RFC 8446, "The Transport Layer Security (TLS) Protocol Version 1.3", August 2018Source of RFC: tls (sec)
Errata ID: 6139
Publication Format(s) : TEXT
Reported By: Ben Smyth
Date Reported: 2020-04-29
Section 188.8.131.52. says:
As servers MAY require the presence of the "server_name" extension, clients SHOULD send this extension, when applicable.
It should say:
As servers MAY require the presence of the "server_name" extension, client SHOULD send this extension.
Since it is unclear when it is applicable for a server to send the extension, dropping "when applicable"
seems appropriate. Alternatively, giving some extra guidance would be useful.