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From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
To: Polytropon <freebsd@edvax.de>
Cc: questions FreeBSD <FreeBSD-questions@freebsd.org>
Subject: Re: Got a panic today
References: <56CB47A6.9080107@bananmonarki.se>
 <20160222191320.bc8ed616.freebsd@edvax.de>
Date: Mon, 22 Feb 2016 18:54:14 -0500
In-Reply-To: <20160222191320.bc8ed616.freebsd@edvax.de> (Polytropon's message
 of "Mon, 22 Feb 2016 19:13:20 +0100")
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Polytropon <freebsd@edvax.de> writes:

> PHY seems to refer to physical characteristics of interfaces.
> Again from "dmesg | grep PHY":
>
> 	nsphy0: <DP83840 10/100 media interface> PHY 24 on miibus0
> 	ukphy0: <Generic IEEE 802.3u media interface> PHY 1 on miibus1
>
> You often see comparable output related to NICs. For example,
> if you search "man rl" for the string "PHY", there are refernces
> to the physical chipset (physical layer, as opposite to the MAC,
> the media-independent layer). It's a reference to the OSI layer 1.

Right, but in practice this is a little less abstract.

MAC is the IEEE 802.3 area of "Media Access Control". Considerate
chip vendors will refer to an EMAC to specify that it's Ethernet,
but really most of the time in networking, if you see the term
MAC, it will refer to Ethernet, and generally it will refer to
the hardware that implements 802.3 MAC. Similarly, "PHY hardware"
will usually mean an Ethernet transceiver.