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

[address@hidden]

Am 17.09.2021 um 10:34 schrieb Tomas Mudrunka:
> Recently there was somebody reporting simillar issue and it turned out
> that some (or most?) browsers use several concurent TCP/HTTP connections
> to load single webpage. Number of these connections was bigger than
> LWIPs default maximum number of concurent TCP connections, so you might
> try to increase that as well...

That's true, but the 10 connections configured below should be enough I
think.

Anyway, if he's reading the pcap and seeing delays due to delayed ACK,
new connections are probably not the problem.

Having access to a trace of this might help, though!

Regeards,
Simon

>
> Tom
>
>
> Dne 2021-09-16 08:49, Marco Giammarini napsal:
>> Dear Simon,
>> Thanks for your reply.
>> I have set 40kB of heap, and every time I stop the microcontroller in
>> debug mode during web site request, the free memory is over 70%.
>> This is my configuration:
>>
>> #DEFINE MEM_SIZE                (40*1024)
>>
>> #DEFINE MEMP_NUM_PBUF           28
>>
>> #DEFINE MEMP_NUM_TCP_PCB        10
>>
>> #DEFINE MEMP_NUM_TCP_PCB_LISTEN 3
>>
>> #DEFINE MEMP_NUM_TCP_SEG        40
>>
>> #DEFINE PBUF_POOL_SIZE          15
>>
>> #DEFINE TCP_MSS                 (1500 - 40)
>>
>> #DEFINE TCP_SND_BUF             (3*TCP_MSS)
>>
>> #DEFINE TCP_SND_QUEUELEN        (6 * TCP_SND_BUF)/TCP_MSS
>>
>> #DEFINE TCP_WND                 (3*TCP_MSS)
>>
>> Is there anything I can change?
>>
>> Regards,
>> Marco
>>
>>> Il giorno 15 set 2021, alle ore 09:55, goldsimon@gmx.de ha scritto:
>>>
>>> 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
>>>
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>