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Re: Design: Adding ASSOCIATED_ONLY

From: Patrick McManus <mcmanus@ducksong.com>
Date: Wed, 19 Jun 2013 14:18:57 -0400
Message-ID: <CAOdDvNocpS7ZMehrBdgvHOqD3UGosJk6JiLqgxUfqeOMUjc4sw@mail.gmail.com>
To: Martin Thomson <martin.thomson@gmail.com>
Cc: James M Snell <jasnell@gmail.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
I think its worth noting that in spdy RST_STREAM was, as Martin says,
specified to terminate all associated streams in addition to the parent
stream. But afaict (willchan, correct me if I'm wrong) *nobody implementing
it did that*. which is a pretty strong signal that the mechanism should
just be removed from the spec rather than extended into priority semantics

On Wed, Jun 19, 2013 at 2:07 PM, Martin Thomson <martin.thomson@gmail.com>wrote:

> On 19 June 2013 10:56, James M Snell <jasnell@gmail.com> wrote:
> > https://github.com/http2/http2-spec/pull/144
> >
> > This was a technical change brought up and discussed as part of the
> > "layering taskforce" breakout but was never discussed in the larger
> > interim discussions.
> >
> > Essentially, this PR would add an "ASSOCIATED_ONLY" flag to PRIORITY
> > and RST_STREAM frames that would allow terminating and reprioritizing
> > promised streams as a group.
> >
> > Sending PRIORITY(ASSOCIATED_ONLY) would ONLY set the priority for
> > associated streams, not the referenced stream.
> >
> > Sending RST_STREAM(ASSOCIATED_ONLY) would terminate ONLY the
> > associated streams, not the referenced stream.
> >
> > Without this, we would have to send PRIORITY and RST_STREAM for each
> > individual associated stream, which is obviously quite inefficient.
> What James omits is:
> RST_STREAM is currently specified to terminate all associated streams
> in addition to the parent stream.  This would remove this coupling,
> which is considered by some to be problematic.
> It's not possible to reprioritise associated streams as a group.  We
> did agree that associated streams would inherit a priority that is
> lower (by one) than the parent stream.  As it stands, changing all of
> them requires first discovering the stream ID that will be used, then
> sending individual PRIORITY frames for each.
> There's not a lot of experience with this area of the specification.
Received on Wednesday, 19 June 2013 18:19:24 UTC

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