[En-Nut-Discussion] Duplicate ACKs with window size = 0

[Harald Kipp]

Hi Stephen,

Ethernut will send window size 0, if the application doesn't read
TCP data fast enough. This is completely OK and part of TCP handshake.

No question, it is not OK to send this every 20 ms. Are you sure?
Usually the other side will poll for an opening window again. If
that side sends poll telegrams each 20 ms, then it's that side, which
is wrong.

May be the other side is an Ethernut board too? OK, OK. :-) Yes, there's
a problem I've been told about, but hadn't time to check it. Usually Ethernut
did not expect the other side being too slow.

Yes, you can fine tune the maximum segment size and the initial window size.
See
    NutTcpSetSockOpt(sock, TCP_MAXSEG, &mss, sizeof(mss));
    NutTcpSetSockOpt(sock, SO_RCVBUF, &tcpbufsiz, sizeof(tcpbufsiz));

I don't know Etherpeak. Do you know Ethereal? If yes, how does it compare?

Harald