Network Layer (L3)
The network layer is intended to route packets through the network toward their destination. Switches within a multi-hop network use this address to decide in which direction to route individual packets. To enable this, a header containing a 7-bit destination address is added by L3 to all L2 data frames. In the example shown in the figure, this allows Device #3 to not only communicate with Device #1, #2 and #5, but also enables it to communicate with Devices #4 and #6.
Version 1.4 of the UniPro spec does not specify the details of a switch, but does specify enough to allow a device to work in a future networked environment.
Read more about this topic: Uni Pro Protocol Stack
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