Very Computer

Hi all,

I observe the symptom that when I make a socket connection (any type of
connection, e.g. telnet, http, ....) to RS6000, it try to probe back the
machine initating the connection using ICMP message. The frequency is about
one probe per minute. Even the connection is dropped, the probe back message
still occurs but I haven't monitored how long it kept.

Our RS6000 is used as a web server. If there is thousands of connection,
there will be thousands of ICMP probe back per min. Will this cause a
serious performance problem for network? I have changed the value
tcp_keepintvl to higher value using command no but the interval is still not
changed.

Any idea.

Thank you very much.

Mike

The probe is AIX trying to check which is the best MTU (packet size) to
talk to that specific client.  It's used to increase the throughput and
reduce the latency on the connection.

Quote:> Our RS6000 is used as a web server. If there is thousands of connection,
> there will be thousands of ICMP probe back per min. Will this cause a
> serious performance problem for network?

No.  One probe per minute vs. the ammount of traffic to each client
isn't a problem.

Quote:> I have changed the value
> tcp_keepintvl to higher value using command no but the interval is still not
> changed.

tcp_keepintvl is the keepalive interval.  It's only used for idle
connections.

--
Doing AIX support was the most monty-pythonesque
activity available at the time.
Eagerly awaiting my thin chocolat mint.

If you are concerned that the probing might affect your performance
you can switch it off altogehter with
"no -a udp_pmtu_discover=0"
"no -a tcp_pmtu_discover=0"

Bye, Stefan...  .  .  . .