Bandwidth drop with more than 1024 bytes with TCP or UDP sockets (nRF9160 DK)

[Isaia Spinelli]

Hello,

I am doing tests on nRF9160 DK and I observe that if I send more than 1024 bytes on a TCP or UDP socket, the bandwidth drops.

Here are some numbers :

for TCP : 

Payload size [B]	Throughput [KB/s]
1000	15.32
1023	15.61
1024	15.57
1025	3.17
1050	3.18

for UDP : 

Payload size [B]	Throughput [KB/s]
1000	24.19
1023	25.44
1024	25.01
1025	12.37
1050	12.58

We can see that the bitrate drops after 1024 bytes. Do you have any idea why ? and if it is possible to avoid that ?

I am using :

- nRF COnnect SDK v1.4.99-dev1

- nRF9160 DK

- BSD library (CONFIG_BSD_LIBRARY=y) & standard POSIX 

Here is the loop I'm using to send the payload : 

The parameter SIZE_BUFFER represents the size of payload.

Thanks 

[Hakon]

Can you do the tests again with modem traces from when the bandwidth drops and when it is fine?

[Isaia Spinelli]

Hello, of course : 

save_trace.zip

a ZIP directory is fine ?

[Hakon]

Thank you, this is just fine.