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[babel] mac-relaxed: window-based

Juliusz Chroboczek <jch@irif.fr> Sun, 22 May 2022 15:38 UTC

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Date: Sun, 22 May 2022 17:38:44 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
To: babel@ietf.org
CC: Toke Høiland-Jørgensen <toke@toke.dk>
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Subject: [babel] mac-relaxed: window-based
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Hi Toke,

Thank you for your contribution.  I've rebased it over draft-ietf-...-00,
and put the result in branch "mac-relaxed-window".  I've put readable HTML
at

  https://www.irif.fr/~jch/software/babel/draft-ietf-babel-mac-relaxed.html#name-window-based-validation

> When using window-based validation, in addition to remembering the
> highest PC value seen from a given neighbour, an implementation
> maintains a fixed-size window of individual sequence numbers above this
> highest PC value.

This contradicts itself: the value is supposed to be the highest seen PC,
but then we're speaking about PCs higher than this value.  I can see two
solutions:

  1. either you reword everything so that the window is below the last
     seen PC, i.e. it covers (lastPC - windowSize, lastPC]; or
  2. you redefine the lastPC field to indicate the last contiguously
     received or discard packet, or something such.

For me, (1) would be much easier, since the lastPC value corresponds to an
easy to explain, well-defined concept in that case.

Also, I think we should be citing RFC 4303 somewhere, perhaps at the very
beginning of the section.

-- Juliusz

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