06-09-2011 07:08 AM
Hi guys,
I'm troubleshooting a CSM with 4.3(1).
We migrated a real server from windows to linux, since then lot's of sessions stuck in closing state until the idle timer expires.
I traced the traffic from the client to the csm and from the csm to the real server what I saw is the following behaviour at the end of a session:
windows real server: client sends FIN -> real server acks the FIN -> real server sends FIN -> client sends RST -> real server sends RST -> CSM deletes session from session table
The linux real server mostly behaves like the windows real server but sometimes behaves as follows:
client sends FIN -> real server sends FIN, but does not ack the FIN sequence number of the client -> real server sends RST -> client sends RST -> CSM does not delete session from session table, it stucks in closing state
Does anybody know how I can solve this problem of half-closed sessions other than decreasing the idle timeout?
Is it possible to configure CSM to close and delete sessions not only on FIN-ACK packets but also on RST packets?
Or to use a different fast idle timeout when sessions are half-closed?
Many thanks in advance,
Thorsten
Solved! Go to Solution.
06-16-2011 04:48 AM
Hi Thorsten,
this is as per design. If the idle timeout is set to 0 it means never timeout, so in these cases the CSM_FAST_FIN_TIMEOUT won't be used. Using a very high idle timeout (non 0 though) will cause the CSM to use the
CSM_FAST_FIN_TIMEOUT when applicable.
Fabrizio
06-16-2011 03:25 AM
Hi Thorsten,
I remember seeing the "CSM_FAST_FIN_TIMEOUT" having a wrong value set by the CSM in some cases. The value was set to 0 instead of 10 seconds or more. Normally this timeout tells after how many seconds we reset the connection where a FIN has been detected.
Might be worth to double check the "show mod csm X variable" to verify if that is the case.
hope this helps,
Fabrizio
06-16-2011 04:25 AM
Hi Fabrizio,
CSM_FAST_FIN_TIMEOUT is already set to 10 seconds.
What I found out while testing is that CSM_FAST_FIN_TIMEOUT works with configurations where idle timeout is configured > 0.
But when idle timeout is configured to 0 (what meas no idle timeout) the csm seems not to use CSM_FAST_FIN_TIMEOUT: Half closed sessions will stuck in closing state.
Any idea why cms behaves this way?
Regards,
Thorsten
06-16-2011 04:48 AM
Hi Thorsten,
this is as per design. If the idle timeout is set to 0 it means never timeout, so in these cases the CSM_FAST_FIN_TIMEOUT won't be used. Using a very high idle timeout (non 0 though) will cause the CSM to use the
CSM_FAST_FIN_TIMEOUT when applicable.
Fabrizio
06-16-2011 05:10 AM
Hi Fabrizio,
is there any piece of documention in cco where I can find a statement concerning this behaviour?
Thorsten
06-16-2011 06:35 AM
Hi Thorsten,
I can't find any pointer on cco regarding this behavior.
Fabrizio
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