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Re: reserved bits for spin bit, etc.

Ted Hardie <ted.ietf@gmail.com> Mon, 27 November 2017 17:27 UTC

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From: Ted Hardie <ted.ietf@gmail.com>
Date: Mon, 27 Nov 2017 09:26:35 -0800
Message-ID: <CA+9kkMDi92awCqi1SrqCnzmHb1GCt+D2ia0uA6FUDa_DP2+D-w@mail.gmail.com>
Subject: Re: reserved bits for spin bit, etc.
To: "Brian Trammell (IETF)" <ietf@trammell.ch>
Cc: Jana Iyengar <jri@google.com>, Christian Huitema <huitema@huitema.net>, Olivier Bonaventure <olivier.bonaventure@tessares.net>, "quic@ietf.org" <quic@ietf.org>, Martin Thomson <martin.thomson@gmail.com>
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Quoting one tiny piece of this for emphasis:

On Sun, Nov 26, 2017 at 11:03 PM, Brian Trammell (IETF) <ietf@trammell.ch>
wrote:


> I'll note that if we go to varints for packet numbers -- which we really
> should -- then there are five bits free in the short header now. We'll
> probably want to reserve all of those for the future, regardless of how
> many of them eventually get used for measurability, so they'll need to be
> greased somehow anyway.
>

I think Brian has this exactly right:  if we reclaim these bits, then they
need to be greased as soon as possible.  Having the greasing algorithms
working and the peer behavior confirmed would be something I'd argue for as
a test for the first implementation draft after the change is made.

We've identified greasing as a strong requirement for avoiding early
ossification in QUIC, and I think this is a useful test of *that*,
regardless of the eventual use of the bits.

regards,

Ted

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