HP -UX 11i Installation And Update Manual page 142

CAUTION
NOTE
Configuring Built-In PCI Networking
Performance
Be careful when adjusting the transmit threshold. While lowering the
threshold may increase performance, it also makes the CORE 100
Base-T interface more susceptible to Transmit Underrun errors.
A large number of transmit underrun errors (more than 1 out of every
1000 packets) may cause a noticeable drop in networking performance.
The performance drop will depend on the application being used.
Applications that send data in a continuous stream (FTP, for example)
may have a more noticeable drop in performance (when more than 1 out
of every 1000 packets have errors) than applications which are
request-response in nature (NFS, for example).
Transmit underrun errors may occur on some HP systems when there is
sufficient bus contention from competing I/O devices on the system I/O
bus. These errors can be monitored in two ways:
1. Examine the output from the netstat -I command. If the number of
output errors is high (more than 1 out of every 1000 packets), then
the system is most likely suffering from transmit underruns on the
specified network interface, and corrective action must be taken to
resolve the problem.
2. Turn on nettl errors and warnings for the network interface being
monitored. The following command will turn on disasters, errors and
warnings for the network interface with Instance number 1:
nettl -log 0xe -e base100 -C 1
Be sure to keep nettl disaster and error logging enabled at all times.
Check the nettl log file /var/adm/nettl.LOG00 for the following message:
HP CORE 10/100BASE-T driver encountered a Transmit Underflow
If a significant number of these messages occur and the timestamps for
each of the messages are within 30 seconds of each other, the specified
networking interface will suffer a noticeable performance drop.
Corrective action must be taken to resolve this problem.
142 Appendix C