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Large Frames, Continuations, Flow Control, and changing HPACK

From: Jeff Pinner <jpinner@twitter.com>
Date: Tue, 8 Jul 2014 08:55:14 -0700
Message-ID: <CA+pLO_jLM_EvePsEU06xVap8Le=HQb4tHExmohMkULNqj4XO+A@mail.gmail.com>
To: HTTP Working Group <ietf-http-wg@w3.org>
I would like to propose that we remove the "reference set" from HPACK.

I think that this would help to alleviate many of the issues that are
being brought up on the list w.r.t large header blocks and their
affect on HOL blocking.

By using the "reference set" of headers, the frame boundary and the
header block boundary are tied together. We have also made the
ordering of headers indeterminate leading to the null-separator hack
and made requirements on the receipt of the ":" headers impossible to
enforce requiring possibly complete buffering before basic routing
decisions can be made.

Removing the "reference set" would allow interleaving of HEADERS
frames from different streams. It would remove the need for large
contiguous frames carrying an entire "header block" since the
termination of these blocks is meaningless. Headers could be more
effectively "streamed" and CONTINUATION frames could be dropped from
the spec.

Since HEADERS frames can now be interleaved even if they do not
contain the complete header set, this would also remove the HOL
blocking issue and open up the possibility to flow control headers as
well as data.

- Jeff
Received on Tuesday, 8 July 2014 15:55:42 UTC

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