TCP/IP timeouts -HELP

TCP/IP timeouts -HELP

Post by Christopher Dav » Sat, 02 May 1992 19:37:51



We are running AIX 3.1.5, with the default TCP/IP settings, on
an RS6000.

A PC talks to the telnet daemon on the RS6000.  If the PC crashes,
then the session stays logged in on the RS6000, and the
socket state ( netstat ) remains in the ESTABLISHED state
for a long time.  What has to be done to reconfigure
TCP/IP to time sockets out more quickly ?

The only other alternatives that we have are:
1.  Write a daemon that will spot the PC rebooting and then
kill off any processes with connections to the PC on the
RS6000.
2. Recompile the telnet daemon - anybody know where to get
the IBM source code for telnetd ? - with appropriate timeouts
in the header files

Any other ideas/experiences will be very gratefully received.

Thanks
Chris

--

Quay Financial Software           Phone   :  +353 1 612377

 
 
 

TCP/IP timeouts -HELP

Post by Peter Jeffe 512.838.40 » Sun, 21 Jun 1992 09:21:31



>A PC talks to the telnet daemon on the RS6000.  If the PC crashes,
>then the session stays logged in on the RS6000, and the
>socket state ( netstat ) remains in the ESTABLISHED state
>for a long time.  What has to be done to reconfigure
>TCP/IP to time sockets out more quickly ?

Sorry for responding so late, but this may be useful to others as
well.  There is an apar ix21955 that allows you to set the keepalive
interval and idle time for the system.  This feature is in 3.2, but
wasn't added to 3.1 until this apar was included in the 2008 release.
There are efixes available for 2006 and 2007, and if you want it on
3005 you could ask real nice :-).

Since telnetd sets keepalive on the socket, after the keepidle time is
up (default 2 hours) with no activity on the connection, tcp will send
a keepalive probe packet to the peer; if it doesn't receive a response
within the keepintvl, it will send another, up to 9 in all.  Then it
will reset the connection.  So if the peer is really alive, no
problem.  If the peer is dead, it will force the connection to close.
And if the peer has rebooted, it should respond to the first packet
with a reset (since that connection no longer exists).

So the apar lets you set the keepidle and keepinvtl periods relatively
short.  Just keep in mind that this also means that if a gateway goes
down or gets very slow, then you may end up blowing away some
connections that you really don't want to.  But if you keep fairly
reasonable times, e.g. 10 minutes for keepidle and 1 minute for
keepintvl, then this shouldn't be a problem.

--


 
 
 

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