As for routing, a message is first passed from
the sending node (e.g., an end device) to its parent.
If addressed to a child of this parent, the
message is sent directly to the destination node.
Otherwise, the message is passed up the tree to
the next parent, which then decides whether the
message should be passed down to one of its
children or up to its own parent. Message propagation
continues in this fashion by routers and
the coordinator maintaining route information.