carey@uiucdcsb.cs.uiuc.edu (02/07/88)
what is FDDI?
kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England)) (02/09/88)
In article <167800007@uiucdcsb> carey@uiucdcsb.cs.uiuc.edu writes: > > >what is FDDI? FDDI stands for Fiber Distributed Data Interface. It's a new MAC level interface coming from the Accredited Standards Committee (ASC) X3T9, a part of ANSI. This committee deals mainly with computer system I/O interface standards. It's a little unusual for a networking standard to come out like this, instead of from IEEE 802.x, but it seems to be working. FDDI is a 100 Mbps token ring that differs in significant respects from the 802.5 IBM-style token ring. I think the chief distinction is an explicit specification of reliability. In addition to station bypass and star-configured wiring and concentrators, FDDI includes a second redundant counter-rotating ring that will allow the FDDI ring to suffer a complete loss of a ring link without affecting connectivity. The nodes on each end of the fault simply pipe the working ring over to the counter-rotating idle ring and the data passes back around to the other end of the failed link where it goes back onto the primary ring. The physical topology goes from double ring to a large "C" folded ring. There is an excellent discussion of FDDI in Stallings Vol 2 of the "Handbook of Computer-Communications Standards" from MacMillan. There must also be some good journal articles by now. I think about all they have to do to finish the standard is get the new duplex fiber optic connectors squared away and perhaps polish up the network management capabilities (how do you keep status on the redundant rings w/o network management protocols?). Kent England, Boston University