ICMP probe back during socket connection

ICMP probe back during socket connection

Post by Mike N » Thu, 09 Jan 2003 11:23:01



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

 
 
 

ICMP probe back during socket connection

Post by Jose Pina Coelh » Tue, 14 Jan 2003 12:11:36



> 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.

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.

 
 
 

ICMP probe back during socket connection

Post by Stefan Llabr » Thu, 16 Jan 2003 06:43:43



> 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

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...  .  .  . .

 
 
 

1. Opening a socket connection while in a socket connection.

Hello,

I am new to using sockets and am working on a project that requires
me to audit services accessed under a client/server program (TCP/IP)
socket connection.

What I want to do is send a datapacket to a collector machine each
time a client accesses a service on the server.  It seems that
I am unable to do this from the server.  Basically, in short form
I need to be able to do the following:

1. Client connects (TCP/IP socket connection) to server
2. Client requests a service from the server
3. At that point I want to send a datapacket to a audit server.

Any Ideas?  I am familiar with most of the concepts involved in
using sockets.  Maybe I have been working on this to long and have
gotten tunnel vision.

Thanks

***********************************************************
Brent Curtiss


Academic Computing Services
The Ohio State University
***********************************************************

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