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Fw:FDDI-Ethernet Conversion



----- Forwarded by Tru H Le/GD_AAAV/GDAS on 10/11/2005 16:39 -----

owner-misc_(_at_)_openbsd_(_dot_)_org 
10/11/2005 16:34

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----- Message from leth_(_at_)_gdls_(_dot_)_com on Tue, 11 Oct 2005 15:37:08 -0400 -----
To:
athompso_(_at_)_commerced_(_dot_)_com
cc:
allison_(_at_)_mail_(_dot_)_arc_(_dot_)_nasa_(_dot_)_gov, tle8464953_(_at_)_aol_(_dot_)_com
Subject:
FDDI->Ethernet mirror/bridge?
I have the same questions too:

Any idea, how I can convert the FDDI to Ethernet and via versa.
"I want to take all traffic on the FDDI ring and 
dump it over to the FastEthernet network."


Thanks,
Tru Le
(tle8464953_(_at_)_aol_(_dot_)_com)
General Dynamics
(W) 703 490 7548



On Thu, 27 Apr 2000, Tyler Allison wrote:
> Anybody have experience with using an OBSD boxes to create a low cost 
FDDI 
> to FastEthernet converter? I want to take all traffic on the FDDI ring 
and 
> dump it over to the FastEthernet network.
> 
> I'm having the darndest time even finding a hardware solution for this 
from 
> any Vendor. Any ideas would be appreciated.

Technically, because FDDI can have enormous frame sizes, you can't
simply produce a "converted" - there's no way to do that at the DLC
layer. 

IP, on the other hand, has a really neat feature called packet
fragmentation :-).  But then, the device you're looking for is called a
"router" - and lots of people make those.

*IF* you can configure every single host on the FDDI ring to use a
framesize of no more than 1545 (?) bytes, then you can use a simple
bridge or media converter.

A media converter is not, strictly speaking, even theoretically
possible.  A media converter simply translates the electrical
characteristics of a signal into some other form.  For example, 10b2
(coax) ethernet to 10bT (twisted pair) ethernet conversion would use a
"media converter" - also commonly known as a "transceiver".

You're asking for the same type of device as an Ethernet-to-Token-Ring
converter.  They only work under very strict conditions, and they wind
up operating (at least) like a bridge, at layer 2.

Take an OpenBSD box.  Add one ethernet card.  Add one FDDI card.
Configure the br0 device - there's been LOTS of discussion recently on
these lists about setting up bridge groups under OpenBSD.

If you want a standalone solution that you don't have to put together,
go to www.blackbox.com, and search (one at a time...) for these product
numbers, and you'll find a number of devices that may suit your needs:
                 LT0003A-4DMI, 38460, LT0002A, WS-C1924F-A, NP-1F-D-MM=
(note - those last two #s are actually Cisco product, which can probably
be found cheaper elsewhere)

Sorry, but ethernet and FDDI just aren't directly compatible.  It's
definitely do-able (I've seen it done with FreeBSD, anyway) but there
are other solutions out there, too.

-Adam

--
Adam Thompson, MCNE, MCSE, CWT, A+
Vice-President / Chief Technology Officer, Commerce Design Inc.
<athompso_(_at_)_commerced_(_dot_)_com>
tel: (204) 942-1648, fax: (204) 989-8080, cell: (204) 782-6198


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