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Re: Getting to Consensus: CONTINUATION-related issues

From: Amos Jeffries <squid3@treenet.co.nz>
Date: Fri, 18 Jul 2014 14:53:26 +1200
Message-ID: <53C88C26.30805@treenet.co.nz>
To: ietf-http-wg@w3.org
On 18/07/2014 12:44 p.m., Mark Nottingham wrote:
> We've had a rollicking discussion about the design tradeoffs in CONTINUATION, especially regarding HOL blocking and DoS considerations.
> 
> I see very little new information entering that discussion, and I think everyone has come to understand the tradeoffs. For a refresher, please see the wiki:
>   https://github.com/http2/http2-spec/wiki/ContinuationProposals
> 
> I proposed two options the other day:
> 
> a) Remove CONTINUATION from the specification and add a new setting that dictates the maximum HEADERS/PUSH_PROMISE frame size (as distinct from max_frame_size) a peer is willing to receive. I.e., the setting refers to the compressed header size.
> 
> b) Keep CONTINUATION in the specification, and add a new setting that advises the maximum header set size (i.e,. uncompressed) a peer is willing to receive (but might not imply PROTOCOL_ERROR or STREAM_ERROR on receipt).
> 
> Although there have been some tentative proposals for additional options since, I haven't heard a clamour for support for them, so I think these are realistically the ways we can go.
> 
> As stated before, there will no doubt be tweaking and adjustments made to these, but I think we're in a place where we can choose a general direction.
> 
> I'd like to hear:
> 
> 1) Your preferred outcome (if any)

(A).

> 2) Whether you can live with the other option, and if not, why

"CONTINUATION without a length limit" adds a great complexity to the
intermediary code and opens us to unacceptible levels of resource
commitments for the rare[1] chance of being useful. In 1.1 this is only
just coped with, in h2 with multiplexing it grows unacceptible.

"CONTINUATION with a length limit" is simpler both for spec and
implementation when written in the form of a Large Frame
unlimited-length value for use only by 1:1 "TCP tunnel" type proxying
where h2 as a whole ceases relevance.

[1] Specifically the unlimited length need is rare. As opposed to
knowable but large lengths, which are far more common.

Amos
Received on Friday, 18 July 2014 02:54:11 UTC

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