I am using multiple gateway:
/ip route add gateway=192.168.1.1,192.168.2.1 check-gateway=ping
how to bind SIP connections to only one WAN?
do you want to set a total limit for the whole network, ie. 2Mbit regardless of what each user gets, or you want to set ie. 256Kbit per each end user?
no, you cannot add your own drivers to RouterOS
maybe, look at '/system resource pci print'...