Re: Ethernet collision

In article <LOSdnT7qcsofv4DanZ2dnUVZWhednZ2d@xxxxxxxxxxx>,
glen herrmannsfeldt <gah@xxxxxxxxxxxxxxxx> wrote:

Rich Seifert wrote:

(snip)

In 1997, the standards body approved 802.3X, which provided for
full-duplex operation of Ethernet at all data rates. Vendors were (and
still are) free to build devices that could operate in half-duplex-only,
full-duplex-only, or both modes.
(snip)
Do they have to state which one they are doing? Might one be
surprised to find a 100baseTX device that wouldn't work on a
half duplex system?


The standards don't require that vendors "state" anything, however any
manufacturer will surely have a data *** that says what the product
does, be it half/full/both. In practice, I don't know of any 10/100 Mb/s
devices that cannot operate in either mode; it's full-duplex-only
Gigabit that is the important case.

In practice, there are no devices operating at 1000 Mb/s in half-duplex
mode; I know of no commercially-available repeaters for Gigabit
Ethernet. (And yes, I am aware of the *very limited* use of half-duplex
Gigabit Ethernet for certain Cisco inter-chassis point-to-point links.)

Do you know of any gigabit NICs that implement half duplex, just
in case they were ever connected to a repeater? Presumably many
implement it when in 10baseT or 100baseTX mode so much of the
logic would already be there.


I'm not up on specific product offerings these days, sorry.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com
.