1. A computer-implemented method in a first node for establishing a connection with a backbone in a network, comprising: determining initial values for a ranking of the first node, the ranking of the first node comprising: a first ranking part reflecting a communication distance to a node having connectivity with the backbone; and a second ranking part reflecting a communication distance to one or more nodes in a first subnetwork of the network, wherein the first subnetwork includes the first node and the one or more nodes; receiving ranking information from a peer node, the ranking information including a ranking for the peer node, the ranking for the peer node relating to connectivity of the peer node with the backbone for preventing isolation of the first node from the network, the ranking for the peer node including: a first ranking part reflecting a communication distance to a node having connectivity with the backbone; and a second ranking part reflecting a communication distance to one or more nodes in a second subnetwork of the network, wherein the second subnetwork includes the peer node and the one or more nodes; attempting by the first node to establish communication with the peer node, based on the ranking information, via Line-of-Sight (LOS) communication; establishing, by the first node, communications with the peer node; updating a first value in the first node's first ranking part, the first value being the same value as the peer node's first ranking part; and updating a second value in the first node's second ranking part, the second value generated from an arithmetic operation applied to the peer node's second ranking part.