[lwip-users] Problem with fragmented TCP packets using slow 3G connection

[Maciej Gajdzica]

Hello

I have a program running on STM32F417 with lwIP working as webserver. When I test it over local network everything works great, page is loading fast and never hangs out. But i have a problem when I try to connect to my website using more complex network. STM is connected to TP-Link router with 3G modem internet connection. Router is configured to forward requests from 3G's port 80 to STM. Most of page content fits in single frame and loads with no errors. But one subpage is larger and it is not loaded when using 3G.

I made two logs with wireshark. In file "local_network_filtered" i saved communication with STM over local network, where everything works well. I load preview.html in single frame (about 1400 bytes), then configuration.html which is fragmented since it has about 3kB. Second file - "3g_network_filtered" contains logs from my attempts to load preview.html (successfull) and configuration.html (unsuccessfull). Then I tried to load these two pages second time with the same effect.

I think that it could be problem with one of these things: 
STM ethernet driver - code from ST is poor and i found here topics about some of its bugs.
Network configuration (3G and router) - I heard that 3G devices sometimes are trying to reduce traffic and could drop some TCP control packets
lwIP - maybe that case with embedded device, router and slow 3G network is rare and lwIP dont handle it proprely.

I use FreeRTOS 7.2 and lwIP 1.4.0 with socket API.

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Best Regards
Maciek

local_network_filtered.pcapng
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3g_network_filtered.pcapng
Description: Binary data