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Re: [Fwd: I-D ACTION:draft-decroy-http-progress-00.txt]

From: Jamie Lokier <jamie@shareable.org>
Date: Tue, 13 Feb 2007 15:21:58 +0000
To: Adrien de Croy <adrien@qbik.com>
Cc: Henrik Nordstrom <henrik@henriknordstrom.net>, ietf-http-wg@w3.org
Message-ID: <20070213152158.GA31785@mail.shareable.org>

Adrien de Croy wrote:
> I am thinking more about your point about using TCP flow control.
> We are able to send a 0 window size, but that won't guarantee that
> the client won't enter into the state where it thinks it is sending
> the body (and would therefore terminate on any 4xx response).

It's not permitted to reduce the TCP advertised window, so you can't
send a 0 window size after you've already opened the window to receive
the request headers of unknown size.

RFC 1122, section 4.2.2.16:

    "A TCP receiver SHOULD NOT shrink the window"

    "Many TCP implementations become confused if the window shrinks
    from the right after data has been sent into a larger window.
    Note that TCP has a heuristic to select the latest window update
    despite possible datagram reordering; as a result, it may ignore a
    window update with a smaller window than previously offered if
    neither the sequence number nor the acknowledgment number is
    increased."

-- Jamie
Received on Tuesday, 13 February 2007 15:22:18 GMT

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