bergonz@keeper.sublink.ORG (Michele Bergonzoni) (03/22/91)
> I would appreciate it if some wise person could help me put some of > these technologies in perspective. It seems there is some overlap > between FDDI-II and 802.6, that's OK. Then they both seem orthogonal > to SONET (or should I be saying SONET ATM?). IMHO, there is some overlap between FDDI and 802.6, but 802.6 (also called DQDB, distributed queue - dual bus) has some added features, like transport of isochronous services (like video and voice). [I'm definitely no FDDI expert] SONET was meant to replace the plesiochronous hierarchy 1.5M, 45M, ... (here 2M, 34M, 565M, ...) as a multiplation scheme. It is possible to transport ATM cells in SONET (or SDH)'s envelopes, but the future of ATM is to be the unique multiplation scheme for everything, without SDH overhead (this according to the best optimistic views of some ATM switches developers :-). The relationship between ATM and 802.6 is that ATM is a multiplation scheme (asynchronos transfer mode) and 802.6 is a standard wich implements ATM over a DQDB. 802.6 is designed to be a bus where all the informations from the various stations go through the same media and through all the intermediate stations, and this is not desirable for a public network. Thus, the CCITT is working on the B-ISDN, wich should implement ATM over point to point links and centralized switching facilities in a mesh topology, but all this matter is currently under heavy study. > SONET seems to make some sense as a line driver between clusters > of buildings, but the only product I am aware of that can > up/down convert a LAN technology like 802.3 or FDDI into SONET > is the Alcatel/proteon combination. Also these types of > conversions might be hard to do (cheaply) at fairly high speeds, > so it would might make more sense to stay with one networking > technology from the desktop through the campus backbone. > As an example you could put SONET ATM boards in your desktop > systems and run this building to building across the network, > posibly remultiplexing or concatenating at building clusters to > gain more throughput. SONET and ATM where thought to be used in public networks, only in a second phase they should be extended to customer premises networks. Thus, you can have your FDDI (or better 802.6, since 802.6 cells are nearly identical to I.121 B-ISDN cells) backbone in your campus, with a terminal adaptor (TA) to exit from the campus to the public WAN, and send data, voice and video at high speed with all the rest of the world [remember, I am talking about what all this things are just SUPPOSED to be]. This is what the Bellcore calls SMDS (Switched Multi-megabit Data Service). Using SONET in the customer premises may be useful if you can use its superior drop/insert capability, but is not supposed to be a common practice. > :-) :-) Does anyone know of a couple sources for SONET/ATM boards > for my IBM PC XT? I could probably spend $3 - 400.00 ea. I > understand Russ Nelson is working on a driver :-) :-) Wait till '92 and ask AT&T for its BNS-2000 product line. :-) :-) Maybe there will be also a TA for the IBM PC bus. Cost forecasts are only slightly more than $3 :-) :-) > I recently heard that fiberchannel would solve all our problems, > problem is I don't know what fiberchannel is. Neither do I :-( > So if anyone can share some info to unscramble my brains I would > appreciate it. Thank You. So do I ! I told you my two cents, but I am very far from unscrambled knowledge. I think all the matter is messy by itself. Ciao Bergonz -- Michele Bergonzoni | This internet: bergonz@keeper.sublink.org | is FidoNet : 2:332/401.7 | not Mail : V. Angelo Custode, 9 | a 40141 Bologna ITALY | pipe