WNM Sleep Caveats
Features > WNM Sleep
There are several issues to take into account when using WNM Sleep with the MM IoT SDK.
Sleep time limitations
There are limits implicitly imposed on the time that the device can remain in WNM Sleep Mode.
BSS Max Idle Period is an AP configuration option that constrains the sleep time. The STA will not be able to sleep for longer than this time without being disassociated by the AP. Instructions for configuring this are provided below.
The PMK lifetime is the maximum lifetime of a secure association between STA and AP. When this limit is reached the STA will disassociate from the AP and reconnect. This is configured to 12 hours for MM IoT SDK devices. If a device is in WNM Sleep when this timeout is reached it will disconnect from the AP, reconnect, and establish WNM Sleep.
Data transmission
Putting the device into WNM Sleep mode only prevents it from waking up to receive traffic. If the IP stack transmits packets these will be sent by the device, even if it is in WNM Sleep mode. It is therefore necessary to ensure the STA does not transmit packets (such as IPv6 router solicitation packets) while in WNM Sleep.