Answer: it is called the "NETWORK LAYER"
Explanation: OSI model means Open System Interconnection model. It have different model layers.
The network layer is the OSI model layer that helps in forwarding packets from network to network, using a network router. It's main function is to connect different network together. It also determine the best virtual circuits(paths) for the data to travel.
Because the question specify that the network is connected to a network router, that means the OSI model layer is network layer.
