25 Jul
2001
25 Jul
'01
4:31 p.m.
----- Original Message -----
From: John Allain <allain(a)panix.com>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, July 26, 2001 1:19 PM
Subject: ThinNet Hub
Correct as necessary.
I know a few things about networking, and that's the
problem, I'm a dozen or so facts short.
I Have learned to network RJ45/10baseT through
?active? hubs and DEC-AUI through DELNI hubs, etc.
So far so, uh, ? good..
Yes.
But I was looking at some DEC branded
BNC-coax/?ThinNet?/10base2 cables and it dawned on
me that this connection method looks hubless, with all the
tee connectors hanging around. Could this be right?
10b2 ?passive?
Correct, it is simply a daisy chain of machines on a common cable segment.
Like most things it has advantages land disadvantages.
By it's nature it has to be half duplex (only one path), restricted to
<10Mbps and a break in the cable will kill
all the workstations on that segment, however, very long runs (180m) are
possible and
NO HUB of any kind is required.
You nead a 50 ohm termination at each end of the daisy chain to make sure
there is equal current distribution, but
that's about it. Cable is more expensive, but for some layouts you need
less of it (if you have several machines close together for instance)
and it can also be connected to a hub with a t piece and allow a common
network. You need a miniumum of about a metre or so between t pieces. It
was common practice at one point to use 10B2 as a trunk to connect distant
hubs, since the 180m segment length was nearly twice the max for 10BT.
Hope this helps
hubs are just tee connectors?
No they are just t-connectors, not hubs at all.
Sorry for the IQ level of this question but I
don't want to blow
up my workstations, even if they were free.
NO stupid questions, only stupid answers, and it would be stupid not to ask.
Cheers
Geoff in Oz