goodloe@xenon.UUCP (Tony Goodloe) (05/03/88)
I feared that my posting didi make it to the net in its entirety, and I can see now that it must not have. My question was "what maximum utilization can one expect to see on an Ethernet?" I know that a csma/cd net is non-deterministic, that's why the question exists, otherwise I could determine it :) I was looking for more sources like "Performance of an Ethernet Local Netwotk: A Preliminary Report" by Shoch and Hupp or "Performance Analysis of CSMA/CDD" by Tobagi and Hunt. I haven't made it through Tobagi and Hunt, but according to Shoch and Hupp they have seen a maximum of ~98% utilization down to maximum ~60% utilization depending on the test conditions. Read the article for more info. I was looking for more info like this, or real live experience. Our net gets up to about 35% and we do have individual nodes capable of more. What I am curious about is what people have seen or caculated (using statistical means (no pun intended)) on other nets with lots of these beasts on them. Maybe this posting will make it out in one piece.
retrac@titan.rice.edu (John Carter) (05/05/88)
In article <48@xenon.UUCP> goodloe@xenon.UUCP (Tony Goodloe) writes: ... >I was looking for more >info like this, or real live experience. Our net gets up to about 35% >and we do have individual nodes capable of more. What I am curious about >is what people have seen or caculated (using statistical means (no pun >intended)) on other nets with lots of these beasts on them. Willy Zwaenepoel and myself have implemented a bulk data transfer protocol under the V System (*not* System V) which can sustain about 92% of the theoretical ethernet bandwidth (8.4 Mbps user memory-to-user memory plus protocol overhead of 90 bytes per 1024 byte data packet). This is on a very busy interdepartmental ethernet (so busy that when we monitored it over a period of a few days we never saw the network load drop below 8%, even in the wee hours of the night - too many fileservers and gateways I guess :-). Yet more proof that you can usefully use all the bandwidth that the ethernet provides... John Carter Internet: retrac@rice.edu Dept of Computer Science CSNET: retrac@rice.edu Rice University UUCP: {internet node or backbone}!rice!retrac Houston, TX