+-----------------+
                  |                 |
                  |                 |
+----+ AC1  +-----+                 +-----+     +----+
| CE1|------|     |                 | PE3 |-----| CE2|
+----+\     | PE1 |     IP/MPLS     |     |     +----+
       \    +-----+     Network     +-----+
        \         |                 |
      AC2\  +-----+                 |
          \ |     |                 |
           \| PE2 |                 |
            +-----+                 |
                  |                 |
                  +-----------------+

  <-802.1Q->  <------PBB over MPLS------>  <-802.1Q->