lcrosby@ALMSA-1.ARPA (Linda Crosby) (11/19/86)
I am in the process of establishing a TCP/IP network that will
run on Broadband ethernet. The prototype installation will consist of
4 mainframe computers (VAX 780) and 8 or 16 users using IBM-PC clones. The
highwater mark could be as many as 8 mainframe computers and 400 IBM-PC
clone users.
I would like to know if 400 users, as described above, running the
standard suite of DOD protocols (TCP/IP, TELNET, FTP, SMTP) can be
supported on a single ethernet ? How many connections would be
reasonable before the network begins to degrade ? Is anyone familiar
with a broadband ethernet, similar to what we are proposing, that is
configured with 400 connections ? Is this reasonable ?
I would like to here from anyone who has covered this ground
before. A successfull installation elsewhere would be a big
confidence builder.
Linda J. Crosby
Technical Liaison
ALMSA-1
(LCROSBY@ALMSA-1)nowicki@SUN.COM.UUCP (11/22/86)
I am in the process of establishing a TCP/IP network that will run on Broadband ethernet. In a way, "Broadband ethernet" is an oxymoron. Ethernet is baseband. There are several companies that build systems that are compatible with Ethernet transciever specs, but use broadband signalling instead of baseband signalling. Although this is an analog issue that is mysterious to software types like me, the fact that you modulate and demodulate should not help collision problems, so you have the usual Ethernet length restrictions. Of course you can exceed the length restrictions, with possible collision problems. The prototype installation will consist of 4 mainframe computers (VAX 780) and 8 or 16 users using IBM-PC clones. Your definition of "mainframe" is interesting, since the workstation on my desk is twice as fast, and is the middle of our line. At any rate, we have many Ethernets with up to about 100 Sun-3 machines. It is interesting that bandwidth is not the first limitation. The main reason you don't want more than about 100 machines is that one faulty machine can bring the whole network down. The probability that someone shorts the cable, or starts to continuously broadcast, or at least has bad collision detection circuitry, becomes pretty close to one with over 100 nodes. Of course this might be because Ethernet networks just evolve, while broadband networks are usually "planned". We make each floor of each building its own Ethernet, with additional Ethernets for labs. You can make a Sun into a gateway just by sliding in another Ethernet controller. It also helps to use transceiver multiplexor boxes such as the ones made by TCL, to reduce the number of actual taps, (less likely to short the cable). So you probably can put 400 PCs onto a single net, but do you want to? -- Bill Nowicki Sun Microsystems