OT: Effective Speed of 10BaseT

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Sun Nov 14 15:50:33 1999

On Nov 14, 12:00, Zane H. Healy wrote:
> I'm wondering what the effective speed of 10Mbit Ethernet is. I've got a
> DEC 3000/300LX that just isn't giveing me the kind of Xfer rates I
> and I'm wondering/suspecting there is a problem with my calculations.
> Using a pair of PDF's totalling 24.6MB as my test I'm getting 8.34MB/Min,
> yet I'd expect it to be closer to 72MB/Min.

You're basing 72MB/Min on 10Mb/s x 60s divided by 8 bits/byte? No way.
 You're forgetting about the packet overheads. And the handshaking
packets. And the delay in setting up the files and buffers at the
receiving end, probably. If you're using 100/10 switchable hubs/routers,
there may be a delay in there, too (they buffer the packets if they have to
switch from their normal speed). If you were using FTP between two
machines running TCP/IP with no other traffic, I'd expect a bit more than
the sort of performance you mention, but for NFS, for example, divide by

> Of course part of this could be the 21064/125 processor, and part of it
> could be the fact I'm using Appletalk.

The processor is fast enough, but a lot depends on the software stack and
the Appletalk-over-Ethernet overheads. I'm slightly surprised you're not
doing better than 8MB/min = 140kB/s, but only slightly.

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York
Received on Sun Nov 14 1999 - 15:50:33 GMT

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