Reply To: firewall problems and workarounds –

I found this associated with windows based systems.  It looks like a standard implementation of tcp includes a default keep alive at 2 hours with a socket open with keepalive modifying it for that socket only. And of course other parms that will cause the socket to close after several failures of the keepalive ack.

I am in the porcess of setting this up between an aix and windows system with a brain dead firewall (60 min global timeout,no notification) and will post the results.

http://www.winguides.com/registry/display.php/891/

and this from another website

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I-322 If your aborted sessions aren’t properly cleaned up or if your idle but live sessions are dropped inadvertently, you may need to adjust these two registry parameters.

Hive: HKEY_LOCAL_MACHINE

Key: SystemCurrentControlSetServicesTcpipParameters

Value Name: KeepAliveTime

Data Type: REG_DWORD

Value: 7,200,000  

I-323 Hive: HKEY_LOCAL_MACHINE

 Key: SystemCurrentControlSetServicesTcpipParameters

 Value Name: KeepAliveInterval

 Data Type: REG_DWORD

 Value: 1000  

Both values are in milliseconds. The default value for KeepAliveTime is 7,200,000, or 2 hours, and the default for KeepAliveInterval is 1000, or 1 second. KeepAliveTime governs how often Windows NT sends a keep alive packet. A specific application can request that keep-alive packets be sent. If the target system is able, it responds with an acknowledgment. The KeepAliveInterval works with the KeepAliveTime and governs how often keep-alive packets are sent until an acknowledgment is received. If the target machine doesn’t respond and the number of retries exceeds the value of TCPMaxDataRetransmissions, the connection is terminated. Restart your machine for any changes to take effect.

Looking at this, the implication is

KeepAliveTime governs how often Windows NT sends a keep alive packet  – every 2 hours the system send a keepalaive packet

A specific application can request that keep-alive packets be sent. If the target system is able, it responds with an acknowledgment. The KeepAliveInterval works with the KeepAliveTime and governs how often keep-alive packets are sent until an acknowledgment is received.

implication – if an app opens a socket with keepalive, a keep alive will be sent every second, if no keepalive ack after 2 hours, ….  While not specifically stated I am assuming the connection may closed ? I thing the other parameters play a bigger part in closing the connection on keepalive timeouts