Re: 505 response a MUST?
Roy T. Fielding (fielding@kiwi.ics.uci.edu)
Fri, 27 Feb 1998 15:33:57 -0800
>> ... and section 3.1 spells out various rules about version number
>> usage, but does not specify that a server MUST send a 505 response
>> if it receives a major version number higher than the highest
>> version it implements.
That isn't why 505 was created. It allows a future server to deny
service to older protocols. Since we cannot know whether HTTP/2.0
is incompatible with HTTP/1.1 (the major version change does not imply
incompatibility, it just removes the requirement for compatibility),
it is inappropriate for a server to be required to respond in error
to a message it might be able to respond to normally. That's why it
is not a MUST, and why Apache responds normally to an HTTP-version of
HTTP/2.0 if it can interpret the request as an HTTP/1.1 server.
....Roy