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Amit585731's avatar
Amit585731
Icon for Nimbostratus rankNimbostratus
Mar 15, 2016

Regarding TCP timeout

Dear Experts,

 

Just wanted to check regarding the issue we are seeing in our environment. Will the timeout value configured at LTM and server will affect the connection. Our LTM is configured with 5 min and server is configured for 1 hour. Our application team continues to complain that their application license count is exceeding while the number of user connected to application at single time is never more than 50%. We took wireshark capture and found that same data is requested by user multiple times. So can this be possible that once idle time at LTM reaches, LTM deletes the connection while the server side connection remains open since we have idle timeout configured at server side is 1 hour?

 

Sorry for this stupid question but I think once the client side connection deleted the server side also should be deleted by LTM. But just wanted to confirm?

 

Regarding VS, we have configured HTTP VIP, no persistence configured.

 

application delivery
LTM
tcp

4 Replies

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  • raduioncu_16351's avatar
    raduioncu_16351
    Icon for Nimbostratus rankNimbostratus
    Mar 15, 2016

    Hi,

    As long as the reset-on-timeout option is enabled on the TCP profile the F5 should send an RST.

    (cfg-sync In Sync)(Active)(/Common)(tmos) list ltm profile tcp tcp all-properties | grep ltm reset-on-timeout
ltm profile tcp tcp {
    reset-on-timeout enabled
  • tatmotiv's avatar
    tatmotiv
    Icon for Cirrostratus rankCirrostratus
    Mar 15, 2016

    RE "So can this be possible that once idle time at LTM reaches, LTM deletes the connection while the server side connection remains open since we have idle timeout configured at server side is 1 hour?":

     

    Yes, this is possible, but the behaviour is dependent on the settings of your TCP profile. If you have reset on timeout enabled, the BigIP will send a TCP reset for the idling connection out to the server once this timeout is reached, pretending it was the client which sent the reset. This should cause the TCP stack of the server to also delete the connection. If you have reset on timeout disabled, you might experience the situation you describe, resulting in a still open connection on the server without according connection entry on the BigIP.

     

  • Krystian_Baniak's avatar
    Krystian_Baniak
    Icon for Altocumulus rankAltocumulus
    Mar 15, 2016

    Do you use OneConnect profile on the VS? Can you share the output of the list ltm virtual command for your virtual server?