| 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 |
I received the following query from a customer. If someone could
provide me some guidance on a response, it would be greatly
appreciated.
Lee
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I don't know if you have been following the standardization procedures
for FDDI over copper twisted pair wiring, but an event took place last
week that potentially impacts on the FDDI network I am installing right
now.
The ANSI committee on FDDI adopted the MLT-3 data encoding scheme that
had been supported by Cresendo and now by Cabletron as opposed to the
NRZI encoding that is being supported by IBM and, I suspect, DEC. (I
am unable to find any reference to this in the DEC documentation).
While
this does not finalize the standard, it does push it much further along
than it has been to date and is a major step toward getting the
standard
approved.
We need to find out what DEC's plans are to support the new ANSI
standard
if, indeed, it isn't now as I believe. As we are building our network
around the DECconcentrator 500s it is imperative that they support the
newly emerging standard. In addition to the concentrators, we also
have
the FDDIcontroller 700-Cs in our workstations. We will need to find
out
about replacing these with ANSI-compliant equipment eventually as well.
As the standard is still evolving, I don't expect DEC to be able to
commit
to immediate changes, but we are concerned that a solution be found for
the future.
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 641.1 | RTPL08::GRAY | Jack of all trades; Master of none | Fri Jul 10 1992 10:12 | 2 | |
I'll try a more straightforward approach. Do the DECconcentartor 500s
and the FDDIcontrol 700-Cs support MLT-3 data encoding?
| |||||
| 641.2 | KONING::KONING | Paul Koning, A-13683 | Fri Jul 10 1992 13:04 | 25 | |
No. Those devices support SHIELDED twisted pair cable (and coax). For those, it suffices simply to put the traditional NRZI FDDI signal onto the cable, and that's what is done. The ANSI work is aimed at supporting UNSHIELDED (Type 5) cable, where this simple approach doesn't work. We can't possibly support the "newly emerging standard", since there isn't anything nailed down to support yet. The MLT-3 decision is an important one, but only one of dozens. There are a lot of other decisions that must be made before ANYONE can build something that implements the "emerging standard". Right now all you can get is a number of different proprietary approaches (of one company, or of a set of companies -- the latter applies to our current products). For example, Crescendo's products implement an approach proprietary to Crescendo. The fact that they use MLT-3 is irrelevant. (Crescendo would like you not to understand this, but it is true...) Given how much effort DEC is putting into all this, you can rest assured that there will be implementations of the emerging standard once there IS an emerging standard... paul | |||||