[lwip-devel] [bug #20506] HTTP server doesn't call tcp_output

[Simon Goldschmidt]

Follow-up Comment #14, bug #20506 (project lwip):

This really is a problem. But it's not the internet explorer that
responds slow, it's the WINDOWS tcpip stack! But this is normal
behaviour known as 'delayed ack'. WINDOWS waits for another packet
so that it doesn't send an ack for every packet but only for every
second packet. Most of the time, this works OK.

But for some reason, the initial window size is 1500 (frame 11 in
'tcp_output_http'). lwIp then responds with 1460 bytes and thus the
window has only 40 bytes left, which is not enough to send another frame
(lwIP chunks the data into mss-size frames if it can). So it has to wait for
a window update, which is only sent after some 200ms from the WINDOWS
side...

Now the question is if this is normal (slow start algorithm in WINDOWS tcpip
stack?) - if so, we should do something about it in lwIP - or not (in which
case the question is: why does your WINDOWS pc start with such a small
receive window?).

Kieran, what do you think?

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