[lwip-devel] [bug #26012] ACKs by SWS avoidance

[Oleg Tyshev]

URL:
  <http://savannah.nongnu.org/bugs/?26012>

                 Summary: ACKs by SWS avoidance
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: olegreen
            Submitted on: Thu 26 Mar 2009 03:43:57 PM GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: 1.3.0

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Details:

In tcp_recved we increase pcb->rcv_ann_wnd only if receive window >= MSS.
That's right.
But tcp_ack(pcb) we call always.
tcp_ack sets TF_ACK_DELAY flag and with next tcp_fasttmr() tick would be
duplicate ACK sent (each 250 ms).

If receive buffer is full and application read data relative slow (e.g. 1
byte per 100 millisecond) would be generated 4 unnecessary duplicate ACKs per
second

I suppose this patch can help



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File Attachments:


-------------------------------------------------------
Date: Thu 26 Mar 2009 03:43:57 PM GMT  Name: sws_acks.patch  Size: 1kB   By:
olegreen

<http://savannah.nongnu.org/bugs/download.php?file_id=17808>

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