[HECnet] FDDI and DECNET, clustering

[Paul Koning]

"Sampsa" == Sampsa Laine <sampsa at mac.com> writes:

Sampsa> Guys, I've just received a DEFPA-DB PCI-FDDI adapter from
Sampsa> ebay, my plan is to install it in CHIMPY and then connect
Sampsa> CHIMPY to CHIMP via this for clustering.

Sampsa> Anybody know how I would go about cabling such a beast, there
Sampsa> are four fibre optic ports on these things?

Wow, that takes me back a bunch of years...

There are two basic FDDI cabling approches: dual ring, and tree of
concentrators.   The DEFPA can be hooked up either way because it has
the two ports (type A and B ports).

If you have other FDDI devices that also have A or B ports, just plug
A to B in a circular fashion, and you have a dual ring.   This is the
topology that FDDI originally started with early in its development.
It has single-fault tolerance, but it doesn't support hierarchical
wiring (wiring closets).   The single-fault tolerance means you can
make a chain instead of closing the ring, that's equivalent to the
ring with a single cable busted.

If you have a concentrator (a box with either A/B ports or S port,
plus a number of M ports) plug either A or B into an M port and leave
the other unused.

Finally, if you have another device with an S port (a "single attached
station") you can plug that into either the A or the B port, leaving
the other port available for another S port, or another A/B port.   I
don't think you should have S to A and B to M, but I don't remember
for sure.   If you have concentrators, the rule is that any single
attached devices plug into M ports, while dual attached devices plug
either into an M port or into the root dual ring.

            paul