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Re: Another CONTINUATION Proposal

From: <K.Morgan@iaea.org>
Date: Tue, 8 Jul 2014 21:34:56 +0000
To: <jpinner@twitter.com>
CC: <ietf-http-wg@w3.org>
Message-ID: <22CED21A-81A5-4A1F-AB74-CD040022CB4C@iaea.org>
On 01 Jul 2014, at 17:18, "jpinner@twitter.com" <jpinner@twitter.com> wrote:
> One of the initial reasons we decided to use CONTINUATION frames over
> multiple HEADERS or PUSH_PROMISE frames was because besides carrying
> the header block, these frames could change stream state. As an
> example, PUSH_PROMISE reserves an stream in the idle state and we
> didn't want to send a PUSH_PROMISE stream with an id of an already
> reserved stream.
>
> We could instead separate frames that contain header fields from those
> that operate on stream state. This would mean modifying the
> PUSH_PROMISE frame so that it only reserved a stream, and introducing
> a new frame, say SYN_STREAM, that only transitioned a stream from the
> idle or reserved states to open or half-closed.
>
> So then we would have the following frames that manipulate stream
> lifecycle that do NOT have priority or header block fields:
>
> PUSH_PROMISE
> SYN_STREAM
> RST_STREAM
>
> [snip]


My understanding is that the problem with PUSH_PROMISE modifying the stream state isn't just that it's changing the state of a stream, but also because it's changing the hpack state. In other words, moving the headers to a different frame type doesn't solve the issue that a frame carrying hpack header blocks changes shared state.

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Received on Tuesday, 8 July 2014 21:39:57 UTC

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