Implementation Status in lastest releases
Client - Stub
Client - Recursive
|Server - Recursive||Server - Auth|
|TCP fast open|
Most of the implementations above use only the STARTTLS/CH/TXT query text to negotiate the upgrade to TLS by default (the TO bit proposed in the draft in NOT used since it is not assigned by IANA, but may be available as an option in some implementations).
* getdns uses libunbound in recursive mode
** Pipelining and OOOP are not applicable for synchronous applications