[Windump] Receive window size problem

[Gianluca Varenni]

Hi Geoff,

sorry for taking so much time in replying.

Unfortunately I'm not an expert about TCP and I don't know exactly what's 
going on in your case. The best suggestion I can give you is posting your 
question to the wireshark-users mailing list. For sure there are a LOT of 
TCP experts hanging out on that mailing list.

Have a nice day
GV

----- Original Message ----- 
From: "Geoff Shipton" <geoffrey.shipton at sbcglobal.net>
To: <windump at winpcap.org>
Sent: Tuesday, June 24, 2008 9:27 PM
Subject: [Windump] Receive window size problem


>I am very new to this and feeling my way a bit, I work for a software 
>company although I am not a software engineer.
>
> I need to figure out why a TCP link we use is failing. The TCP link 
> streams data from an instrument to a logging system continuously over a 
> dedicated NIC pair.  The data volume is quite high although in general the 
> Network usage rarely exceeds 10% (of a Gigabit link).
>
> I have installed and run Windump successfully and I am able to see what 
> happens immediately prior to the failure.
>
> The failure always occurs eventually, but sometimes only after many hours. 
> On every occasion I notice that even whiel the link is "up" the TCP 
> receive window size varies  from the  default maximum  up and down 
> sometimes dropping very low (104) and usually recovering.  But at some 
> point the size drops to zero at which point the instrument stops sending 
> and goes into "persist timer" then all I see is occasional (60 secs) 
> requests from the instrument to the logging system; each time the logger 
> responds with recieve window zero so the connection is effectively dead.
>
> Simply going online and online at the logging end restores the connection.
>
> The programmers I work with seem not have many ideas about this problem so 
> any help is much appreciated.
>
> Geoff
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