| Let me clarify my initial statement.
Synoptics and Cabletron manufacture Ethernet "concentrators" that come in
various configurations. There are cards with fiber connections that
allow multiple Synoptics boxes to connect to each other, and there are
also unshielded twisted pair ethernet cards with 8 ports on each card.
As a result, you have a Ethernet "HUB" (Perhaps that is what confused
the issue... I probably used the wrong term. Sorry about that...)
that has the ability to connect to other Synoptics HUBS and form an
large Ethernet LAN.
So, my customer has a heavy investment in Synoptics Ethernet HUBS.
The article in the trade rag indicated DEC, Synoptics, and Cabletron
announced FDDI over copper products that would allow their products to
interoperate.
My assumption, given that the Ethernet HUBS are 10MB
environments, (The backplanes in these boxes do in fact support speeds
up to 300 Mbits/sec, but Ethernet is Ethernet, so for practical
purposes everything today is running at 10Mbits/sec.) As a result, the
addition of a FDDI copper card into the HUB would require this card to
perform 10/100 bridge functionality, allowing the existing Ethernet HUB
environment to connect to the FDDI backbone.
Are these cards being bulit by DEC or have we just shared SPEC
information that will ensure interoperability? More importantly, do
these cards do TRANSLATION, or ENCAPSULATION? Frankly, I don't care
who builds the thing as long as its a TRANSLATING card.
Thanks again for any pointers, or information.
Regards,
John Edelmann
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| You missed what the announcment was. Copper is a replacement for fiber
for connections 100m or less. It has nothing to do with 10/100
bridging. It is simply a lower cost cabling method. Also, the copper
allows for higher density on the concentrators. We are supplying
concentrator boards which can accept 6 copper connections vs. 4 fiber
connections. You can mix and match these cards in our concentrators.
We and the other vendors support shielded twisted pair types 1,2,6 and
Digital thinwire cable.
We got together with a set of companies to come out with a de facto
industry standard until the official international standard can be
worked out for copper FDDI connections. This allow us and the other
vendors to interoperate at the physical level. We are also coming out
with low cost controller cards for the turbochannel, namely the DEC
LANcontroller 700 for the DECstations will now have a copper option
which costs only $4500/card.
In regard to 10/100 bridging, nothing has changed. Digital bridges are
translating, other vendors such as cisco are encapsulating. All bridges
can be physically connected on the same ring or concentrator, but
encapsulating bridges of a vendor can only send packets to
encapsulating bridges made by the same vendor. Our translating bridges
can interoperate with any other translating bridge. It means that any
packet our bridge gets from an encapsulating bridge can't be understod
and forwarded to Ethernets attached to our 10/100 bridge.
In regard to copper controllers, don't expect the new XMI FDDI card to
ever be copper. The engineering costs to make this happen would
represent a loss to Digital. Simply put a fiber card in the
concentrator to support fiber-only SAS stations such as the VAX-6000
and VAX-9000 series CPUs.
Does this explain it?
|
| Thanks for the explanation! I dug up the May 27, 1991 issue of Network
World, and yes, now that I read it again, that's exactly what the
article says.
My initial note simply resulted from a need expressed by my customer to
allow them to connect their existing Synoptics ethernet hubs to their
proposed FDDI backbone. The vision they had was a Fiber FDDI card that
could be plugged into their Hubs (They have 3 to 6 hubs on each of 8
floors of their building), and my assumption was such a card would
have to be 10/100 bridge cards.
A meeting with the Cabletron rep this past week uncovered the fact that
they will be introducing a router card for their ethernet hub based on
Cisco technology. I'm not exactly sure, but a Cisco based router card may
also be in the works for Synoptics. Given DEC seems to be the clear
leader in translating 10/100 bridge technology, couldn't we team with
the major ethernet hub vendors for a 10/100 translating bridge card for
Synoptics and Cabletron. For that matter, how about such a module for
the new DEChub? (I'm thinking out loud here..)
At the same time, I can understand possible push back from DEC saying "
just use the new DECbridge 5xx or 6xx product to get your hub onto the FDDI
backbone. (The new 3 port ethernet module certainly makes it more
economically palletable for a 3 hub per floor situation than it had
been) Still, I'm not real happy with the implementation, in that the
Synoptics hubs my customer has, have no thin wire ethernet, or AUI
connection points. The cards are either fiber cards connecting the 3
hubs on a particular floor, or UTP port cards. The only way to get it to
connect to the DECbridge is to run a AUI transciever cable from the
DECbridge to a small Synoptics "transciever" box which adapts a standard AUI
connection to a UTP port. (Sort of like a DESTA but adapting AUI to
UTP)
In short, I see this as a Kludge, not to mention an opportunity to get
into trouble with possible ethernet specification violations. (How
long can the AUI cable be? 40M? How long can the UTP wire run be between
the Synoptics AUI/UTP "transciever" and the Synoptics hub?)
Sad but true, this is a REAL WORLD situation in my backyard. My
customers' frustration at this point is that he has FDDI compliant
fiber in place tying his existing hubs together. Wouldn't it be great
to just move the fibers comming into the central hub to a DEC FDDI
concentrator, and plug the other end into a 10/100 translating bridge
card that happens to be cleanly neatly seated in the backplane of my
Synoptics or Cabletron hub! Maybe I'm asking too much... Consider,
though, with Cisco based router cards on the horizon for both Cabletron
and Synoptics, how far behind are Cisco FDDI cards that plug into the
same hubs?
Some thoughts from the field, from a DECIE and a customer getting ready
to face the bleeding edge of technology...
John
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