DNS/1/EDNS/broken serversについて、ここに記述してください。

Removing EDNS Workarounds
　DNS-OARC 28, San Juan, PR　9. March 2018
https://indico.dns-oarc.net/event/28/contributions/515/attachments/490/799/Removing_EDNS_Workarounds.pdf

Background

EDNS standard (RFC 2671, 1999; updated by RFC 6891)

DNS software vendors added various workarounds for broken servers

Broken servers:
 * Doesn’t respond at all
 * Respond with non-FORMERR error code

== 計画 ==
Retry on error with EDNS again unless FORMERR is received