[lwip-users] Frequent window closing (zero window) when receiving MP3 stream

[Norbert Morawski]

Hello,

I'm not sure if this is a problem, but my MP3 radio streamer (lwip @ 
RP2040) frequently closes the window. This is caused by a initial inrush 
of data from the server, which pushes the window from 12kB to almost 0. 
Then it only oscillates between 0 and 4kB with a period of about 2 seconds.

Isn't there a way to prevent the initial depletion of window size? I'd 
be much comfortable if it'd oscillate around half of the window size. 
Changing window size didn't help. Current config is:
TCP_MSS                     1460
TCP_WND                    (8 * TCP_MSS) = 11680 bytes

The app ACKs data as it decodes the MP3 frames, which would be 2 fast 
calls to tcp_recved of around 400 bytes each 50 ms. Here are some images 
regarding the problem. A chart of advertised window size from lwip 
client to the server and a wireshark dump where initial 8 packets of 
size 87% of the window are received in about 0.2ms 
(https://imgur.com/gallery/TVVcTp2)

Or I have nothing to worry about and this is a normal TCP behavior?

Regards,
Norbert.