14 Nov
1999
14 Nov
'99
7:50 a.m.
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
expect,
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
10.
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