From: rfranken@mcs213i.cs.umr.edu (Richard Brett Frankenberger)
Subject: Re: Token Ring vs. Ethernet
Date: Fri, 20 Nov 1992 19:23:41 GMT
Organization: University of Missouri - Rolla

In article <sjaos6c@rhyolite.wpd.sgi.com> vjs@rhyolite.wpd.sgi.com (Vernon Schryver) writes:
>How does a station on a single ring like token ring "remove itself" if
>the cable between it and a neighbor is cut?  No, you can't bring in
>hubs, because there are also hubs for ethernet with very robust
>per-link fault detection and isolation stuff.  (The answer is that
>the ring is broken and dead.)
 
All token-ring networks (that is, IEEE 802.5 or IBM TR) use 'hubs' or,
as they are usually called (in TR), MAUs.  Ethernet can be hubbed, but in
general, it is not, except for 10BaseT.  10BaseT, of course, is then as
robust as token-ring.  I 10BaseT hub is more expensive than a passive MAU;
however.  There is no cable running from one workstation to the next to
break.
 
>I don't know about Novell, but that is not true with a Real Protocol (tm).
>Any decent machine can saturate an ethernet today with IP.  No decent
>machine does less than 8Mbit/sec over ethernet with IP.  8Mbit/sec is
>more than will fit in a 4Mb/s token ring.  In my book, 16Mbit/sec is a
>puny speed at any packet size above 1KByte.  There are performance
>hurdles with 16Mb TR, but as I understand them, they are related to
>common silicon, and not the stations.

Thats comparing apples and oranges.  IP is a protocol.  Novell is a network
operating system.  Novell servers can run IP.  Unix workstations can run
IPX (Novell's protocol of choice).  Of course, one station saturating an
Ethernet will increase hte probably of collisions and wasted bandwidth.
Token-ring have very little wasted bandwidth (the 3byte token), and will
slow down proportionally at high loads, the give everyone a fair chance.
 
>Not so.  I am somewhat immodest about some FDDI stuff; to the best of
>my knowledge, the TCP/IP/FDDI stations I work on are among the fastest
>in the world.  No one will ever be any faster, at least on 125Mbaud FDDI.
>However, FDDI will never, ever replace ethernets.  Like comparing a
>Model T Ford and a Porshe, FDDI is about 10 times faster than ethernet,
>but less reliable, more difficult to install, and more expensive.
>There are a host of cold technical reasons why those facts will not
>change.  Ever.  (Yes, I've heard of CDDI; check my email address.)

Do they still sell model T's?  :)         
 
>Ethernet will endure forever like RS-232, just as RS-232 endures
>despite the improvements of the standards bodies for these last 25 or
>30 years.  Ethernet is too cheap, easy to build, install, and run.

Probably true.  Token-Ring and E-Net will be around for a long time.
 
>There are ways to kill an entire ethernet, but not really with a pin.
>(e.g.  power off the 10baseT hub, cut the coax, get creative with "coax
>drop cables", reprogram MAC addresses on PC cards)  Have you ever tried
>to stick a pin into yellow hose or even thinnet?  Without a drill?

I've seen it done.  Not sure exactly what metal object was used or how much
force is required.

>What if you stick a pin thru the wire connecting TR hubs?

A standard passive MAU (Hub)?  The ring will go down.  (But said connecting
wire is not usually running to any desk where any general user can do it. 
Putting a pin through a lobe cable will remove that workstation only)

On a active hub, (similar to the ACTIVE EtherNet hubs (no such thing as a
passive EtherNet Hub), that cable will be removed from service, the backup
cable will be used, and the ring well remain up. (Not to imply that a similar
thing couldn't be the case with E-Net - you could probably have two hubs
connected with redundant cables)
  
>Vernon Schryver,  ejs@sgi.com

      - Brett    (rfranken@cs.umr.edu)