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Re: Expect: 100-continue and proxies

From: Jeffrey Mogul <Jeff.Mogul@hp.com>
Date: Mon, 22 Feb 2010 14:51:44 -0800
Message-Id: <201002222251.o1MMpixY006389@pobox-pa.hpl.hp.com>
To: Joe Orton <joe@manyfish.co.uk>
cc: ietf-http-wg@w3.org, Jeff.Mogul@hp.com
Just an FYI: before anyone fiddles with the Expect/Continue
mechanism, you should definitely read this paper:

      author = {Adam D. Bradley and Azer Bestavros and Assaf J. Kfoury},
      title = {Safe Composition of Web Communication Protocols for Extensible
       Edge Services},
      booktitle = {In Workshop on Web Caching and Content Delivery (WCW},
      year = {2002}

  Available via:

The title is a bit of a red herring; the paper is mostly about
the specific case of the Expect/Continue mechanism.  In particular,
very subtle issues can create deadlocks when trying to interoperate
between proxies, clients, and servers implementing slightly different
versions of Expect/Continue.

I wouldn't expect the working group to use the same formal-verification
techniques that these authors used (not that it would be a bad idea
to do so, just that I don't think it will happen), but at least
people should try to understand the causes of the problems exposed
by this paper, before changing anything here.

Received on Monday, 22 February 2010 22:52:48 UTC

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