Re: Fibonaccing CID lengths
Kazuho Oku <kazuhooku@gmail.com> Thu, 23 May 2019 03:37 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>
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From: Kazuho Oku <kazuhooku@gmail.com>
Date: Thu, 23 May 2019 04:36:54 +0100
Message-ID: <CANatvzx4rxk6UU48omk-EfpoYzfg_zWR+N49zMWi_5rv722uQg@mail.gmail.com>
Subject: Re: Fibonaccing CID lengths
To: Christian Huitema <huitema@huitema.net>, Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com>, IETF QUIC WG <quic@ietf.org>
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2019年5月22日(水) 21:04 Dmitri Tikhonov <dtikhonov@litespeedtech.com>: > > On Wed, May 22, 2019 at 10:19:38AM -0700, Christian Huitema wrote: > > Yes, that looks like a proposal that we should seriously consider. > > 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. I'd argue that the downside of compression is that endpoints would be required to use a CID that is longer than necessary. For example, if we are to allow only CID length of even-number bytes, there would be in average one byte (8-bit) overhead per CID. That dwarfs the benefit of saving 4-bit in the length of the CIDL field. While I think using a 4-bit CIDL field could be beneficial for avoiding ossification, I think I might agree with Martin Duke that CIDL is currently an invariant that we are happy to accept ossification. So, what's the benefit? > > What if instead we do the following: > > 0 -> 0 > 1 -> 1 > 2 -> 2 > 3 -> 3 > 4 -> 4 > 5 -> 6 > 6 -> 8 > 7 -> 12 > 8 -> 16 > 9 -> 20 > 10 -> 24 > 11 -> 28 > 12 -> 32 > 13 -> 40 > 14 -> 48 > 15 -> 64 > > This is as valid an approach as encoding the length in 8 bits and > having to deal with invalid values or using a varint and having > to deal with even more invalid values. > > - Dmitri. > -- Kazuho Oku
- Fibonaccing CID lengths Dmitri Tikhonov
- Re: Fibonaccing CID lengths Mikkel Fahnøe Jørgensen
- Re: Fibonaccing CID lengths Christian Huitema
- Re: Fibonaccing CID lengths Dmitri Tikhonov
- Re: Fibonaccing CID lengths Kazuho Oku
- Re: Fibonaccing CID lengths Roberto Peon
- Re: Fibonaccing CID lengths Dmitri Tikhonov
- Re: Fibonaccing CID lengths David Schinazi
- Re: Fibonaccing CID lengths Marten Seemann
- Re: Fibonaccing CID lengths Mikkel Fahnøe Jørgensen
- Re: Fibonaccing CID lengths Dmitri Tikhonov
- Re: Fibonaccing CID lengths Christian Huitema