Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site sdcrdcf.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!akguc!mtunh!ariel!vax135!cornell!uw-beaver!tektronix!hplabs!sdcrdcf!darrelj
From: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Newsgroups: net.lan
Subject: Re: Ethernet capabilities/limitations query
Message-ID: <2480@sdcrdcf.UUCP>
Date: Thu, 28-Nov-85 10:35:57 EST
Article-I.D.: sdcrdcf.2480
Posted: Thu Nov 28 10:35:57 1985
Date-Received: Tue, 10-Dec-85 05:31:17 EST
References: <464@mot.UUCP>
Reply-To: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Distribution: net
Organization: System Development Corporation R&D, Santa Monica
Lines: 24

In my experience with a variety of workstations and VAXen is that most
systems become CPU bound by the time they are using from 100,000 to 300,000
bits per second (and I mean for fairly simple, but real, tasks like file
transfer).  What this means that it takes more than 50 machines to saturate
an Ethernet doing real work.  A recent note from ISI in ACM SIGCOMM reported
results of monitoring one of their Ethernet's traffic.  A net with some 70
assorted workstations and mainframes had some interesting statistics.  The
day-long average traffic was under 3000 bits per second and even in the two
hour peak of midafternoon, the average traffic was around 25,000 bits per
second.  Ethernet runs at 10 million bits per second not because anyone
believes you can use that much bandwidth, it's so that there is so much
excess capacity that it can provide service for almost any transient need.

In most systems disk bandwidth is not the limiting factor on
transfers from disk either, but seek and rotational latency are.
-- 
Darrel J. Van Buer, PhD
System Development Corp.
2525 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
                                                            !sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA