+------------------------+
                      | Underlay Network Fabric|
                      +------------------------+

              +-----+   +-----+       +-----+   +-----+
              | PE1 |   | PE2 |       | PE3 |   | PE4 |
              +-----+   +-----+       +-----+   +-----+
                \\         //           \\         //
                 \\ ESI-1 //             \\ ESI-2 //
                  \\     //               \\     //
                  +\\---//+               +\\---//+
                  | \\ // |               | \\ // |
                  +---+---+               +---+---+
                      |                       |
                     CEs                     CEs