Common operational misconceptions
michael at rancid.berkeley.edu
Thu Feb 16 19:10:45 UTC 2012
On 02/16/12 05:17, Ray Soucy wrote:
> I've found starting off with some history on Ethernet (Maine loves Bob
> Metcalfe) becomes a very solid base for understanding; how "Ethernet"
> today is very different; starting with hubs, bridges, collisions, and
> those problems, then introducing modern switching, VLANs, broadcast
> domain's etc.
There was an old cruddy 1950s building on the UCB campus called Stanley
Hall. (Now there's a new, nice, modern building on the UCB campus
called Stanley Hall in place of the old one.) The old building had both
UCB net and Lawrence Berkeley Lab (LBNL) net running through it. The
LBNL net was fed from fiber using a 10base-FL-to-AUI repeater. The AUI
connected into the coax spine.
The cool thing is that the coax spine was provisioned exactly as you
would expect in an old ethernet textbook. The spine ran through the
hallway (usually just tied to a pipe, but sometimes with a J-hook) and
every 1.5 meters, there was a vampire tap and (usually) a transceiver
with an AUI cable connected to it that went into an office and dropped
down through the ceiling.
Amazingly, the UCB network was somewhat more modern. There were DEC
Delni MPTs (or "AUI hubs") coming off the UCB coax. There were even
some 10base-T hubs and concentrators that fed offices that had newer
cat-3 or even cat-5 wiring.
It was great to take students on tours through this operational museum.
(Well, the LBNL net was sort of operational. It would just stop
working for minutes on end and then come back mysteriously.) You could
basically see the first 10-15 years of the evolution of ethernet, and it
was installed and working.
The new Stanley is plumbed to the gills with cat-5e, gigabit switches,
and vlans all over the place. A modern LAN, yes, but no sense of history.
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