wallace@cme.nbs.gov (Evan Wallace) (12/22/89)
I am interested in what products exist to provide ethernet service over broadband (midsplit). We are mostly a sun shop and would like this to support diskless nodes, which means coping with 8KB data bursts. We now have some chipcom ethermodems front ended by DEC lanbridges in special service (supporting two diskless sun based CAD systems). Our experience when we expanded the user base on this channel was a catastrophic degradation of service. These were by no means rigorous tests and their is no way to isolate the Lanbridges from the equation; however it does not inspire confidence in this technology. I ask the net: What products are available ethernet over broadband? (even just a vendor name would be helpful) What experiences have people had with broadband enet (good and bad and be specific)? If anyone is interested in the results of this info request, send me a mailgram. Evan K. Wallace National Instititute of Standards and Technology internet: wallace@cme.nist.gov uunet: uunet!cme-durer!wallace
dd@ariel.unm.edu (dd) (12/23/89)
In article wallace@cme.nbs.gov (Evan Wallace) writes: >[...] >We now have some chipcom ethermodems front ended by DEC lanbridges >in special service (supporting two diskless sun based CAD systems). >Our experience when we expanded the user base on this channel was a >catastrophic degradation of service. These were by no means >rigorous tests and their is no way to isolate the Lanbridges from >the equation; however it does not inspire confidence in this >technology. I may be mistaken, but I believe the Chipcom stuff is 10BROAD36 compliant. That means that it performs as well as an Ethernet. Period. Well, almost period... How long is your broadband? The catastrophic performance degradation may occur if your collision detection is not functioning correctly, and the only mechanism I see for that is that you may not be adhering to the maximum length specifications of 10BROAD36? If this is the problem, you might actually want to go with something that has a lower signalling rate, and a greater network radius (we use UB buffered repeaters here, providing CSMA/CD 5 Mbps channels), because you will actually get higher thruput out of this configuration. We have diskless and disked workstations separated by the broadband system, but we have a company policy that paging and swapping are not allowed over the broadband. We experience some less-than-optimal response, but no catastrophic collapse. Anyway, vendors you might try: Ungermann Bass Lanex But I really think Chipcom makes a very good product. -- Don Doerner dd@ariel.unm.edu University of New Mexico CIRT 2701 Campus Blvd, NE Albuquerque, NM, 87131 (505) 277-8036
haas@cs.utah.edu (Walt Haas) (12/23/89)
In article <2389@morticia.cme.nbs.gov> wallace@cme.nbs.gov (Evan Wallace) writes: >I am interested in what products exist to provide ethernet service >over broadband (midsplit). We are mostly a sun shop and would like >this to support diskless nodes, which means coping with 8KB data >bursts. We use the Sytek (now Hughes LAN Systems) model 8200 on our high-split system. I imagine they make a mid-split version. This product is a learning bridge that interfaces an Ethernet to a broadband. It uses 802.4 token bus as the broadband protocol, which makes it possible to go much longer distances than would be possible using 802.3 as the Ethermodem does. The 8200 is a generally good product and the vendor has been quite responsive to any gripes we have had. There is enough internal buffering in the 8200 to permit it to absorb a burst of packets from a Sun server, holding on to them until the token comes around and the packets can be forwarded. We have been running six of these boxes for most of 1989 and are getting quite good performance from them. They work by encapsulating the Ethernet frame in an 802.4 frame, rather than attempting a conversion. Since we don't have any other 802.4 anywhere on our campus we don't find this approach limiting. I have no connection with Sytek other than being a generally satisfied customer. Cheers -- Walt Haas haas@cs.utah.edu utah-cs!haas