Stability problems.

[Peter Van Epp]

	A possibly unrelated point: in the latest Usenix login: there is a 
conference report from the Linux kernel developers conference (which one would
not expect to be biased against Linux :-)). The point of interest is a 
discussion that the Linux 2.4 kernel hangs at around 24K PPS yet a BSD 
kernel doesn't hang until 200K PPS. They didn't specify a link speed (possibly
gig), but this flys in the face of measured experience here (Linux does at
least as well and usually better than FreeBSD), It is also unclear (although
one wouldn't expect it at a kernel developer's conference) what board/drivers
this was with. Some drivers exhibit this behaviour (Realtec and the 3Com
3c905 driver) but there are better drivers.
	More related to Chris's problem: I have a patch set which will allow
tcpreplay to simulate a full duplex link using two capture files and two 
Enet cards. When last I tried it (some time ago) with a single IDE disk it
would do about 160 megs per sec (likely disk limited). The fly in the ointment
is that you would need to carefully adjust the capture files to start 
identically in order to run the files at full speed (otherwise the reply
packets can come in before the packet that caused it goes out, which would
undoubtably confuse argus). Somewhere down my list of interesting things to
do is write a "dump file optimiser" that would deal with this (i.e. reorder
the packets in a tcpdump file so that the packet sequence will be correct
when played back at full speed) but it hasn't even been started yet.
	Given this and a test bed you can effectively test the failing case
(since you know all the packets that should appear) and see where (if anywhere)
you are losing things and what you are losing.

Peter Van Epp / Operations and Technical Support 
Simon Fraser University, Burnaby, B.C. Canada