The network layer moves data from the perception layer to wherever it is stored and used. In practice it is a chain of very different links: a short-range radio such as BLE or Zigbee from the sensor to a hub, a gateway that converts to IP, then Ethernet, Wi-Fi or cellular to the internet. Low-power wide-area technologies such as LoRaWAN collapse part of that chain by reaching the gateway directly over kilometers.
The term is borrowed loosely from the OSI model and should not be confused with OSI layer 3; in IoT architecture diagrams it bundles the whole transport path. Each hop adds latency, cost and a place to fail, so the layer is chosen as a package of range, data rate, power and price. The IoT connectivity overview compares the options.
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