Adds a count for TCP packets received out of orders. This can be an
indication that there is packet loss on the way packets travel towards
this server. In that case, the sender will retransmit (and we can
already monitor the Tcp_RetransSegs there), but we have no way to
monitor the packet loss on the receiver side. When a packet is received
and the receiver detects previous one missing, it will increase the
TCPOFOQueue counter and reply with selective ACK to the sender, both
possible indications of packet loss. Confirmation of packet loss can be
achieved by taking packet captures, ignoring wireshark analysis, and
carefully looking at data being retransmitted based on the TCP seq.
Just like RetransSegs, TCPOFOQueue should be interesting for any
deployment as a mean to detect packet loss, so here suggesting adding it
to the default list.
Signed-off-by: François Rigault <frigo@amadeus.com>
Co-authored-by: François Rigault <frigo@amadeus.com>
