Provided is a multi network and method to transmit packets. The multi network includes a mesh network, a tree network, and a network interface connected to the mesh network and the tree network and configured to transmit, through the mesh network and the tree network, a packet generated by a processing unit, of a processing system having plural processing units, at a starting point to a destination point for another processing unit of the processing system and configured to selectively inject the packet into one of the mesh network and the tree network to transmit the packet to the other processing unit.