This is also sometimes referred to as TCP retransmission due to RTO (Retransmit Timeout). TCP Retransmissions - These are the normal (althought not so normal if it happens quite often) everyday retransmissions in which the Packets sent are not acknowledged by receiver within a certain amount time (derived from SRTT. Here is a good write-up RFC 6298 if you want to get more information on how RTO is calculated.

This timer is dynamically adjusted according to RTT and other factors. Every TCP segment as it is sent to the IP layer has a timer associated with it and an ACK should be received before this timer expires. In Wireshark, TCP retransmissions are classified as one of three categories. After some investigation, I found out what these mysterious Spurious retransmissions really are.

started to wonder what this really means. It reads ' not being what it purports to be false or fake'. First time I saw on 'TCP Spurious Retransmissions' on Wireshark, I had to look up the definition of Spurious on Google as I've never heard that word before :).

Rto wireshark