ethernet and switches, was Re: [rescue] Mozilla Firefox

Charles Shannon Hendrix shannon at
Fri Apr 23 17:45:56 CDT 2004

Fri, 23 Apr 2004 @ 07:10 +0100, Mike Meredith said:

> On Thu, 22 Apr 2004 17:12:07 -0400, Charles Shannon Hendrix wrote:
> > Thu, 22 Apr 2004 @ 14:02 -0400, Dave McGuire said:
> > 
> > [subject changed]
> > 
> > >   It's kinda like taking a poorly-performing Ethernet network and 
> > > making it fully switched to alleviate congestion.  That's modifying
> > > a very basic underlying part of the design of Ethernet (the whole
> > > point of CSMA/CD) in order to make it perform well.
> > 
> > OK... but what is the proper solution there?
> Replace with FDDI/CDDI.

Nice if you have the option.  It's a goal of mine to build a net with a
nice backbone, partly because I want it, and partly because it is a good
learning and experimentation setup.  Right now I just have very little
networking equipment (or servers, or bandwidth, or storage, or...).

Can you control traffic on segments with FDDI like you can with
ethernet without breaking the bank?  

Some fairly cheap stuff is showing up on eBay now, but then the fast
ethernet is even cheaper still.  I keep having to make annoying choices
between what I want and what will do the job for the least cost.

At work I've only worked with FDDI for backbones, and for isolating
certain kinds of traffic.  The expense of the equipment often meant we
had to limit what we used it for.

I worked at an ISP which used FDDI because we had a lot of high speed
data streams from multiple hosts, and had a fairly heavy stream of data
going to a backup server and a tape robot.

FDDI worked out nicely for that, and as a general backbone.  We did hit
the 100Mbit barrier, so we actually had multiple FDDI rings.  Everything
else was ethernet, and we had a DEC network backplane to connect it all

At NASA, we had SGI stuff and HIPPI networks, and some SANs.  I kept
hoping by some miracle some of the older stuff would show up at one of
the auctions.

Hmm... this makes me think of questions, even though I won't be using
this stuff for awhile:

Is going to multiple FDDI rings a good idea, or should you just drop
FDDI and move to something faster?  Multiple rings is the solution in
most shops I've been in, but it sometimes got more complicated than just
having a faster pipe.

In terms of cost, is the equipment to run multipe FDDI rings cheap
enough yet?  Or would it be cheaper to find used HIPPI or something

I'd like to see a nice FDDI setup used for more than just a backbone.
Most places I've been in so far used it for backbones or data-heavy
applications because of its ability to get high utilization, but that
was about it.

I'm also wonder about this application:

    * one huge and fast SMP server
    * a series of X terminals and clients
    * horribly inefficient GUI apps on the server, like Gnome and
      Open Office

This will generate a lot of X traffic.  GigE seems like a good choice
for an X backbone network, but would FDDI be a good idea to try?

Can you buy X terminals that do FDDI, or any non-ethernet?

Many years ago, I set up X terminals on X-only backbone networks to keep
the traffic off the main net, but never did anything beyond 10baseT.

Another application I used to work on but haven't in years is isolating
terminal traffic on a private backbone.  Anyone doing tty-only traffic
in isolation due to very high volume and latency issues?

shannon "AT" -- ["We have nothing to prove" -- Alan Dawkins]

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