Clients (e.g., SONET/SDH and Ethernet)

    |   |   |                           |   |   |
    |   |   |                           |   |   |
    |   |   |                           |   |   |
+---+---+---+----+                      |   |   |
|      OPUj      |                      |   |   |
+----------------+                      |   |   |
|      ODUj      |                      |   |   |
+----------------+----------------------+---+---+----------+
|                                                          |
|                       OPUk                               |
+----------------------------------------------------------+
|                                                          |
|                       ODUk       k in {0,1,2,2e,3,4,flex}|
+-------------------------+-----+--------------------------+
|                         |     |                          |
| OTUk, OTUk-SC, OTUk-V   |     |          OPUCn           |
+-------------------------+     +--------------------------+
                                |                          |
                                |          ODUCn           |
                                +--------------------------+
                                |                          |
                                |          OTUCn           |
                                +--------------------------+