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From: koning@koning.enet.dec.com (Paul Koning)
Newsgroups: comp.dcom.lans
Subject: Re: FDDI question: bridges, routers, interoperability ...
Keywords: FDDI, bridges, routers
Message-ID: <22951@shlump.lkg.dec.com>
Date: 28 May 91 20:40:32 GMT
References: <1779@ariadne.csi.forth.GR> <22755@shlump.lkg.dec.com> <1793@ariadne.csi.forth.GR>
Sender: newsdaemon@shlump.lkg.dec.com
Reply-To: koning@koning.enet.dec.com
Distribution: comp
Organization: Digital Equipment Co., distributed systems architecture
Lines: 47


|>>|>I have a host A connected to an ethernet segment. The ethernet segment is
|>>|>connected on an FDDI bridge and the bridge on an FDDI ring. I have a
|>>|>host B connected to an ethernet segment. The ethernet segment is connected
|>>|>on a FDDI ethernet router and the router on the ring.
|>>|>
|>>|>My question is: Will A talk to B?
|>>|>
|>>|>The bridge will be Dec compatible translation bridge.
|>
|>>Yes.  At the datalink level, A talks to the router's FDDI port; the
|>>router in turn forwards over its Ethernet port to B.  Since you said
|>>that the bridge is a translating bridge, it will turn A's Ethernet packet
|>>into the corresponding FDDI packet, which the router will understand.
|>
|>>This ONLY works with translating bridges -- not encapsulating bridges.
|>
|>Dear Paul,
|>
|>Bridge vendors tell me that this works but router vendors tell me no it
|>does not. The router acts like a router and there is no transilation
|>function turned on. Have you SEEN this working. Where? So I contact them
|>and find out my self because vendors answers confuse me more than enlighten me.
|>
|>Some router vendors say that only if the router has the ability to
|>act as a translation bridge otherwise no. Some say if the protocol is TCP/IP
|>then it will work for other protocols no.
|>
|>All bridge vendors say yes but most have not tested it.
|>
|>Anyone out there has installed FDDI bridges and FDDI routers (acting as 
|>routers only) and made them inoperate?

Well, I didn't actually personally run the tests.  But we make it our habit
to claim something works only if we have actually tested it.  And I 
definitely do know we ran a number of tests in this particular area.

The final test is always your own...  The set of potential bugs, whether
our own or someone else's, is quite large.  In spite of best effort of
everyone involved there will always be strange cases (strange configurations,
strange bugs, new bugs in previously working code, whatever) that cause
trouble.

But based on what I know we have done, I'm quite comfortable in saying that
DEC bridges will do the right thing here.

	paul