IDLE timeout and Keepalive Interval

Here are some results I found when testing keepalives on TCP and FastL4 virtual servers on 9.4.7 and 10.2.1. I would guess the 10.2.1 results would be similar to what you'd see in 11.x, but haven't tested to confirm.

The customer was considering using keepalives on TMM to alleviate issues with apps that can’t generate keepalives and are slow to generate and start sending the response content.

Based on the results, if the app needs keepalives it makes sense to enable them on both the client and serverside profiles. This ensures that if the client intentionally or unintentionally drops the connection without closing it, that TMM will detect this after 3x the TCP keepalive interval and reset the connection.

You'd want to extend the idle timeout so it's (much) longer than the keepalive interval.

See below for the test results.

Aaron

Keepalive (30 second keepalive, 120 second idle timeout)

VS type |clientside |serverside |result of client disconnecting |description

fastL4 |enabled |n/a |serverside connection is reset after 3x keepalive interval passes |TMM sends keepalive ACKs alternating from client then to server with one keepalive sent per interval

fastL4 with loose open/close enabled |enabled |n/a |connection is preserved as TMM does not send keepalives with loose init/close enabled |

|    |    |    |

TCP |not enabled |enabled |connection is preserved as server responds to keepalive probes |ACKs from server are not proxied through to client so TMM never sees the clientside connection as down.

TCP |enabled |enabled |serverside connection is reset after 3x keepalive intervals pass |

Keepalive (30 second keepalive, 120 second idle timeout)

VS type |clientside |serverside |result of client disconnecting |description

fastL4 |n/a |n/a |keepalives not supported on 9.4.x FastL4 profile |

fastL4 with loose open/close enabled |n/a |n/a |keepalives not supported on 9.4.x FastL4 profile |

|    |    |    |

TCP |not enabled |enabled |connection is preserved as server responds to keepalive probes |ACKs from server are not proxied through to client so TMM never sees the clientside connection as down.

TCP |enabled |enabled |serverside connection is reset after 3x keepalive intervals pass |