ndt-users list created

I'm troubleshooting data transfers between New Jersey and California over 
internet2.  The slowest link is 155 Mbps, rtt is 90 ms, servers and switches 
are gigabit.

Tuning tcp buffers only gets the throughput to 11.9 Mbits/sec.  If I change 
the switch port to 100 Full, the throughput increases to 84.4 Mbits/sec.

ndt reports packet loss and duplicate acks when the connection is gigabit, 
the 100 full connection has no packet loss.

The relevant ndt output is below.  iperf also backs up these results.

Is there a known problem with gig switch negotiation?  No tcp buffer setting 
improves the performance when gigabit.

Thanks

ndt:

gigabit connection:

running 10s outbound test (client to server) . . . . .  13.67 Mb/s
running 10s inbound test (server to client) . . . . . . 14.30 Mb/s

There were 7 packets retransmitted, 178 duplicate acks received, and 245 SACK 
blocks received
Packets arrived out-of-order 2.64% of the time.
The connection stalled 1 times due to packet loss.
The connection was idle 0.30 seconds (3.00%) of the time.


100 full connection:

running 10s outbound test (client to server) . . . . .  11.80 Mb/s
running 10s inbound test (server to client) . . . . . . 20.46 Mb/s

No packet loss was observed.


iperf:

gigabit:

[  3]  0.0-60.1 sec  85.3 MBytes  11.9 Mbits/sec


100 full:

[  3]  0.0-60.2 sec    606 MBytes  84.4 Mbits/sec