| Title: | FDDI - The Next Generation |
| Moderator: | NETCAD::STEFANI |
| Created: | Thu Apr 27 1989 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2259 |
| Total number of notes: | 8590 |
1. Thruout the "FDDI System Level Description" document is states that the MAC in a Concetntrator is optional. If MAC is responsible for such things as: fair and equal access to the ring, claiming, beaconing, frame construction etc., how can MAC be optional in the CON. How does a MAC-less CON function? 2. Is the MAC required on the CON in orded to manage the CON with DECelms. 3. The above referenced document suggest implementing the dual ring on only several of the CONs (Main Distribution Ring). However, if we must install fiber to the other buildings (eg a campus environment), and the DECconecntrator500 is a DAC, why would we not want all the CONs to also be part of the DUAL-ring? 4. If FDDI is a point-to-point topology why is it recommended that 24 pair fiber cables be run between CONs - when would the other 22 pairs ever be used?
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 111.1 | some basic answers | BAGELS::LEVY | Thu Aug 16 1990 15:34 | 41 | |
<<< Note 111.0 by FDCV06::IZZO >>>
-< Basic FDDI questions >-
>1. Thruout the "FDDI System Level Description" document is states that
> the MAC in a Concetntrator is optional. If MAC is responsible for such
> things as: fair and equal access to the ring, claiming, beaconing,
> frame construction etc., how can MAC be optional in the CON. How does
> a MAC-less CON function?
Like a dumb repeater.
Think of it as a fiber-optic DEMPR. (Just as dumb, just as invisible to
network management.)
>2. Is the MAC required on the CON in orded to manage the CON with DECelms.
Yes. See above.
>3. The above referenced document suggest implementing the dual ring on
> only several of the CONs (Main Distribution Ring). However, if we
> must install fiber to the other buildings (eg a campus environment),
> and the DECconecntrator500 is a DAC, why would we not want all the CONs
> to also be part of the DUAL-ring?
Because it's not a good idea to have the dual ring leave the MDF. See
Jerry Hutchison's IEEE paper for the full explanation.
The DECconcentrator 500 can act as a DAC or a SAC. SAC's are treed off
the dual ring of DAC's.
>4. If FDDI is a point-to-point topology why is it recommended that 24 pair
> fiber cables be run between CONs - when would the other 22 pairs ever
> be used?
The guidelines in DECconnect cover all potential applications (full
motion video, security, voice, etc.), not just FDDI.
| |||||
| 111.2 | KONING::KONING | NI1D @FN42eq | Thu Aug 16 1990 19:40 | 6 | |
Please do NOT call the dec concentrator a SAC or say that it can act like one. It is not and does not act like one. The correct statement is that a SAC is permitted only in the tree, and a DAC is permitted both in the tree and in the dual ring -- which is why we built a DAC. paul | |||||
| 111.3 | CVG::PETTENGILL | mulp | Fri Aug 17 1990 21:48 | 9 | |
The cost of running cable, any cable, almost always is greater than the cost of the cable itself. In the case of fiber, this is still true. Fiber is generally installed in REAL orange hose which first must be installed like conduit and then the fiber is pulled thru the hose. Based on the size of the hose, you figure that you can stick a lot of cables in it, but the catch is that you pretty much need to do it all at once. If you try to later pull additonal fibers thru the same hose, you run the risk of damaging both the existing cable and the new cable because of heat buildup and other stresses the happen because of the fiction between the cables. | |||||
| 111.4 | FDDI - DEMFA and LAT | SUBWAY::HILTON | the light at the end of the tunnel is an Oncomming..(crunch) | Wed Apr 01 1992 14:20 | 12 |
some LAT based questions on FDDI
will two DEMFA's automatically fail-over between themselves if one
dies? IE: run LAT on one and then when it dies. AUTOMATICALLY failover
to the second unit WITHOUT loss of LAT sessions?
can LAT run on two DEMFA's simultaniously IE: can I run LAT on two
independent rings from a vax connected to both? If so...does lat
have enough smarts to deal with what logical connection goes where?
| |||||