Tcp Keepalive Offload - Infineon AIROC CYW43012 Manual

Low-power system design with AIROC™ Wi-Fi & Bluetooth® combo
chip and PSoC™ 6 MCU
WLAN power optimization techniques
3.3.3

TCP keepalive offload

TCP keepalive packets, as the name suggests, are used to keep an established TCP/IP connection between two
hosts active. These are empty TCP packets that are transmitted at a periodic rate, typically 45 or 60 seconds, by
a host. The peer host is expected to ACK the packet; if it does not ACK for a pre-configured number of TCP
keepalive packets, the connection is considered dead.
In idle case, after establishing a TCP connection, the host wakes periodically to send TCP keepalive packets.
Whenever any other activity is detected in the TCP connection such as incoming traffic, the host wakes up to
process that as well. Figure 8
disabled. Notice how the host has to repeatedly wake up from Deep Sleep to handle the transactions.
Figure 8 TCP activity when TCP keepalive offload is disabled
When the offload is configured and enabled, after the TCP connection is established, the host MCU configures
the WLAN device to send TCP keepalive packets. The host MCU then enters Deep Sleep. When a TCP keepalive
request is received, the WLAN device takes care of responding to it. If there is any incoming TCP traffic or a TCP
keepalive timeout, the WLAN device wakes up the host for processing.
TCP keepalive offload is configured. Notice how the host can stay in Deep Sleep longer and wakes up only when
responding to incoming TCP traffic.
Application note
shows the TCP transactions that take place when the TCP keepalive offload is
Figure 9
21
shows the TCP activity when the
002-27910 Rev. *C
2023-05-29