the HTTP specification states that the Transfer-Encoding header is allowed for requests - but what error code should a server respond if it doesn't understand that given Transfer-Encoding.
As far as I know the HTTP standard doesn't cover this possibility, but maybe I have just overlooked it.
An unknown transfer-encoding should raise a HTTP error 501 "NOT IMPLEMENTED". That's what Apache does, at least.
Also see http://argray.com/unixfaq/httpd_error_codes.shtml
Edit: pointer to the corresponding RFC section: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.2
I agree that the answer to this is non-obvious, and have followed up on the HTTP WG's mailing list.
UPDATE: Björn H. rightfully points out:
Section 3.6 of RFC 2616:
A server which receives an entity-body with a transfer-coding it does not understand SHOULD return 501 (Unimplemented), and close the
connection.So it does address this already.
Mostly a personal opinion.
i always thought 5xx errors were actual programming errors, like something fell over. If a server doesnt understand the request i would say a 4xx error is a better response as the problem is with the request not so a failed process on the server. Im not sure which 4xx but there are a few so selecting one should not be hard.
A request with an invalid Transfer-Encoding for the HTTP version is malformed. Therefore, the server should respond with 400 Bad Request.
Arguably failing to understand chunked encoding ought to be a 500 Internal Server Error rather than 501, because RFC-2616 says the server MUST understand it.
However, if a server chooses not to accept requests with chunked bodies, and it wants to blame the client for this, one way to do so legally would be 411 Length Required -- since one must not use Content-Length and Transfer-Encoding at the same time, and it is not practical to send a request without either anyway.
The RFC is a bit unclear, but IMHO it should be 406 Not Acceptable.
Transfer-Encoding, what a PITA.