Please consider my network topology:

```
(Machine A0) --- [Switch A] ============ [Switch B] --- (Machine B0)

                                             |

                                             |
                                        (Machine B1)

```

As you could observe `Machine A0` is physically connected to `switch A` (respectively `machines B0,B1` are physically connected to `switch B`). `Switches A and B` are connected directly to each other.

`Machine A0` multicasts a message `m`.

Should m be dulplicated directly on `machine A0`, on `switch A` or on `switch B`?