Thread View: comp.dcom.lans.fddi
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Started by Rob Warnock
Tue, 12 Jan 1993 07:31
Re: CDDI interoperability status
Author: Rob Warnock
Date: Tue, 12 Jan 1993 07:31
Date: Tue, 12 Jan 1993 07:31
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vhalkka@klaava.Helsinki.FI (Vesa Halkka) writes: +--------------- | Quite many vendors are selling CDDI stuff, and there is a standard, but +--------------- But the standard isn't completely settled yet. vjs@rhyolite.wpd.sgi.com (Vernon Schryver) writes: +--------------- | For now, given that few others besides Crescendo are building CDDI | concentrators, it seems likely that CDDI interoperability is not a problem. +--------------- Well, there's what Crescendo has *now* [same as what we were showing at Interop in Fall '92], and what the X3T9.5 standards committee is going to agree on. Already there have been changes. The "scrambler" coding recently agreed on by the committee is incompatible with the existing Crescendo implementation [which caused a lot of semiconductor manufacturers to have to re-spin their chips]; the final standards for "equalization" (filtering), wiring, and connectors have yet to be settled. Since some people seem to be deploying the existing Crescendo stuff, I expect that we'll end up with at least two versions: the existing Crescendo stuff and the "ANSI Standard" version. Fortunately, since most uses of CDDI are for SAS configurations (i.e., station to concentrator), you should be able to intermix the two in the same ring (possibly even in the same concentrator, if Crescendo makes their CDDI modules pluggable). -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com Silicon Graphics, Inc. (415)390-1673 2011 N. Shoreline Blvd. Mountain View, CA 94043
Re: CDDI interoperability status
Author: Gary Rima
Date: Tue, 12 Jan 1993 20:59
Date: Tue, 12 Jan 1993 20:59
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In article <up79aqc@sgi.sgi.com> rpw3@rigden.wpd.sgi.com (Rob Warnock) writes: >vhalkka@klaava.Helsinki.FI (Vesa Halkka) writes: >+--------------- >| Quite many vendors are selling CDDI stuff, and there is a standard, but >+--------------- > >But the standard isn't completely settled yet. > How true, unfortunately! > >vjs@rhyolite.wpd.sgi.com (Vernon Schryver) writes: >+--------------- >| For now, given that few others besides Crescendo are building CDDI >| concentrators, it seems likely that CDDI interoperability is not a problem. >+--------------- > >Well, there's what Crescendo has *now* [same as what we were showing at >Interop in Fall '92], and what the X3T9.5 standards committee is going >to agree on. Already there have been changes. The "scrambler" coding >recently agreed on by the committee is incompatible with the existing >Crescendo implementation [which caused a lot of semiconductor manufacturers >to have to re-spin their chips]; the final standards for "equalization" >(filtering), wiring, and connectors have yet to be settled. > >Since some people seem to be deploying the existing Crescendo stuff, I expect >that we'll end up with at least two versions: the existing Crescendo stuff >and the "ANSI Standard" version. Fortunately, since most uses of CDDI are >for SAS configurations (i.e., station to concentrator), you should be able >to intermix the two in the same ring (possibly even in the same concentrator, >if Crescendo makes their CDDI modules pluggable). > Unfortunately, its a bit more complicated than that. What Crescendo "has" now and showed at fall Interop is NOT what they've been widely shipping under the CDDI banner! What has been shipping is actually NRZI, and therefore is totally different than the MLT-3 based system which will ultimately come out of ANSI. So there's much more involved than just the scrambler. Now, that doesn't mean that what's been shipped can't still be upgraded to ANSI standard at some point in time - I believe Crescendo does promise that. What we've seen in the field doesn't appear to be "field (plug)" replaceable, though, so adapters and concentrators may need to be returned to Crescendo for the upgrade. Also, note that although Crescendo has trademarked the term "CDDI" to refer to its product, others are using the term in data sheets to refer to products which do NOT interoperate with Crescendo (either NRZI or MLT-3!). So it's buyer beware at this point. The one copper solution which is available today with interoperability among multiple vendors is the "SDDI" shielded twisted pair implementation. There are at least 12-15 vendors offering compatible SDDI using off-the-shelf commercial parts from Technitrol and others. Interphase has chosen to support SDDI to offer customers an interoperable solution in advance of the final ANSI standard. We will be offering an upgrade from SDDI to ANSI UTP similar to the Crescendo approach from their proprietary offerings to ANSI. Caveat: As an employee of a major industry FDDI supplier, I don't claim to be totally unbiased about this topic. The above comments should be considered in that light. Regards, -Gary- -- Gary L. Rima Interphase Corp. PP-ASEL-IA (214) 919-9226 Centurion N7358E garyr@iphase.com N0GR CompuServe 76050,231
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