The device will send every 20 seconds (default) an UDP/TCP package to the platform to keep the NAT firewall open.
New in software 2.42.0 or higher
UDP
NAT refresh timer is set by default to 0 seconds
Timer = 0 means feature is disabled
Timer can be changed via auto-provisioning ("SipProvider.0.UDPKeepAliveTimerValue")
TCP
Is activated automatically and set for 90 seconds
Feature is an platform setting, if device has more SIP accounts, it does not send an UDP package per SIP account. It sends only one package every 20 seconds.
Nx70 will send UDP / TCP packages containing only 2 x CR,LF