[CentOS] Weird TCP problem

Fri Sep 5 23:51:51 UTC 2008
Gordon Messmer <yinyang at eburg.com>

Stephen Harris wrote:
> Sounds like the remote server may actually be busy and the number of
> outstanding connections is reaching the listen() backlog queue, so the
> remote server isn't doing an accept() and so the three way handshake
> isn't completing.

That thought crossed my mind, too.  However, it doesn't explain why the 
problem only affects new connections from Linux hosts.  Also, I believe 
that the listen queue is per-port, and this problem affects all ports 
equally, including oddball ports used by the web server.  I'm the only 
one connecting to those ports.

There are certainly differences between the SYN packets from Linux hosts 
and those from Windows.  On Linux, I see a window size of 5840, and tcp 
options: MSS=1460, SACK permitted, timestamps, and window scale: 7.

On Windows, the window size is 65535, MSS=1460, and SACK permitted.

However, I have no idea why any of those differences would cause a 
problem intermittently.