Packet Filter Offload - Infineon AIROC CYW43012 Manual

Low-power system design with AIROC™ Wi-Fi & Bluetooth® combo
chip and PSoC™ 6 MCU
WLAN power optimization techniques
Because ARP request and response packets are a common activity in any WLAN network, the host device
usually gets flooded by many requests; the host needs to remain active to respond to such requests, especially
in a crowded network. ARP requests packets from a peer and usually wakes the host if it is sleeping. The ARP
offloading feature in AIROC™ Wi-Fi & Bluetooth® combo chip handles responding to ARP requests from a peer so
that these requests will not disturb the host. The AIROC™ Wi-Fi & Bluetooth® combo chip device holds a cache
(of 8 entries); the host will be woken up only if there is a cache miss as shown in
In addition to auto-replying to peers, AIROC™ Wi-Fi & Bluetooth® combo chip can use the cache to reply to the
host (PSoC™ 6 MCU) as well when the host sends an ARP request to the network. This host auto-reply feature
works similarly to a Peer auto-reply, where a cache miss is forwarded to the network and a cache hit returns an
ARP response immediately to the host. This feature is complemented by the ability of the AIROC™ Wi-Fi &
Bluetooth® combo chip device to snoop ARP info from host-network communication, i.e., whenever a host
sends an ARP response packet over to the network, the [IP:MAC] information is cached into the AIROC™ Wi-Fi &
Bluetooth® combo chip ARP cache table.
Figure 6 ARP offload feature
3.3.2

Packet filter offload

Packet filters allow the host to limit the types of packets that get passed up to the host processor from the
WLAN device. This is useful to keep out unwanted packets from the network that might otherwise wake the
host out of a power-saving Deep Sleep mode or prevent it from entering Deep Sleep mode.
In general, whenever a WLAN packet is destined for the host, the WLAN device must awaken the host (if it is
asleep) so that the host can retrieve the packet for processing. Often, the host network stack processes the
packet only to discover that the packet should be thrown away because it is not needed such as when the
packet is destined for a port or service that is not being used. Packet filters allow these types of packets to be
filtered and discarded by the WLAN processor itself so that the host is not interrupted.
In short, packet filters are useful when:
You want to keep the host processor in Deep Sleep for as long as possible (or enter Deep Sleep as soon as
•
possible) by filtering unwanted traffic.
Application note 18
Figure 6.
002-27910 Rev. *C
2023-05-29