Workshop

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Whoa! You have eight possible ports on your two four-port hubs, but only four stations are listed. A quick
glance at the hubs reveals that, in fact, only four lights are lit out of a possible eight. First of all, NAUN
lists reveal only who is on the network while they are on the network. A NAUN lister can’t list something
that isn’t there. Still, you work quickly, hoping that you’ll do your figuring before anybody kicks in or out
of the ring. By looking at the hubs and correlating the lights that are on to the NAUN list, you deduce that
because your workstation with the NAUN lister is #1 on the list and #3 on the hub, then MY-BOSS is #4
on hub #2, HER-BOSS is #2 on hub #1, and OUR-SERVER is #3 on hub #1.
Most of the time, I just do this to quickly figure out the identity of the machine I need to take out of the
network. You really, really don’t want to rely on this as a method for after-the-fact documentation, mostly
because people are always clicking in and out of the network at exactly the wrong time. This will start to
drive you crazy before too long.
You’ll get large numbers of “frame copied” errors on a switched Token-Ring network if you’re using an
analyzer that wasn’t designed with switching in mind. The analyzer is telling you that somebody claims
they got the frame, but it wasn’t the intended recipient.
In fact, because the switch has joined two separate Token-Rings, the receiving station could not have
received it without the help of the switch. The switch had to grab it. The switch grabs the frame on the
source network and throws it onto a different destination network, where the destination workstation can
get it. The destination network is a separate, physical Token-Ring segment and, as such, has a separate
active monitor and so on; it’s a separate conference table in a separate room. Therefore, it’s okay for the
switch to grab the frame meant for the destination—otherwise, it would never get to the destination. In
other words, the analyzer is fretting about nothing. Here’s the bottom line: Don’t worry about “frame
copied” errors in this scenario.
Let’s Get Physical
Like Ethernet, Token-Ring has overly complex rules about how long the wires can be at what speed using
what type of wire, and so on. The most common cable used to be IBM Type 1. Type 1 shielded twisted
pair (STP) cable is huge and very resistant to EMI (electromagnetic interference), but hard to work with.
Token-Ring comes in two speeds: 4Mb and 16Mb. If you’re using 4Mb, it’s time to change. I can’t even
think of a place where I could get a Token-Ring card that doesn’t also do 16Mb, and I buy used
equipment shamelessly! As an incentive for you to treat yourself to 16Mb (and to keep the discussion
simple) I’m only going to talk about 16Mb rules.