Moura


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