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Re: Can the response entity be transmitted before all the request entity has been read?

From: Jamie Lokier <jamie@shareable.org>
Date: Tue, 16 Mar 2004 06:40:51 +0000
To: Jeffrey Mogul <Jeff.Mogul@hp.com>
Cc: Alex Rousskov <rousskov@measurement-factory.com>, HTTP WG <ietf-http-wg@w3.org>
Message-ID: <20040316064051.GB13637@mail.shareable.org>

Jeffrey Mogul wrote:
> Also, as I understand the paper, what they showed is that while
> if everyone fully (and correctly) implemented the 100-Continue
> specification of RFC2616, everything would be fine, we didn't
> successfully design this feature to interoperate with RFC2068.
> We also apparently said "MAY" instead of "MUST" in at least one
> place, so partial (but legal) implementations of RFC2616 might
> be a problem.

Thank you!  It is a most excellent paper.

The conclusion for someone writing an RFC2616 server is that "MAY send
a 100 [...] in response to an HTTP/1.1 PUT or POST request" must be
implemented as "MUST, after a timeout, ..." (or with no timeout), to
avoid certain deadlocks.

Other conclusions apply for someone writing a proxy or client.

Neither Apache 1 nor 2 actually do that, so I presume the theoretical
deadlock isn't a problem in practice.

Probably because the few clients which do wait for 100 (Continue), if
there are any at all, implement a reasonably short timeout before
sending the request entity anyway, even though that's prohibited by
RFC2068.

How wonderfully unclear.

- Jamie
Received on Tuesday, 16 March 2004 01:41:00 GMT

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