The value was picked heuristically after measuring through Ganglia and a set of CLI tools the average TCP dialog duration between a set of mobile devices and our database and then performing a set of tests with varying TIMEWAIT lengths. The 20 second period is a sweet (and round :)) spot with < 0.01% of packets / day arriving after FIN. It's a good approach all in all, since our expected payload packet set is extremely small (just 1 on broadband connections with large MTUs).

- Panagiotis Papadomitsos, Head of Infrastructure @ BugSense