Further, when sensor data is explicitly sent to one or more receivers, routing is considered
node-centric. Most routing protocols focus on unicast routing, that is, forwarding of sensor
data to exactly one receiver. Multicast and broadcast routing approaches, on the other hand,
disseminate data to multiple or all nodes, respectively. Data-centric routing is used when
nodes are not explicitly addressed, but instead receivers are implicitly described by certain
attributes. For example, a query issued by the gateway device may request temperature
readings and only sensors that can collect such information respond to the query