jbn@glacier.STANFORD.EDU (John B. Nagle) (12/23/88)
In article <12670010@eecs.nwu.edu> gore@eecs.nwu.edu (Jacob Gore) writes: >Just to make sure I understand you correctly: are you actually splicing >a piece of thin Ethernet into a thick Ethernet? Yes. It works. Loss per unit length is higher in the thin cable, but unless you are pushing the length limits of the Ethernet cable, adding a few feet of thin cable isn't that important. You might think that the transition would produce reflections, but my experience is that it doesn't. Find a TDR and check for yourself. If you have a farm of NeXT machines or other small machines with thin Ethernet connectors, it might be better to tie them all together on thin cable and only have one thick/thin transition. But this is not mandatory. Always check the machines at the ends of the cable for high retransmit rates. This is the first symptom of excessive losses, and indicates that collisions are being undetected due to cumulative loss in the cable. This means the cable is too long, or too lossy; time to get out a TDR or put a repeater in the middle. If your thick/thin mixed cable falls within the length limitations for thin Ethernets, everything should work fine. Only beyond that length should it be necessary to worry much about the electrical properties of the cabling. John Nagle
gore@eecs.nwu.edu (Jacob Gore) (12/23/88)
/ comp.sys.next / jbn@glacier.STANFORD.EDU (John B. Nagle) / Dec 22, 1988 / > In article <12670010@eecs.nwu.edu> gore@eecs.nwu.edu (Jacob Gore) writes: > >Just to make sure I understand you correctly: are you actually splicing > >a piece of thin Ethernet into a thick Ethernet? > > Yes. It works. Oh, I'm not surprised that it works. It just struck me as a rather inconvenient thing to do. When we have several thin-connector machines near each other, we do connect them all with thin-net, as you suggested. Except that our thick-cable networks are usually large-spread nets, with multi-user hosts on them as well as scattered workstations. We just don't like splicing into that net, even for inline transceivers. We use thick/thin repeaters for this kind of stuff. A repeater with one thick port and one thin port plus its transceiver and drop cable (for the think side) cost us about $1,000. If you are putting 5 or more stations on the thin side, the cost is quite reasonable. But for a single workstation, it's rather steep... Jacob Gore Gore@EECS.NWU.Edu Northwestern Univ., EECS Dept. {oddjob,gargoyle,att}!nucsrl!gore
jbn@glacier.STANFORD.EDU (John B. Nagle) (12/24/88)
I certaintly agree that a repeater to isolate important multi-user
systems and servers from farms of little machines where the cables are
accessable to many people is a valuable addition to a network. I was
merely pointing out that thich/thin Ethernet transitions are not difficult
to accomplish, should one wish to do so.
Some people have found repeaters, as an active device and a single
point of failure, to cause more trouble than they prevent. But that
information is a few years old, and repeaters may be more reliable now.
John Nagle128a-3db@e260-3b.berkeley.edu (Jonathan Dubman) (05/12/89)
I keep hearing about thin and thick-cable Ethernet. What is the difference? Unless the answer is of general interest, it might be wise to respond via mail. -Jonathan Dubman 128a-3db@web.berkeley.edu