Hi, Matt,
> On Nov 6, 2024, at 7:09 AM, Matt Mathis <matt.mat...@gmail.com> wrote:
>
> The deck is pretty much self explanatory and only 11 slides. Networks are
> Analog but MTU is not
> <https://datatracker.ietf.org/meeting/121/materials/slides-121-intarea-analog-blockers-to-wide-employment-of-jumbo-mtus-in-the-production-internet-00>
>
> Key points:
> - At L1, Ethernet is really analog
> - IEEE specifies waveforms, thresholds, tolerances and testing
> methodology
> - L1 MTU limit is derived from non-digital parameters, such as clock
> stability
Ethernet was self-clocking (still is, electrically - Manchester encoding), so
there’s no reason clock stability would come into play.
The minimum size was (64 bytes) based on trying to “capture” the largest
shared-media segment with a signal to ensure no others were transmitting; as
speeds increased, the length of that broadcast segment decreased until it
effectively disappeared with switched (non-broadcast) Ethernet. I would expect
the largest packet was limited by a combination of memory cost and the desire
to avoid blocking the segment too long - both arguably digital driven, not just
analog.
But, FWIW, why not ask Bob on the Internet History list??
Joe
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