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TCP stops sending ACKs after 32 mesg...

To: <netdev@xxxxxxxxxxx>
Subject: TCP stops sending ACKs after 32 mesg...
From: "Saurabh Bansal" <sbansal@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 30 Aug 2002 16:47:30 +0530
Cc: <linux-net@xxxxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
Hi,

    It has been more than a week since I posted this query to the LINUX group 
and haven't heard anything from the group-side in this context. Is my query 
under processing/observation OR something else??

Hope to get some positive response from your side this time!

Thanks And Regards
Saurabh

----- Original Message ----- 
From: Saurabh Bansal 
To: netdev@xxxxxxxxxxx 
Cc: linux-net@xxxxxxxxxxxxxxx 
Sent: Wednesday, August 21, 2002 1:26 PM


Hi all,

    I did this experiment with the a set of two processes behaving as a 
sender/receiver set on the same Linux machine. What the experiment was that---

"The sender has to send some fixed-size (20 bytes) mesgs to the receiver but 
the receiver has not to pick-up anyone of them."

 What has been observed is, TCP buffers the first 32 messages into the receive 
socket queue of receiver, AND THEN it stops sending ack's for next mesg. As a 
result, the sender keeps on trying to send the 33rd mesg, but gets no ack's and 
connection gets down within 15-20 minutes. Another important observations about 
this experiment are :

1) These two processes were running on the same Linux system with kernel 
version 2.2.xx. This problem doesn't come with Linux-kernel 2.4.xx.

2) If these processes are run on different Linux m/c's with kernel 2.2.xx, the 
problem doesn't appear.

3) The socket APIs used for sending/receiving mesg are send()/recv().

4) The problem has no relevance with the size of mesg. I have seen the same 
behavior with 1-byte mesg to 1k-byte mesg.

Can anyone tell me if there is any bug/limitation with the Linux-kernel 2.2.xx 
in comparison to kernel 2.4.xx in the above problem-context??


Saurabh Bansal



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