| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 530.1 | Clarification and options | LARVAE::HARVEY | Baldly going into the unknown... | Wed Apr 08 1992 04:54 | 25 |
|
If your customer only has 6 fibres between the sites I assume you mean
they will use 4 of them in order to make an FDDI "ring". However, this
sounds like it would be a "ring in a single pipe", so any damage to this
cabling would likely result in a double break in the FDDI ring and thus
segmentation of the FDDI system.
Installing in this fashion does not really enable FDDI to offer its fault
tolerance capabilities, ie. the ability to continue operation after
sustaining damage to a cable run between ring "stations" or a failure to
such a ring station etc.
Would it help if you simply linked say, 2 concentrators together between
the two sites via 2 cores of the fibre cabling ? This would provide FDDI
access in each site but with no ring "resilience"....
I have not heard of anything which would "multiplex" FDDI along with
something else down a common cable and would be interested to hear
whether the standards allow for such ideas and if anyone is doing it.
In the end you "pays your money and ....... "
ttfn
Rog
|
| 530.2 | WHat about WDM? | POLAR::HOFFE | | Wed Apr 08 1992 12:52 | 11 |
| Is the fiber all multimode? There is a concept called "wavelength
division multiplexing" which allows two(or more) different wavelengths
to be combined onto a fiber,propagated and then each wavelength split
off to its own optical receiver. Such devices are more common for
singlemode.
WDM would allow independent traffic on the same fiber,but it has
problems of its own. FOr example,if the second wavelength is in the 850
nm region,fiber attenuation will be higher. I'd be happy to discuss the
concept with you.
Ron
|
| 530.3 | | KYOA::KOCH | It never hurts to ask... | Wed Apr 08 1992 15:52 | 4 |
| This is a 20+ mile installation, thus single-mode fiber.
Also, is it legal to connect 2 DECconcentrators with only 2 fibers?
Will the concentrator complain about this in any way?
|
| 530.4 | | KONING::KONING | Paul Koning, A-13683 | Wed Apr 08 1992 18:44 | 11 |
| Sure it's legal. There are two ways to do it:
1. (Recommended) Connect M port at one site to B port of the other.
This is the "Tree" configuration.
2. (Legal but not recommended) Connect A port of one concentrator to B
port of the other. This is equivalent to the dual ring with a
broken connection (in this case, the "break" is simply the
non-installed connection) which gives you a wrapped ring.
paul
|
| 530.5 | | KYOA::KOCH | It never hurts to ask... | Tue Nov 17 1992 12:53 | 7 |
| A little follow-up on this.
The customer called DECdirect and was told that they could connect both
sites together by putting a 2x2 SMF/MMF card in the DECconcentrator 500
at both sites and simply hook the SMF M-ports together using 2 fibers.
Is this a legal configuration?
|
| 530.6 | | QUIVER::STEFANI | You guys had enough? Never! | Tue Nov 17 1992 16:53 | 4 |
| M-M connections are illegal in FDDI ring topology and will be rejected
by the concentrators.
- Larry
|
| 530.7 | Please refresh the rules for me... | KYOA::KOCH | It never hurts to ask... | Wed Nov 18 1992 12:17 | 21 |
| So, in order to create trees, every lower concentrator that connects to an
M-port on an upper concentrator must have an A/B management card in it?
----------
|A B|
----------
|M M M M |
----------
^
|
|
v
----------
|A B|
----------
|M M M M |
----------
If I don't want to dual home the configuration, what do I do with B
port on the lower concentrator?
|
| 530.8 | | KONING::KONING | Paul Koning, A-13683 | Wed Nov 18 1992 15:13 | 7 |
| Normally a single connection is to B, not A, though it doesn't really matter.
In any case, if you don't want to use dual homing, you leave the other port
unused. Don't plug in a loopback connector, just leave it disconnected.
(You may want to plug in a dust cover, of course.)
paul
|