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Re: Fibonaccing CID lengths

Marten Seemann <martenseemann@gmail.com> Thu, 23 May 2019 15:14 UTC

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References: <20190522141238.GA23472@ubuntu-dmitri> <CAN1APdfBMeKGzsdLR__OLUHQ7pg=YM76C2Qxn6VDCXu680JQyA@mail.gmail.com> <ab64bdc2-805b-a86d-c525-41d076deac40@huitema.net> <20190522200406.GA28789@ubuntu-dmitri> <CANatvzx4rxk6UU48omk-EfpoYzfg_zWR+N49zMWi_5rv722uQg@mail.gmail.com> <20190523082129.GA6712@ubuntu-dmitri> <CAPDSy+6SpSjSeiMOjZWbC2x4mnpmsPf3PQq08s6KBru3aSRt0w@mail.gmail.com>
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From: Marten Seemann <martenseemann@gmail.com>
Date: Thu, 23 May 2019 16:13:39 +0100
Message-ID: <CAOYVs2rrppV=iyfn=Tfpw_QFyvJo6RtY65S81J5OqL5Tuj9ydg@mail.gmail.com>
Subject: Re: Fibonaccing CID lengths
To: David Schinazi <dschinazi.ietf@gmail.com>
Cc: Kazuho Oku <kazuhooku@gmail.com>, Christian Huitema <huitema@huitema.net>, Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com>, IETF QUIC WG <quic@ietf.org>
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Using an 8-bit encoding would also prevent ossification of the first two
bits of each connection ID length field. These bits would always be 0 (in
QUIC v1), since connection ID lengths above 48 can never occur.

On Thu, May 23, 2019 at 4:08 PM David Schinazi <dschinazi.ietf@gmail.com>
wrote:

> This encoding would be harder to deploy on our servers than having two
> 8-bit lengths. The only benefit of this is saving 8 bits on long headers,
> and that's not worth the complexity.
>
> On Thu, May 23, 2019 at 9:21 AM Dmitri Tikhonov <
> dtikhonov@litespeedtech.com> wrote:
>
>> On Thu, May 23, 2019 at 04:36:54AM +0100, Kazuho Oku wrote:
>> > 2019年5月22日(水) 21:04 Dmitri Tikhonov <dtikhonov@litespeedtech.com>:
>> > > While the example is lighthearted, the proposal is serious: that is,
>> > > remap 0 - 15 values of the nybble to a different set.  Do we need to
>> > > represent every intermediate number between 0 and 48 (the maximum of
>> > > the current PR)?
>> >
>> > The question is what you gain by compressing the length to 4 bits.
>> >
>> ----- 8< --- 8< --- 8< ---
>> >
>> > So, what's the benefit?
>>
>> Smaller change to the drafts -- and existing code.
>>
>>   - Dmitri.
>>
>>

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