Performance crash when setting TOS bits

[Kevin Oberman]

Under FreeBSD 8.2 we have found that something goes haywire when TOS
bits are set. When the TOS is 0 (default), we can get 9 Gbps performance
with one of our test systems running perfSONAR
(http://www.perfsonar.net). When we set the TOS bits to 32, the
performance drops to about 4Mbps. This does not happen with FreeBSD 7.3.

We ran a tcptrace on the data and found very large numbers of
retransmits and duplicate ACKs. I would attach the traces, but I know
the mail list would remove them.

Has anyone else seen this? Any idea what might be happening?
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751