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From William A Rowe Jr <>
Subject Re: About Interim Response Headers (was: Content-Length header for 1xx status codes)
Date Thu, 08 Dec 2016 00:00:54 GMT
On Dec 7, 2016 5:04 PM, "Jacob Champion" <> wrote:

[combining replies to your last two emails]

No, not reject -- conforming clients parse (and may discard) 1xx's they
don't understand, treating them like 100 Continue, and proxies must forward
as-is (unless the proxy was the agent requesting the 1xx response). Right?

RFC 7231, sec. 6.2:

   A client MUST be able to parse one or more 1xx responses received
   prior to a final response, even if the client does not expect one.  A
   user agent MAY ignore unexpected 1xx responses.

   A proxy MUST forward 1xx responses unless the proxy itself requested
   the generation of the 1xx response.  For example, if a proxy adds an
   "Expect: 100-continue" field when it forwards a request, then it need
   not forward the corresponding 100 (Continue) response(s).

Consider for a moment the case of an HTTP/1.1 upgrade request unrecognized
by a proxy agent. The 101 switching protocols response is garbage to the
proxy agent, but passed along. The proxy agent attempts to read the
response and gets nothing meaningful, the originating user agent gets the
101 response and is busy in the new protocol and reads the 500 error as
garbage input.

The entire idea of forwarding unrecognized/in handled 1xx responses is

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