Blasting UDP packets on a 1-Gbps link

[Long Le]

Hi all,

I've been trying to get iperf to blast UDP packets for 10 minutes on
a 1-Gbps link. However, iperf stops after a few seconds and complains
that it can't write to the socket because no buffer space is available.

'netstat -m' shows that there are lots of mbufs available. I modified
iperf source code to set the socket's send buffer to 200000 bytes (*)
but it didn't really help much. In another attempt, I modified iperf
source code such that it would not quit after failing to write to
the socket. However, this caused iperf to hang. I use iperf 1.7.0
and FreeBSD 4.5. The machine I am using has a 1-GHz CPU and 1 Gbytes
of memory. I could try to write my own program to blast UDP packets
but would prefer to use available software if possible.

Has anyone successfully blasted UDP packets on a 1-Gbps link for a
sustained period and can anyone give me some useful hints?

Thanks,
Long

(*) Apparently, iperf doesn't have an option to set the socket buffer for
UDP sockets. And there seems to be a limit that doesn't allow to set a
larger buffer size than around 200000 bytes (this is not related to iperf
but FreeBSD in general).