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

[Michael Richardson via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

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> From: Michael Richardson <mcr () sandelman ca>
>
> Date: Tue, 14 Jun 2022 10:49:48 -0400
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> Tomasz Moń via tcpdump-workers wrote:
>     >> When low-speed capture is performed, it has to be performed at the leaf
>     >> (in graph-theory sense) connection. Full-speed traffic never make it to
>     >> the low-speed cables, so the capture will contain only low-speed
>     >> packets.
>
>     > Is there anything still to discuss here? I have opened the pull
>     > requests [1] [2] few weeks ago. I have also prepared Wireshark [3]
>     > change that I would like to merge before Wireshark 4.0 release.
>
>     > I think I have summed up whole discussion in the libpcap commit
>     > message. High-speed and Low-speed are pretty much clear, as these links
>     > never observe other speed packets. Full-speed is the only disputable
>     > one, but I believe the PRE packets are really a corner case that is not
>     > worth per-packet speed encoding. If the user has obsolete setup to
>     > trigger the corner case in the first place, then such user will
>     > definitely know to just capture at the downstream link for low-speed
>     > traffic.
>
> I think that Guy and I thought that you'll be better off with a single
> LINKTYPE with a subtype header, but if you want to go with three, I don't
> object.
>
> --
> ]               Never tell me the odds!                 | ipv6 mesh networks [
> ]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
> ]     mcr () sandelman ca  http://www.sandelman.ca/        |   ruby on rails    [
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>
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