+----------------+
                           | Time-          |
                           | Synchronized   |------R
                           | Network        |
                           +----------------+
                                   |
                                   |
                         ----------+-----------
                  ^                |
                  |            +---+---+
                  |            | 6LBR  |
         Upward   |            |       |
         routing  |            +------++
                  |        (F)/      /| \
                  |       /  \      / |  \
                  |      /    \   (C) |  (D)
                  |    (A)    (B)  |  | / |\
                  |    /|\     |\  : (E)  : :
                  |   S : :    : :   / \
                                    :   :