Re: The first octet

<alexandre.ferrieux@orange.com> Wed, 08 August 2018 13:44 UTC

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Subject: Re: The first octet
To: Ian Swett <ianswett@google.com>
CC: Martin Thomson <martin.thomson@gmail.com>, IETF QUIC WG <quic@ietf.org>, Kazuho Oku <kazuhooku@gmail.com>
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From: <alexandre.ferrieux@orange.com>
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Date: Wed, 8 Aug 2018 15:44:21 +0200
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Sure:

  - spin+VEC are documented in draft-trammel-spin-03

  - 7 bits for packet loss were presented at
      http://snaggletooth.akam.ai/IETF-101-HotRFC/10-Ferrieux.pdf

Re "I'm curious why you'd even want them": please clarify which applies:

  (a) you recognize the criticality of loss location, but you have a cleverer 
algorithm to do the same with fewer than 7 bits

  (b) you don't believe network operators need to locate losses


On 08/08/18 15:29, Ian Swett wrote:
> I'm having a hard time understanding why you'd need 7 bits to measure packet 
> loss(1 seems sufficient in most cases), can you send a link to the spin + VEC 
> and 7 bit proposals you mentioned?
> 
> I'll also note I think the chances the WG will agree to 7 bits is extremely 
> close to 0, but I'm curious why you'd even want them.
> 
> On Wed, Aug 8, 2018 at 9:22 AM <alexandre.ferrieux@orange.com 
> <mailto:alexandre.ferrieux@orange.com>> wrote:
> 
>     On 08/08/18 12:05, Martin Thomson wrote:
>      >
>      > I know you discussed taking more bits and even bytes, but the case
>      > hasn't been made in this working group to my knowledge.  I certainly
>      > don't think that's justified; it improved fidelity of measurements,
>      > but the spin bit appears to be pretty good at that without the extra
>      > overheads.
> 
>     Fidelity is indeed the criterion to decide 1 (spin bit) vs 3 (spin bit + VEC)
>     for RTT measurements, right.
> 
>     However, measurements also include packet loss, which is typically more
>     widespread than delay in big pipes (which don't have enough RAM to keep a
>     packet
>     for too long at line rate). And spin+VEC do not address packet loss at all,
>     hence our 7-bit spin counter proposal shown in London.
> 
>     I admit that 7 is hefty if you're starting from Christian's songle spin bit ;
>     however:
> 
>        - I assume nobody will emit any doubt about the criticality of
>     non-delay-related (big pipe) loss location. Unless everybody here has perfect
>     networks and ideal reporting, that is.
> 
>        - Stick the spin bit on top of these 7, make that an extra easurement
>     byte and
>     you've got your three spare bits again in the first byte.
> 
> 
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