Re: [lwip-users] LWIP slow web server only with Windows OS request

[address@hidden]

Am 15.09.2021 um 08:55 schrieb Marco Giammarini:
> Dear All, 
> I’m studying this problem more in-depth (with Wireshark), and I found
> that sometimes Windows reply with ACK after 40ms at every packet. In
> this case, with a file of 800kB, a packet of 1460B, we have more or less
> 500 packets, that multiplied for 40ms reach 20 seconds each file.
> I found that this problem is very common for Windows PC:
> *  https://developpaper.com/lets-talk-about-the-magical-40-ms-of-tcp/
> <https://developpaper.com/lets-talk-about-the-magical-40-ms-of-tcp/>
> * 
> https://docs.microsoft.com/it-it/troubleshoot/windows-server/networking/registry-entry-control-tcp-acknowledgment-behavior
> <https://docs.microsoft.com/it-it/troubleshoot/windows-server/networking/registry-entry-control-tcp-acknowledgment-behavior>
>
> Is there any way to solve the problem (or a workaround) by modify some
> parameters of lwIP?

You should not have a speed problem even if the ACKs get delayed
further. Having a problem here suggests that your lwIP (memory) options
limit the send window in such amount that transmission stalls until the
next ACK is received.

Unless you're really short on memory, you should probably review your
TCP and memory related options in lwipopts.h

Regards,
Simon