Sena HelloDevice Pro PS110 Series User Manual page 39

  TCP keep-alive time:
This represents the time interval between the last data transmission and keep-alive packet
submissions by the Pro Series. These "keep-alive" messages are sent to the remote host to
confirm that the session is still open. The default time value is 15 sec.
  TCP "keep-alive" probes:
This represents how many "keep-alive" probes will be sent to the remote host, until it decides that
the connection is dead. Multiplied with the "TCP ' keep-alive' intervals", this gives the time that a
link is forced to close after a "keep-alive" packet has been sent for the first time. The default is 3
times
  TCP keep-alive intervals:
This represents the waiting period until a "keep-alive" packet is retransmitted. The default value is
5 seconds.
By default, the Pro Series will send the keep-alive packets 3 times with 5 seconds interval after 15
seconds have elapsed since the time when there' s no data transmitted back and forth.
Figure 3-13 TCP keep-alive configuration
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