Wake-on-LAN can be a difficult technology to implement, because it requires appropriate BIOS, network card and, sometimes, operating system and router support to function reliably. In some cases, hardware may wake from one low power state but not from others. This means that due to hardware issues the computer may be waking up from the "fully off state" (S5) but doesn't wake from sleep or hibernation or vice versa. Also, it is not always clear what kind of magic packet a NIC expects to see.