Network speed: 10Mbs = 1Mbs ?
Michael Wechter
on a Microsoft W98 network with coax BNC using NETBEUI the speed is supposed
to be 10Mbs, but I have tried to measure the actual speed, and it seems to
be more like 1 Mbs.
Is there any way to make it faster without changing cables and so on ?
Michael W.
Brian K. Dore'
Michael Wechter wrote:
>on a Microsoft W98 network with coax BNC using NETBEUI the speed is
supposed
>to be 10Mbs, but I have tried to measure the actual speed, and it seems to
>be more like 1 Mbs.
The rated speed of Ethernet over coax is 10Mbps. That is ten million bits
of information per second. One byte is 8 bits, so that comes out to about
1.25 million BYTES per second. That is a common misunderstanding.
Another issue to consider when measuring performance is that data is
transmitted over Ethernet in frames. A frame has to have information about
the computer sending the data, the computer receiving the data, some
information about the data and a checksum. You have about 20 bytes of data
here, and the maximum packet size is about 1500 bytes, so you can see that a
small but measurable percentage of your available network bandwith is being
used to send this information. Higher level protocools, like NETBEUI and
TCP/IP also take up some of these 1500 bytes for their addressing
information...
Also, there has to be a waiting period between packets where nothing can be
transmitted on the network. That also reduces the throughput you measure.
When you have multiple machines on an ethernet, they take turns
transmitting, so it gets very complex to measure performance with multiple
machines. They share the available bandwith.
There are lots of other issues, but you should get the idea that measuring
performance is a little more complicated than it seems.
Finally, you should consider the possibility that your computers are the
slow part of your network. Most file transfers over the network involve one
computer reading the data off of its hard disk and the other computer
writing the data to a hard disk. There is a very good chance that you are
being limited by the speed of your disk drives, not your network. For
reasons similar to those above, just because you have a 33Mbps IDE disk
doesn't by any means that is the rate that data is transfered between the
drive and your RAM memory. Unless you have a fairly new high performance
system it is unlikely you would see any difference in transfer rate even if
you switched to 100Mbps Ethernet.
>Is there any way to make it faster without changing cables and so on ?
Ethernet over coax cable is limited to 10Mbps by the specification, so to go
to a 100Mbps network you will have to change your adapters, cable and
introduce a 100Mbps hub or switch if you have more than 2 computers.
Try creating a ramdisk on each system and benchmark your transfers from the
memory of one computer to the memory of another. If you get a significant
performance increase, then faster disk drives might be an option.
This is by no means a complete discussion of network performance, but it
should give you some ideas where to look.
Brian Dore'
Lafayette, LA
Stephen Hammill
Brian...
The only thing I might suggest would be downloading a copy of Sniffer
Basic from:
http://www.nai.com/products/network_visibility/sniffer_basic/basic.asp
By using the monitor of this tool, you can watch it happen...and when
the capture is stopped, you can see exactly all the overhead you were
talking about.
Good job!
On Sat, 19 Sep 1998 14:20:49 -0500, "Brian K. Dore'" <b...@usl.edu>
wrote:
Michael Wechter
thanks alot for qualified explanation and advice.
Michael W.