+-----------------+          +-----------------+
 |      LSP        |          |      LSP        |
 |     Label       |          |     Label       |
 |  (May be PHPed) |          |  (May be PHPed) |
 +-----------------+          +-----------------+
 |                 |          |                 |
 |  Application    |          | Synonymous Flow |
 |     Label       |          |     Label       |
 +-----------------+ <= BoS   +-----------------+ <= Bottom of Stack
 |                 |          |                 |
 |   Payload       |          |   Payload       |
 |                 |          |                 |
 +-----------------+          +-----------------+

"Normal" Label Stack         Label Stack with SFL