Jeff <jcoppock1@attbi.com> [2002-09-16 14:19:34 -0700]: > Robert Ian Smit, 2002-Sep-16 22:25 +0200: > > I suppose so. Is it still true that on a busy lan you only get 40% > > or less troughput? The guy who told me this years ago said that > > ethernet was dead and tokenring the thing to have since you're > > throughput would always be near 100%. Aesthetically ethernet was > > never a thing of beauty, but it's cheap and it works. > > On a busy Ethernet segment that's shared, not switched, it's more like > 60% throughput. The collisions and subsequent back-off routines But if you keep putting more and more talkers on the bus you will eventually see even more decay of performance. Because it is a collision detect and backoff process it is load dependent. Back in the days of coax we would meltdown to around 40% before things stabilized. I agree the 60% number is probably more typical of a badly loaded ethertwist lan. I have seen 65% considered normal. > create a lot of overhead since all the hosts are sharing the same > bandwidth and are part of the same collision domain. Going to a > switch where every port is it's own segment with it's own bandwidth > simply breaks up the collision domains, thus reducing the amount of > hosts per collision domain. Agreed. > Token Ring is yet another example where it doesn't matter if the > technology is better. I think the "cheap and it works" is what did > the trick for Ethernet. Agreed. Also you might remember a 100VG protocol which was a collisionless protocol. It would give you sustainable bandwidth utilization regardless of load and the number of transceivers on the bus. But it could not compete with 100baseT being mostly a simple frequency push of 10baseT. I think the hardware was the same price. It just scared people that it used a slightly different technology than they were used to. Also for some reason it was only available on MS-Windows, where network performance was not considered critical, and not available for the longest time on unix servers where network performance was considered critical. Sigh. Bob
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