[lwip-users] Receive window problem

[lwip]

Hello!

I'm an lwIP newbie and try to evaluate the receive performance for an audio 
streaming application; target is a AVR32 + FREETOS.

Before going into detail here are my config parameters:
TCP_WND: 6144
PBUF_POOL_SIZE: 8
PBUF_POOL_BUFSIZE:1536

I encountered the following problem:
With the start of transfer the receive window is 6144.
The transmitter sends the first two segments, each 1460 Byte. After the second 
segment lwIP acknowledged the second segment with receive window 3224. Then the 
transmitter sends the next two segments (1460 Byte) and lwip acknowledged the 
last segment with receive window 304.
Then lwIP sends a window Update with window 3224.

Here seams to be a problem, because the new window should be 6144. For what 
I've seen is that the window update message is generated after the data is 
given to the application.

In all next transfers the receive window never reaches the initial value of 
6144 again, so that buffer is vasted and newer used again.

I should add, that for receiving the data I used the netconn_recv in an endless 
loop.

Thank you for your suggestions.

Juergen