Managing TCP Retransmission Timeout

RE: Managing TCP Retransmission Timeout

Charlie — Thu, 07 Nov 2024 09:07:04 GMT

Hi,

The retransmission count feature is built on top of the basic TCP/IP socket and is not inherently part of the core TCP stack. Due to the limited resources on the modem running on the nRF9151, this feature is not supported.

As I mentioned, I would recommend referring to the Zephyr TCP stack. Zephyr's implementation provides enhanced capabilities, including retransmission counting. If resource constraints are a concern, you might consider porting only the specific parts of the code relevant to your needs to minimize size increases

Best regards,

Charlie

RE: Managing TCP Retransmission Timeout

vytautas — Tue, 05 Nov 2024 13:50:44 GMT

Using the native Zephyr TCP/IP stack isn't an option due to the increased size of the firmware.

Is there no alternative way to control the timeout mechanism for the modem TCP/IP stack?

RE: Managing TCP Retransmission Timeout

Charlie — Tue, 05 Nov 2024 12:54:42 GMT

Hi,

nRF91 modem only proivde socket for straight forward TCP connection, and it does not have an comprehensive TCP stack like Zephyr network libary.

Cellular: Modem Shell sample has an implementiaon that demostrates run nRF91 Series DK with Zephyr native TCP/IP stack. You can refer to it or adding you own implmentaion for TCP retry count based funtion on current TCP socket simple usage.

Best regards,

Charlie

RE: Managing TCP Retransmission Timeout

vytautas — Mon, 04 Nov 2024 12:35:12 GMT

[quote userid="93921" url="~/f/nordic-q-a/115927/managing-tcp-retransmission-timeout/508482"]THanks for checking with us. Looks https://docs.nordicsemi.com/bundle/ncs-2.7.0/page/kconfig/index.html#CONFIG_NET_TCP_RETRY_COUNT is what you need, it has default 9.[/quote]

The CONFIG_NET_TCP_RETRY_COUNT is only applicable to Zephyr's native networking stack. It is not used in Nordic's offloaded sockets. While SO_SNDTIMEO doesn't seem to do anything.

RE: Managing TCP Retransmission Timeout

Charlie — Wed, 30 Oct 2024 09:57:31 GMT

Hi,

THanks for checking with us. Looks https://docs.nordicsemi.com/bundle/ncs-2.7.0/page/kconfig/index.html#CONFIG_NET_TCP_RETRY_COUNT is what you need, it has default 9.

The following two configuration may also help to avoide retransimisson.

MQTT Keep-Alive: CONFIG_MQTT_KEEPALIVE

Socket Timeout: You can also set a timeout on the socket to prevent indefinite waiting. For example:

err = setsockopt(client.transport.tls.sock, SOL_SOCKET , SO_SNDTIMEO, &timeout_mqtt, sizeof(timeout_mqtt));

Best regards,

Charlie