“ Working groups make decisions through a "rough consensus" process.
IETF consensus does not require that all participants agree although
this is, of course, preferred. In general, the dominant view of the
working group shall prevail. (However, it must be noted that
"dominance" is not to be determined on the basis of volume or
persistence, but rather a more general sense of agreement.) Consensus
can be determined by a show of hands, humming, or any other means on
which the WG agrees (by rough consensus, of course). Note that 51%
of the working group does not qualify as "rough consensus" and 99% is
better than rough. It is up to the Chair to determine if rough
consensus has been reached.”
alt Hacker News
Within the IETF it’s not 100%.
See section 3.3 of one of their RFCs for proof.
https://www.rfc-editor.org/rfc/rfc2418.html#section-3.3
“ Working groups make decisions through a "rough consensus" process. IETF consensus does not require that all participants agree although this is, of course, preferred. In general, the dominant view of the working group shall prevail. (However, it must be noted that "dominance" is not to be determined on the basis of volume or persistence, but rather a more general sense of agreement.) Consensus can be determined by a show of hands, humming, or any other means on which the WG agrees (by rough consensus, of course). Note that 51% of the working group does not qualify as "rough consensus" and 99% is better than rough. It is up to the Chair to determine if rough consensus has been reached.”