[CentOS] Re: Weird TCP problem

Scott Silva ssilva at sgvwater.com
Mon Sep 8 16:23:45 UTC 2008


on 9-5-2008 4:51 PM Gordon Messmer spake the following:
> 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.
Unless there is a router in between somewhere that is broken on its dealing 
with window scaling. I have had that problem in the past.

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