Re: CVS commit: src/sys/net

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Mon, 28 Sep 2020 16:13:44 -0400 (EDT)
    From:        Mouse <mouse%Rodents-Montreal.ORG@localhost>
    Message-ID:  <202009282013.QAA05380%Stone.Rodents-Montreal.ORG@localhost>

  | Is it a bridge, a switch, neither, what?  Why?

Typically (though the labels are largely marketing speak) a hub is
a multi-port repeater - basically just adds power to the incoming
signal, so it can be transmitted further, but subtracts preamble
bits (it has to recognise an incoming frame before it starts transmitting)
so there's a limit on how many can appear on one link (1 or 2, its
been so long).   Both sides of the hub/repeater form parts of the
same collision domain (a collision on one side is repeated out the other).
They are L1 devices.

bridges/switches are L1 endpoints, and retransmit packets after some
delay (how much buffering, and how much delay in the best case varies).
Ports on bridges/switches are in separate collision domains.  There's
no limit (except your bankbook, and how much transit delay you're
prepared to tolerate) on how many you can connect together in a single
L2 LAN.

None of this terminology discussion is important however, it really
doesn't matter in the slightest what it is called, and picking something
based just on some marketing label would by silly - what matters are
the performance characteristics and limits, not what the marketing dept
decided to write on the box.

kre