Re: Deadlocking in the transport

Martin Thomson <martin.thomson@gmail.com> Wed, 10 January 2018 23:59 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Thu, 11 Jan 2018 10:59:47 +1100
Message-ID: <CABkgnnXprsWX-u2-yA9Pt9-ScddH0vmuAU889A+YWy2NzLeQvw@mail.gmail.com>
Subject: Re: Deadlocking in the transport
To: =?UTF-8?Q?Mikkel_Fahn=C3=B8e_J=C3=B8rgensen?= <mikkelfj@gmail.com>
Cc: Jana Iyengar <jri@google.com>, "Charles 'Buck' Krasic" <ckrasic@google.com>, QUIC WG <quic@ietf.org>
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On Thu, Jan 11, 2018 at 9:56 AM, Mikkel Fahnøe Jørgensen
<mikkelfj@gmail.com>; wrote:
> I think that this needs to be in the main spec. Failing to document
> this sort of pitfall could be fatal. Does anyone disagree?
>
> I agree with the idea which I find it important. But I disagree with strict
> priorities. It should be possible to for lower priorities to communicate
> with reduced throughput which is readily handled by a pacing algorithm.
> There need to be some guarantees for priority 0 though.

See what I mean when I said that talking about this in terms of
priorities is hazard?  If you have a concrete dependency, then
reducing throughput doesn't solve the issue.  At best, it might hide
the issue by reducing probability.

The language problem is that we can sometimes express a dependency in
a priority scheme, such as the one in h2.  This is fundamentally
different to that particular scheme in that it isn't something that
can be fudged or ignored.