Re: Speed specific Link-Layer Header Types for USB 2.0

[Tomasz Moń via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

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> From: Tomasz Moń <desowin () gmail com>
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> Date: Tue, 10 May 2022 06:41:30 +0200
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> On Mon, 2022-05-09 at 13:19 -0700, Guy Harris wrote:
> > On May 9, 2022, at 1:02 PM, Tomasz Moń <desowin () gmail com> wrote:
> >
> > > The same as why URB level captures are confusing. Maybe not to the
> > > same
> > > level as that would be just a single byte (and the URB metadata
> > > contains way more information), but it would still raise the
> > > questions
> > > like "where in USB specification this byte is defined?",
> >
> > To what extent are people analyzing 802.11 captures raising the
> > question "where in the 802.11 specification are the fields of the
> > radiotap header defined?"
>
> Probably low, as the 802.11 is *really* complex.
>
>
> > If the answer is "to a minimal extent" or "it doesn't happen", what
> > about USB would make the answer different?
>
> I would say the differentiating factor between network protocols and
> USB is the fact that USB does not adhere to Open Systems
> Interconnection model (OSI model) but network protocols generally do.
>
> For USB you can check [1], but it was presented before usbll dissector
> was written. Not sure much much it answers your question though.
>
> > > "Why this doesn't match all the documents on USB that I have
> > > read?".
> >
> > What is the "this" that wouldn't match?
>
> Packet Bytes as shown by Wireshark. Also Wireshark would have to show
> "USB Full/Low speed capture" section with only the single byte denoting
> full or low speed, followed by "USB Link Layer" (as shown currently for
> usbll captures).
>
> [1] https://youtu.be/67swnr1NCP4?t=321
>
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