Re: TCP/IP Fiber Optic Ring Backbone


Steve Smith (cos!smith@uunet.uu.net)
4 Apr 88 23:40:50 GMT


In article <8803292224.AA13808@trout.nosc.mil> carrs@TROUT.NOSC.MIL (Stephen M. Carr) writes:

>[Asks for info on an "802.3 fiber optic ring network" from Fibercom]

I am not familiar with Fibercom or their products. However, there is
currently an effort within the IEEE 802.3 committee to come up with a
standard fiber optic star network (FOSTAR). This network would be
compatible with all other 10 MBit/sec 802.3 networks at the AUI level -
all you'd need to change to go to fiber optics would be the MAU (or tap
tranceiver, for you non 802.3 types :-)

Technically, the problem with using fiber optics in a bus topology is
that (unless you're No Such Agency :-) there is no such thing as a high
impedance tap. As a result, you either have to have a true ring
topology (as in FDDI) or have some kind of gizmo (called a hub) in the
middle of your network to handle signal distribution. The hub can be
either passive or active. Both ways have their adherents. Passive
systems are cheaper and don't need power for the hub. Active systems
can cover longer distances, handle more nodes, and are easier to
balance.

Unfortunately, the two types are not compatible, except through
repeaters. Also, some of the discussions within the FOSTAR committee
seem to be approaching the holy war state, and it looks like we may end
up with two separate, incompatible standards (active hub and passive
hub).

Since you want to use this stuff as a backbone, you might investigate a
new standard, IEEE 802.3, Section 9.9, December 1987, "Vendor
Independant Fiber Optic Inter Repeater Link". It might be closer to
what you need.

(Anything that looks like an Official Opinion probably isn't.)

--
		-- Steve
(smith@cos.com)	   ({uunet sundc decuac	hqda-ai	hadron}!cos!smith)
"Truth is stranger than	fiction	because	fiction	has to make sense."



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