Hi,
yes, these two values are especially relevant for SIP/RTP.
I can’t give a general advice which values to set in your case, but it’s worth trying to slightly increase these values.
Furthermore, have a read of this thread: http://forum.mikrotik.com/t/connection-tracking-timeout-values/77167/1
Usually, the problem is the “keep alive” of the NAT mapping.
Do you have the possibility to periodically re-register your phones?
I’m using freeswitch and periodically re-registering my public extensions to the providers SIP gateway solved the problem for me as it keeps the NAT mapping in the router.
Regards,
Ape