+-------------------+
                       | Time-Synchronized |
                       |      Network      |
                       +---------+---------+
                                 |
                                 |
                                 |
                  +--------------+--------------+
                  |                             |
               +-----+                       +-----+
               |     | Backbone              |     | Backbone
          o    |     | router                |     | router
               +-----+                       +-----+
          o                  o               o
              o    o   o               o  o   o  o   o  o
         o      LLN    o                 o  LLN   o  o
            o   o    o      o             o o o     o  o
      6LoWPAN Network (subnet N1)   6LoWPAN Network (subnet N2)