Re: [TCLUG:11328] connect to network without ethernet?

["Eric M. Hopper" <hopper@omnifarious.mn.org>]

On Mon, Dec 20, 1999 at 03:05:55AM -0600, Scott wrote:
> On Mon, 20 Dec 1999, Dave Erickson wrote:
> 
> > How does one use a token ring card? Should I just skip it and get one of
> > those NIC's for $6.00?
> 

>      Token ring is a different kind of network than ethernet.  It
> was/is an ibm thing if I remember correctly, and supposedly has
> better performance numbers than ethernet, but didn't become the
> dominant style due to cost reasons.  You *can* mix & match to some
> extent, but generally it probably isn't worth it unless you're going
> to do it for educational reasons.

	Actually, it wasn't so much card cost that made it fail, but the
difficulty in setting it up and keeping it running.  Like SCSI vs. IDE,
if everybody just switched to SCSI and bit the cost, suddenly SCSI
drives would be as cheap is IDE ones are now.

	Conceptually an ethernet network and a wireless radio LAN have
lots in common.  You just start broadcasting your data, and if you
notice someone else did it at the same time, you wait a random amount of
time, and then broadcast it again.

	This means that you can just string a wire between a bunch of
Ethernet computers, and it'll work, even if one of the computers crashes
or something.  Certain kinds of wiring problems can wreak havoc though,
hence the reason hubs are almost always used nowadays.

	In a token ring network, only one computer has permission to
broadcast at a time, and when the permission to broadcast proceeds from
computer to computer in a well defined fashion.  Conceptually, this
looks like a token being passed around a ring from computer to computer.
If one of the computers die, or a wire is broken, then the ring is
broken and the token ring has to 'heal' itself.  This process is rather
error prone and difficult, especially since you can't rely on a
broadcast protocol since in some token rings the physical topology
matches the logical topology, and they are not actually broadcast
networks.  As an odd side-note IBM mainframes still actually use token
ring.

	In a token ring network, Because only one computer can broadcast
at a time, it's theoretically possible to use 100% of the available
bandwidth.

	With Ethernet, as you edge close to 100% utilization, you start
getting a lot of 'collisions'.  This is the problem that switching hubs
solve for Ethernet.

	Of course, if you have an actual, physical ring for your token
ring network, you have the bandwidth of any given link, multiplied by
the number of links.  This _will_ go underutilized in a token ring
network.  In Ethernet, if you have a good switching hub, it's
theoretically possible to get 100% bandwidth utilization out of every
single wire going into the hub.

	You can't mix and match token ring and ethernet on the same
wire.  You have to have a router (often called a bridge because it's
main function is to 'bridge' two different kinds of network) between the
two.

Have fun (if at all possible),
-- 
Its name is Public Opinion.  It is held in reverence. It settles everything.
Some think it is the voice of God.  Loyalty to petrified opinion never yet
broke a chain or freed a human soul.     ---Mark Twain
-- Eric Hopper (hopper@omnifarious.mn.org  http://omnifarious.mn.org/~hopper) --

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