From: "Robert Comer" 

Why are you using such a small -b for a gigabit ethernet? That's limiting
the connection.

- Bob Comer


"Gregg N"  wrote in message
news:428a3454{at}w3.nls.net...
> We have an application that sends UDP datagrams over gigabit ethernet. It
> was not achieving the performance we expected, so we ran some tests. When
> the packet size is 1024 bytes or less, we can send 40,000 packets per
> second, or about 312.5 Mbps. Not great, but acceptable. However, with
> packet sizes greater than 1024 bytes, we could not send more than about
> 3700 packets per second, or about 28.9 Mbps (note this is on a 1Gb
> interface!). The process is not CPU bound, so that is not what is causing
> the limitation.
>
> We verified this using the iperf tool from this location:
>
> http://www.noc.ucf.edu/Tools/Iperf/default.htm
>
> which you can try yourself. Use the command
>
> iperf -u -l 1024 -c dummytarget -i 1 -b 500m -w 256k
>
> and see what it shows with -l 1024 and -l 1025. You can substitute a
> smaller value for -b (bandwidth) on a 100 Mb interface.
>
> Apparently, this has been encountered by others. For example, see
>
> http://groups.google.co.uk/group/comp.protocols.tcp-ip/browse_frm/thread/7ec2
673b5471490f/409197bb36320ace?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=
off&rnum=1&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26s
afe%3Doff%26selm%3D2003-01-27-01-42.0%2540chch.demon.co.uk#409197bb36320ace
>
> and
>
> http://groups.google.co.uk/group/alt.winsock.programming/browse_frm/thread/f0
5890d2b6b71452/8d8873987d71893b?tvc=1&q=alanjmcf+1024&hl=en#8d8873987d7
1893b
>
> and
>
> http://www.chch.demon.co.uk/wintest/wintest.html
>
> However, I could not find anything about this on the MS web site. Does
> anyone have any idea what is causing this?
>
> Thanks.
>
> Gregg
>

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