Is there a way to find out how long an active connection has been established for?
It's a tricky question, there can be multiple answers, depends which one you're looking for.
Imagine you have an open TCP connection that's been established a week ago and all it does sends 1second keep alive every 59 minutes (to avoid default 1hr timeout).
What number are you looking for? Technically connection has been up for 7 days. It has been sending data 1s every hour so 1s x 24 x 7 = 168s? Or 1s within last hour..
Connection established time is in your logs. Session counter for bytes (optionally) in logs. Idle timer countdown in connection table (fw tab -t connections) - so you can calculate when it was last active.
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